Patent Application
20230304932
The present disclosure generally relates to energy transfer dye conjugate pairs comprising a donor dye covalently attached to an acceptor dye. The disclosure further relates to uses of energy transfer dye conjugate pairs, for example, as an energy transfer dye conjugate reporter moiety covalently attached to an analyte with or without a quencher moiety, for biological applications including, for example, quantitative polymerase chain reaction (qPCR) and digital PCR (dPCR). The present disclosure further relates to systems, devices, and methods for observing, testing, and/or analyzing one or more biological samples by qPCR, and more specifically to systems, devices, and methods comprising optical systems for observing, testing, and/or analyzing one or more biological samples by qPCR using the energy transfer dye conjugate pairs disclosed herein.
Current analyses of cell and tissue functionality often require extracting as much information as possible from materials that are often limited. For example, samples such as tumor biopsies are difficult to collect and usually yield only a small amount of usable nucleic acid. PCR detection and measurement of a single target analyte, referred to as a single-plex assay, has been the gold standard for analyzing clinical research samples on the nucleic acid level, and has been invaluable in extending the limits of biological knowledge for more than a quarter century.
However, the limited amount of nucleic acid obtained from clinical research specimens often forces choices to be made about how best to utilize these precious samples. Furthermore, if the sample is limited, the number of loci that can be analyzed is also limited, reducing the amount of information that can be extracted from a single sample. Finally, the additional time and materials required to set up multiple single-assay reactions could increase the expense of a complex project significantly.
Real-time systems for quantitative PCR (qPCR) are frequently used to conduct assays on cell and tissue samples. Nucleic acid detection/amplification methods, such as in real-time polymerase chain reactions, frequently use dual-labeled probes to detect and/or quantify target nucleic acids like specific gene sequences or expressed messenger RNA sequences. Fluorogenic probes for use in such methods are often labeled with both a reporter and a quencher moiety. In such cases, fluorescence from the reporter is unquenched when the two moieties are physically separated via hybridization of the oligonucleotide probe to a nucleic acid template and/or via nuclease activity which removes one of the quencher or reporter moieties components from the oligonucleotide probe.
Fluorescence resonance energy transfer (FRET) within dual-labeled oligonucleotide probes is widely used in assays for genetic analysis. FRET has been utilized to study DNA hybridization and amplification, the dynamics of protein folding, proteolytic degradation, and interactions between other biomolecules. FRET can occur between reporter and quencher groups and can involve different modes of energy transfer (ET). For example, energy transfer can involve fluorescence quenching mechanisms whereby an excitation electron can be transferred from a donor molecule to an acceptor molecule via a non-radiative path when there is interaction between the donor and acceptor. FRET also can occur between two dye molecules when excitation is transferred from a donor molecule to an acceptor molecule without emission of a photon.
Multiplex PCR analysis of nucleic acids, a strategy where more than one target is amplified and quantified from a single sample aliquot, is an attractive solution to problems associated with running multiple single-plex assays. In multiplex PCR, a sample aliquot is queried with multiple probes that contain fluorescent dyes in a single PCR reaction. This increases the amount of information that can be extracted from that sample. With multiplex PCR, significant savings in sample and materials can be realized. To increase the utility of this method, multiplexed PCR using several pairs of gene-specific primers and probes to amplify and measure multiple target sequences simultaneously have been developed. Multiplexing PCR provides the following advantages: 1) Efficiency: multiplexed PCR helps conserve sample material and avoid well-to-well variation by combining several PCR assays into a single reaction. Multiplexing makes more efficient use of limited samples, such as those harboring a rare target that cannot be split into multiple aliquots without compromising the sensitivity; 2) Economy: even though the targets are amplified in unison, each one is detected independently by using a gene-specific probe with a unique reporter dye to distinguish the amplifications based on their fluorescent signal. Once optimized, a multiplexed assay is more cost effective than the same assays amplified independently.
However, currently there are limitations to the number of targets that can be analyzed in a single multiplex PCR assay. The experimental design for multiplex PCR is more complicated than for single reactions. The probes used to detect individual targets must contain unique reporter moieties with distinct spectra. The settings for excitation and emission filters of real-time detection systems vary from manufacturer to manufacturer; therefore, instruments must be calibrated for each dye moiety as part of the experiment optimization process. Thus, one limitation in the development of multiplex PCR assays is the number of fluorophores, and hence probes, that can be effectively measured in a single reaction. Another limitation in multiplexed PCR results from signal interference (“cross-talk”) between different fluorescence reporters that can compromise quantification or cause false positives or inaccurate quantification. Using traditional systems, it is therefore important to select fluorophores with minimal spectral overlap. Thus, when designing multiplexed reactions, different targets should be labeled with fluorophores that avoid overlapping excitation and/or emission profiles to avoid possible crosstalk issues. Additionally, the emission and excitation spectra of the fluorophores must be compatible with the PCR instrument to be used, and specifically, the band-pass specifications for each filter-set.
Signal cross-talk also can be minimized by using probes that quench well. When designing a fluorescent probe, it is necessary to ensure that the reporter and quencher moieties are compatible, given the type of detection chemistry. Previously, the most common dye/quencher combination for a TaqMan probe is a FAM fluorophore with a TAMRA quencher. More recently, however, “dark quenchers”, such as Dabcyl and Black Hole Quenchers (BHQ), have largely replaced fluorescent quenchers such as TAMRA. Dark quenchers emit the energy they absorb from the fluorophore as heat rather than light of a different wavelength. “Dark quenchers” tend to give results with lower background, and are especially useful in a multiplex reaction where it is important to avoid emitted light from the quencher creating cross-talk signal with one of the reporter dyes. Thus, highly efficient “dark quenchers” considerably reduce background fluorescence from fluorophore and quencher moieties leading to increased sensitivity and end-point signal. This is particularly useful for multiplex reactions because having several fluorophores in the same tube causes higher background fluorescence.
In general, multiplex PCR reactions have been limited due, for example, to complexities in the chemistry introduced when a large number of different probes are present within a single reaction mixture. For example, in duplex reactions, the most popular combination used is FAM and HEX (JOE/VIC®); in triplex reactions, dyes such as FAM, HEX (JOE/VIC®), NED or Cy5 are typically used; and in quadriplex reactions, dyes such as FAM, HEX (JOE/VIC®), Texas Red®, and Cy5 dyes are typically used. Until recently, the most common multiplex PCR instruments could take advantage of only four unique dye-quencher pairs. However, certain commercial instruments have the optical capability to perform higher levels of multiplexing, e.g., 6-plex PCR, 8-plex PCR, 10-plex PCR, 20-plex PCR, and the like.
Chemical complexities notwithstanding, higher-plex qPCR assays have also been limited by instrument capabilities or the way in which existing instruments are utilized. Currently available qPCR instruments divide a broad excitation and emission spectrum into distinct spectra (EX/EM “channels”) that are compatible with the excitation/emission spectra of corresponding sets of dyes or probes. For example, matched sets of EX/EM channels have typically been used up to accommodate quadriplex reactions, as discussed above. However, due at least in part to the unavailability of suitable probes, a fuller range of EX/EM channel combinations have yet to be utilized to provide assays able to quantify more than 4 targets in a common sample.
Thus, there is a need to provide additional probes that include unique fluorophore/quencher combinations that allow for increased multiplex reactions and detection through the additional spectral channels already available on some commercial instruments. Further, there is a need for new fluorophores and fluorophore/quencher combinations with unique optical properties that can facilitate even higher order multiplexing once instruments with additional channels and other related hardware and software improvements become available.
In one aspect, the present disclosure provides an energy transfer fluorescent dye conjugate the includes i. a donor dye capable of absorbing light at a first wavelength and emitting excitation energy in response; ii. an acceptor dye capable of absorbing the excitation energy emitted by the donor dye and emitting light at a second wavelength in response; and iii. a linker covalently attaching the donor dye to the acceptor dye, wherein the linker includes one or more of an alkyl portion, an amino-alkyl portion, an oxy-alkylene portion, an amino-alkylene-dialkoxy portion, an alkenylene portion, an alkynylene portion, a polyether portion, an arylene portion, an amide portion, or a phosphodiester portion.
In certain embodiments, the energy transfer dye conjugates described herein can be linked to an analyte and have a basic structure selected from one of:
Representative examples of donor dyes include, without limitation, a xanthene dye, a cyanine dye, a BODIPY dye, a pyrene dye, a pyronine dye, and a coumarin dye. Representative examples of acceptor dyes include, without limitation, a fluorescein dye, a cyanine dye, a rhodamine dye, a BODIPY dye, a pyrene dye, a pyronine dye, and a coumarin dye.
In another aspect, an oligonucleotide probe is described that includes: i. an oligonucleotide; and ii. an energy transfer dye conjugate as described herein that is covalently attached to the oligonucleotide.
In yet another aspect, a composition is described that includes a fluorescently-labeled oligonucleotide probe that includes: an oligonucleotide probe covalently attached to the energy transfer dye conjugate as described herein. In some embodiments, the composition includes the oligonucleotide probe attached to the energy transfer dye conjugate and an aqueous medium, such as a buffer, master mix, or reaction mixture. In some embodiments, the composition includes the oligonucleotide probe attached to the energy transfer dye conjugate and a non-aqueous medium, such as a lyophilized or freeze-dried buffer, master mix, or reaction mixture
In another aspect, a method of detecting or quantifying a target nucleic acid molecule in a sample is described that includes:
In yet another aspect, a method of detecting or quantifying a target nucleic acid molecule in a sample by polymerase chain reaction (PCR) is described that includes:
In yet another aspect, a kit for polymerase chain reaction (PCR) is described that includes: i. one or more buffering agents, a nucleic acid synthesis enzyme; and ii. an oligonucleotide probe as described herein; and iii. instructions for performing a PCR assay, and optionally a purification medium or an organic solvent.
In yet another aspect, compositions are provided herein. For example, the composition can include: a) a first labeled oligonucleotide including an energy transfer dye conjugate as described herein; and b) a polymerase. In another embodiment, the composition can include: a) a fluorescent energy transfer dye conjugate as disclosed herein; and b) a nucleic acid molecule. In yet another embodiment, the composition can include: a) a fluorescent energy transfer dye conjugate as disclosed herein; and b) an enzyme. In yet another embodiment, the composition can include: a) a fluorescent energy transfer dye conjugate as disclosed herein; and b) a fluorophore having an excitation wavelength that is within 20 nm of the excitation wavelength of the donor dye in the energy transfer dye conjugate or within 20 nm of the emission wavelength of the acceptor dye in the energy transfer dye conjugate.
In still another aspect, a system comprises a first radiant source, an optional second radiant source, a detector, a first emission spectral element, and an optional second emission spectral element. The system may further include at least one processor comprising at least one memory including instructions. The first radiant is source characterized by a first average excitation wavelength, while the second radiant source, when present, is characterized by a second average excitation wavelength that is different than the first average excitation wavelength. A sample is disposed to receive radiation from the radiant source(s), wherein the sample comprises a first dye, a second dye and an optional third dye. The detector is configured to measure emissions from the sample. The first emission spectral element is characterized by a first average emission wavelength and the optional second emission spectral element is characterized by a second average emission wavelength that is different than the first average emission wavelength. The memory includes instructions to illuminate the sample with the first radiant source and, in response, (1) measure emissions from the sample using the detector and the first emission spectral element and (2) optionally measure emissions from the sample using the detector and the second emission spectral element. When present, the memory also includes instructions to illuminate the sample with the second radiant source and, in response, measure emissions from the sample using the detector and the second emission spectral element. The first dye comprises a first absorption spectrum comprising a first maximum absorption wavelength and the second dye comprises a second absorption spectrum comprising a second maximum absorption wavelength that is equal to or substantially equal to the first maximum absorption wavelength. Additionally or alternatively, the second dye comprises a second emission spectrum comprising a second maximum emission wavelength and the third dye comprises a third emission spectrum comprising a third maximum emission wavelength that is equal to or substantially equal to the second maximum emission wavelength.
Additional embodiments, features, and advantages of the disclosure will be apparent from the following detailed description and through practice of the disclosure. It will be understood that any of the embodiments described herein can be used in connection with any other embodiments described herein to the extent that the embodiments do not contradict one another.
Embodiments of the present disclosure may be better understood from the following detailed description when read in conjunction with the accompanying drawings. Such embodiments, which are for illustrative purposes only, depict novel and non-obvious aspects of the present disclosure. The drawings include the following figures:
Reference will now be made in detail to certain embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. It is to be understood that both the general description and detailed description the embodiments discussed herein are generally directed to devices, systems, compositions and methods used in nucleic acid synthesis, such as polymerase chain reaction (PCR) devices, systems, compositions and methods, including for example, real-time PCR (qPCR) devices, systems, compositions and methods and end-point PCR devices, systems, compositions and methods, including, but not limited to digital PCR (dPCR) or melt curve analysis devices, system, compositions or methods. It is to be understood that both the general description and detailed description provided herein are exemplary and explanatory only and are not restrictive of the teachings. While the disclosure will be described in conjunction with the illustrated embodiments, it will be understood that they are not intended to limit the disclosure to those embodiments. On the contrary, the disclosure is intended to cover all alternatives, modifications, and equivalents, which may be included within the disclosure as defined by the appended claims.
For the purposes of interpreting of this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims unless a contrary meaning is clearly intended (for example in the document where the term is originally used). It is noted that, as used in this specification and the appended and claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. The use of “or” means “and/or” unless stated otherwise. The use of “comprise,” “comprises,” “comprising,” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term “comprising,” those skilled in the art would understand that, in some specific instances, the embodiment or embodiments can be alternatively described using the language “consisting essentially of” and/or “consisting of.”
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages, or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about,” to the extent they are not already so modified. “About” indicates a degree of variation that does not substantially affect the properties of the described subject matter, e.g., within 10%, 5%, 2%, or 1%. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed considering the number of reported significant digits and by applying ordinary rounding techniques.
The section headings used herein are for organizational purposes only and are not to be construed as limiting the desired subject matter in any way. In the event that any literature incorporated by reference contradicts any term defined in this specification, this specification controls. While the present teachings are described in conjunction with various embodiments, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art.
To facilitate understanding of this disclosure, a number of terms are defined below. Unless stated otherwise, the following terms and phrases as used herein are intended to have the following meanings.
As used herein, “energy transfer (ET)” refers to FRET or Dexter energy transfer. As used herein, “FRET” (also referred to as fluorescence resonance energy transfer or Förster resonance energy transfer) refers to a form of molecular energy transfer (MET) by which energy is passed non-radiatively between a donor molecule and an acceptor molecule. Without being bound by theory, it is believed that when two fluorophores whose excitation and emission spectra overlap are in close proximity, excitation of one fluorophore can cause the first fluorophore to transfer its absorbed energy to the second fluorophore, causing the second fluorophore, in turn, to fluoresce. Stated differently, the excited-state energy of the first (donor) fluorophore is transferred by a process sometimes referred to as resonance induced dipole-dipole interaction to the neighboring second (acceptor) fluorophore. As a result, the lifetime of the donor molecule is decreased and its fluorescence is quenched, while the fluorescence intensity of the acceptor molecule is enhanced and depolarized. When the excited-state energy of the donor is transferred to a non-fluorophore acceptor, such as a quencher, the fluorescence of the donor is quenched without subsequent emission of fluorescence by the acceptor. Pairs of molecules that can engage in ET are termed ET pairs. In order for energy transfer to occur, the donor and acceptor molecules must typically be in close proximity (e.g., up to 70 to 100 Angstroms). As used herein, “Dexter energy transfer” refers to a fluorescence quenching mechanism whereby an excitation electron can be transferred from a donor molecule to an acceptor molecule via a non-radiative path. Dexter energy transfer can occur when there is interaction between the donor and acceptor. In some embodiments, the Dexter energy transfer can occur at a distance between the donor and acceptor of about 10 Angstroms or less. In some embodiments, in the Dexter energy transfer, the excited state may be exchanged in a single step. In some embodiments, in the Dexter energy transfer, the excited state may be exchanged in a two separate steps.
Commonly used methods for detecting nucleic acid amplification products require that the amplified product (i.e., amplicon) be separated from unreacted primers. This is often achieved either through the use of gel electrophoresis, which separates the amplification product from the primers on the basis of a size differential, or through the immobilization of the product, allowing washing away of free primer. Other methods for monitoring the amplification process without separation of the primers from the amplicon, such as for real-time detection, have been described. Some examples include TaqMan® probes (Roche Molecular Systems), molecular beacons, double-stranded intercalator dyes, such as SYBR® GREEN indicator dye (Life Technologies Corporation), LUX primers, and others. The principal drawback to intercalator-based detection of PCR product accumulation, such as using SYBR® GREEN indicator dye, is that both specific and nonspecific products generate a signal. Typically, intercalators are used for single-plex detection assays and are not suitable for use for multiplex detection.
Real-time systems for quantitative PCR (qPCR) are frequently used to conduct assays on cell and tissue samples (e.g., blood, saliva, semen, urine). Quantitative PCR assays that are probe-based provide a significant improvement over intercalator-based PCR product detection. One probe-based method for detection of amplification product without separation from the primers is the 5′ nuclease PCR assay (also referred to as the TaqMan® assay or hydrolysis probe assay). This alternative method provides a real-time method for detecting only specific amplification products. During amplification, annealing of the detector probe, sometimes referred to as a “TaqMan probe” (e.g., 5′nuclease probe) or hydrolysis probe, to its target sequence generates a substrate that is cleaved by the 5′ nuclease activity of a DNA polymerase, such as a Thermus aquaticus (Taq) DNA polymerase, when the enzyme extends from an upstream primer into the region of the probe. This dependence on polymerization ensures that cleavage of the probe occurs only if the target sequence is being amplified.
The term “reporter,” “reporter group” or “reporter moiety” is used in a broad sense herein and refers to any identifiable tag, label, or moiety. In some embodiments, the reporter is a fluorescent reporter moiety or dye.
In general, a TaqMan detector probe can include an oligonucleotide covalently attached to a fluorescent reporter moiety or dye and a quencher moiety or dye. The reporter and quencher dyes are in close proximity, such that the quencher greatly reduces the fluorescence emitted by the reporter dye by FRET. Probe design and synthesis has been simplified by the finding that adequate quenching is typically observed for probes with the reporter at the 5′ end and the quencher at the 3′ end.
During the extension phase of PCR, if the target sequence is present, the detector probe anneals downstream from one of the primer sites and is cleaved by the 5′ nuclease activity of a DNA polymerase possessing such activity, as this primer is extended. The cleavage of the probe separates the reporter dye from quencher dye by releasing them into solution, and thereby increasing the reporter dye signal. Cleavage further removes the probe from the target strand, allowing primer extension to continue to the end of the template strand. Thus, inclusion of the probe does not inhibit the overall PCR process. Additional reporter dye molecules are cleaved from their respective probes with each cycle, effecting an increase in fluorescence intensity proportional to the amount of amplicon produced.
The advantage of fluorogenic detector probes over DNA binding dyes, such as SYBR GREEN®, is that specific hybridization between probe and target is required to generate fluorescent signal. Thus, with fluorogenic detector probes, non-specific amplification due to mis-priming or primer-dimer artifact does not generate a signal. Another advantage of fluorogenic probes is that they can be labeled with different, distinguishable reporter dyes. By using detector probes labeled with different reporters, amplification of multiple distinct sequences can be detected in a single PCR reaction, often referred to as a multiplex assay.
As used herein, the term “probe” or “detector probe” generally refers to any of a variety of signaling molecules indicative of amplification, such as an “oligonucleotide probe.” As used herein, “oligonucleotide probe” refers to an oligomer of synthetic or biologically produced nucleic acids (e.g., DNA or RNA or DNA/RNA hybrid) which, by design or selection, contain specific nucleotide sequences that allow it to hybridize under defined stringencies, specifically (i.e., preferentially) to a target nucleic acid sequence. Thus, some probes or detector probes can be sequence-based (also referred to as “sequence-specific detector probe”), for example 5′ nuclease probes. Various detector probes are known in the art, for example (TaqMan® probes described herein (See also U.S. Pat. No. 5,538,848) various stem-loop molecular beacons (See, e.g., U.S. Pat. Nos. 6,103,476 and 5,925,517 and Tyagi and Kramer, 1996, Nature Biotechnology 14:303-308), stemless or linear beacons (See, e.g., WO 99/21881), PNA Molecular Beacons™ (See, e.g., U.S. Pat. Nos. 6,355,421 and 6,593,091), linear PNA beacons (See, e.g., Kubista et al., 2001, SPIE 4264:53-58), non-FRET probes (See, e.g., U.S. Pat. No. 6,150,097), Sunrise®/Amplifluor® probes (U.S. Pat. No. 6,548,250), stem-loop and duplex Scorpion™ probes (Solinas et al., 2001, Nucleic Acids Research 29:E96 and U.S. Pat. No. 6,589,743), bulge loop probes (U.S. Pat. No. 6,590,091), pseudo knot probes (U.S. Pat. No. 6,589,250), cyclicons (U.S. Pat. No. 6,383,752), MGB Eclipse™ probe (Epoch Biosciences), hairpin probes (U.S. Pat. No. 6,596,490), peptide nucleic acid (PNA) light-up probes, self-assembled nanoparticle probes, and ferrocene-modified probes described, for example, in U.S. Pat. No. 6,485,901; Mhlanga et al., 2001, Methods 25:463-471; Whitcombe et al., 1999, Nature Biotechnology. 17:804-807; Isacsson et al., 2000, Molecular Cell Probes. 14:321-328; Svanvik et al., 2000, Anal Biochem. 281:26-35; Wolffs et al., 2001, Biotechniques 766:769-771; Tsourkas et al., 2002, Nucleic Acids Research. 30:4208-4215; Riccelli et al., 2002, Nucleic Acids Research 30:4088-4093; Zhang et al., 2002 Shanghai. 34:329-332; Maxwell et al., 2002, J. Am. Chem. Soc. 124:9606-9612; Broude et al., 2002, Trends Biotechnol. 20:249-56; Huang et al., 2002, Chem Res. Toxicol. 15:118-126; and Yu et al., 2001, J. Am. Chem. Soc 14:11155-11161. Detector probes can include reporter dyes such as, for example, the novel dyes described herein as well as 6-carboxyfluorescein (6-FAM) or tetrachlorofluorescin (TET) and other dyes known to those of skill in the art. Detector probes can also include quencher moieties such as those described herein as well as tetramethylrhodamine (TAMRA), Black Hole Quenchers (Biosearch), Iowa Black (IDT), QSY quencher (Molecular Probes), and Dabsyl and Dabcyl sulfonate/carboxylate Quenchers (Epoch). In some embodiments, detector probes can also include a combination of two probes, wherein for example a fluor is on one probe, and a quencher on the other, wherein hybridization of the two probes together on a target quenches the signal, or wherein hybridization on a target alters the signal signature via a change in fluorescence.
“Primer” as used herein can refer to more than one primer and refers to an oligonucleotide, whether occurring naturally or produced synthetically, which is capable of acting as a point of initiation of synthesis when placed under conditions in which synthesis of a primer extension product which is complementary to a nucleic acid strand is induced i.e., in the presence of nucleotides and an agent for polymerization such as DNA polymerase, at a suitable temperature for a sufficient amount of time and in the presence of a buffering agent. Such conditions can include, for example, the presence of at least four different deoxyribonucleoside triphosphates (such as G, C, A, and T) and a polymerization-inducing agent such as DNA polymerase or reverse transcriptase, in a suitable buffer (“buffer” includes substituents which are cofactors, or which affect pH, ionic strength, etc.), and at a suitable temperature. In some embodiments, the primer may be single-stranded for maximum efficiency in amplification. The primers herein are selected to be substantially complementary to the different strands of each specific sequence to be amplified. This means that the primers must be sufficiently complementary to hybridize with their respective strands. A non-complementary nucleotide fragment may be attached to the 5′-end of the primer (such as having a “tail”), with the remainder of the primer sequence being complementary, or partially complementary, to the target region of the target nucleic acid. Commonly, the primers are complementary, except when non-complementary nucleotides may be present at a predetermined sequence or sequence range location, such as a primer terminus as described. In some embodiments, such non-complementary “tails” can comprise a universal sequence, for example, a sequence that is common to one or more oligonucleotides. In certain embodiments, the non-complementary fragment or tail may comprise a polynucleotide sequence such as a poly (T) sequence to hybridize, for example, to a polyadenylated oligonucleotide or sequence.
As used herein, a “sample” refers to any substance containing, or presumed to contain, one or more biomolecules (e.g., one or more nucleic acid and/or protein target molecules) and can include one or more of cells, a tissue or a fluid extracted and/or isolated from an individual or individuals. Samples may be derived from a mammalian or non-mammalian organism (e.g., including but not limited to a plant, virus, bacteriophage, bacteria, and/or fungus). As used herein, the sample may refer to the substance contained in an individual solution, container, vial, and/or reaction site or may refer to the substance that is partitioned between an array of solutions, containers, vials, and/or reaction sites (e.g., substance partitioned over an array of microtiter plate vials or over an array of array of through-holes or reaction regions of a sample plate; for example, for use in a dPCR assay). In some embodiments, a sample may be a crude sample. For example, the sample may be a crude biological sample that has not undergone any additional sample preparation or isolation. In some embodiments, the sample may be a processed sample that had undergone additional processing steps to further isolate the analyte(s) of interest and/or clean up other debris or contaminants from the sample.
As used herein, the terms “target”, “target molecule”, “target biomolecule”, “target analyte”, “target sequence”, “target nucleic acid molecule”, or the like, refers to a molecule having a particular chemical structure that is distinct from that of one or more other “targets”, “target molecules”, “target biomolecules”, “target analytes”, “target sequences”, “target nucleic acid molecules”, or the like. In general, each “target”, “target molecule”, “target biomolecule”, “target analyte”, “target sequence”, “target nucleic acid molecule”, or the like contains a structure or sequence that is distinct from any structure or sequence of the others and that may be utilized to attached to a particular probe or dye contained in sample or sample solution.
As used herein, the term “amplification” or “amplify” refers to an assay in which the amount or number of one or more target biomolecules is increased, for example, by an amount to allow detection and/or quantification of the one or more target biomolecules. For example, in some embodiments, a PCR assay may be used to amplify a target biomolecule. As used herein, a “polymerase chain reaction” or a “PCR”, unless specifically defined otherwise, refers to either singleplex or multiplex PCR assays, and can be real time or quantitative PCR (wherein detection occurs during amplification) or end-point PCR (when detection occurs at the end of a PCR or after amplification; e.g., a dPCR assay). Other types of assays and methods of amplification or amplifying are also anticipated such as, for example, isothermal nucleic acid amplification and are readily understood by those of skill in the art.
As used herein, the terms “nucleic acid,” “polynucleotide,” and “oligonucleotide” can refer to primers, probes, oligomer fragments to be detected, oligomer controls—either labeled or unlabeled, and unlabeled blocking oligomers and shall be generic to polydeoxyribonucleotides (containing 2-deoxy-D-ribose), polyribonucleotides (containing D-ribose), and any other type of polynucleotide which is an N-glycoside of a purine or pyrimidine base, or modified purine or pyrimidine bases. There is no intended distinction in length between the term “nucleic acid,” “polynucleotide,” and “oligonucleotide,” and these terms will be used interchangeably. “Nucleic acid”, “DNA”, “RNA”, and similar terms can also include nucleic acid analogs. The oligonucleotides, as described herein, are not necessarily physically derived from any existing or natural sequence but may be generated in any manner, including chemical synthesis, DNA replication, reverse transcription or a combination thereof.
The term “analog” or “analogue” includes synthetic analogs having modified base moieties, modified sugar moieties, and/or modified phosphate ester moieties. As used herein, the term “modified base” refers generally to any modification of a base or the chemical linkage of a base in a nucleic acid that differs in structure from that found in a naturally occurring nucleic acid. Such modifications can include changes in the chemical structures of bases or in the chemical linkage of a base in a nucleic acid, or in the backbone structure of the nucleic acid. (See, e.g., Latorra, D. et al., Hum Mut 2003, 2:79-85. Nakiandwe, J. et al., plant Method 2007, 3:2.)
Oligonucleotides described herein, especially those functioning as a probe and/or primer, can include one or more modified bases in addition to the naturally occurring bases adenine, cytosine, guanine, thymine and uracil (represented as A, C, G, T, and U, respectively). In some embodiments, the modified base(s) may increase the difference in the Tm between matched and mismatched target sequences and/or decrease mismatch priming efficiency, thereby improving not only assay specificity, but also selectivity. Modified bases can be those that differ from the naturally-occurring bases by addition or deletion of one or more functional groups, differences in the heterocyclic ring structure (i.e., substitution of carbon for a heteroatom, or vice versa), and/or attachment of one or more linker arm structures to the base. Such modified base(s) may include, for example, 8-Aza-7-deaza-dA (ppA), 8-Aza-7-deaza-dG (ppG), locked nucleic acid (LNA) or 2′-O,4′-C-ethylene nucleic acid (ENA) bases. Other examples of modified bases include, but are not limited to, the general class of base analogues 7-deazapurines and their derivatives and pyrazolopyrimidines and their derivatives (e.g., as described in PCT WO 90/14353, herein incorporated by reference). These base analogues, when present in an oligonucleotide, can strengthen hybridization and improve mismatch discrimination. All tautomeric forms of naturally occurring bases, modified bases and base analogues can be included. Modified internucleotide linkages can also be present in the oligonucleotides described herein. Such modified linkages include, but are not limited to, peptide, phosphate, phosphodiester, phosphotriester, alkylphosphate, alkanephosphonate, thiophosphate, phosphorothioate, phosphorodithioate, methylphosphonate, phosphoramidate, substituted phosphoramidate and the like. Several further modifications of bases, sugars and/or internucleotide linkages, that are compatible with their use in oligonucleotides serving as probes and/or primers, will be apparent to those of skill in the art.
In some embodiments, a modified base is located at (a) the 3′-end, (b) the 5′-end, (c) at an internal position, or at any combination of (a), (b) and/or (c) in the oligonucleotide probe and/or primer.
In some embodiments the primer and/or probes as disclosed herein are designed as oligomers that are single-stranded. In some embodiments, the primers and/or probes are linear. In other embodiments, the primers and/or probes are double-stranded or include a double-stranded segment. For example, in some embodiments, the primers and/or probes may form a stem-loop structure, including a loop portion and a stem portion. In some embodiments, the primers and/or probes are short oligonucleotides, having a length of 100 nucleotides or less, more preferably 50 nucleotides or less, still more preferably 30 nucleotides or less and most preferably 20 nucleotides or less with a lower limit being approximately 3-5 nucleotides. In some embodiments, the primer and/or probes as disclosed herein are between 5 to 35 nucleotides long. In some embodiments, the primers and/or probes as disclosed herein are 10, 15, 20, 25, 30, or any length in between 10 to 30 nucleotides long. In some embodiments, the primer and/or probes as disclosed herein are between 5 to 35 nucleotides long. In some embodiments, the primers and/or probes as disclosed herein are 10, 15, 20, 25, 30, or any length in between 10 to 30 nucleotides long.
In some embodiments, the Tm of the primers and/or probes disclosed herein range from about 50° C. to about 75° C. In some embodiments, the primers and/or probes are between about 55° C. to about 65° C. In some embodiments, the primers and/or probes are between about 60° C. to 70° C. For example, the Tm of the primers and/or probes disclosed herein may be 56° C., 57° C., 58° C., 60° C., 61° C., 62° C., 63° C., 64° C., 65° C., 66° C., etc. In some other embodiments, the Tm of the primers and/or probes disclosed herein may be 56° C. to 63° C., 58° C. to 68° C. 61° C. to 69° C., 62° C. to 68° C., 63° C. to 67° C., 64° C. to 66° C., or any range in between. In some embodiments, the Tm of the primers is lower than the Tm of the probes as used herein. In some embodiments the Tm of the primers as used herein is from about 55° C. to about 65° C. and the Tm of the probes as used herein is from about 60° C. to about 70° C. In some embodiments, the Tm range of the primers used in a PCR is about 5° C. to 15° C. lower than the Tm range of the probes used in the same PCR. In yet other embodiments, the Tm of the primers and/or probes is about 3° C. to 6° C. higher than the anneal/extend temperature in the PCR cycling conditions employed during amplification.
In some embodiments, the probes include a non-extendable blocker moiety at their 3′-ends. In some embodiments, the probes can further include other moieties (including, but not limited to additional non-extendable blocker moieties that are the same or different, quencher moieties, fluorescent moieties, etc) at their 3′-end, 5′-end, and/or any internal position in between. In some embodiments, the non-extendable blocker moiety can be, but is not limited to, an amine (NH2), biotin, PEG, DPI3, or PO4. In some preferred embodiments, the blocker moiety is a minor groove binder (MGB) moiety.
As used herein, the terms “MGB,” “MGB group,” “MGB compound,” or “MBG moiety” refers to a molecule that binds within the minor groove of double stranded DNA. When conjugated to the 3′ end of an oligonucleotide, an MGB group can function as a non-extendable blocker moiety. MGB moieties can also increase the specificity of an oligonucleotide probe and/or primer. In some embodiments, the Tm of an oligonucleotide, such the probes as disclosed herein, may be reduced by the inclusion of an MGB moiety. For example, the Tm of a probe as disclosed herein which comprises an MGB moiety may range from about 45° C. to 55° C. In some, embodiments, the Tm of a probe is reduced by about 10° C. to 20° C. with the inclusion of an MGB moiety in the same probe.
Although a general chemical formula for all known MGB compounds cannot be provided because such compounds have widely varying chemical structures, compounds which are capable of binding in the minor groove of DNA, generally speaking, have a crescent shape three dimensional structure. Most MGB moieties have a strong preference for A-T (adenine and thymine) rich regions of the B form of double stranded DNA. Nevertheless, MGB compounds which would show preference to C-G (cytosine and guanine) rich regions are also theoretically possible. Therefore, oligonucleotides including a radical or moiety derived from minor groove binder molecules having preference for C-G regions are also within the scope of the present invention.
Some MGBs are capable of binding within the minor groove of double stranded DNA with an association constant of 103 M−1 or greater. This type of binding can be detected by well-established spectrophotometric methods such as ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopy and also by gel electrophoresis. Shifts in UV spectra upon binding of a minor groove binder molecule and NMR spectroscopy utilizing the “Nuclear Overhauser” (NOESY) effect are particularly well known and useful techniques for this purpose. Gel electrophoresis detects binding of an MGB to double stranded DNA or fragment thereof, because upon such binding the mobility of the double stranded DNA changes.
A variety of suitable minor groove binders have been described in the literature. See, for example, Kutyavin, et al. U.S. Pat. No. 5,801,155; Wemmer, D. E., and Dervan P. B., Current Opinion in Structural Biology, 7:355-361 (1997); Walker, W. L., Kopka, J. L. and Goodsell, D. S., Biopolymers, 44:323-334 (1997); Zimmer, C.& Wahnert, U. Prog. Biophys. Molec. Bio. 47:31-112 (1986) and Reddy, B. S. P., Dondhi, S. M., and Lown, J. W., Pharmacol. Therap., 84:1-111 (1999) (the disclosures of which are herein incorporated by reference in their entireties). A preferred MGB in accordance with the present disclosure is DPI3. Synthesis methods and/or sources for such MGBs, some of which may be commercially available, are also well-known in the art. (See, e.g., U.S. Pat. Nos. 5,801,155; 6,492,346; 6,084,102; and 6,727,356, the disclosures of which are incorporated herein by reference in their entireties).
As used herein, the term “MGB blocker probe,” “MBG blocker,” or “MGB probe” is an oligonucleotide sequence and/or probe further attached to a minor groove binder moiety at its 3′ and/or 5′ end. Oligonucleotides conjugated to MGB moieties form extremely stable duplexes with single-stranded and double-stranded DNA targets, thus allowing shorter probes to be used for hybridization based assays. In comparison to unmodified DNA, MGB probes have higher melting temperatures (Tm) and increased specificity, especially when a mismatch is near the MGB region of the hybridized duplex. (See, e.g., Kutyavin, I. V., et al., Nucleic Acids Research, 2000, Vol. 28, No. 2: 655-661).
In some embodiments, the nucleotide units, which are incorporated into the oligonucleotides acting as a probe, can include a minor groove binder (MGB) moiety. In some embodiments, such MGB moieties can have a cross-linking function (an alkylating agent) covalently bound to one or more of the bases, through a linking arm. Similarly, modified sugars or sugar analogues can be present in one or more of the nucleotide subunits of an oligonucleotide disclosed herein. Sugar modifications include, but are not limited to, attachment of substituents to the 2′, 3′ and/or 4′ carbon atom of the sugar, different epimeric forms of the sugar, differences in the alpha- or beta-configuration of the glycosidic bond, and other anomeric changes. Sugar moieties include, but are not limited to, pentose, deoxypentose, hexose, deoxyhexose, ribose, deoxyribose, glucose, arabinose, pentofuranose, xylose, lyxose, and cyclopentyl. In some embodiments, the sugar or glycoside portion of some embodiments of oligonucleotides acting as a probe, e.g., one including an MGB moiety, can include deoxyribose, ribose, 2-fiuororibose, 2-O alkyl or alkenylribose where the alkyl group may have 1 to 6 carbons and the alkenyl group 2 to 6 carbons. In some embodiments, the naturally occurring nucleotides and in the herein described modifications and analogs the deoxyribose or ribose moiety can form a furanose ring, and the purine bases can be attached to the sugar moiety via the 9-position, the pyrimidines via the I-position, and the pyrazolopyrimidines via the I-position. And in some embodiments, especially in the oligonucleotides acting as a probe (e.g., the third and/or sixth oligonucleotide, target site-specific probe), the nucleotide units of the oligonucleotides can be interconnected by a “phosphate” backbone, as is well known in the art and/or can include, in addition to the “natural” phosphodiester linkages, phosphorothiotes and methylphosphonates. Other types of modified oligonucleotides or modified bases are also contemplated herein as would be understood by those of ordinary skill in the art.
When two different, non-overlapping (or partially overlapping) oligonucleotides anneal to different regions of the same linear complementary nucleic acid sequence, and the 3′ end of one oligonucleotide points toward the 5′ end of the other, the former may be called the “upstream” oligonucleotide and the latter the “downstream” oligonucleotide.
As used herein, the terms “target sequence,” “target nucleic acid,” “target nucleic acid sequence,” and “nucleic acid of interest” are used interchangeably and refer to a desired region of a nucleic acid molecule which is to be either amplified, detected or both.
“Primer” as used herein can refer to more than one primer and refers to an oligonucleotide, whether occurring naturally or produced synthetically, which is capable of acting as a point of initiation of synthesis when placed under conditions in which synthesis of a primer extension product which is complementary to a nucleic acid strand is induced i.e., in the presence of nucleotides and an agent for polymerization such as DNA polymerase, at a suitable temperature for a sufficient amount of time and in the presence of a buffering agent. Such conditions can include, for example, the presence of at least four different deoxyribonucleoside triphosphates (such as G, C, A, and T) and a polymerization-inducing agent such as DNA polymerase or reverse transcriptase, in a suitable buffer (“buffer” includes substituents which are cofactors, or which affect pH, ionic strength, etc.), and at a suitable temperature. In some embodiments, the primer may be single-stranded for maximum efficiency in amplification. The primers herein are selected to be substantially complementary to the different strands of each specific sequence to be amplified. This means that the primers must be sufficiently complementary to hybridize with their respective strands. A non-complementary nucleotide fragment may be attached to the 5′-end of the primer (such as having a “tail”), with the remainder of the primer sequence being complementary, or partially complementary, to the target region of the target nucleic acid. Commonly, the primers are complementary, except when non-complementary nucleotides may be present at a predetermined sequence or sequence range location, such as a primer terminus as described. In some embodiments, such non-complementary “tails” can comprise a universal sequence, for example, a sequence that is common to one or more oligonucleotides. In certain embodiments, the non-complementary fragment or tail may comprise a polynucleotide sequence such as a poly (T) sequence to hybridize, for example, to a polyadenylated oligonucleotide or sequence.
The complement of a nucleic acid sequence as used herein refers to an oligonucleotide which, when aligned with the nucleic acid sequence such that the 5′ end of one sequence is paired with the 3′ end of the other, is in “antiparallel association.” Complementarity need not be perfect; stable duplexes may contain mismatched base pairs or unmatched bases.
Stability of a nucleic acid duplex is measured by the melting temperature, or “Tm.” The Tm of a particular nucleic acid duplex under specified conditions is the temperature at which half of the base pairs have disassociated.
As used herein, the term “Tm” or “melting temperature” of an oligonucleotide refers to the temperature (in degrees Celsius) at which 50% of the molecules in a population of a single-stranded oligonucleotide are hybridized to their complementary sequence and 50% of the molecules in the population are not-hybridized to said complementary sequence. The Tm of a primer or probe can be determined empirically by means of a melting curve. In some cases it can also be calculated using formulas well known in the art (See, e.g., Maniatis, T., et al., Molecular cloning: a laboratory manual/Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.: 1982).
As used herein, the term “sensitivity” refers to the minimum amount (number of copies or mass) of a template that can be detected by a given assay. As used herein, the term “specificity” refers to the ability of an assay to distinguish between amplification from a matched template versus a mismatched template. Frequently, specificity is expressed as ΔCt=Ctmismatch−Ctmatch. In some embodiments, improvement in specificity or “specificity improvement” or “fold difference” is expressed as 2(□Ct_condition1−(□Ct_condition2).
As used herein, the term “Ct” or “Ct value” refers to threshold cycle and signifies the cycle of a PCR amplification assay in which signal from a reporter that is indicative of amplicon generation (e.g., fluorescence) first becomes detectable above a background level. In some embodiments, the threshold cycle or “Ct” is the cycle number at which PCR amplification becomes exponential.
The term “complementary to” is used herein in relation to a nucleotide that can base pair with another specific nucleotide. Thus, for example, adenosine is complementary to uridine or thymidine and guanosine is complementary to cytidine.
The term “identical” means that two nucleic acid sequences have the same sequence or a complementary sequence.
“Amplification” as used herein denotes the use of any amplification procedures to increase the concentration of a particular nucleic acid sequence within a mixture of nucleic acid sequences.
“Polymerization”, which may also be referred to as “nucleic acid synthesis”, refers to the process of extending the nucleic acid sequence of a primer through the use of a polymerase and a template nucleic acid.
The term “label” as used herein refers to any atom or molecule which can be used to provide or aid to provide a detectable and/or quantifiable signal, and can be attached to a biomolecule, such as a nucleic acid or protein. Labels may provide signals detectable by fluorescence, radioactivity, colorimetry, gravimetry, magnetism, enzymatic activity or the like. Labels that provide signals detectable by fluorescence are also referred to herein as “fluorophores” or “fluors” or “fluorescent dyes.” As used herein, the term “dye” refers to a compound that absorbs light or radiation and may or may not emit light. A “fluorescent dye” refers to a molecule that emits the absorbed light to produce an observable detectable signal (e.g., “acceptor dyes”, “donor dyes”, “reporter dyes”, “big dyes”, “energy transfer dyes”, “on-axis dyes”, “off-axis dyes”, and the like). A “quencher dye” refers to a molecule that is designed to absorb emission from a corresponding fluorescent dye.
In some embodiments, the term “fluorophore,” “fluor,” or “fluorescent dye” can be applied to a fluorescent dye molecule that is used in a fluorescent energy transfer pairing (e.g., with a donor dye or acceptor dye). A “fluorescent energy transfer conjugate,” as used herein typically includes two or more fluorophores (e.g., a donor dye and acceptor dye) that are covalently attached through a linker and are capable of undergoing a fluorescence energy transfer process under the appropriate conditions.
The term “quencher,” “quencher compound,” “quencher group,” “quencher moiety” or “quencher dye” is used in a broad sense herein and refers to a molecule or moiety capable of suppressing the signal from a reporter molecule, such as a fluorescent dye.
The term “overlapping” as used herein (when used in reference to oligonucleotides) refers to the positioning of two oligonucleotides on its complementary strand of the template nucleic acid. The two oligonucleotides may be overlapping any number of nucleotides of at least 1, for example by 1 to about 40 nucleotides, e.g., about 1 to 10 nucleotides or 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nucleotides. In other words, the two template regions hybridized by oligonucleotides may have a common region which is complementary to both the oligonucleotides.
The terms “thermally cycling,” “thermal cycling,” “thermal cycles,” or “thermal cycle” refer to repeated cycles of temperature changes from a total denaturing temperature, to an annealing (or hybridizing) temperature, to an extension temperature, and back to the total denaturing temperature. The terms also refer to repeated cycles of a denaturing temperature and an extension temperature, where the annealing and extension temperatures are combined into one temperature. A total denaturing temperature unwinds all double stranded fragments into single strands. An annealing temperature allows a primer to hybridize or anneal to the complementary sequence of a separated strand of a nucleic acid template. The extension temperature allows the synthesis of a nascent DNA strand of the amplicon. The term “single round of thermal cycling” means one round of denaturing temperature, annealing temperature and extension temperature. In a single round of thermal cycling, for example, there may be internal repeating cycles of an annealing temperature and an extension temperature. For example, a single round of thermal cycling may include a denaturing temperature, an annealing temperature (i.e., first annealing temperature), an extension temperature (i.e., first extension temperature), another annealing temperature (i.e., second annealing temperature), and another extension temperature (i.e., second extension temperature).
The terms “reaction mixture,” “amplification mixture,” or “PCR mixture” as used herein refer to a mixture of components necessary to amplify at least one amplicon from nucleic acid templates. The mixture may comprise nucleotides (dNTPs), a thermostable polymerase, primers, and a plurality of nucleic acid templates (e.g., a target nucleic acid). The mixture may further comprise a Tris buffer, a monovalent salt, and/or Mg′. The working concentration range of each component is well known in the art and can be further optimized or formulated to include other reagents and/or components as needed by an ordinary skilled artisan.
The terms “amplified product” or “amplicon” refer to a fragment of a nucleic acid amplified by a polymerase using a pair of primers in an amplification method such as PCR or reverse transcriptase (RT)-PCR.
As defined herein, “5′→3′ nuclease activity” or “5′ to 3′ nuclease activity” or “5′ nuclease activity” refers to that activity of a cleavage reaction including either a 5′ to 3′ nuclease activity traditionally associated with some DNA polymerases, whereby nucleotides are removed from the 5′ end of an oligonucleotide in a sequential manner, (i.e., E. coli DNA polymerase I has this activity whereas the Klenow fragment does not), or a 5′ to 3′ endonuclease activity wherein cleavage occurs to more than one phosphodiester bond (nucleotide) from the −5′ end, or both, or a group of homologous 5′-3′ exonucleases (also known as 5′ nucleases) which trim the bifurcated molecules, the branched DNA structures produced during DNA replication, recombination and repair. In some embodiments, such 5′ nuclease can be used for cleavage of the labeled oligonucleotide probe annealed to target nucleic acid sequence.
As used herein, the term “alkyl” refers to a straight or branched, saturated, aliphatic radical having the number of carbon atoms indicated. For example, C1-C6 alkyl includes, but is not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, iso-propyl, iso-butyl, sec-butyl, tert-butyl, and the like. As used herein, the term “alkylene” refers to a straight or branched, saturated, aliphatic diradical having the number of carbon atoms indicated. For example, C1-C6 alkyl includes, but is not limited to, methylene, ethylene, propylene, butylene, pentylene, hexylene, and the like. It will be appreciated that alkyl and alkylene groups can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the alkyl and alkylene group.
As used herein, the term “alkenyl” refers to either a straight chain or branched hydrocarbon radical having the number of carbon atoms indicated, and having at least one double bond. For example, C2-C6 alkenyl, includes, but is not limited to, vinyl, propenyl, isopropenyl, butenyl, isobutenyl, butadienyl, pentenyl, hexadienyl, and the like. As used herein, the term “alkenylene” refers to either a straight chain or branched hydrocarbon diradical having the number of carbon atoms indicated, having at least one double bond. For example, C2-C6 alkenyl, includes, but is not limited to, vinyl, propenyl, isopropenyl, butenyl, isobutenyl, butadienyl, pentenyl, hexadienyl, and the like. It will be appreciated that alkenyl and alkenylene groups can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the alkenyl and alkenylene group.
As used herein, the term “alkoxy” refers to alkyl radical with the inclusion of at least one oxygen atom within the alkyl chain or at the terminus of the alkyl chain, for example, methoxy, ethoxy, and the like. “Halo-substituted-alkoxy” refers to an alkoxy where at least one hydrogen atom is substituted with a halogen atom. For example, halo-substituted-alkoxy includes trifluoromethoxy, and the like. As used herein, the term “oxy-alkylene” refers to alkyl diradical with the inclusion of an oxygen atom, for example, —OCH2, —OCH2CH2—, —OC1-C10 alkylene-, —C1-C6 alkylene-O—C1-C6 alkylene-, poly(alkylene glycol), poly(ethylene glycol) (or PEG), and the like. “Halo-substituted-oxy-alkylene” refers to an oxy-alkylene where at least one hydrogen atom is substituted with a halogen atom. It will be appreciated that alkoxy and oxy-alkylene groups can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the alkoxy and oxy-alkylene group.
As used herein, the term “alkynyl” refers to either a straight chain or branched hydrocarbon radical having the number of carbon atoms indicated, and having at least one triple bond. For example, C2-C6 alkynyl, includes, but is not limited to, acetylenyl, propynyl, butynyl, and the like. As used herein, the term “alkynylene” refers to either a straight chain or branched hydrocarbon diradical having the number of carbon atoms indicated, and having at least one triple bond. Examples of alkynylene groups include, but are not limited to, —C≡CCH2CH2—, —CH2C≡CCH2—, and the like. It will be appreciated that alkynyl and alkynylene groups can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the alkynyl and alkynylene group.
As used herein, the term “aryl” refers to a cyclic hydrocarbon radical having the number of carbon atoms indicated, and having a fully conjugated π-electron system. For example, C6-C10 aryl, includes, but is not limited to, phenyl, naphthyl, and the like. As used herein, the term “arylene” refers to a cyclic hydrocarbon diradical having the number of carbon atoms indicated, and having a fully conjugated π-electron system. For example, C6-C10 arylene, includes, but is not limited to, phenylene, naphthylene, and the like. It will be appreciated that aryl and arylene groups can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the aryl and arylene group.
As used herein, the term “phosphodiester portion” refers to a linkage comprising at least one —O—P(O)(OH)—O— functional group. It will be appreciated that a phosphodiester portion can include other groups, such as alkyl, alkylene, alkenylene, oxy-alkylene, such as PEG, in addition to one or more —O—P(O)(OH)—O— functional groups. It will be appreciated that the other groups, such as alkyl, alkylene, alkenylene, oxy-alkylene, such as PEG, can be optionally substituted with one or more substituents by replacement of one or more hydrogen atoms on the group.
As used here, the term “sulfo” refers to a sulfonic acid, or salt of sulfonic acid (sulfonate).
As used here, the term “carboxy” refers to a carboxylic acid or salt of carboxylic acid.
As used here, the term “phosphate,” refers to an ester of phosphoric acid, and includes salts of phosphate.
As used here, the term “phosphonate,” refers to a phosphonic acid and includes salts of phosphonate.
As used herein, unless otherwise specified, the alkyl portions of substituents such as alkyl, alkoxy, arylalkyl, alkylamino, dialkylamino, trialkylammonium, or perfluoroalkyl are optionally saturated, unsaturated, linear or branched, and all alkyl, alkoxy, alkylamino, and dialkylamino substituents may be optionally substituted by carboxy, sulfo, amino, or hydroxy.
As used herein, “substituted” refers to a molecule wherein one or more hydrogen atoms are replaced with one or more non-hydrogen atoms, functional groups or moieties. Exemplary substituents include but are not limited to halogen, e.g., fluorine and chlorine, C1-C8 alkyl, C6-C14 aryl, heterocycle, sulfate, sulfonate, sulfone, amino, ammonium, amido, nitrile, nitro, lower alkoxy, phenoxy, aromatic, phenyl, polycyclic aromatic, heterocycle, water-solubilizing group, linkage, and linking moiety. In some embodiments, substituents include, but are not limited to, —X, —R, —OH, —OR, —SR, —SH, —NH2, —NHR, —NR2, —NR3+, —N═NR2, —CX3, —CN, —OCN, —SCN, —NCO, —NCS, —NO, —NO2, —N2+, —N3, —NHC(O)R, —C(O)R, —C(O)NR2, —S(O)2O—, —S(O)2R, —OS(O)2OR, —S(O)2NR, —S(O)R, —OP(O)(OR)2, —P(O)(OR)2, —P(O)(O)2, —P(O)(OH)2, —C(O)R, —C(O)X, —C(S)R, —C(O)OR, —C(S)OR, —C(O)SR, —C(S)SR, —C(O)NR2, —C(S)NR2, —C(NR)NR2, where each X is independently a halogen and each R is independently —H, C1-C6 alkyl, C6-C14 aryl, heterocycle, or linking group.
Unless indicated otherwise, the nomenclature of substituents that are not explicitly defined herein are arrived at by naming the terminal portion of the functionality followed by the adjacent functionality toward the point of attachment. For example, the substituent “arylalkyloxycarbonyl” refers to the group (aryl)-(alkyl)-O—C(O)—.
The compounds disclosed herein may exist in unsolvated forms as well as solvated forms, including hydrated forms. In some embodiments, the compounds disclosed herein are soluble in an aqueous medium (e.g., water or a buffer). For example, the compounds can include substituents (e.g., water-solubilizing groups) that render the compound soluble in the aqueous medium. Compounds that are soluble in an aqueous medium are referred to herein as “water-soluble” compounds. Such water-soluble compounds are particularly useful in biological assays. These compounds may exist in multiple crystalline or amorphous forms. In general, all physical forms are equivalent for the uses described herein and are intended to be within the scope of the present disclosure. The compounds disclosed herein may possess asymmetric carbon atoms (i.e., chiral centers) or double bonds; the racemates, diastereomers, geometric isomers and individual isomers of the compounds described herein are within the scope of the present disclosure. The compounds described herein may be prepared as a single isomer or as a mixture of isomers.
Where substituent groups are specified by their conventional chemical formulae and are written from left to right, they equally encompass the chemically identical substituents, which would result from writing the structure from right to left, e.g., —CH2O— will be understood to also recite —OCH2—.
It will be understood that the chemical structures that are used to define the compounds disclosed herein are each representations of one of the possible resonance structures by which each given structure can be represented. Further, it will be understood that by definition, resonance structures are merely a graphical representation used by those of skill in the art to represent electron delocalization, and that the present disclosure is not limited in any way by showing one particular resonance structure for any given structure.
Where a disclosed compound includes a conjugated ring system, resonance stabilization may permit a formal electronic charge to be distributed over the entire molecule. While a particular charge may be depicted as localized on a particular ring system, or a particular heteroatom, it is commonly understood that a comparable resonance structure can be drawn in which the charge may be formally localized on an alternative portion of the compound.
As used herein, the term “protecting group” or “PG” refers to any group as commonly known to one of ordinary skill in the art that can be introduced into a molecule by chemical modification of a reactive functional group, such as an amine or hydroxyl, to obtain chemoselectivity in a subsequent chemical reaction. It will be appreciated that such protecting groups can be subsequently removed from the functional group at a later point in a synthesis to provide further opportunity for reaction at such functional groups or, in the case of a final product, to unmask such functional group. Protecting groups have been described in, for example, Wuts, P. G. M., Greene, T. W., Greene, T. W., & John Wiley & Sons. (2006). Greene's protective groups in organic synthesis. Hoboken, N.J: Wiley-Interscience. One of skill in the art will readily appreciate the chemical process conditions under which such protecting groups can be installed on a functional group. In the various embodiments described herein, it will be appreciated by a person having ordinary skill in the art that the choice of protecting groups used in the preparation of the energy transfer dye conjugates described herein can be chosen from various alternatives known in the art. It will further be appreciated that a suitable protecting group scheme can be chosen such that the protecting groups used provide an orthogonal protection strategy. As used herein, “orthogonal protection” refers to a protecting group strategy that allows for the protection and deprotection of one or more reactive functional group with a dedicated set of reaction conditions without affecting other protected reactive functional groups or reactive functional groups.
As used herein, “PAG” refers to a poly(alkylene glycol) moiety, where alkylene can be a C2-C6 linear or branched alkylene chain. It will be appreciated that a poly(alkylene glycol) can be represented by —(C2-C6 alkylene-O—C2-C6 alkylene)n-, where n is an integer from 1 to about 20, or the formula —(C2-C6 alkylene-O—C2-C6 alkylene)n-, where n is an integer from 1 to about 100. Suitable PAG moieties taken together with the O-P linker bonds include but are not limited to penta(ethylene glycol) (a.k.a. PEG), penta(propylene glycol) (a.k.a. PPG), penta(1,2-butylene glycol), and the like.
As used herein, “water-solubilizing group” refers to a moiety that increases the solubility of the compounds in aqueous solution. Exemplary water-solubilizing groups include but are not limited to hydrophilic group, as described herein, polyether, polyhydroxyl, boronate, polyethylene glycol, repeating units of ethylene oxide (—(CH2CH2O)—), and the like.
As used herein, “hydrophilic group” refers to a substituent that increases the solubility of the compounds in aqueous solution. Exemplary hydrophilic groups include but are not limited to —OH, —O−Z+, —SH, —S−Z+, —NH2, —NR3+Z−, —N═NR2+Z−, —CN, —OCN, —SCN, —NCO, —NCS, —NO, —NO2, —N2+, —N3, —NHC(O)R, —C(O)R, —C(O)NR2, —S(O)2O—Z+, —S(O)2R, —OS(O)2OR, —S(O)2NR, —S(O)R, —OP(O)(OR)2, —P(O)(OR)2, —P(O)(O−)2Z+, —P(O)(OH)2, —C(O)R, —C(S)R, —C(O)OH, —C(O)OR, —CO2−Z+, —C(S)OR, —C(S)O—Z+, —C(O)SR, —C(O)S−Z+, —C(S)SR, —C(S)S−Z+, —C(O)NR2, —C(S)NR2, —C(NR)NR2, and the like, where R is H, C1-C6 alkyl, C1-C6 alkylC6-C10 aryl, or C6-C10 aryl, and optionally substituted.
As used herein, “reactive functional group” or “reactive group” means a moiety on the compound that is capable of chemically reacting with a functional group on a different compound to form a covalent linkage, i.e., is covalently reactive under suitable reaction conditions, and generally represents a point of attachment for another substance. Typically the reactive group is an electrophile or nucleophile that can form a covalent linkage through exposure to the corresponding functional group that is a nucleophile or electrophile, respectively. In some embodiments, the “reactive functional group” or “reactive group” can be a hydrophilic group or a hydrophilic group that has been activated to be a “reactive functional group” or “reactive group.” In some embodiments, a “reactive functional group” or “reactive group” can be a hydrophilic group such as a C(O)OR group. In some embodiments, a hydrophilic group, such as a —C(O)OH, can be activated by a variety of methods known in the art to become a reactive functional group, such as by reacting the —C(O)OH group with N,N,N,N-tetramethyl-O—(N-succinimidyl)uronium tetrafluoroborate (TSTU) to provide the NHS ester moiety —C(O)O—NHS (a.k.a. the active ester).
Alternatively, the reactive group is a photoactivatable group that becomes chemically reactive only after illumination with light of an appropriate wavelength.
Exemplary reactive groups include, but not limited to, olefins, acetylenes, alcohols, phenols, ethers, oxides, halides, aldehydes, ketones, carboxylic acids, esters, amides, cyanates, isocyanates, thiocyanates, isothiocyanates, amines, hydrazines, hydrazones, hydrazides, diazo, diazonium, nitro, nitriles, mercaptans, sulfides, disulfides, sulfoxides, sulfones, sulfonic acids, sulfinic acids, acetals, ketals, anhydrides, sulfates, sulfenic acids isonitriles, amidines, imides, imidates, nitrones, hydroxylamines, oximes, hydroxamic acids thiohydroxamic acids, allenes, ortho esters, sulfites, enamines, ynamines, ureas, pseudoureas, semicarbazides, carbodiimides, carbamates, imines, azides, alkynes (including strained alkynes, such as MO and DBCO), azo compounds, azoxy compounds, and nitroso compounds. Reactive functional groups also include those used to prepare bioconjugates, e.g., N-hydroxysuccinimide esters (or succinimidyl esters (SE)), maleimides, sulfodichlorophenyl (SDP) esters, sulfotetrafluorophenyl (STP) esters, tetrafluorophenyl (TFP) esters, pentafluorophenyl (PFP) esters, nitrilotriacetic acids (NTA), aminodextrans, cyclooctyne-amines and the like. Methods to prepare each of these functional groups are well known in the art and their application to or modification for a particular purpose is within the ability of one of skill in the art (see, for example, Sandler and Karo, eds., Organic Functional Group Preparations, Academic Press, San Diego, 1989). Exemplary reactive groups or reactive ligands include NHS esters, phosphoramidites, and other moieties listed in Table 1 below. Nucleotides, nucleosides, and saccharides (e.g., ribosyls and deoxyribosyls) are also considered reactive ligands due to at least their ability to form phosphodiester bonds through enzymatic catalysis. For the avoidance of doubt, saturated alkyl groups are not considered reactive ligands.
As used herein, the term “solid support,” as used herein, refers to a matrix or medium that is substantially insoluble in liquid phases and capable of binding a molecule or particle of interest. Solid supports suitable for use herein include semi-solid supports and are not limited to a specific type of support. Useful solid supports include solid and semi-solid matrixes, such as aerogels and hydrogels, resins, beads, biochips (including thin film coated biochips), microfluidic chip, a silicon chip, multi-well plate (also referred to as a microtitre plate or microplate), array (such as a microarray), membranes, conducting and nonconducting metals, glass (including microscope slides) and magnetic supports. More specific examples of useful solid supports include silica gels, polymeric membranes, particles, derivatized plastic films, glass beads, cotton, plastic beads, alumina gels, polysaccharides such as SEPHAROSE (GE Healthcare), poly(acrylate), polystyrene, poly(acrylamide), polyol, agarose, agar, cellulose, dextran, starch, FICOLL (GE Healthcare), heparin, glycogen, amylopectin, mannan, inulin, nitrocellulose, diazocellulose, polyvinylchloride, polypropylene, polyethylene (including poly(ethylene glycol)), nylon, latex bead, magnetic bead, paramagnetic bead, superparamagnetic bead, starch and the like.
A hydrolysis probe assay can exploit the 5′ nuclease activity of certain DNA polymerases, such as a Taq DNA polymerase, to cleave a labeled probe during PCR. One specific example of a hydrolysis probe is a TaqMan probe. In some embodiments, the hydrolysis probe contains a reporter dye at the 5′ end of the probe and a quencher dye at the 3′ end of the probe. During the PCR reaction, cleavage of the probe separates the reporter dye and the quencher dye, resulting in increased fluorescence of the reporter. Accumulation of PCR products is detected directly by monitoring the increase in fluorescence of the reporter dye. When the probe is intact, the close proximity of the reporter dye to the quencher dye results in suppression of the reporter fluorescence primarily by Forster-type energy transfer (Förster, 1948; Lakowicz, 1983). During PCR, if the target of interest is present, the probe specifically anneals between the forward and reverse primer sites. The 5′ to 3′ nucleolytic activity of the Taq DNA polymerase cleaves the probe between the reporter and the quencher only if the probe hybridizes to the target. The probe fragments are then displaced from the target, and polymerization of the strand continues. In some embodiments, the 3′ end of the probe is blocked to prevent extension of the probe during PCR. In general, hybridization and cleavage process occurs in sequential cycles and does not interfere with the exponential accumulation of the product.
Without being bound to these parameters, the general guideline for designing TaqMan probes and primers is as follows: design the primers as close as possible to, but without overlapping the probe; the Tm of the probe should be about 10° C. higher than the Tm of the primers; select the strand that gives the probe more C than G bases; the five nucleotides at the 3′ end of the primer should have no more than two G and/or C bases, and the reaction should be run on the two-step thermal profile with the annealing and extension under the same temperature of 60° C.
The following description of the fluorescent dyes, i.e., fluorophores, and quencher compounds provides general information regarding construction of the energy transfer conjugates and probes described herein. As described herein, the fluorescent dyes, e.g. donor dye and acceptor dye, can be covalently bound to one another through a linker to form an energy transfer dye conjugate (e.g. a reporter moiety). In some embodiments, an energy transfer dye or an energy transfer dye conjugate and a quencher compound can be covalently bound to one another through an analyte. In some embodiments the analyte is a probe, such as an oligonucleotide probe. The disclosed FRET conjugates and probes that include unique fluorophore/quencher combinations disclosed herein allow for increased multiplex reactions and detection through the additional spectral channels already available on some commercial instruments. Further, the new fluorophores, FRET conjugates and fluorophore/quencher and probe combinations provide unique optical properties that can facilitate even higher order multiplexing once instruments with additional channels and other related hardware and software improvements become available.
Energy Transfer Dyes
In some embodiments, the energy transfer dye conjugate described herein includes two or more fluorescent dyes. The two or more fluorescent dyes include a donor dye and an acceptor dye. Any fluorescent dye having the appropriate optical and physical properties can be utilized in construction of the dye conjugates disclosed herein. In some embodiments, the emission spectrum of the donor dye overlaps with the absorption spectrum of the acceptor dye. In some embodiments, the acceptor dye can have an emission maximum that is a longer wavelength than the emission maximum of the donor dye. It will be appreciated that the identity of either the donor dye or the acceptor dye is not particularly limited in the energy transfer dye conjugates described herein, provided that the donor dye and the acceptor dye pair and linker are selected such that the donor dye can transfer energy to the reporter dye.
Suitable fluorescent dyes, i.e. the donor dye and the acceptor dye, in an energy transfer dye conjugate as described herein can independently be a xanthene dye (e.g., a fluorescein or rhodamine dye), a silicon-rhodamine dye, a cyanine dye, a boron-dipyrrornethene (referred to herein as “BODIPY”) dye, a pyrene dye, or a coumarin dye. In some embodiments, the cyanine dye included in the ET conjugate is an azaindole cyanine compound (i.e., a cyanine compound that includes at least one azaindole group). In some embodiments, the cyanine dye included in the ET conjugate is an azaindole (i.e., pyrrolopyridine) cyanine compound (i.e., a cyanine compound that includes at least one azaindole group). As used herein, “azaindole” and “pyrrolopyridine” are used interchangeably to refer to a heterocyclic aromatic organic compound having a bicyclic structure that includes a pyrrole ring fused to a pyridine ring. As used herein, “azaindole cyanine” and “pyrrolopyridine cyanine” are used interchangeably to refer to a cyanine compound that includes at least one azaindole group. Certain azaindole cyanine compounds can include one or two optionally substituted azaindole groups. For compounds including two azaindole groups, the azaindole groups can be the same or different. Examples of dyes that can be used in connection with the present disclosure include those described in U.S. Pat. Nos. 5,863,727, 6,448,407, 6,649,769, 7,038,063, 6,162,931, 6,229,055, 6,130,101, 5,188,934, 5,840,999, 7,179,906, 6,008,379, 6,221,604, 5,231,191, 5,366,860, 7,595,162, 7,550,570, 5,936,087, 8,030,096, 6,562,632, 5,846,737, 5,442,045, 6,716,994, 5,582,977, 5,321,130, 5,863,753, 6,977,305, 7,566,790, 7,927,830, 7,888,136, 4,774,339, 5,248,782, 5,187,288, 5,451,663, 5,433,896, 9,040,674, 9,783,560, 9,040,674, 6,255,476, 6,020,481, 6,303,775, and 6,020,481, the disclosure of each of which is incorporated herein by reference in its entirety as they relate to dyes and methods for conjugating dyes to oligonucleotides.
In some embodiments, the donor dye or acceptor dye can be a cyanine dye such as described in U.S. Pat. No. 6,974,873. Suitable cyanines include those having the Formula (I):
wherein,
each R1′ is independently H or C1-C6 alkyl, wherein each hydrogen atom in C1-C6 alkyl is independently optionally substituted with one or more hydrophilic groups or hydrophilic group containing moieties (e.g., —C1-C6 alkylOH, —C1-C6 alkylCO2H, or alkylaryl);
each R2′ is independently H, C1-C6 alkyl, C1-C6 alkylC6-C10 aryl, or C6-C10 aryl, wherein each hydrogen atom in C1-C6 alkyl, C1-C6 alkylC6-C10 aryl, or C6-C10 aryl is independently optionally substituted with one or more hydrophilic groups or hydrophilic group containing moieties (e.g., —C1-C6 alkylOH, —C1-C6 alkylCO2H, or alkylaryl);
each R3′, R4′, R5′, and R6′ is independently H, C1-C6 alkyl, C6-C10 aryl, a hydrophilic group, a hydrophilic group containing moiety, or each pair of R3′ and R4′, R4′ and R5′, or R5′ and R6′, taken together with the carbon atoms to which they are attached, independently optionally form a fused six-membered aryl ring optionally substituted with one or more hydrophilic groups or hydrophilic group containing moieties; and
each R7′ or R8′ is independently H, C1-C6 alkyl, —C1-C6 alkylSO3H, alkylSO3Z, alkylOH, or —C1-C6 alkylCO2H,
wherein one of R1′, R2′, R7′ or R8′ comprises a linker (L1, L2, or L3) as disclosed herein.
In some embodiments, the donor dye or acceptor dye can be a rhodamine dye or a derivative thereof such as described in U.S. Pat. No. 9,040,674 or PCT/US2019/067925 (now WO 2020/132487); a dichlororhodamine (e.g., 4,7-dichlororhodamine) such as described in U.S. Pat. No. 5,847,162; an asymmetric rhodamine such as described in Appl. No. PCT/US2019/068111No. (now WO 2020/132607); or a silicon rhodamine such as described in Appl. No. PCT/US2019/045697 (now WO 2020/033681).
A representative class of rhodamine dyes that can serve as the donor dye or acceptor dye is depicted in Formula (II):
In some embodiments, the donor dye or acceptor dye can be a rhodamine dye of the Formula (III):
In some embodiments, the donor dye or acceptor dye can be a silicon-rhodamine dye (also referred to as a “silyl rhodamine). An exemplary structure for a silicon-rhodamine dye has the Formula (IV):
Typically, R1″, R2″, or R3″ includes a linker structure to the donor or acceptor dye.
In some embodiments, the donor dye or acceptor dye can be a fluorescein or a derivative thereof. An exemplary structure for a fluorescein dye has the Formula (V):
In some embodiments, R7 is phenyl:
The fluorescent dyes disclosed herein can be provided in a protected or unprotected form. Various dyes (e.g., rhodamines), as well as their unprotected counterparts, can be in a closed, spirolactone form. In certain embodiments, the dye is provided in a closed, spirolactone form. In certain embodiments, the dye is provided in an open, acid form of the compound. The open, acid form of certain rhodamine dyes disclosed herein can be fluorescent (or exhibit an increase in fluorescence) relative to the closed, spirolactone form of the compound. Thus, also provided herein are fluorescent compounds and fluorescently-labeled nucleic acid probes and primers that include compounds in deprotected, open lactone form.
The energy transfer dye conjugates described herein can include different combinations of donor dyes and acceptor dyes, depending on the desired excitation and/or emission profile. Representative classes of dyes that can be used in ET conjugates include those in which the donor or acceptor dye is a xanthene dye (e.g., a fluorescein or rhodamine), a cyanine dye, a BODIPY dye, a pyrene dye, a pyronine dye, or a coumarin dye, where the acceptor dye is a compound that emits at a longer wavelength than the donor dye. Although certain donor-acceptor dye combinations are described herein as being suitable for construction of FRET conjugates, many other examples of donor-acceptor combinations that are not explicitly described can be implemented to provide FRET conjugates using the chemistries disclosed herein.
One suitable combination includes a fluorescein as the donor dye (e.g., FAM or VIC) and a rhodamine as the acceptor dye. Another suitable combination includes a coumarin as the donor dye (e.g., Coumarin 343, ATTO 425, or Pacific Blue), and a rhodamine as the acceptor dye. Yet another suitable combination includes fluorescein as the donor dye and a cyanine as the acceptor dye. Examples of cyanine dyes suitable for use an acceptor dye in ET conjugates disclosed herein include, without limitation, those commercially available under the tradename ALEXA FLUOR from Thermo Fisher Scientific (e.g., AF-647, AF-680, AF-700, and AF-750). In yet another suitable combination, the donor dye is a rhodamine and the acceptor dye is a cyanine dye. In yet another suitable combination, the donor dye is a rhodamine, and the acceptor dye is a rhodamine that emits at a longer wavelength than the donor dye, e.g., TAMRA and ROX, a silyl rhodamine, or a pyronine dye. In some embodiments, the donor dye is a cyanine dye (e.g., AF-647) and the acceptor dye is a compound that emits at a longer wavelength than the donor, such as, a silyl rhodamine or cyanine. In some embodiments, the acceptor dye is a cyanine dye. For example, the donor dye can be FAM and the acceptor dye can be a cyanine dye, with substituents as described herein. In some embodiments, the acceptor dye is an NH-rhodamine, as described herein. For example, the donor dye can be FAM and the acceptor dye can be an NH-rhodamine. Additional examples of donor-acceptor dye pairs that can be utilized in the ET dye conjugates described herein are listed in Table 3.
In some embodiments, the donor dye or acceptor dye can have one or more hydrophilic groups, as described herein, at any of the positions shown in the dye structures described herein. In some embodiments, the donor dye or acceptor dye can have one of more hydrophilic group containing moieties, as described herein, at any of the positions shown in the dye structures described herein.
In some embodiments, each dye can have a structure including multiple sulfonate groups. Sulfonate groups are known in the art to improve the solubility of dye compounds in an aqueous medium. In some embodiments, the dye includes one or more reactive functional groups or a protected reactive functional groups for linking the dye to another substance. In some embodiments, the dye is provided as a phosphoramidite derivative which can be used to conjugate the dye to a molecule, such as an oligonucleotide during automated nucleic acid synthesis, as is known in the art.
In some embodiments, the water-solubilizing groups, hydrophilic groups, dyes and ET dyes described herein have an overall electronic charge. It is to be understood that when such electronic charges are shown to be present, they are balanced by the presence of an appropriate counterion, which may or may not be explicitly identified. Where the water-solubilizing group, hydrophilic group, dye or ET dye described herein is positively charged, the counterion is a negatively charged moiety, typically selected from, but not limited to, chloride, bromide, iodide, sulfate, alkanesulfonate, arylsulfonate, phosphate, perchlorate, tetrafluoroborate, tetraarylboride, nitrate and anions of aromatic or aliphatic carboxylic acids. Where the water-solubilizing group, hydrophilic group, dye or ET dye described herein is negatively charged, the counterion is a positively charged moiety, typically selected from, but not limited to, alkali metal ions, such as Li+, Na+, K+, and the like, ammonium or substituted ammonium, such as NMe4+, Pr2NHEt+, and the like, or pyridinium ions. In some embodiments, the counterion is biologically compatible, is not toxic as used, and does not have a substantially deleterious effect on biomolecules. Counterions are readily changed by methods well known in the art, such as ion-exchange chromatography, or selective precipitation.
It is to be understood that the dyes as disclosed herein have been drawn in one or another particular electronic resonance structure. Every aspect discussed above applies equally to dyes that are formally drawn with other permitted resonance structures, as the electronic charge on the subject dyes are delocalized throughout the dye itself
Linkers
In some embodiments, the energy transfer dyes conjugates include a linker covalently attaching the donor dye to the acceptor dye.
The identity of the linker will depend, in part, upon the identities of the dyes being linked to one another. In general, the linkers include a spacing group that can include virtually any combination of atoms or functional groups stable to the synthetic conditions used for the synthesis of labeled biomolecules, e.g., oligonucleotides, such as the conditions commonly used to synthesize oligonucleotides by the phosphite triester method, and can be linear, branched, or cyclic in structure, or can include combinations of linear, branched and/or cyclic structures. The spacing group can be monomeric in nature, or it can be or include regions that are polymeric in nature. The spacing group can be designed to have specified properties, such as the ability to be cleaved under specified conditions, or specified degrees of rigidity, flexibility, hydrophobicity and/or hydrophilicity.
Representative examples of linkers that can be used to prepare ET conjugates as disclosed herein can include one or more of an alkyl portion, an amino-alkylene portion, and an oxy-alkylene portion, and amino-alkylene-dialkoxy portion, an alkenylene portion, an alkynylene portion, a polyether portion, an arylene portion, an amide portion, or a phosphodiester portion. Alternatively, the linker can be a covalent bond.
In some embodiments, the linker has one of the following structures:
In certain embodiments, the L1 linker includes an arylene portion of the formula
wherein
In some embodiments, L1 linker includes an arylene portion and one or more of a bis-alkylamino portion or a bis-carboxyamidyl portion, wherein the L1 linker further includes a point of attachment to A, wherein the attachment to A is through a covalent bond or through a spacer comprising one or more intervening atoms.
The L2 linker can include an arylene portion of the formula
In certain embodiments, the linker includes a fragment of the formula
wherein each R2, m and * is as defined above.
The L3 linker can include a fragment of the formula.
In the energy transfer dye conjugate shown above, L4 linker can include a phosphodiester portion of the formula
wherein Y includes one or more of an alkoxy portion, an alkyl portion, an arylene portion, or an oligonucleotide portion;
p is an integer from 0 to 10;
D2 or A comprises an oxygen atom, wherein each * represents a point of attachment of the phosphodiester portion to the oxygen atom in D2 or A, wherein the attachment of the phosphodiester to the oxygen atom in D2 or A is through a covalent bond or through a spacer comprising one or more intervening atoms.
In certain embodiments, Y is C1-C10 alkyl or poly(alkylene glycol).
In certain embodiments, the combination of the L3 and L4 linker can include a structure having the formula:
wherein
In some embodiments, the PAG is pentaethylene glycol.
In any of the linker structures described above, the analyte (A) can be a biological molecule, such as, e.g., a nucleic acid molecule, a peptide, a polypeptide, a protein, and a carbohydrate.
The different linker structures provided herein each have their own particular advantages, and selection of an appropriate linker design depends on the particular dyes that are used to form the ET conjugate, as well as the type of analyte that will be coupled to the ET conjugate. Linker L1 (also referred to as a “Y-linker”) can be used in combination with a particularly large variety of potential donor and acceptor dyes, as L1 does not require the use of a dual functional group containing dye to form a link to the analyte and to its ET partner, as required when using linker L2. Because linker L1 does not require that the dye bear a second functional group, any pair of dye NHS esters can be linked together with the Y-linker. The versatility of the Y-linker structure universalizes the use of different donor and acceptor dyes and thereby facilitates construction of a vast array of different donor-acceptor pair conjugates.
Another advantage of linker L1 is that this linker includes a third functional group that can be attached to the probe or analyte after construction of the ET conjugate. As a result, ET conjugates can prepared and purified before addition to the oligonucleotide probe or analyte. While purification prior to probe attachment is also feasible with the L2 linker (but not with linker L3), purification of the ET conjugate prior to probe attachment can provide for significantly improved yield and purity of the final product. However, the L2 linker having orthogonally reactive linkage sites to D1 and D2 precludes formation of regio-isomers that are produced with use of L1 without use of additional selective protecting group derivatization.
Linker L3 can be readily used to prepare ET conjugates using automated coupling chemistry. But for all practical purposes, linker L3 requires at least one dye phosphoramidite coupling step. Thus, coupling of donor and acceptor dyes using linker L3 requires that at least one dye, and preferably both dyes, be derivatized with a phosphoramidite group. Not all dye molecules can be readily made into phosphoramidite derivatives. Therefore, linker L3 is less versatile as compared to L1. Although it is feasible to first attach linkers L3 and L4 to a solid support before dye addition using protected phosphoramidite linker derivatives, the dyes must be separately added to the linker on the support in two secondary coupling steps using selective deprotection chemistry and NHS coupling chemistry. Such a multi-step synthetic scheme negates the advantages of automation (e.g., high yield and purity with less steps and labor) that can be achieved through use of at least one dye phosphoramidite in synthesis of the ET conjugate.
Conjugates of Energy Transfer Dyes
In one aspect, the present disclosure provides energy transfer dye conjugates that include one or more energy transfer dyes as described herein, covalently attached to an analyte. The analyte can be, e.g., an oligonucleotide probe, either directly or through an optional linker. In some embodiments, the energy transfer dye conjugates described herein can be further covalently attached to a quencher dye (Q), either directly or through an optional linker. In some embodiments, the quencher dye (Q) is covalently attached to an oligonucleotide portion of an energy transfer dye conjugate of the disclosure.
In some embodiments, a conjugation reaction between a donor dye and acceptor dye to form the energy transfer dye conjugate and the analyte or substance to be conjugated results a new linkages attaching the donor and acceptor dyes and the conjugated analyte through complementary Z and ZR groups. Suitable examples of complementary reactive groups and linkages are shown below in Table 1, where the reaction of an electrophilic group and a nucleophilic group yields a covalent linkage.
The covalent linkage binds the reactive group Z to form an energy transfer dye as described herein, either directly or through an optional linker portion. It will be appreciated that the optional linker portion covalently attaching an energy transfer dye conjugate to an analyte, such as an oligonucleotide probe, is not particularly limited by structure. The optional linker portion can be a combination of stable chemical bonds, optionally including single, double, triple or aromatic carbon-carbon bonds, as well as carbon-nitrogen bonds, nitrogen-nitrogen bonds, carbon-oxygen bonds, phosphorus-oxygen bonds. The optional linker portion can include functional moieties such as ether, thioether, carboxamide, sulfonamide, urea, urethane or hydrazine moieties. in some embodiment, the optional linker portion can include 1-20 non-hydrogen atoms selected from the group consisting of C, N, O, P, and S and are composed of any combination of ether, thioether, amine, carboxamide, sulfonamide, hydrazide bonds and aromatic or heteroaromatic bonds. In some embodiments, the optional linker portion can be a combination of single carbon-carbon bonds and carboxamide or thioether bonds.
In some embodiments, the energy transfer dye conjugate is covalently attached to an analyte, such as an oligonucleotide probe, through the linker portion of the energy transfer dye. In some embodiments, the energy transfer dye conjugate is covalently attached to an analyte, such as an oligonucleotide probe, through the linker portion of the energy transfer dye conjugate by an additional linker connecting the energy transfer dye linker portion to the analyte. In some embodiments, the energy transfer dye conjugate is covalently attached to an analyte, such as an oligonucleotide probe, by attachment of the analyte to the donor dye or the acceptor dye through an additional linker. In some embodiments, the energy transfer dye conjugate is covalently attached to an analyte, such as an oligonucleotide probe, by attachment of the analyte to the donor dye or the acceptor dye.
In some embodiments, the energy transfer dye conjugate is covalently attached to an analyte, such as an oligonucleotide probe, with a covalent bond to a reactive functional group on the analyte.
It will be appreciated that the choice of reactive groups used for attachment of the energy transfer dye conjugate to the analyte can be a function of the functional group present on the analyte to be conjugated and/or the type or length of covalent linkage desired.
Reactive groups for conjugating the ET dyes to an analyte are well-known to those skilled in the art. Typically, the reactive group will react with an amine, a thiol, an alcohol, an aldehyde or a ketone. In some embodiments, the reactive group reacts with an amine or a thiol functional group. In some embodiments, the reactive group is an acrylamide, a reactive amine (including a cadaverine or ethylenediamine), an activated ester of a carboxylic acid (typically a succinimidyl ester of a carboxylic acid), an acyl azide, an acyl nitrile, an aldehyde, an alkyl halide, an anhydride, an aniline, an aryl halide, an azide, an aziridine, a boronate, a carboxylic acid, a diazoalkane, a haloacetamide, a halotriazine, a hydrazine (including hydrazides), an imido ester, an isocyanate, an isothiocyanate, a maleimide, a phosphoramidite, a sulfonyl halide, or a thiol group.
In some embodiments, ET conjugates described herein can be attached to a nucleic acid base, nucleoside, nucleotide, or a nucleic acid polymer, including those that are modified to possess an additional linker or spacer for attachment of the energy transfer dye conjugate, such as an alkynyl linkage, an aminoallyl linkage, or a heteroatom-substituted linker, or other linkage.
In some embodiments, the additional linker portion connecting an energy transfer dye conjugate with the analyte, either through the linker portion on the energy transfer dye conjugate or through the donor dye or acceptor dye, comprises one or more of an alkyl portion, an amino-alkylene portion, and an alkoxy portion, and amino-alkylene-dialkoxy portion, an alkenylene portion, an alkynylene portion, a polyether portion, an amide portion, or an arylene portion.
Any donor dye and acceptor dye with appropriate functional groups can be attached to the linkers disclosed herein. However, in certain embodiments, the energy transfer dye conjugate does not include a fluorescein dye covalently attached to a rhodamine dye when the linker comprises an alkyl portion, a polyether portion, and a phosphodiester portion.
In some embodiments, the additional linker portion is a substituted or an unsubstituted polymethylene, arylene, alkylarylene, arylenealkyl, or arylthio. In some embodiments, the additional linker portion comprises a fragment of the formula
In some embodiments, the additional linker portion comprises a fragment of the formula —(CH2)d(CONH(CH2)e)z′—, —(CH2)d(CON(CH2)4NH(CH2)e)z′—, —(CH2)d(CONH(CH2)eNH2)z′—, or —(CH2)d(CONH(CH2)eNHCO)z′—, where d is 0-5, e is 1-5, and z′ is 0 or 1.
In another embodiment, the point of conjugation of the analyte can be a nucleoside or nucleotide analog that links a purine or pyrimidine base to a phosphate or polyphosphate moiety through a noncyclic spacer.
In some embodiments, the energy transfer dye conjugate can be further conjugated to the carbohydrate portion of a nucleotide or nucleoside, including, but not limited to, through a hydroxyl group, through a thiol, or through an amino group. In some embodiments, the conjugated nucleotide is a nucleoside triphosphate or a deoxynucleoside triphosphate or a dideoxynucleoside triphosphate. It will be appreciated that incorporation of methylene moieties or nitrogen or sulfur heteroatoms into the phosphate or polyphosphate moiety may also be useful. Purine and pyrimidine non-natural bases such as 7-deazapurines and nucleic acids containing such bases can also be coupled to energy transfer dye conjugates as described herein. Nucleic acid adducts prepared by reaction of depurinated nucleic acids (e.g., ribose derivatives) with amine, hydrazide or hydroxylamine derivatives provide an additional means of labeling and detecting nucleic acids.
In some embodiments, labeled nucleic acid polymer conjugates include single-, double-, or multi-stranded, natural or synthetic DNA or RNA, DNA or RNA oligonucleotides, or DNA/RNA hybrids, or incorporate a linker such as morpholine derivatized phosphates (AntiVirals, Inc., Corvallis, OR), or peptide nucleic acids such as N-(2-aminoethyl)glycine units. When the nucleic acid is a synthetic oligonucleotide, such as an oligonucleotide probe, the oligonucleotide can contain from about 5 to about 50 nucleotides. In some embodiments, the oligonucleotide contains from about 5 to about 25 nucleotides. In some embodiments, energy transfer dye conjugates of peptide nucleic acids (PNA) are provided. It will be appreciated that such energy transfer dye conjugates of peptide nucleic acids may be useful for some applications because of their generally faster hybridization rates.
In some embodiments, fluorescent nucleic acid polymers can be prepared from labeled nucleotides or oligonucleotides using oligonucleotide-primed DNA polymerization, such as by using the polymerase chain reaction or through primer extension, or by terminal-transferase catalyzed addition of a labeled nucleotide to a 3′-end of a nucleic acid polymer. In some embodiments, fluorescent RNA polymers are typically prepared from labeled nucleotides by transcription. In some embodiments, the energy transfer dye conjugate is attached via one or more purine or pyrimidine bases through an amide, ester, ether or thioether bond; or is attached to the phosphate or carbohydrate by a bond that is an ester, thioester, amide, ether or thioether. In some embodiments, an energy transfer dye conjugate may be simultaneously labeled with a hapten, such as biotin or digoxigenin, or to an enzyme such as alkaline phosphatase, or to a protein such as an antibody. In some embodiments, energy transfer dye nucleotide conjugates can be incorporated by DNA polymerase and can be used for in situ hybridization and nucleic acid sequencing.
In some embodiments, biological polymers, such as oligonucleotides and nucleic acid polymers, are labeled with at least one energy transfer dye conjugate to form an energy-transfer probe. Referring to
In some embodiments, biological polymers, such as oligonucleotides and nucleic acid polymers, are labeled with at least one energy transfer dye conjugate and at least one non-fluorescent dye to form an energy-transfer probe. In some embodiments, the non-fluorescent dye is a quencher.
In some embodiments, the labeled probe functions as an enzyme substrate, and enzymatic hydrolysis disrupts the energy transfer between the energy transfer dye conjugate and the quencher. In some embodiments, the 5′ to 3′ nuclease activity of a nucleic acid polymerase cleaves the oligonucleotide, thus releasing the energy transfer dye conjugate and the quencher from their proximate location and thereby removing or substantially removing the quenching effect (referred to as ET2) on the fluorescence produced by the energy transfer dye conjugate by the quencher.
In some embodiments, an oligonucleotide is covalently attached to a first reporter moiety, wherein the reporter moiety is an ET dye conjugate. In some embodiments, the ET dye conjugate comprises a first donor dye and a first acceptor dye. In some embodiments, the first donor dye is a first fluorophore and the acceptor dye is a second fluorophore. In some embodiments, an oligonucleotide comprises a first fluorophore, a second fluorophore, and a first quencher. In some embodiments, the first fluorophore and the second fluorophore are covalently linked by any of the linkers described herein. In some embodiments, the first and second fluorophores are different. In some embodiments, the reporter moiety comprising the first donor dye and the first acceptor dye are located at one terminus of the oligonucleotide and the first quencher moiety is located at the opposite terminus. In some embodiments, the reporter moiety is located within about 5 nucleotides from one terminal end of the oligonucleotide and the first quencher moiety is located within 5 nucleotides from the opposing terminal end of the oligonucleotide. In some embodiments, the reporter moiety is located at or within 5 nucleotides from the 5′-end and the quencher moiety is located at or within 5 nucleotides from the 3′-end of the oligonucleotide. In some embodiments, the reporter moiety is located at or within 5 nucleotides from the 3′-end and the quencher moiety is located at or within 5 nucleotides from the 5′-end of the oligonucleotide.
Quenchers
In some embodiments, a quencher is a derivative of 3- and/or 6-amino xanthenes that are substituted at one or more amino nitrogen atoms by an aromatic or heteroaromatic quenching moiety, Q. In some embodiments, a quencher is a derivative of dabcyl. In some embodiments, a quencher is dabcyl. In some embodiments, a quencher is of the Formula (Q1):
In some embodiments, the described quenching compounds typically have absorption maxima above 530 nm, have little or no observable fluorescence and efficiently quench a broad spectrum of fluorescence, such as is emitted by the fluorophores as disclosed herein. In some embodiments, the quenching compound is a substituted rhodamine. In another embodiment, the quenching compound is a substituted rhodol. In yet another embodiment, the quencher is a chemically reactive compound. Chemically reactive quenching compounds possess utility for labeling a wide variety of substances, including biomolecules, such as nucleic acids. These labeled substances are highly useful for a variety of energy-transfer assays and applications, particularly when used in combination with a fluorophore.
As used herein, each quenching moiety, Q, is an aromatic or heteroaromatic ring system, having 1-4 fused aromatic or heteroaromatic rings, attached to the amino nitrogen by a single covalent bond. Where the Q moiety is fully aromatic and contains no heteroatom, Q comprises 1-4 fused six-membered aromatic rings. Where the Q moiety is heteroaromatic, Q incorporates at least one 5- or 6-membered aromatic heterocycle that contains at least 1 and as many as 4 heteroatoms that are selected from the group consisting of O, N, and S in any combination, that is optionally fused to an additional six-membered aromatic ring, or is fused to one 5- or 6-membered heteroaromatic ring that contains at least 1 and as many as 3 heteroatoms that are selected from the group consisting of O, N, and S in any combination.
In some embodiments, each Q moiety is bound to the xanthene compounds at a 3- or 6-amino nitrogen atom via a single covalent bond. In some embodiments, the amino nitrogen substituents, taken in combination, form a 5- or 6-membered heterocycle that is a piperidine, a morpholine, a pyrrolidine, a pyrazine, or a piperazine, and the Q moiety is fused to the resulting heterocycle adjacent to the xanthene nitrogen, so as to be formally bound to the amino nitrogen via a single bond. The Q moiety may be bound to the amino nitrogen atom at either an aromatic or heteroaromatic ring, provided it is attached at a carbon atom of that ring.
Typically, the Q moieties are substituted or unsubstituted phenyl, naphthyl, anthracenyl, benzothiazole, benzoxazole, or benzimidazole. Where the amino nitrogen substituents form a 5- or 6-membered heterocycle and the Q moiety is fused to the resulting heterocycle, the heterocycle is typically a pyrrolidine ring and the Q moiety is typically a fused six-membered aromatic ring. In some embodiments, Q is a phenyl or substituted phenyl.
In various embodiments, each Q moiety is optionally and independently substituted by hydrogen, halogen, cyano, sulfo, alkali or ammonium salt of sulfo, carboxy, alkali or ammonium salt of carboxy, nitro, alkyl, perfluoroalkyl, alkoxy, alkylthio, amino, monoalkylamino, dialkylamino or alkylamido.
In various embodiments, the quenching compounds have the Formula (Q2)
wherein the K moiety is O or N+R18aR19a.
In various embodiments of quenching compounds described herein, at least one of R8a, R9a, R18a, and R19a is a Q moiety. Alternatively, either R8a taken in combination with R9a, or R18a taken in combination with R19a, forms a saturated 5- or 6-membered heterocycle that is a piperidine, or a pyrrolidine that is fused to a Q moiety. Typically one of R8a and R9a and one of R18a and R19a are each a Q moiety, which are the same or different. In another embodiment, each of R8a, R9a, R18a and R19a is a Q moiety, which may be the same or different.
The remainder of R8a, R9a, R18a, and R19a are independently H, C1-C6 alkyl, C1-C6 carboxyalkyl, C1-C6 sulfoalkyl, a salt of C1-C6 carboxyalkyl, or a salt of C1-C6 sulfoalkyl, wherein the alkyl portions are optionally substituted by amino, hydroxy, carboxylic acid, a salt of carboxylic acid, or a carboxylic acid ester of a C1-C6 alkyl. Alternatively, where Rea in combination with R9a, or R18a in combination with Riga, or both, forms a saturated 5- or 6-membered heterocyclic ring that is a piperidine, a morpholine, a pyrrolidine, a pyrazine, or a piperazine, that is optionally substituted by methyl, sulfonic acid, a salt of sulfonic acid, carboxylic acid, a salt of carboxylic acid, or a carboxylic acid ester of a C1-C6 alkyl. Alternatively, one or more of R8a in combination with R8a, R9a in combination with R3a, R18a in combination with R4a, or R19a in combination with R5a, forms a 5- or 6-membered ring that is saturated or unsaturated, and that is optionally substituted by one or more C1-C6 alkyls or CH2SO3Xa, where Xa is H or a counterion.
In some embodiments, R1a and R6a are H, or one or more of R1a in combination with R2a, or R6a in combination with R5a, is a fused six-membered aromatic ring.
In some embodiments, substituents R2a, R3a, R4a, and R5a are independently H, F, Cl, Br, I, CN; or C1-C18 alkyl, or C1-C18 alkoxy, where each alkyl or alkoxy is optionally further substituted by F, Cl, Br, I, a carboxylic acid, a salt of carboxylic acid, or a carboxylic acid ester of a C1-C6 alcohol; or —SO3Xa.
In some embodiments, the pendant group R10a is H, CN, a carboxylic acid, a salt of carboxylic acid, or a carboxylic acid ester of a C1-C6 alcohol. Alternatively R10a is a saturated or unsaturated, branched or unbranched C1-C18 alkyl that is optionally substituted one or more times by F, Cl, Br, carboxylic acid, a salt of carboxylic acid, a carboxylic acid ester of a C1-C6 alcohol, —SO3Xa, amino, alkylamino, or dialkylamino, the alkyl groups of which have 1-6 carbons. In another embodiment, R10a has the formula
where R12a, R13a, R14a, R15a and R16a are independently H, F, Cl, Br, I, —SO3Xa, a carboxylic acid, a salt of carboxylic acid, CN, hydroxy, amino, hydrazino, azido; or C1-C18 alkyl, C1-C18 alkoxy, C1-C18 alkylthio, C1-C18 alkanoylamino, C1-C18 alkylaminocarbonyl, C2-C36 dialkylaminocarbonyl, C1-C18 alkyloxycarbonyl, or C7-C18 arylcarboxamido, the alkyl or aryl portions of which are optionally substituted one or more times by F, Cl, Br, I, hydroxy, carboxylic acid, a salt of carboxylic acid, a carboxylic acid ester of a C1-C6 alcohol, —SO3Xa, amino, alkylamino, dialkylamino or alkoxy, the alkyl portions of each having 1-6 carbons. Alternatively, a pair of adjacent substituents R13a and R14a, R14a and R15a, or R15a and R16a, taken in combination, form a fused 6-membered aromatic ring that is optionally further substituted by carboxylic acid, or a salt of carboxylic acid.
The compounds are optionally substituted by a reactive group (Rx) or conjugated analyte or substance (Sc) that is attached to the compound by a covalent linkage, L, as described in detail above. Typically, the compound is substituted by an -L-Rx or -L-Sc moiety at one or more of R8a, R9a, R12a, R13a, R14a, R15a, R16a, R18a, or R19a, e.g., at one of R12a-R16a, or at R12a, R14a or R15a, or as a substituent on a Q moiety. Alternatively, an -L-Rx or -L-Sc moiety is present as a substituent on an alkyl, alkoxy, alkylthio or alkylamino substituent. In some embodiments, exactly one of R8a, R9a, R12a, R13a, R14a, R15a, R16a, R18a, or R19a is an L Rx or -L-Sc moiety. In another embodiment, exactly one of R12a, R13a, R14a, R15a, or R16a is an -L-Rx or -L-Sc moiety. In some embodiments, one of R12a, R14a, and Rica is an -L-Rx or an -L-Sc moiety.
In embodiments where the K moiety is N+R18aR19a, the compounds are rhodamines, and have the Formula (Q3):
wherein at least one of R8a, R9a, R18a and R19a is a Q moiety. In some embodiments, at least one of R8a and R9a is a Q moiety and at least one of R18a and R19a is a Q moiety, which may be the same or different.
In embodiments where the K moiety is 0, the compounds are rhodols, and have the Formula (Q4):
wherein at least one of R8a and R9a is a Q moiety.
In some embodiments, the instant compounds have the Formula (Q5):
wherein J is O—R7a or NR18aR19a and each of R1a-R19a is as defined above.
The precursors to the quenching compounds typically do not function as quenchers unless or until the aromaticity of the ring system is restored, as for the quenching compounds described above. In these precursors R7a is H, C1-C6 alkyl, C1-C6 carboxyalkyl, C1-C6 sulfoalkyl, a salt of C1-C6 carboxyalkyl, or a salt of C1-C6 sulfoalkyl, wherein the alkyl portions are optionally substituted by amino, hydroxy, carboxylic acid, a salt of carboxylic acid, or a carboxylic acid ester of a C1-C6 alkyl. Alternatively, R7 is a monovalent radical formally derived by removing a hydroxy group from a carboxylic acid, a sulfonic acid, a phosphoric acid, or a mono- or polysaccharide, such as a glycoside.
In some embodiments, R10a is as defined previously, and R11a is H, hydroxy, CN or alkoxy having 1-6 carbons. Alternatively, R11a in combination with R11a forms a 5- or 6-membered spirolactone ring, or R11a in combination with R12a forms a 5- or 6-membered spirolactone ring, or a 5- or 6-membered sultone ring.
These precursor compounds are readily converted to the fully conjugated quenching compounds by chemical, enzymatic, or photolytic means. Typically, the colorless precursors are substituted by an -L-Rx moiety, or are conjugated to an analyte or substance (Sc).
Exemplary quencher compounds include, but are not limited to, the following:
In some embodiments, the quencher is
In some embodiments, the quencher includes one or more sulfonate or SO3H substituents, such as, e.g.,
Also provided herein is an oligonucleotide probe coupled to an ET conjugate, as disclosed herein, that is further coupled to a quencher, wherein the quencher is a dibenzoxanthene compound. In certain embodiments, the dibenzoxanthene compound is an imino-dibenzoxanthene compound, such as a substituted 3-imino-3H-dibenzo[c,h]xanthen-11-amine compound.
Specific examples of quenchers that can used to prepare oligonucleotide probes that are coupled to the ET conjugates described herein are provided in Table 2.
Conjugates of Reactive Compounds
In some embodiments, the compound (quenching compound or precursor compound) is substituted by at least one group -L-Rx, where Rx is the reactive group that is attached to the compound by a covalent linkage L, as described in detail above for the dyes. The compounds with a reactive group (Rx) label a wide variety of organic or inorganic substances that contain or are modified to contain functional groups with suitable reactivity, resulting in chemical attachment of the conjugated analyte or substance (Sc), represented by -L-Sc.
In some embodiments, the conjugated analyte or substance (Sc) is a natural or synthetic nucleic acid base, nucleoside, nucleotide or a nucleic acid polymer, including those that are protected, or modified to possess an additional linker or spacer for attachment of the compounds, such as an alkynyl linkage, an aminoallyl linkage, or other linkage. In some embodiments, the conjugated nucleotide is a nucleoside triphosphate or a deoxynucleoside triphosphate or a dideoxynucleoside triphosphate.
Exemplary nucleic acid polymer conjugates are labeled, single-, double-, or multi-stranded, natural or synthetic DNA or RNA, DNA or RNA oligonucleotides, or DNA/RNA hybrids, or incorporate an unusual linker such as morpholine derivatized phosphates or peptide nucleic acids such as N-(2-aminoethyl)glycine units. When the nucleic acid is a synthetic oligonucleotide, it typically contains fewer than 50 nucleotides, more typically fewer than 25 nucleotides. Larger nucleic acid polymers are typically prepared from labeled nucleotides or oligonucleotides using oligonucleotide-primed DNA polymerization, such as by using the polymerase chain reaction or through primer extension, or by terminal-transferase catalyzed addition of a labeled nucleotide to a 3′-end of a nucleic acid polymer. Typically, the compound is attached via one or more purine or pyrimidine bases through an amide, ester, ether or thioether bond; or is attached to the phosphate or carbohydrate by a bond that is an ester, thioester, amide, ether or thioether. Alternatively, the compound is bound to the nucleic acid polymer by chemical post-modification, such as with platinum reagents, or using a photoactivatable molecule such as a conjugated psoralen. In some embodiments, the quenching moiety is attached to the nucleotide, oligonucleotide or nucleic acid polymer via a phosphoramidite reactive group, resulting in a phosphodiester linkage.
The quenching compounds can accept energy from a wide variety of fluorophores, provided that the quenching compound and the fluorophore are in sufficiently close proximity for quenching to occur, and that at least some spectral overlap occurs between the emission wavelengths of the fluorophore and the absorption band of the quenching compound. This overlap may occur with emission of the donor occurring at a lower or even higher wavelength emission maximum than the maximal absorbance wavelength of the quenching compound, provided that sufficient spectral overlap exists. In some embodiments, the quenching compound is only dimly fluorescent, or essentially non-fluorescent, so that energy transfer results in little or no fluorescence emission. In one aspect, the quenching compound is essentially non-fluorescent and has a fluorescence quantum yield of less than about 0.05. In another aspect, the quenching compound has a fluorescence quantum yield of less than about 0.01. In yet another aspect, the quenching compound has a fluorescence quantum yield of less than about 0.005.
It should be readily appreciated that the degree of energy transfer, and therefore quenching, is highly dependent upon the separation distance between the reporter moiety (e.g., fluorophore) and the quenching moiety. In molecular systems, a change in fluorescence quenching typically correlates well with a change in the separation distance between the fluorophore molecule and the quenching compound molecule. A fluorophore with sufficient spectral overlap and proximity with a quenching compound is generally a suitable donor for the various applications contemplated herein. The greater the degree of overlap and proximity, the greater the potential for overall quenching.
In some embodiments, the disassembly, cleavage or other degradation of a molecular structure comprising the described fluorophore and quencher is detected by observing the partial or complete restoration of fluorescence of a fluorophore. In some embodiments, the initially quenched fluorescence of a fluorophore associated with the structure becomes dequenched upon being removed from the close proximity to a quenching compound by changes to secondary structure, disassembly, cleavage, or degradation of the molecular structure. The quenching compound is optionally associated with the same molecular structure as the fluorophore, or the donor and acceptor are associated with adjacent but distinct subunits of the structure. The following systems, among others, can be analyzed using the described energy transfer pairs to detect and/or quantify structural disassembly: detection of protease activity using fluorogenic substrates (for example HIV protease assays); detection of enzyme-mediated protein modification (e.g. cleavage of carbohydrates/fatty acids, phosphates, prosthetic groups); immunoassays (via displacement/competitive assays); detection of DNA duplex unwinding (e.g. helicase/topoisomerase/gyrase assays); nucleic acid strand displacement; ds DNA melting; nuclease activity; lipid distribution and transport; and TaqMan assays.
Structure disassembly is typically detected by observing a partial or complete restoration of fluorescence, as a conjugated analyte is exposed to a degradation conditions of interest for a period of time sufficient for degradation to occur. A restoration of fluorescence indicates an increase in separation distance between the fluorophore and quenching compound, and therefore a degradation of the conjugated analyte. Structure changes can be monitored during a biological assay (e.g., using a polymerase or other enzymatic disassembly cleavage mechanism), and the extent of disassembly can provide valuable information about the biological system under study.
Probe
In some embodiments, the energy transfer dye conjugates described herein can be reporter dyes for detection in PCR implementing multiple excitation and multiple emission (i.e., detection) channels, such as those involving excitation at about 480+/−10 nm (blue) and a detection channel at about 587+/−10 nm (yellow/orange), excitation at about 480+/−10 nm (blue) and a detection channel at about 623+/−14 nm (orange/red), excitation at about 550+/−10 nm (green) and a detection channel at about 682+/−14 nm (red), or excitation at about 550+/−10 nm (green) and a detection channel at about 711+/−12 nm (red). In some embodiments, the energy transfer dye conjugates described herein can be reporter dyes for detection in PCR implementing 7th, 8th, 9th, 10th, etc. reporter dyes. In some embodiments, additional reporter dyes, such as 7th, 8th, 9th, 10th, etc. reporter dyes, can be provided as a phosphoramidite precursor. It will be appreciated that phosphoramidite precursors of reporter dyes can facilitate synthesis of PCR probes in high quality and at reduced cost. In some embodiments, the described probe(s) are included in a multiplex PCR assay as the higher wavelength, such as 5th, 6th, 7th, 8th, etc., probes. In some embodiments, the assay can also include probes having dye/quencher combinations where the quencher can be any of those known to those of skill in the art, include, for example Dabcyl, Dabsyl, Eclipse™ Quencher, QSY7, QSY21, and Black Hole Quenchers 1, 2, and 3 (see also Table 2 for additional examples). In some embodiments, the described probes include a minor groove binder (MGB) moiety at the 3′ end that increases the melting temperature (Tm) of the probe and stabilizes probe-target hybrids. In some embodiments, the use of a MGB or a locked nucleic acid (LNA) in the probe allows the probe to be shorter than traditional probes, which can provide better sequence discrimination and flexibility to accommodate more targets.
In some embodiments, the described probe comprises one of the energy transfer dye conjugates as described herein (as the fluorophore) and one of the quenchers described herein, where the fluorophore and the quencher are each covalently conjugated to an oligonucleotide. Examples of probes suitable for multiplex PCR applications can include an energy transfer dye conjugate, as described herein, that emits in the spectral region for detection in one or more emission channels of a PCR instrument that includes multiple excitation and emission channels. In some embodiments, such a probe comprising an energy transfer dye conjugate as described herein is a detector probe which can be used for the detection of a complementary target nucleic acid molecule.
The described probe can be synthesized according to methods known in the art. For example, in some embodiments, the fluorophore and the quencher are covalently conjugated to the termini of an oligonucleotide using the conjugation chemistries and reactive groups described above. In another example, the quencher or probe may be conjugated to a solid support and the oligonucleotide is synthesized from the attached quencher or probe using standard oligonucleotide synthesis methods, such as a DNA synthesizer, and then the other of the quencher or probe is covalently attached to the terminus of the synthesized oligonucleotide.
Methods and Kits
Also provided herein are methods of making energy transfer conjugates and linking of such conjugates to biological molecules (e.g., oligonucleotides). Examples of synthetic routes for preparing energy transfer conjugates including linkers L1-L4 are depicted in
Also provided herein are methods for using the fluorescent energy transfer conjugates in biological assays and kits for performing such assays. For example, the energy transfer dye conjugates provided herein can be used in real-time and end-point PCR assays. Fluorescent ET conjugates can be prepared that can be excitable and emit across a wide range of wavelengths. By adjusting the type and length of linker between donor dye, acceptor dye and analyte, the optical properties of the resulting conjugate can be tuned to offer precise excitation and emission profiles. Because the conjugates can be tailored to suit the desired excitation and emission profile, the conjugates are particularly useful in the construction of oligonucleotide probes for use in multiplex biological assays (e.g., qPCR assays), either alone or in combination with one or more other fluorophores.
Thus, in another aspect, ET transfer dye conjugates described herein can be used in the practice of multiplex assays. Any fluorescent ET conjugate with the appropriate excitation and emission profile can be used in the practice of such multiplex assays. Various manufacturers provide instruments capable of detecting multiplex PCR assays. As one example, Thermo Fisher Scientific (Waltham, MA) provides 4-plex TaqMan assays for real time detection of nucleic acids targets on Thermo Fisher Scientific instruments, such as, Vii7, Quant Studio, and the like, where certain real time qPCR instruments have the optical capability to run up to a 6-plex TaqMan assay.
The unique ET conjugates provided herein allow for expansion of qPCR assays beyond 6-plex, e.g., 7-plex, 8-plex, 9-plex, 10-plex, etc
Thus, in a further aspect, methods of performing singleplex or multiplex PCR, such as qPCR or end-point PCR, using the described ET conjugates are provided. End point PCR is the analysis after all cycles of PCR are completed. Unlike qPCR, which allows quantification as template is doubling (exponential phase), end point analysis is based on the plateau phase of amplification.
In particular, a method for amplifying and detecting multiple target DNA sequences comprising providing a composition or reaction mixture comprising the described probe, subjecting the reaction mixture to a thermocyling protocol such that amplification of said multiple target sequences can take place, and monitoring amplification by detecting the fluorescence of the described probe at least once during a plurality of amplification cycles. In some embodiments, the method comprises a 5-plex or 6-plex multiplex qPCR assay where the described probes allow for detection of the 5th and/or 6th nucleic acid target. In some embodiments, the method comprises a 7-plex or 8-plex multiplex qPCR assay where the probes use the ET reporters described herein that allow for detection of the 7th and/or 8th nucleic acid targets. In some embodiments, the method comprises a 9-plex or 10-plex multiplex qPCR assay where the described probes allow for detection of the 9 or 10 nucleic acid targets. ET conjugates described herein can be used in higher order multiplex assays. For example, multiplex assays for evaluation of 6-20 (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20) or more nucleic acid targets can be facilitated using the ET conjugates described herein. In some embodiments, the method comprises up to a 6-plex multiplex qPCR assay where the described probes allow for detection of 6 nucleic acid targets. In some embodiments, the method comprises up to a 10-plex multiplex qPCR assay where the described probes allow for detection of 10 nucleic acid targets. In some embodiments, the method comprises up to a 20-plex multiplex qPCR assay where the described probes allow for detection of 20 nucleic acid targets. In some embodiments, the method comprises enough assays for a 5-plex up to a 30-plex multiplex qPCR assay (or any plexy in between) where the described probes are provided in a manner that allows for detection of between 5 to 30, or any number in between, nucleic acid targets.
The ET transfer dye conjugate described herein can be used in the practice of multiplex assays. Any fluorescent ET conjugate with the appropriate excitation and emission profile can be used in the practice of such multiplex assays. In certain embodiments, the donor dye has an excitation maximum from about 450 nm to about 580 nm, and the acceptor dye has an emission maximum from about 580 nm to about 750 nm. Representative examples of donors and reporters that can be used to prepare ET dye conjugates using the linkers described herein for use in the practice of a multiplex qPCR assay, with their associated excitation and emission wavelengths, are shown in Table 3
An appropriate linker can be chosen to maximize energy transfer efficiency between the donor dye and the acceptor dye. In certain embodiments, the donor dye is a fluorescein or rhodamine dye covalently linked through a linker having the structure (LI) to a rhodamine acceptor dye, pyronine or cyanine acceptor dye. In yet other embodiments, the donor dye is a fluorescein or rhodamine dye covalently linked through a linker having the structure (LII) to a rhodamine, pyronine or cyanine acceptor dye. In yet other embodiments, the donor dye is a fluorescein or rhodamine dye covalently linked through a linker having the structure (LIII) to a rhodamine acceptor dye. In yet other embodiments, the donor dye is a fluorescein or rhodamine dye covalently linked through a linker having the structure (LIII) to a pyronine or cyanine acceptor dye. In any of these embodiments, linker (LI), (LII), or (LIII) can be the donor and acceptor dye can be further linked to an analyte (e.g., an oligonucleotide or a protein).
The detection of the signal may be accomplished using any reagents or instruments that detect a change in fluorescence from a fluorophore. For example, detection may be performed using any spectrophotometric thermal cycler. Examples of spectrophotometric thermal cyclers include, but are not limited to, Applied Biosystems (AB) PRISM® 7000, AB 7300 real-time PCR system, AB 7500 real-time PCR system, AB PRISM® 7900HT, Bio-Rad Cycler IQ™, Cepheid SmartCycler® II, Corbett Research Rotor-Gene 3000, Idaho Technologies R.A.P.I.D.™, MJ Research Chromo 4™, Roche Applied Science LightCycler®, Roche Applied Science LightCycler®2.0, Stratagene Mx3000P™, and Stratagene Mx4000™.
Representative examples of dyes that can used to expand the dye set to beyond 10-plex include without limitation: the donor dye is Coumarin 343 and the acceptor dye is FAM. In some embodiments, the donor dye is ATTO 425 (ATTO-Tec, GmbH) and the acceptor dye is FAM. In some embodiments, the donor dye is Pacific Blue (Thermo Fisher Scientific) and the acceptor dye is FAM. In some embodiments, the donor dye is ATTO 425 and the acceptor dye is FAM. In some embodiments, the donor dye is ALEXA FLUOR 405 and the acceptor dye is FAM. In some embodiments, the donor dye is Coumarin 343 and the acceptor dye is VIC. In some embodiments, the donor dye is ATTO 425 and the acceptor dye is VIC. In some embodiments, the donor dye is Pacific Blue and the acceptor dye is VIC. In some embodiments, the donor dye is ATTO 425 and the acceptor dye is VIC. In some embodiments, the donor dye is Alexa Fluor 405 and the acceptor dye is VIC. Similarly, the dye matrix can be expanded to include reporter dyes that include an acceptor that emits above the m6 emission channel, such as cyanine dyes such as Cy 7 (GE Healthcare), azaindoline cyanine dyes, Alexa Fluor 750, or a silylrhodamine. In certain embodiments, the donor dye is a rhodamine or a cyanine dye, and the reporter dye is a cyanine dye (e.g., an azaindoline cyanine) that emits in the far-red or near-IR region of the spectrum.
The nucleic acid target(s) of the described method may be any nucleic acid target known to the skilled artisan. Further, the targets may be regions of low mutation or regions of high mutation. For example, one particularly valuable use of the methods disclosed herein involves targeting highly mutated nucleic acids, such as RNA viral genes, or regions of high genetic variability, such a single nucleotide polymorphisms (SNPs). In some embodiments, the targets may be fragmented or degraded, such as material from forensic samples and/or fixed (e.g., by formalin) tissues. The targets may be any size amenable to amplification. One particularly valuable use of the methods and compositions provided herein involves the identification of short fragments, such as siRNA and miRNA. Another particularly valuable use is for samples that may have fragmented and/or degraded nucleic acid, such as fixed samples or samples that have been exposed to the environment. Thus, the methods may be used to biopsy tissues and forensic DNA samples for example. The targets may be purified or unpurified. The targets may be produced in vitro (for example, a cDNA target) or can be found in biological samples (for example, an RNA or a genomic DNA (gDNA) target). The biological sample may be used without treatment or the biological samples may be treated to remove substances that may interfere with the methods disclosed herein.
Samples in which nucleic acid targets may exist include, for instance, a tissue, cell, and/or fluid (e.g., circulating, dried, reconstituted) sample obtained from a mammalian or non-mammalian organism (e.g., including but not limited to a plant, virus, bacteriophage, bacteria, and/or fungus). In some embodiments, the sample may be derived from, for example, mammalian saliva, buccal epithelial cells, cheek tissue, lymph, cerebrospinal fluid, skin, hair, blood, plasma, urine, feces, semen, a tumor sample (e.g., cancer cells/tissue), cultured cells, and/or cultured tumor cells. The target polynucleotide may be DNA in genomic form, or it may be cloned in plasmids, bacteriophage, bacterial artificial chromosomes (BACs), yeast artificial chromosomes (YACs), and/or other vectors. Other types of samples may also be useful in the methods described herein which may be related, for example, to diagnostic or forensic assays. In some embodiments, the probes described herein may be used for detection of viral DNA sequences.
The probes provided herein may be used in methods of diagnosis, e.g., SNP detection, identification of specific biomarkers, etc., whereby the probes are complementary to a sequence (e.g., genomic) of an infectious disease agent, e.g., of human disease including but not limited to viruses, bacteria, parasites, and fungi, thereby diagnosing the presence of the infectious agent in a sample having nucleic acid from a patient. The target nucleic acid may be a genomic DNA (gDNA), cDNA, or RNA, such as mRNA, siRNA, or miRNA; or synthetic DNA, human or animal; or of a microorganisms, etc. In other embodiments, the probes may be used to diagnose or prognose a disease or disorder that is not caused by an infectious agent. For example, the probes may be used to diagnose or prognose cancer, autoimmune diseases, mental illness, genetic disorders, etc. by identifying the presence of an infective agent, such as a virus, or a host, a mutation, polymorphism, or allele in a sample from a human or animal. In some embodiments, the probe comprises the mutation or polymorphism. Additionally, the probes may be used to evaluate or track progression of treatment for an infection, a disease or disorder.
Also provided are compositions, such as a reaction mixture or master mix, comprising the described probe. In some embodiments, the composition for PCR, such as for real-time or quantitative PCR or end-point PCR, comprises at least one of the described probes. In some embodiments, the composition or reaction mixture or master mix for PCR (e.g., qPCR or end-point PCR) comprises probes for allowing for detection of at least 4 target nucleic acids and the described probe(s) allowing for detection of at least one of a 5th and/or a 6th target nucleic acid, at least one of the described probes consisting of an ET donor dye and an ET acceptor dye, where the fluorophore has an emission maximum between about 650 and 720 nm. The absorbance maximum of the acceptor as described herein is between 660-668 nm. The absorbance range of the quencher as described herein is 530-730 nm. In an alternate embodiment, labeling reagents are provided for conjugating the described fluorophore and quencher to an oligonucleotide of choice.
In addition, such a composition or reaction mixture or master mix may comprise one or several compounds and reagents selected from the following list: Buffer, applicable for a polymerase chain reaction, deoxynucleoside triphosphates (dNTPs), DNA polymerase having 5′ to 3′ exonuclease activity, at least one pair or several pairs of amplification primers and/or additional probes, a uracil DNA glycosylase, PCR inhibitor blocking agents (such as a combination of a gelatin and albumin mixture), a hot start component and/or modification, at least one salt, such as magnesium chloride and/or potassium chloride, a reference dye, and at least one detergent. Other compounds and reagents suitable for inclusion in the compositions, reaction mixtures, and master mixes as disclosed herein may be contemplated by those of skill in the art.
In some embodiments, the compositions or master mixes as described herein can comprise components, including probes as described herein, that are appropriate for lyophilization (e.g., “lyo-ready”), are already in lyophilized form, and/or are otherwise stabilized (e.g., freeze-dried), dried down, or prepared as an evaporated composition or component.
In certain embodiments, kits are provided that may be used to carry out hybridization, extension and amplification reactions using the oligonucleotides provided herein. Preferred kits may comprise one or more containers, such as vials, tubes and the like, configured to contain the reagents used in the methods described herein and optionally may contain instructions or protocols for using such reagents. The kits described herein may comprise one or more components selected from the group consisting of one or more oligonucleotides described herein, including but not limited to, one or more probes described herein, and a polymerase. In other embodiments, the kits may also include one or more primers.
In yet another aspect, a kit comprising at least one of the described probe(s) is provided. In addition, a kit may comprise one or several other compounds and reagents selected from the following list: Buffer, applicable for a polymerase chain reaction, deoxynucleoside triphosphates (dNTPs), DNA polymerase having 5′ to 3′ exonuclease activity, at least one or multiple pairs of amplification primers. The kit may also comprise an internal control DNA or standard. Each of the components disclosed above may be stored in a single storage vessel and packaged separately or together. Yet, any combination of components for storage within the same vessel is possible as well. In some embodiments, the probe(s) and/or other components included in the kit may be lyophilized or otherwise stabilized for storage and/or shipment, and reconstituted as desired by the user. Instructions for use of the kit can also be included.
Another aspect provided herein is a method of detecting or quantifying a target nucleic acid molecule in a sample by polymerase chain reaction (PCR), such as by quantitative real-time polymerase chain reaction (qPCR). In some embodiments, the method includes: (i) contacting a sample comprising one or more target nucleic acid molecules with a) at least one probe, such as those described herein, being sequence specific for the target nucleic acid molecule, where the at least one probe undergoes a detectable change in fluorescence upon amplification of the one or more target nucleic acid molecules; and with b) at least one oligonucleotide primer pair; (ii) incubating the mixture of step (i) with a DNA polymerase under conditions sufficient to amplify one or more target nucleic acid molecules; and (iii) detecting the presence or absence or quantifying the amount of the amplified target nucleic acid molecules by measuring fluorescence of the probe. In some embodiments, the probe is a hydrolysis probe, such as a TaqMan probe.
Another aspect provided herein is a kit for PCR, such as quantitative real-time polymerase chain reaction (qPCR). In some embodiments the kit includes a probe, such as those described herein, instructions for conducting the PCR, and one or more of the following: a buffering agent, deoxynucleotide triphosphates (dNTPs), an organic solvent, an enzyme, enzyme cofactors, and an enzyme inhibitor. In yet further aspects provided herein are compositions, such as a “master mix” for PCR comprising the described probe along with other components that are used in PCR. The term “amplification reaction mixture” and/or “master mix” as used herein refers to an aqueous solution comprising the various (some or all) reagents used to amplify a target nucleic acid. Such reactions may also be performed using solid supports (e.g., an array). The reactions may also be performed in single or multiplex format as desired by the user. These reactions typically include enzymes, aqueous buffers, salts, amplification primers, target nucleic acid, and nucleoside triphosphates. Depending upon the context, the mixture can be either a complete or incomplete amplification reaction mixture. The method used to amplify the target nucleic acid may be any available to one of skill in the art. Any in vitro means for multiplying the copies of a target sequence of nucleic acid may be utilized. These include linear, logarithmic, and/or any other amplification method. While this disclosure may generally discuss PCR as the nucleic acid amplification reaction, it is expected that the modified detergents describe herein should be effective in other types of nucleic acid amplification reactions, including both polymerase-mediated amplification reactions (such as helicase-dependent amplification (HDA), recombinase polymerase amplification (RPA), and rolling circle amplification (RCA)), as well as ligase-mediated amplification reactions (such as ligase detection reaction (LDR), ligase chain reaction (LCR), and gap-versions of each), and combinations of nucleic acid amplification reactions such as LDR and PCR (see, for example, U.S. Pat. No. 6,797,470). For example, the modified detergents may be used in, for example, various ligation-mediated reactions, where for example ligation probes are employed as opposed to PCR primers. Additional exemplary methods include polymerase chain reaction (PCR; see, e.g., U.S. Pat. Nos. 4,683,202; 4,683,195; 4,965,188; and/or 5,035,996), isothermal procedures (using one or more RNA polymerases (see, e.g., PCT Publication No. WO 2006/081222), strand displacement (see, e.g., U.S. Pat. No. RE39007E), partial destruction of primer molecules (see, e.g., PCT Publication No. WO 2006/087574)), ligase chain reaction (LCR) (see, e.g., Wu, et al., Genomics 4: 560-569 (1990)), and/or Barany, et al. Proc. Natl. Acad. Sci. USA 88:189-193 (1991)), Q˜ RNA replicase systems (see, e.g., PCT Publication No. WO 1994/016108), RNA transcription-based systems (e.g., TAS, 3SR), rolling circle amplification (RCA) (see, e.g., U.S. Pat. No. 5,854,033; U.S. Patent Application Publication No. 2004/265897; Lizardi et al. Nat. Genet. 19: 225-232 (1998); and/or Barrer et al. Nucleic Acid Res., 26: 5073-5078 (1998)), and strand displacement amplification (SDA) (Little, et al. Clin. Chem. 45:777-784 (1999)), among others. These systems, along with the many other systems available to the skilled artisan, may be suitable for use in polymerizing and/or amplifying target nucleic acids for use as described herein.
In some embodiments, the master mix is prepared such that it requires less than a 3× dilution prior to use in PCR, e.g., 2× dilution, 1.5× dilution, 1.2× dilution, etc. In some embodiments, the compositions or master mixes as described herein include stabilizing components or are able to be processed to provide stabilization for storage and/or shipment. For example, the master mixes can be prepared as compositions that are stable for approximately two years at −20° C.; approximately one year at 4° C.; approximately three to six months at room temperature; and/or approximately one to two months at a temperature higher than room temperature. In some embodiments the compositions or master mixes provided herein are dry (e.g., lyophilized) or in a solution of water or TE buffer. Kits, described herein, may also include a buffer or the like for reconstitution of lyophilized or otherwise stabilized compositions (e.g., by addition of water or a buffer such as TE or Tris.
Polymerases
As disclosed herein, the compositions, reaction mixtures and kits can also comprise at least one polymerase (e.g., a DNA polymerase) and at least one source of nucleotides (e.g., dNTPs). The polymerase can be a DNA polymerase with 5′ to 3′ exonuclease activity. In some embodiments, the polymerase can be a “thermostable polymerase,” which refers to an enzyme that is heat-stable, heat-resistant, and/or not irreversibly inactivated when subjected to elevated temperatures for the time necessary to effect destabilization of single-stranded nucleic acids or denaturation of double-stranded nucleic acids during amplification (e.g., will not irreversibly denature at about 90° to about 100° C. under conditions such as is typically required for amplification (e.g., in a polymerase chain reaction (PCR)) and catalyzes polymerization of deoxyribonucleotides to form primer extension products that are complementary to a target polynucleotide strand. Thermostable polymerases may be obtained, for example, from a variety of thermophilic bacteria that are publically available (for example, from American Type Culture Collection, Rockville, Md.) using methods that are well-known to one of ordinary skill in the art (See, e.g., U.S. Pat. No. 6,245,533). Bacterial cells may be grown according to standard microbiological techniques, using culture media and incubation conditions suitable for growing active cultures of the particular species that are well-known to one of ordinary skill in the art (See, e.g., Brock, T. D., and Freeze, H., J. Bacteriol. 98(1):289-297 (1969); Oshima, T., and Imahori, K, Int. J. Syst. Bacteriol. 24(1):102-112 (1974)). Suitable for use as sources of thermostable polymerases are the thermophilic bacteria Thermus aquaticus, Thermus thermophilus, Thermococcus litoralis, Pyrococcus furiosus, Pyrococcus woosii, and other species of the Pyrococcus genus, Bacillus stearothermophilus, Sulfolobus acidocaldarius, Thermoplasma acidophilum, Thermus flavus, Thermus ruber, Thermus brockianus, Thermotoga neapolitana, Thermotoga maritima, and other species of the Thermotoga genus, and Methanobacterium thermoautotrophicum, and mutants of each of these species. Exemplary thermostable polymerases can include, but are not limited to, any of the SuperScript, Platinum, TaqMan, MicroAmp, AmpliTaq, and/or fusion polymerases. Exemplary polymerases can include but are not limited to (Thermus aquaticus) Taq DNA polymerase, AmpliTaq™ DNA polymerase, AmpliTaq™ Gold DNA polymerase, DreamTaq™ DNA Polymerase, recombinant, modified form of the (Thermus aquaticus) Taq DNA polymerase gene expressed in E. coli (Thermo Fisher Scientific), iTaq™ (Bio-Rad), Platinum Taq DNA Polymerase High Fidelity, Platinum™ II Taq™ Hot-Start DNA Polymerase, Platinum SuperFi DNA Polymerase, AccuPrime Taq™ DNA Polymerase High Fidelity, Tne DNA polymerase, Tma DNA polymerase, Phire Hot Start II DNA polymerase, Phusion U Hot Start DNA Polymerase, Phusion Hot Start II High-Fidelity DNA Polymerase, iProof High Fidelity DNA Polymerase (Bio-Rad); HotStart Taq Polymerase (Qiagen)), a chemically modified polymerase that for instance blocks its activity at a particular temperature such as room temperature, and/or mutants, derivatives and/or fragments thereof. In some embodiments, an oligonucleotide or aptamer may also be used as a hot start agent, and/or the hot start function may result from a chemical modification to a polymerase that blocks its activity at a particular temperature (e.g., room temperature) (e.g., TaqGold, FlashTaq, Hot-Start Taq). In some embodiments, the hot start component may be one or more antibodies directed to (i.e., have binding specificity for) a thermostable polymerase in the mixture (as available from Thermo Fisher Scientific in, e.g., Platinum™ II Hot-Start Green PCR Master Mix; DreamTaq™ Hot Start Green PCR Master Mix, Phusion U Green Muliplex PCR Master Mix, Phire Green Hot Start II Master Mix, or AmpliTaq® Gold 360 Master Mix (Thermo Fisher Scientific)). In some embodiments, a dual hot start mechanism may be used. For example, a first hot start component, such as an oligonucleotide may be used as a hot start agent in conjunction with a second hot start component, such as one or more antibodies. In some embodiments, the first and second hot start components of the dual hot start mechanism, may be the same type or different (oligo-based; antibody-based; chemical-based, etc.). In some embodiments, the first and second hot start components of the dual hot start mechanism may be inhibitory to the same polymerase (e.g., a dual hot start mechanism which employs an inhibitory antibody directed to Taq DNA polymerase and an inhibitory oligonucleotide specific to Taq DNA polymerase). In some embodiments, the polymerase can be a fusion or chimeric polymerase which refers to an enzyme or polymerase that is comprised of different domains or sequences derived from different sources. For example, a fusion polymerase may comprise a polymerase domain, such as a Thermus aquaticus (Taq) polymerase domain, fused with a DNA binding domain, such as a single- or double-stranded DNA binding protein domain. Fusion or chimeric polymerases may be obtained, for example, using methods that are well-known to one of ordinary skill in the art (See, e.g., U.S. Pat. No. 8,828,700), the disclosure of which is incorporated by reference in its entirety. In some embodiments, such fusion or chimeric polymerases are thermostable. In some embodiments, the mixtures can comprise a mixture that is a master mix and/or a reaction mixture (e.g., TaqPath™ ProAmp™ Master Mix (Applied Biosystems™), TaqPath™ ProAmp™ Multiplex Master Mix (Applied Biosystems™), TaqMan™ PreAmp Master Mix (Applied Biosystems™), TaqMan™ Universal Master Mix II with UNG (Applied Biosystems™), TaqMan™ Universal PCR Master Mix II (no UNG) (Applied Biosystems™), TaqMan™ Gene Expression Master Mix II with UNG (Applied Biosystems™), EXPRESS qPCR Supermix, universal (Invitrogen), TaqMan™ Fast Advanced Master Mix (Applied Biosystems™, TaqMan™ Multiplex Master Mix (Applied Biosystems™), TaqMan™ PreAmp Master Mix Kit (Applied Biosystems™), TaqMan™ Universal PCR Master Mix, no AmpErase™ UNG (Applied Biosystems™), PowerUp SYBR Green Master Mix (Applied Biosystems™), or FlashTaq HotStart 2× MeanGreen Master Mix (Empirical Biosciences)). In some embodiments, the mixtures can further comprise one or more of at least one detergent; glycerol; PCR inhibitor blocking agents, including combinations of gelatin and albumin; uracil DNA glycosylase (UDG), and at least one reference dye (e.g., ROX™, Mustang Purple™). In some embodiments, the reaction mixture further can comprise an amplicon(s) comprising the target polynucleotide sequence (e.g., first sequence) of the target polynucleotide strand. In some embodiments, the mixture does not include an amplicon that includes a sequence of a second polynucleotide strand (e.g., of a major allelic variant).
Reverse Transcriptases
In some embodiments, the compositions, reaction mixtures, and kits as disclosed herein can also comprise at least one reverse transcriptase (RT) and related components, such as for reverse transcription PCR (RT-PCR). RT-PCR may be performed using the compositions, reaction mixtures and kits described herein, when, for example, RNA is the starting material for subsequent analysis. In some embodiments, the RT-PCR may be a one-step procedure using one or more primers and one or more probes as described herein. In some embodiments, the RT-PCR may be carried out in a single reaction tube or reaction vessel, such as in 1-step or 1-tube RT-PCR. Suitable exemplary RTs can include, for instance, a Moloney Murine Leukemia Virus (M-MLV) Reverse transcriptase, SuperScript Reverse Transcriptases (Thermo Fisher Scientific), SuperScript IV Reverse Transcriptases (Thermo Fisher Scientific), or Maxima Reverse Transcriptases (Thermo Fisher Scientific), or modified forms of any such RTs. The compositions, reaction mixtures, and kits may also comprise any other components necessary for carrying out such RT-PCR reactions, such as may be found in SuperScript IV VILO Master Mix (Thermo Fisher Scientific), or any other suitable RT-PCR master mixes (including those described above).
As used herein, the terms “wavelength range”, “wavelength band”, or the like, may mean a “full width at half maximum” (FWHM) wavelength range or wavelength band. As used herein, the terms FWHM wavelength range or FWHM wavelength band means a wavelength range or wavelength band having an extent equal to a difference between maximum and minimum wavelength values at which the radiation through, from, or off an optical element (e.g., a source of radiation or a spectral filter, mirror, beamsplitter, grating, or the like) is equal to one half a maximum value within the wavelength range or wavelength band of that element.
For a spectrum defined by a spectral function (e.g., an absorption, excitation, or emission spectral function) over a wavelength range, as used herein, a “peak wavelength” or “maximum wavelength” (e.g., “maximum absorption wavelength”, “maximum excitation wavelength”, “maximum emission wavelength”) means a wavelength at which the spectrum function decreases as the wavelength increases or decreases about the maximum or peak wavelength (e.g., the absorption, excitation, or emission decreases as the wavelength increases or decreases from the maximum or peak wavelength—for example, increases or decreases by 2 nanometers). As used herein, the peak or maximum wavelength may be a local peak or maximum over a predetermined portion of a total spectrum or may be an “absolute peak” or “absolute maximum” in which the value of the spectral function is greater than at any other wavelength over an entirety of the spectrum.
As used herein, the peaks or maximums of two or more spectra (e.g., an absorption, excitation, or emission spectra of two or more dyes) may be considered “equal”, “near”, or “substantially equal” to one another when the difference between the peaks or maximums of two or more spectra is less than or equal to 15 nanometers. As used herein, a peak or maximum of a spectrum (e.g., an absorption, excitation, or emission spectrum of a dye) may be considered “near” a referenced wavelength band (e.g., of an excitation or emission channel, spectral element, or filter) when the peak or maximum of the spectrum is within 15 nanometers of a minimum or maximum limit of the referenced wavelength band. As used herein, a peak or maximum of a spectrum (e.g., an absorption, excitation, or emission spectrum of a dye) may be considered “nearest” or “closest” to a referenced wavelength band belonging to a set of available wavelength bands (e.g., the wavelength bands of a set of excitation or emission channels, spectral elements, or filters) when the integrated value of the spectrum over the referenced wavelength band is greater than the integrated value of the spectrum over any of other wavelength band of the set of available wavelength bands.
As used herein a “radiant generator” or “generator” means a source capable of producing electromagnetic radiation. The radiant generator may comprise a single source of light, for example, an incandescent lamp, a gas discharge lamp (e.g., Halogen lamp, Xenon lamp, Argon lamp, Krypton lamp, etc.), a light emitting diode (LED), a white light LED, an organic LED (OLED), a laser (e.g., chemical laser, excimer laser, semiconductor laser, solid state laser, Helium Neon laser, Argon laser, dye laser, diode laser, diode pumped laser, fiber laser, pulsed laser, continuous laser), or the like. Alternatively, the radiant generator may comprise a plurality of individual radiant generators (e.g., a plurality of LEDs or lasers) each configured to produce a different wavelength range or band that may be non-overlapping or partially overlapping with the other individual radiant generators. The radiant generator may be characterized by electromagnetic radiation that is primarily within the visible light range (e.g., a “light source” emitting electromagnetic radiation within a wavelength in the range of 400 nanometers to 700 nanometers or in the range of 380 nanometers and 800 nanometers), near infrared range, infrared range, ultraviolet range, or other ranges within the electromagnetic spectrum. The radiant generator may provide continuous or pulsed illumination, and may comprise either a single beam or a plurality of beams that are spatially and/or temporally separated.
Referring to
Each emission spectral element 121a, 121b may be further characterized by wavelength band or range. The wavelength band or range of emission spectral elements 121a, 121b may be selected so that the wavelength band or range of emission spectral elements 121a does not overlap, or only partially overlaps, that of emission spectral element 121b. When the first target molecule and/or second target molecules are present in sample 110, emissions from corresponding first and/or second dyes are directed from sample 110 to detector 115 along an emission optical path 126. Emission spectral elements 121a, 121b may comprise respective filters passing or reflecting a wavelength band suitable for detecting and/or measuring a respective dye.
System 1000 may be configured to perform an amplification assay on sample 110. Optionally, the amplification assay may be performed on a separate system and further processed and/or examined using system 1000. System 1000 may also comprise at least one computer or processor 130 comprising at least one memory (not shown) including instructions to perform an amplification assay on sample 110. During and/or after the amplification assay, system 1000 is configured to illuminate sample 110 using radiant source 101a and to detect and/or measure emissions from any target molecules present using detector 115 in combination with emission spectral elements 121a, 121b. The memory associated with processor 130 may include instructions to, at least once during or after an amplification assay, illuminate sample 110 with first radiant source 101a and, in response, (1) to measure emissions from sample 110 using detector 115 and emission spectral element 121a and (2) to measure emissions from sample 110 using detector 115 and second emission spectral element 121b. As discussed in further detail below, the memory may comprise instructions to determine an amount of any target molecule present in sample 110, for example, by correlating measured emissions from sample 110 using first and second emission spectral elements 121a, 121b with an amount of the first and second target molecules, respectively.
Referring to
System 2000 may be configured to perform an amplification assay on sample 110. Optionally, the amplification assay may be performed on a separate system and subsequently processed and/or examined using system 2000. During and/or after the amplification assay, system 2000 is configured to illuminate sample 110 using radiant sources 101a, 101b and to detect and/or measure emissions from any target molecules present using detector 115 in combination with first emission spectral element 121a, when present. The memory associated with processor 130 in system 2000 may include instructions to perform an amplification assay on sample 110. The memory associated with processor 130 may include instructions to, at least once during or after an amplification assay, (1) illuminate sample 110 with first radiant source 101a and, in response, measure emissions from sample 110 using detector 115 and, optionally, first emission spectral element 121a and (2) illuminate sample 110 with second radiant source 101b and, in response, measure emissions from sample 110 using detector 115 and, optionally, first emission spectral element 121a. As discussed in further detail below, the memory may further comprise instructions to determine an amount of the first target molecule and/or an amount of the second target molecule when present in sample 110, for example, by correlating measured emissions from sample 110 when illuminating with first and second radiant sources 101a, 101b with an amount of the first and second target molecules, respectively. Where applicable, system 2000 may incorporate any of the elements or features discussed above herein regarding system 1000. Where applicable, processor 130 and associated memory of system 2000 may incorporate any of the elements or features of the processor 130 discussed above herein regarding system 1000.
With further reference to
System 3000 may be configured to perform an amplification assay on sample 110. Optionally, the amplification assay may be performed on a separate system and further processed and/or examined using system 3000. During and/or after the amplification assay, system 1000 is configured to illuminate sample 110 using radiant sources 101a, 101b and to detect and/or measure emissions from any target molecules present using detector 115 in combination with emission spectral elements 121a, 121b. System 3000 may be configured to perform an amplification assay on sample 110. Optionally, the amplification assay may be performed on a separate system and further processed and/or examined using system 3000. During and/or after the amplification assay, system 3000 is configured to, at least once during or after the amplification assay, (1) illuminate sample 110 at least once with first radiant source 101a and, in response, detect or measure emissions from sample 110 using detector 115 and first emission spectral element 121a and detect or measure emissions from sample 110 using detector 115 and second emission spectral element 121b and (2) illuminate sample 110 with second radiant source 101b and, in response, detect or measure emissions from sample 110 using detector 115 and second emission spectral element 121b. As discussed in further detail below, the memory may comprise instructions to determine an amount of the first target molecule, the second target molecule, and/or the third target molecule when present in sample 110, for example, by correlating measured emissions from sample 110 when illuminating with first or second radiant sources 101a, 101b with an amount of the first, second, and third target molecules, respectively.
Where applicable, system 3000 may incorporate any of the elements or features discussed above herein regarding systems 1000, 2000. Where applicable, processor 130 of system 3000 may incorporate any of the elements or features of the processor 130 and associated memory discussed above herein regarding systems 1000, 2000. The embodiments of spectral elements 121a, 121b, 141a, 141b and sources 101a, 101b discussed above in relation to
In certain embodiments, any of systems 1000, 2000, or 3000 may comprise at least one beam steering optical element 135 that steers or fold radiation from radiant sources 101a, 101b to sample 110. Alternatively, any of systems 1000, 2000, 3000 may be configured so that emissions from sample 110 are steered or directed to detector 115 using at least one beam steering optical element 135. Using that beam steering optical element 135, excitation and emission optical paths 125, 126 may comprise a common path portion where optical paths 125, 126 overlap from beam steering optical element 135 to sample 110. In other embodiments, excitation and emission optical paths 125, 126 do not overlap or have a common path portion except at sample 110. For example, emission beam optical path 126 may disposed normal or perpendicular to surface of sample holder 112, while excitation optical path 125 may be disposed at an off-axis angle from the surface that is not normal or perpendicular to the surface of sample holder 112. Systems 1000, 2000, 3000 may additionally or alternatively incorporate other optical configurations known in the art. For example, rather than in the reflective arrangement shown in
Referring to
System 4000 further comprises detector 115 and a plurality of emission spectral elements 421 (421a-421f in the illustrated embodiment) for use in combination with radiant sources 421a-f. Sample 110 may comprise three dyes associated with three target molecules, as discussed regarding system 3000. Because of the additional number radiant sources 401 and emission spectral elements 421, system 4000 is configured to detect and/or measure more than three dyes. Using six radiant sources 401 and six associated emission spectral elements 421, prior art systems are only able to detect and deconvolve at most six dyes to determine amounts of at most six corresponding target molecules. As discussed in further detail below herein, system 4000 is configured to detect and deconvolve more than six dyes so as to determine amounts of more than six corresponding target molecules. In certain embodiments, system 4000 may include a field lens 445 or other optical elements suitable for conditioning radiation from radiant generator 132 and/or emissions from sample 112.
While
Where applicable, the elements or components of system 4000 may take the form of embodiments of any corresponding element discussed above regarding any of systems 1000, 2000, 3000. For example, the radiant generator 132, sample 110, sample holder 112, and processor(s) 130 and associated memory(ies) may take the form of those same elements or components discussed above with regard to any of systems 1000, 2000, 3000. Any or all of excitation spectral elements 441 may take the form of any of the embodiments discussed above regarding excitation spectral element 141a or excitation spectral element 141b. Any or all emission spectral elements 421 may take the form of any of the embodiments discussed above regarding emission spectral element 121a or excitation spectral element 121b. Any or all radiant sources 401a-f may take the form of any of the embodiments discussed above regarding radiant source 101a or radiant source 101b.
Systems 1000, 2000, 3000, 4000 may incorporate other lenses, filters, mirror, prisms, diffractive optical element, or the like, that known in the biological instruments and systems art. In certain embodiments, further lenses or other imaging optical elements may be included along the excitation and emission optical paths of systems 1000, 2000, 3000, 4000 (e.g., optical paths 125, 126). For example, a field lens may be located proximal sample holder 112 (e.g., field lens 445 shown proximal sample holder 112 in
Optical element 123 or any other imaging optical elements along the excitation and/or emission optical paths of systems 1000, 2000, 3000, 4000 may comprise one or more of a refractive lens, a mirror, a diffractive or holographic optical element, or the like. One or more of spectral elements 121, 141, 421, 441 may comprise one or more of a colored substrate, a dichroic element such as a filter, mirror, or beamsplitter, or a dispersive optical element such as a prism, diffractive grating, or holographic grating. For any of the systems 1000, 2000, 3000, 4000, detector 115 may comprise may comprise one or more individual photodetectors including, but not limited to, photodiodes, photomultiplier tubes, bolometers, cryogenic detectors, quantum dots, light emitting diodes (LEDs), semiconductor detectors, HgCdTe detectors, or the like. Additionally or alternatively, detector 115 may comprise an array sensor including an array of sensors or pixels. The array sensor may comprise one or more of a complementary metal-oxide-semiconductor sensor (CMOS), a charge-coupled device (CCD) sensor, a plurality of photodiodes detectors, a plurality of photomultiplier tubes, or the like. In certain embodiments, detector 115 comprises two or more array sensors.
System 4000 may include a plurality of beam steering optical elements 435 to direct excitation beams along excitation optical path from radiant generator 132 to sample 110 and/or to direct emissions along an emission optical path from sample 110 to detector 115. In the illustrated embodiment, each excitation spectral element 441 if coupled on a rotation 449. Beam steering optical elements 135, 435 may take the form of any of the embodiments discussed above regarding beam steering optical elements 135 discussed above regarding systems 1000, 2000, 3000. In the illustrated embodiment shown in
Spectral elements 121 (e.g., 121a, 121b), 141 (e.g., 141a, 141b), 421 (e.g., 421a-f), 441 (e.g., 441a-f) illustrated in
Any of radiant sources 101 (e.g., 101a and/or 101b), 401 illustrated in
Sample holder 112 in systems 1000, 2000, 3000, 4000 may comprise a plate or surface in which sample 110 is disposed on sample holder 112 or disposed within sample holder 112, for example, within a sample well, through-hole, or surface region. In embodiments, sample 110 comprises a plurality of spatially separated sample portions, for example, a sample solution separated into a plurality of spatially separated sample sites such as a plurality of sample wells, through-holes, or surface regions. Each sample portion may contain an identical, or substantially identical, amount of one or more target molecules, may contain different amounts or types of one or more target molecules, or contain no target molecules (e.g., dPCR sample portions). Sample holder 112 may comprise a strip or microtiter plate (e.g., a strip of 4, 6, or 8 wells or a microtiter plate comprising 24 wells, 48 well, 96 wells, 384 wells, 1536 wells, or 3456 wells). Alternatively, sample holder 112 may comprises a card or plate comprising an array of reaction sites or chambers that each contain a portion of sample 110 (e.g., a card or plate comprising 384 or 9,216 sample chambers or reaction sites). In some embodiments, sample holder 112 comprises a plate or chip including an array of spatially separated through-holes that each contain a portion of sample 110 (e.g., a through-hole plate or chip containing 3,072 through-holes, 20,000 through-holes, 50,000 through-holes, 100,000 through-holes, or more than 100,000 through-holes). In certain embodiments, sample holder 112 comprises a tube, channel, or capillary comprising a plurality of sample droplets or slugs containing a portion of sample 110 and, optionally, an immiscible fluid or oil disposed between the droplets. Each droplet or slug may contain an identical, or substantially identical, amount of one or more target molecules, may contain different amounts or types of one or more target molecules, or contain no target molecules (e.g., dPCR sample droplets or slug).
Where applicable, processor 130 and associated memory of system 4000 may incorporate any of the elements or features of the processor 130 discussed above herein regarding systems 1000, 2000, 3000. In the illustrated embodiment shown in
In certain embodiments, any of systems 1000, 2000, 3000, 4000 may comprise a single system or instrument having one or more processors 130 and associated memory containing instructions discussed above herein for the respective system. Alternatively, any of systems 1000, 2000, 3000, 4000 may comprise a second system or instrument configured to perform one or more of these tasks. In such embodiments, systems 1000, 2000, 3000, 4000 may comprise two or more systems or instruments that each perform some of these tasks. Each such system or instrument may have its own processor and/or memory or, alternatively, share a common processor and/or memory, for example using a centralized storage system, such as a cloud storage system, and/or a centralized processor or processor system, such as a cloud computing processor or system.
Systems 1000, 2000, 3000, 4000 may be an end-point system or instrument configured to provide measure emissions from one or more dyes in sample 110 after the conclusion of an amplification assay, such as a PCR assay (e.g., a qPCR or dPCR system or instrument or a system or instrument configured to perform a melt assay). Referring to
Referring to
Each entry in the row labeled “Em” is an emission “channel” of system 4000, where each Em or emission channel represents emissions (e.g., fluorescent emissions) from sample 110 that are received by detector 115 after being transmitted, reflected, and/or diffracted by a respective one of the emission spectral elements 421 (e.g., 421a-f). The number shown for each emission channel is an average or central emission wavelength for a respective one of emission spectral element 421. The wavelength band for each emission channel is indicated by a “±” numerical value in nanometers about the average or central transmission wavelength for that emission or Em channel (e.g., the wavelength band of emission or Em channel m1 in the illustrated embodiment is 520±15 nanometers, or 505 nanometers to 535 nanometers). In certain embodiments, the selection of the average or central emission wavelength may be vary from that shown in
The remaining elements to the right of the Ex column and below the Em role in
The excitation/emission channel combinations labeled A1-A6 may be referred to as “on-axis channels” or “on-axis channel combinations”, where dyes having a corresponding maximum excitation wavelength and maximum emission wavelength may be referred to as “on-axis dyes”. All other excitation/emission channels combinations that are not on-axis channels in
As used herein, an “on-axis channel combination” or “on-axis ex-em channel pair” is a pair of ex-em channels in which an average or central wavelength of the Em channel is shifted by an amount that is less than or equal to 60 nanometers from the corresponding Ex channel. Alternatively, for a set of Ex and Em channels, an “on-axis channel combination” or “on-axis ex-em channel pair” comprises a given Ex channel and the Em channel that has the smallest average or central wavelength shift from average or central wavelength of the given Ex channel. Under these definitions, an “off-axis channel combination” or “off-axis ex-em channel pair” is any pair of ex-em channels that is not an “on-axis channel combination” or “on-axis ex-em channel pair”.
Unless otherwise noted, as used herein in the context of a system or instrument comprising one or more on-axis/off-axis channel combinations and one or more on-axis/off-axis ex-em channel combinations, an “off-axis dye” is defined as a dye having a first maximum absorption or excitation wavelength that is an absolute maximum over an entire spectrum of the dye and having a second maximum absorption or excitation wavelengths that is a local maximum and is separated from the first maximum absorption or excitation wavelength by at least 60 nanometers (e.g., see
Some on-axis dyes may be a “broadened dye”. As used herein, a “broadened dye” is defined as an on-axis dye having a first maximum absorption or excitation wavelength that is an absolute maximum over an entire spectrum of the dye and having a second maximum absorption or excitation wavelengths that is a local maximum and is separated from the first maximum absorption or excitation wavelength by less than 60 nanometers. A broadened dye may be used in combination with another on-axis dyes to increase the number of dyes that can be detected or measured using a combination of on-axis and off-axis channel combinations. For example, a first, on-axis dye may be selected that produces a maximum signal using an on-axis channel combination (e.g., the A1 channel combination) and used in combination with second, broadened dye that produces a higher signal in an adjacent off-axis channel combination (e.g. the B12 channel combination) than that produced by the first dye for an equal concentration of both dyes.
In certain embodiments, an “off-axis dye” is comprises a “big dye” or “energy transfer dye conjugate”, where the off-axis dye comprises two “on-axis dyes”: a “donor dye” and an “acceptor dye” (e.g., see U.S. Pat. No. 5,800,996, herein incorporated by reference in its entirety) covalently attached via a linker. This definition of an off-axis dye may be irrespective of the amount of shift between any pair of local maximum absorption or excitation wavelengths. The donor dye and the acceptor dye are linked by linker, wherein the donor dye is a dye capable of absorbing light at a first wavelength to produce excitation energy and the acceptor dye is dye which is capable of absorbing at least a portion of the excitation energy produced by the donor dye and, in response, fluorescing at a second wavelength that is equal to or substantially equal to a maximum emission wavelength of the acceptor dye by itself (i.e., when not linked to the donor dye).
In certain embodiments, a pair of dyes may be considered an “on-axis dye” or an “off-axis dye” in terms of their spectral characteristic as compared to one another. For example, a first dye within a sample may be considered an “on-axis dye” and a second dye may be considered an “off-axis dye” when the first and second dyes have the same or nearly the same maximum absorption or excitation wavelength (e.g., absorption or excitation maximums that are within 5 nanometers of one another or absorb a maximum amount of radiations from a common excitation channel of an instrument or system), but a maximum emission wavelength of the second dye that is at least 50 nanometers greater than that of the first dye (e.g., referring to
In the case of six excitation channels and six corresponding emission channels, as shown in
The combination of six excitation channels x1-x6 and six emission channels m1-m6 shown in
The inventors have identified various combinations of dyes for which it is possible to detect and/or quantify amounts of one or more off-axis dye and, as a consequence, detect and/or quantify amounts target nucleic acids associated with respective ones of the on-axis/off-axis dyes. Various methods and dye combinations including at least one off-axis dye will now be discussed for identifying three dyes, five dyes, and ten dyes in a sample or in each sample of an array of samples.
Referring to
Systems 2000, 3000, 4000, or 5000 may be used to perform method 700, in which case the radiant sources may be any of those discussed herein with regard to radiant sources 101, 401, for example, radiant generator 132 in combination with excitation spectral elements 141 or 441. The first and second emission measurements from the sample may be made using one or more detectors 115 in combination with emission spectral elements 121 or 421. Referring to element 710, the assay may be a PCR assay such as a qPCR assay, a dPCR assay, a post PCR assay such as melt curve analysis, or the like.
Using method 700 the amounts of the A3 and B13 may be determined using the excitation channels x1, x3 and emission channel m3 (i.e., channel combinations x1/m3 and x3/m3). Method 700 may also be used with other two dye combinations, such as disclosed herein or otherwise, that have a common or similar maximum emission wavelength (e.g., maximum emission wavelengths that are equal to one another, are within ±1 nanometer of one another, within ±2 nanometers of one another, within ±5 nanometers of one another, or within ±10 nanometers of one another) and with other ex-em channel combinations having spectral bandwidths that contains or is near to the maximum excitation and emission wavelengths of the two dyes. In the current example, the off-axis dye B13 comprises a maximum emission wavelength that is equal to or substantially equal to the maximum emission wavelength of the on-axis dye A3. In some embodiments, the dyes may comprise maximum emission wavelengths that are within 2 nanometers of one another, within 5 nanometers of one another, within 10 nanometers of one another, or within 15 nanometers of one another. In embodiments with more complex sample mixtures having more than two dyes, the selection of the emission channel m3 is selected such that the integrated energy of either or both of the two target dyes over the m3 channel bandwidth is greater than that of any other dyes within the sample solution when illuminated by the x1 channel and/or x3 channel.
Referring to the nominal absorption plot shown in
The illustrated ex-em space for the A1 and B13 dyes in the current example are for a sample containing equivalent amounts of these dyes and using an instrument configured like system 4000 and the selected ex-em channel bandwidths shown. The detected signals for the first and second emission measurements in method 700 are values labeled “Total” in
Referring to elements 720, 730, 735 and with reference to
In certain embodiments, the adjusted second measurement can be used to provide an adjusted first measurement, since the contribution of the dye A3 signal in the x1-m3 channel can now be approximated and subtracted from the first measurement. Further iterations can also be implemented to, for example, provide a further adjusted second measurement based on the adjusted first measurement. In other embodiments, the method 700 may be modified to incorporate a system of equations that are simultaneously solved to determine or measure amounts of the A3 and B13 dyes and the associated target molecules. In any of these embodiments of the method 700, ex-em space data (
The following paragraphs explain advantages of the current teachings in terms of plots shown in
However, these correlations are not exact. For example, the A1 dye has a small but measurable amount of emission in the m3 emission channel, which therefore can reduce the correlation to the A3 dye. This type of unwanted signal contribution is referred to as “cross-talk” or “signal interference”. While the cross-talk is relatively small in the present example, it can be more significant when there are more than two on-axis dyes in a sample (e.g., A1, A2, and A4, or A1, A2, A3, and A4) and/or when, for a particular assay, there is a large amount of one target molecule and much less of another target molecule. These effects may be minimized by proper assay design, the use of calibration plates, and deconvolution algorithms for processing the raw emission data from each channel. The use of various off-axis channel combinations may also be used to enhance deconvolution, and thus improve the accuracy.
To compensate and/or correct for signal interference or cross-talk and other such effects, calibration plates may be used. A calibration plate contains known amounts multiple dyes. Thus, when illuminated with radiation from one or more excitation channels, the resulting fluorescent signal from each dye can be determined and the system can be corrected for cross-talk between the dyes under various illumination conditions. The calibration plate may comprise the known dye combinations in one or more reaction sites (e.g., the wells or vials of a 96 or 384 well microtiter plate), which correspond to one or more reaction sites of a test plate containing unknown amounts of a combination of target molecules. One commercially available example of a calibration plate is the Thermo Fisher calibration plate A26337. The A26337 establishes a pure dye spectra and multicomponent values for ABY™ JUN™ and MUSTANG PURPLE™ dyes on Applied Biosystems's QuantStudio™ 3 and 5, 96-well 0.1-mL real-time PCR systems. The formulations of the dyes in this plate improve results with multiplexing by more accurately representing the fluorescent spectra of the respective probes in your real-time PCR experiments.
The inventors have discovered that the off-axis channels may be used not only to improve deconvolution algorithms to improve the accuracy of multiple on-axis dyes, but that added information from these off-axis channels can be used to include additional, off-axis dyes into a sample, without the need to increase the number of excitation or emission channel. For example, six on-axis dyes may be identified in a sample using the six Ex channels x1-x6 and the six Em channels m1-m6 discussed herein. In order to increase the number of on-axis dyes that may be detected beyond six, additional Ex and Em channels would be needed using prior art techniques. Not only does this increase system costs and complexity, but there may be technical issues that, for example, make it difficult to increase the number of wavelength bands that can be provided utilizing optical components that are suitable for operation within the visible wavelength band.
The inventors have discovered that additional off-axis dyes may be included in sample 110 to increase the number of dyes and corresponding target molecules that can be measured with the same set of excitation and emission channels. This result was unexpected, since the introduction of additional off-axis dyes increases the problem of cross-talk discussed above in regard to multiplexing multiple on-axis dyes in the same sample. To appreciate, reference is again made to
However, it has been discovered that the data from both the on-axis and off-axis channel combinations can be used to help mitigate such problems. For example, in the present case, the B13 channel combination may be used to help determine the amount dye B13 present in the sample 110. With this information, the contribution of dye B13 to the signal in the A3 channel combination may be calculated and used to modify the m3 signal to determine the amount of dye A3. This can be explained as follows. As seen in the absorption plot in
Referring to
Systems 2000, 3000, 4000, or 5000 may be used to perform method 1100, in which case the radiant sources may be any of those discussed herein with regard to radiant sources 101 or 401, for example, radiant generator 132 in combination with excitation spectral elements 141 or 441. The emission measurements from the sample may be made using one or more detectors 115 in combination with, respectively, emission spectral elements 101a, 101b or two of the emission spectral elements 421a-f. Referring to element 1110, the assay may be a PCR assay such as a qPCR assay, a dPCR assay, a post PCR assay such as melt curve analysis, or the like. Where appropriate, any aspects of method 700 discussed above herein may also apply to method 1100, for example, regarding dyes, radiant sources, and/or emission filtering characteristics or methods of use.
Using method 1100 the amounts of the A1, A3 and B13 may be determined using the excitation channels x1, x3 and emission channels x1, m3 (i.e., channel combinations x1/m3, x1/m1, and x3/m3). Method 1100 may also be used with other three dye combinations, such as disclosed herein or otherwise, where one of the on-axis dyes has a common or similar maximum emission wavelength with the off-axis dye and the other on-axis dye has a common or similar maximum excitation wavelength with the off-axis dye. Method 1100 may also be used with other ex-em channel combinations having a spectral bandwidth that contain or are near to the maximum emission and excoriation wavelengths of the three dyes. In the current example, the off-axis dye B13 comprises a maximum emission wavelength that is equal to or substantially equal to the maximum emission wavelength of the on-axis dye A3. Additionally, the off-axis dye B13 comprises a maximum excitation wavelength that is equal to or substantially equal to the maximum emission wavelength of the on-axis dye A1. In some embodiments, the dyes may comprise maximum emission wavelengths that are within 2 nanometers of one another, within 5 nanometers of one another, within 10 nanometers of one another, or within 15 nanometers of one another. In embodiments with more complex sample mixtures having more than three dyes, the selection of the emission channel m1 and m3 are selected such that the integrated energy of the three target dyes over each of the x1, x3, m1, and m3 channel bandwidths is greater than that of any other dyes within the sample when illuminated by the x1 channel and/or x3 channel and/or emitting energy in the m1 and/or m3 channels.
Referring to the nominal absorption plot shown in
The illustrated ex-em space for the A1, A3, B13 dyes in the current example are for a sample containing equivalent amounts of these dyes and using an instrument configured like system 4000 and the selected ex-em channel bandwidths shown. The detected signals for the first, second, and third measurements in method 1100 are values labeled “Total” in
Referring to elements 1120, 1130, 1135, 1140 and to the ex-em space plots in
In similar fashion, the contribution to the total signal in the third emission measurement (channel combination x3-m3) includes significant emission signals from off-axis dye, B13, as well as from on-axis dye, A3; however, the adjusted second emission measurement (channel combination x1-m3) provides a good estimate of the amount of B13 dye present in the sample. Based on the estimated amount of B13 from the adjusted second emission measurement, the contribution of dye B13 to the third measurement (total x3-m3 signal) can be estimated, since the spectral characteristic of the dyes are known from the ex-em data shown in
In certain embodiments, the adjusted second measurement and/or the adjusted third measurement can be used to provide an adjusted first measurement, since the contribution of the B13 dye signal and the A3 dye signal in the x1-m1 channel can now be approximated and subtracted from the first measurement (since these spectral characteristics of these dyes in any emission channel can be determined from the data in
Referring to element 1150, in certain embodiments, the first and second dyes are associated with and/or configured to bind or attach to different target molecules, such as first and second target polynucleotides, first and second proteins, or the like.
Referring to again to
Referring to again to
In various embodiments, method 700 or method 1100 may further comprises performing an amplification assay on sample 110 using any of systems 1000, 2000, 3000, 4000, 5000. In such embodiments, method 700, 1100 may be performed using the various embodiments discussed herein for these systems. Embodiments of method 700, 1100 may include performing elements 715-70, 1115-1130 either during the amplification assay. For example, the amplification assay may be a real-time polymerase chain reaction (qPCR) assay in which sample 110 heated and cool over various cycles using a thermal cycler. At one or more points during one or more of the cycles, any or all of elements 715-70, 1115-1130 may be performed on sample 110. Additionally or alternatively, method 700, 1100 may be performed after the conclusion of PCR or other amplification assay. For example, after the last cycle of a PCR assay, during a melt assay after an amplification assay, or digital PCR (dPCR) assessment after an amplification assay.
Referring to
As seen in
Comparing
The inventors have found that for more complex samples having ten or more dyes (e.g., combinations six on-axis dyes and four off-axis dyes from Table 2) and their associated target molecules, the unique ex-em space signature or fingerprint of each dye in the ex-em space can be utilized to multiplex all the on-axis/off-axis dyes simultaneously in a common sample.
The inventors have found that for assays including both on-axis and off-axis dyes (e.g., the 8 dyes shown in
Systems 4000 and/or 5000 may be used to perform methods discussed here for 10-plex sample assays of conducting a multiplex assay on a sample containing three on-axis dyes and two off-axis dyes and to analyze the resulting data to simultaneously determine or measure the amounts of ten or more dyes and their associated target molecules. In certain embodiments, such 10-plex or higher-plex assays comprise a PCR assay such as a qPCR assay, a dPCR assay, a post PCR assay such as melt curve analysis, or the like.
Referring to
The inventors have discovered that the unique signature or fingerprint of off-axis dyes, as discussed above herein, may be used increase the accuracy of measuring or calculating amounts of various dyes in a sample and/or their associated target molecules in assays in which one or more dyes produce a fluorescence signal exceeding a background fluorescence in fewer cycles than other dyes within the same sample (e.g., where one or more dyes have a lower threshold cycle, Ct, or crossing point, Cp). It will be recalled that the ex-em space plots shown in
For example, referring to
Fluorescein donor dyes were synthesized according to the general procedure in Scheme 1 shown for 2,7-difluoro-sulfo-fluorescein 3. A resorcinol derivative, such as 1, is heated with a 2-sulfo-terephthalic acid derivative, such as 2, in methanesulfonic acid and isolated by normal phase chromatography. The fluorescein dye is O-protected, such as shown for conversion of Dye 3 to t-BOC protected Dye 4, and converted to the corresponding NHS ester 5 by standard procedures.
A mixture of 4-fluororesorcinol (1, 490 mg, 3.825 mmol) and 2-sulfo-terephthalic acid sodium salt (2, 513 mg, 1.913 mmol) in methanesulfonic acid (5 mL) was heated at 110° C. for 6 h. The reaction mixture was cooled to room temperature and stirring was continued for 3 days. Ice-H2O (100 mL) was added and the resulting suspension was filtered. The filter cake was washed with portions of ice-H2O and then was suspended in 5 mL of MeOH. The suspension was diluted with 50 mL of Et2O and filtered. The solid product was washed with Et2O and dried in vacuo to give 555 mg (65%) of 3 as a yellowish solid.
F-Dye 1 (3, 184 mg, 0.410 mmol) was suspended in 10 mL of MeCN and treated with diisopropylethylamine (0.644 mL) and di-t-butyl dicarbonate (537 mg, 2.46 mmol) at room temperature for 3 days. H2O (0.5 mL) was added and stirring was continued for 30 min. The reaction mixture was loaded directly onto a silica (Iatrobeads 6RS-8060) column (2×22 cm) and the column was eluted with 10% to 30% MeOH/DCM. Evaporation of the appropriate fractions gave 216 mg (65%) of 4 as brown foam.
A mixture of 4 (210 mg, 0.260 mmol), N-hydroxysuccinimide (150 mg, 1.3 mmol), and dicyclohexylcarbodiimide (107 mg, 0.52 mmol) in DCM (5 mL) was stirred at room temperature for 3 h. The reaction was quenched with H2O (0.1 mL) and stirred for additional 15 min. The resulting suspension was filtered and the filtrate was loaded directly onto a silica (Iatrobeads 6RS-8060) column (2×15 cm). The column was eluted with 1:0:20:80 to 1:30:20:50 AcOH/MeOH/EtOAc/DCM. The fractions containing the desired product were evaporated to give 185 mg (92%) of 5 as brown foam.
By employing the general procedure of Example 1 for synthesis of sulfo-fluorescein 3 from the fluororesorcinol 1, resorcinol 6 and the pyridyl resorcinol (U.S. Pat. No. 6,221,604) 7, were used to make the corresponding sulfo-fluorescein dyes 8 and 9, as shown in Scheme 2 from sulfo-terphthalate 2.
Compound 9 is excitable at 520 nm and emits at 544 nm due to the presence of the pyridyl substituents, making this dye compatible for use in the X2/m2 (green) channel of a real-time PCR instrument. The structures of sulfo FAM and pyridyl FAM products were confirmed by MS analysis (data not shown)
Dichloro sulfoterephalate 13 was synthesized and used to make the sulfo-fluorescein 15, as shown in Scheme 3, employing the general procedure of Example 1 for synthesis of sulfo-fluorescein 3. The dye 15 was O-protected and converted to the NHS ester 17.
To 17.5 g (0.1 mol) of 2,5-dichloro-p-xylene 10, was added 53.2 mL (0.8 mol) of chlorosulfuric acid. The reaction mixture was stirred at room temperature for 3 days and then diluted with 350 mL of DCM. The DCM solution was added very slowly to 350 g of ice and stirred for 1 h. The mixture was transferred to a separatory funnel and the organic layer was separated, dried (Na2SO4), evaporated, and dried in vacuo to give 25.56 g (93%) of 11 as white solid. 1H NMR (CDCl3) □ 7.63 (s, 1, 4-H), 2.84, 2.46 (2×s, 6, 2×CH3). MS (ion trap MS) m/z 273.0 (calcd. MH+=272.9).
To a solution of 15.307 g (60 mmol) of 11 in 200 mL of MeOH, was added slowly 75 mL (150 mmol) of 2 N LiOH. The reaction mixture was stirred at room temperature for 18 h. MeOH was removed by evaporation and the resulting suspension of the product in H2O was filtered. The filter cake was washed with 20 mL of cold H2O and then air-dried to give 14.5 g of 12 as a white crystalline compound. A second crop of product was isolated from the filtrate. The total yield of 3× was 15.24 g (97%). 1H NMR (CD3OD) □ 7.42 (s, 1, 4-H), 2.76, 2.38 (2×s, 6, 2×CH3). MS m/e 253.0 (calcd. [M-Li]−=253.0).
To a solution of 25.286 g (160 mmol) of KMnO4 in 400 mL of H2O, was added 5.221 g (20 mmol) of 12. The reaction mixture was stirred and heated at gentle reflux for 22 h. Excess KMnO4 was destroyed by slow addition of 100 mL of MeOH while maintaining refluxing and stirring for 30 min. The reaction mixture was filtered while hot. The filter cake was again suspended in a mixture of H2O/MeOH (200 mL/50 mL), heated to boil and filtered while hot. The combined filtrate was evaporated to dryness and re-dissolved in 50 mL of H2O. The H2O solution was filtered and the filtrate was evaporated. The residue was purified on a Dowex 50W-X8 H+ column (4×34 cm, 450 mL of resin, eluted with 350 mL of H2O). Evaporation of the H2O solution gave 4.6 g (73%) of 13 as white solid. 1H NMR (CD3OD) □ 7.80 (s, 1, 6-H). MS m/e 313.0 (calcd. [M-H]−=312.9).
A mixture of 473 mg (1.5 mmol) of 13 and 561 mg of pyrido-resorcinol 14 in 6 mL of MeSO3H was stirred at 170° C.-180° C. for 28 h., then cooled to room temperature, and precipitated in 160 mL of Et2O. The solid was collected by centrifugation and then re-dissolved in 30 mL of H2O. The pH value of the H2O solution was adjusted to ˜5 with 20% NaOH. The resulting suspension was centrifuged and the supernatant was decanted. The solid was re-suspended in 30 mL of water, sonicated, centrifuged and the H2O washing process was repeated one more time. The crude solid product was re-suspended in 20 mL of MeoH, sonicated, diluted with 40 mL of EtOAc, vortexed, and centrifuged. The solid product was air-dried, then dried in vacuo to give 502 mg (53%) of 15 as dark red solid. 1H NMR (CD3OD) □ 8.73 (d, 2), 8.46 (dd, 2), 7.96 (m, 2), 7.64 (s, 1), 7.45 (m, 2), 7.17 (s, 2), 6.84 (s, 2). MS m/z 635.0 (calcd. [MH]+=635.0).
A mixture of 64 mg (0.1 mmol) of 15 and 46 mg (0.2 mmol) of Ph2NCOCl in 6 mL of pyridine was stirred at room temperature for 2 h. H2O (0.1 mL) was added and stirring was continued for 1 h. Volatile materials were removed by evaporation and co-evaporation with 1:50:50 i-Pr2Net/DCM/PhCH3 (2×). The residue was dissolved in 10% MeOH/DCM (25 mL) and washed with H2O (25 mL). The H2O solution was extracted with 10% MeOH/DCM (25 mL×4). The organic layer and extracts were combined and evaporated. The residue was purified by silica (Iatrobeads 6RS-8060 from Shell-USA) column chromatography using 0-20% H2O/MeCN as eluant. Evaporation of the appropriate fractions gave 39 mg (47%) of 16. MS m/z 830.0 (calcd. [MH]+=830.0).
To a solution of 39 mg (0.047 mmol) of 16 and 27 mg (0.235 mmol) of N-hydroxysuccinimide (NHS) in 1.5 mL of DCM, was added 19 mg (0.094 mmol) of dicyclohexylcarbodiimide (DCC). The reaction mixture was stirred at room temperature for 3 h and then quenched with 10% HCl (0.1 mL). Volatile materials were removed by evaporation and the residue was dissolved in 5% MeOH/DCM (5 mL) and purified by silica (Iatrobeads 6RS-8060 from Shell-USA) column chromatography using a gradient (1:5:95-1:30:70) of AcOH/MeOH/DCM as eluant. Evaporation of the appropriate fractions gave 31 mg (71%) 17.
A synthetic approach to prepare an L1 type energy transfer linker 24 (referred to herein as a “Y-linker”) is outlined below in Scheme 4. Bromination of methyl 2,5-dimethylbenzoate 18 with N-bromosuccinimide gave the dibromide 19. Subsequent treatment of 19 with sodium azide was followed by saponification of the intermediate diazide 20. The resulting acid 21 was activated with N,N,N′,N′-tetramethyl-O—(N-succinimidyl)uronium tetrafluoroborate (TSTU) and then quenched with a large excess of 2,2′-(ethylenedioxy)bis(ethylamine) to afford the amine derivative 22. Further reaction of 22 with glutaric anhydride gave the carboxylic acid derivative 23, which was converted to the desired Y-linker 24 by hydrogenation in the presence of Raney-Nickel.
To a solution of 18 (11.5 g, 70 mmol) in carbon tetrachloride (100 mL), were added N-bromosuccinimide (23.7 g, 133.2 mmol) and benzoyl peroxide (1.7 g, 7 mmol). The reaction mixture was stirred at 80° C. for 6 h. It was cooled to room temperature and diluted with hexane (50 mL). The resulting suspension was filtered and the filtrate was evaporated. Fractional re-crystallization of the residue from hexane gave 6.7 g (31%) of 19 as a white crystalline compound.
A solution of 19 (6.7 g, 20.8 mmol) in DMF (40 mL) was treated with sodium azide (6.8 g, 104.0 mmol) at room temperature for 16 h. The reaction mixture was diluted with DCM (50 mL) and filtered. The filtrate was evaporated and the residue was re-dissolved in DCM (150 mL). The DCM solution was washed with H2O (100 mL), Brine solution (100 mL), dried (Na2SO4), and filtered. Evaporation of the filtrate and drying of the residue in vacuo gave 5.06 g (99%) of 20 as syrup.
To a solution of 20 (5.05 g, 20.5 mmol) in MeOH (80 mL) was added a solution of LiOH/H2O (1.72 g, 41.0 mmol). The reaction mixture was stirred at room temperature for 16 h and then was acidified with a solution of 10% HCl (14.8 mL). Volatile materials were removed by evaporation and the residue was dissolved in DCM (150 mL). The DCM solution was washed with H2O (100 mL), Brine solution (100 mL), dried (Na2SO4), and filtered. The filtrate was evaporated and the residue was re-crystallized from EtOAc/hexane to give 4.17 g (2 crops, 88%) of 21 as white crystalline needles.
A solution of 21 (929 mg, 4.0 mmol), diisopropylethylamine (1.394 mL, 8.0 mmol), and TSTU (1.806 g, 6.0 mmol) in DCM (20 mL) was stirred at room temperature for 1 h. This reaction mixture was then added slowly to a solution of 2,2′-(ethylenedioxy)bis(ethylamine)/DCM (2.929 mL/20 mL) and stirred for additional 3 h. DCM (100 mL) was added and the DCM solution was washed with brine solution (100 mL×2), dried (Na2SO4), and filtered. The filtrate was evaporated and the residue was purified on a silica (Iatrobeads 6RS-8060) column (2.5×17 cm) using 1:10:90 to 1:35:65 Et3N/MeOH/DCM as eluants. Evaporation of the appropriate fractions gave 1.15 g (79%) of 22 as syrup.
To a solution of 22 (1.142 g, 3.151 mmol) in DCM (15 mL), were added diisopropylethylamine (1.098 mL, 6.302 mmol) and glutaric anhydride (0.539 g, 4.727 mmol). The reaction mixture was stirred at room temperature for 17 h. H2O (0.2 mL) was added and stirring was continued for 15 min. Volatile materials were removed by evaporation and the residue was re-dissolved in DCM (120 mL). The DCM solution was washed with 0.1 N HCl (100 mL), dried (Na2SO4), and filtered. The filtrate was evaporated and the residue was purified on a silica (Iatrobeads 6RS-8060) column (2×20 cm) using 1:5:95 to 1:10:90 Et3N/MeOH/DCM as eluants. Evaporation of the appropriate fractions gave 1.43 g (95%) of 23 as syrup.
A suspension of 23 (300 mg, 0.630 mmol) and Raney-Nickel (— 200 mg, wet weight) in MeOH (15 mL) was stirred under H2 for 20 h. The reaction mixture was then filtered through Celite and the filtrate was evaporated. The residue was co-evaporated with MeOH and dried in vacuo to afford 260 mg (97%) of 24 as foam.
The synthesis of a dye linker intermediate follows in general the procedure outlined below in Scheme 5 for formation of t-BOC-protected Sulfo-FAM-ET-linker NETS ester 28. The ET-linker, such as 24, is coupled to the t-Boc-protected Dye NHS ester, such as 25, to give the Dye Linker intermediate, such as 26 as a mixture of regioisomers. After silica column purification, the pure regioisomer amino group could be protected with a trifluoroacetyl group for use in stepwise analyte labeling or used directly for labeling with the second Dye NHS to create the ET dye. To create the Dye-linker intermediate NHS, the free amino is protected, such as shown below with a TFA group, and the carboxylic acid group activated to give the t-Boc-Dye-ET-linker NHS ester 28.
To a mixture of linker (24, 130 mg, 0.306 mmol) and diisopropylethylamine (0.07 mL) in DCM (5 mL), was added t-Boc-Dye NHS ester (25, 148 mg, 0.2 mmol). The reaction mixture was stirred at room temperature for 2 h. Volatile materials were removed by evaporation and the residue was purified on a silica (Iatrobeads 6RS-8060) column (2×26 cm) using 5% to 20% H2O/MeCN as eluants. Evaporation of the appropriate fractions afforded 80 mg (44%) of 26 as regioisomers.
A mixture of 26 (77 mg, 0.084 mmol), diisopropylethylamine (0.2 mL), and ethyl trifluoroacetate (0.3 mL) in MeOH (3 mL) was stirred at room temperature for 18 h. Volatile materials were removed by evaporation and the residue was co-evaporated with MeCN and DCM to give the carboxylic acid 27. This material was used directly in the subsequent reaction without further purification.
Step 3: Synthesis of t-Boc-Dye-linker NHS ester (28). To a solution of 27 (from the previous reaction) in DCM (10 mL), were added diisopropylethylamine (0.1 mL) and TSTU (50 mg, 0.167 mmol). The reaction mixture was stirred at room temperature for 2.5 h. Solvents were removed by evaporation and the residue was purified on a silica (Iatrobeads 6RS-8060) column (2×16 cm) using 1:5:95 to 1:20:80 AcOH/MeOH/DCM as eluants. Evaporation of the appropriate fractions afforded 81 mg (87% overall) of Dye-linker NHS intermediate 28 as a solid.
The synthesis of the a dye linker intermediate follows in general the procedure outlined below in Scheme 6 for formation of Cy3-FRET-linker NHS ester 32. The linker, such as 24, is coupled to the Cy3 Dye NHS ester, such as 29, to give the Dye Linker intermediate, such as 30 as a mixture of regio-isomers. After silica column purification, the pure regioisomer amino group could be protected with a trifluoroacetyl group for use in stepwise analyte labeling or used directly for labeling with the second Dye NHS to prepare the ET dye. To prepare the Dye-linker intermediate NHS 28, the free amino in 26 is protected, such as shown below with a TFA group to provide 27, and the carboxylic acid group activated to Cy3-FRET-linker NHS ester 28.
To a mixture of the ET-linker (24, 130 mg, 0.306 mmol) and diisopropylethylamine (0.07 mL) in DMF (5 mL), was added Cy3 NHS ester (29, 0.2 mmol). The reaction mixture was stirred at room temperature for 2 h. The reaction solution was added to 20 mL of diethyl ether. The mother liquors were decanted from the resulting oily precipitate and the precipitate suspended in 10% MeOH/CH2Cl2 purified by normal phase chromatography eluting with 10% MeOH/CH2Cl2/1% AcOH. Evaporation of the appropriate fractions afforded 30 as a mixture of regioisomers.
Step 2: Protection of 30 with a trifluoroacetyl group. A mixture of 30 (77 mg), diisopropylethylamine (0.2 mL), and ethyl trifluoroacetate (0.3 mL) in MeOH (3 mL) was stirred at room temperature for 18 h. Volatile materials were removed by evaporation and the residue was co-evaporated with MeCN and DCM to give the carboxylic acid 31. This material was used directly in the subsequent reaction without further purification.
To a solution of 31 (from the previous reaction) in DCM (10 mL), were added diisopropylethylamine (0.1 mL) and TSTU (50 mg, 0.167 mmol, 2 equivalents). The reaction mixture was stirred at room temperature for 2.5 h. Solvents were removed by evaporation and the residue was purified on a silica (Iatrobeads 6RS-8060) column (2×16 cm) using 1:5:95 to 1:20:80 AcOH/MeOH/DCM as eluants. Evaporation of the appropriate fractions afforded of Cy3-linker NHS intermediate 32 as a solid.
Pure isomer Cy3-Linker intermediate 30 (10 mgs) was suspended in 3 mL of anhydrous DMF and 6 equivalents of diisopropylethylamine (11 μL). Cy5.5-NHS ester 33 from GE Healthcare (1.2 equiv, 12 mg) suspended in 2 mL DMF was added and the reaction stirred at room temp for 5 hours. The crude product was isolated by addition of acetonitrile/diethyl ether and collection of the precipitated solid. The ET dye carboxylic acid product 34 was isolated by normal phase column chromatography (Iatrobeads 6RS-8060) using 5% to 20% H2O/MeCN/1% NEt3 as eluants. ET dye 34 was suspended in DMF with 6 equivalents DIPEA. Solid TSTU (3 equiv) was added and the mixture stirred for 3 hour at room temperature. Crude bichromophoric Cy3-Cy5.5 ET dye NHS 35 was precipitated by addition of ethyl acetate. The resulting solid precipitate was collected and resuspended in AcCN and the residue collected and used without further purification. The procedure of Scheme 7 can be implemented with other types of dyes provided in NHS form in place of Cy3, such as, e.g., AF 555, FAM, BODIPY 530/550, BODIPY R6G, and BODIPY TMR, which are all available from Thermo Fisher Scientific (Waltham, MA). Other dyes that can be utilized in place of Cy3 in the procedure shown in Scheme 7 include NHS derivatives of fluorescein and rhodamine dyes, such as, e.g., NED, VIC, HEX, or JOE. In Scheme 7, other cyanine dyes in NHS form that can be utilized instead of Cy5.5 include, e.g., AF647, AF660, and AF680, available from Thermo Fisher Scientific.
Labeling of the desired target analyte follows either a single step or two step labeling procedure depending on the substrate where an analyte amine is coupled to a preformed donor/acceptor ET dye NHS ester to directly give the desired ET dye labeled analyte, or the amino protected Dye-linker intermediate NHS can be added in a first step, the analyte-linker-dye labeled intermediate isolated, N-deprotected, and subsequently labeled in a second step with the complementary dye NHS to generate the ET dye labeled analyte (see,
Single-step oligonucleotide labeling was performed following the general procedure outlined in Scheme 9 for labeling of an amino group derivatized oligonucleotide with preformed ET dye, such as dye 35. Amino group derivatized oligomer (30,000 pM) is suspended in 250 μL of 100 molar NaHCO3DI water. 3 equivalents (0.2 mg) of 35 suspended in 5 μL DMSO is added. The reaction is stirred for 5 hours, loaded onto an LH-20 size exclusion column equilibrated with 1×TEAA and the faster moving oligo-Dye labeled band collected 40. The pure product was isolated by RP HPLC purification eluting with from 5 to 60% AcCN in 1×TEAA.
Using a two-step labeling process, a series of ET dyes were synthesized employing fluorescein-linker NETS intermediate 28 or Cy3-linker NHS intermediate 32 in combination with an appropriate reporter dye NHS ester to yield the series of ET dyes shown below in Scheme 10. A method for preparing the dye-labeled oligonucleotides shown in Scheme 10 is shown in Scheme 11.
First the substrate is labeled with a Dye-linker NHS intermediate, such as Cy3-linker NHS intermediate 32 to give dye-linker labeled oligonucleotide intermediate 41 which is purified by reverse phase HPLC and subsequently labeled with a Cy5.5 dye NHS in DMF and DIPEA to give the ET dye labeled oligonucleotide 42.
The quencher compound may be attached to a solid support, e.g., a bead, to provide a substrate for construction of a probe using an oligonucleotide synthesizer, in accordance with the following reaction in Scheme 12.
The following exemplary synthetic procedure may be easily generalized to any of the quenchers described above.
In some embodiments, a representative derivatized quencher 44 can be synthesized according to the following procedure. Representative quencher 43 NHS ester (100 mg, 0.123 mmol) was dissolved in 1 mL of anhydrous DCM. 1-O-DMT-2-(4-Aminobutyl)-1,3-propanediol (61 mg, 0.14 mmol) dissolved in 1213 μL of DCM (a 5% solution) was mixed with diisopropylethylamine (32 μL, 0.19 mmol). This was added dropwise to representative quencher 43 NHS ester at room temperature and stirred for 30 min under nitrogen. The crude representative quencher 44 in DCM solution was diluted with DCM (50 mL) and washed with 1% citric acid, water, and then brine. The organic layer was dried over Na2SO4 and evaporated to dryness. Further high vacuum drying overnight provided 125 mg (88% yield) of 44 as a dark blue solid. The product was used in the next step without further purification. 1H NMR (400 MHz, CD2Cl2): δ 8.14 (1H, d), 7.83 (2H, m), 7.60 (2H, d), 7.50-7.10 (22H, m), 6.80 (4H, m) 4.40 (2H, m), 4.25 (2H, m), 3.75 (6H, s), 3.62-3.50 (4H, m), 3.30 (6H, m), 3.05 (2H, m), 2.51 (2H, t), 2.40 (1H, t), 1.72 (2H, d), 1.50-1.20 (7H, m). LC/HRMS (Ho Calcd for [M+] 1113.48; found 1113.47. Elutions were done with a 20 minute linear gradient from 40 to 100% acetonitrile (against 0.1 M triethylammonium acetate). 1.0 ml/min flow rate. Detection at 285 nm and 655 nm.
In another embodiment, a representative quencher including a diglycolic linker 45 can be synthesized according to the following procedure. Representative quencher 44 (125 mg, 0.109 mmol) was dissolved in 3 mL of anhydrous DCM. DIPEA (47 μL, 0.27 mmol) was added, followed by diglycolic anhydride (25 mg, 0.22 mmol). The solution was stirred for 30 min under nitrogen. The reaction solution was concentrated and the residue re-dissolved in 1% TEA/DCM and purified on silica gel column chromatography (pre-equilibrated in 10%-1% TEA/DCM) using 5-15% MeOH/DCM/1% TEA eluent. The purified pool was concentrated and then washed with 1% citric acid, water, and brine. The organic layer was dried over anhydrous Na2SO4, evaporated to dryness, and then further dried under high vacuum to yield representative quencher diglycolic linker (45) (96 mg, 69% yield) as a dark blue solid. 1H NMR (400 MHz, CD2Cl2): δ 8.14 (1H, d), 7.85 (2H, m), 7.60 (2H, d), 7.52-7.10 (22H, m), 6.79 (4H, d), 4.35 (2H, m), 4.25 (2H, m) 4.05 (3H, s/m), 3.80 (2H, s), 3.72 (6H, s), 3.28 (6H, m), 3.00 (2H, m), 2.90 (2H, m), 2.50 (2H, t), 2.32 (1H, t), 1.65 (2H, m), 1.50-1.10 (7H, m). LC/HRMS (ESI+) Calcd for [M+] 1229.49; found 1229.49. Elutions were done with a 20 minute linear gradient from 40 to 100% acetonitrile (against 0.1 M triethylammonium acetate). 1.0 ml/min flow rate. Detection at 285 nm and 655 nm.
Representative quencher 45 can be linked to a solid support, e.g., polystyrene bead, according to the following procedure to provide 46. Representative quencher diglycolic linker 45 (357 mg, 0.20 mmol) was dissolved in 50 mL of anhydrous DMF. To this was added aminomethyl polystyrene (6.77 g, 0.223 mmol, 33 □mol/g amine), DIPEA (194 □L, 1.12 mol), and COMU or 1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate (287 mg, 0.669 mmol). The mixture was shaken for 3 hr. The solvent was removed and the resin was washed 3 times each with 50 mL of DMF, MeCN, and DCM. Any remaining amine groups on the resin were then capped by reacting with 50 mL acetic anhydride/pyridine in THF mixed with 50 mL of 1-N-methylimidazole in THF and shaken for 1 hr. The solvent was removed and the resin washed 3 times each with THE, MeCN, and DCM. The resin was then dried overnight under high vacuum to yield 6.60 g of light blue powder representative quencher 46. The resin support was tested for any residual amine groups using the ninhydrin test and found to be 0.94 □mol/g amine (negligible). The amount of representative quencher coupled to the support was determined by cleaving off the DMT group of a weighed aliquot of the representative quencher PS sample with a known volume of 0.1M toluenesulfonic acid in MeCN. The absorbance at 498 was obtained and using the extinction coefficient (76,500M−1cm−1), mass, and volume, the loading of representative quencher per g of polystyrene was found to be 22 μmol/g. The typical range found for this coupling condition was 20-27 μmol/g.
The quencher compound and ET dye may be attached to a solid support, e.g., a bead, to provide a substrate for construction of a probe using an oligonucleotide synthesizer, to provide a quencher-ET dye oligonucleotide probe construct in accordance with the following reaction scheme which utilize an L3 (i.e., 47)-L4 (i.e., 49) type linker (see,
Pack a 0.25 μmole QSY21 3900 column by weighing out 11 mg of QSY21 Bulk Solid Support (22 μmole/g loading) and pour into 3900 column body. Prepare Biolytics 3900 Synthesizer with all standard reagents including the Dye phosphoramidite 50, and linker phosphoramidites (47 and 49) according to 3900 Synthesis standard protocol. Install 28% DIPA/Acetonitrile reagent in Position 6 on 3900. Prepare specialty reagents at 0.1M concentration in anhydrous acetonitrile. Open 3900. Sequence Template in Microsoft Excel, and type in the relevant oligonucleotide sequence information for each oligonucleotide sequence. Load QSY21 columns into DNA synthesizer by placing them into each bank in the column positions designated on the synthesis page. Prime the reagents lines. Start the oligonucleotide synthesis. Once oligonucleotide synthesis steps are complete dry down the QSY support completely to remove any residual acetonitrile by placing synthesis columns on vacuum plate and placing vacuum plate on vacuum manifold and turn on vacuum for 5 minutes. Add 50/50 amine/methanol/water cleavage solution to column and wait for 10 minutes. Drain out all of the wash solution. Repeat. Place capped column vials into savant or equivalent set at 65° C., and heat for 4-5 hours. Remove vials and place in freezer for 10 minutes to cool down. After cool remove cap from vial and place in savant or equivalent and dry oligonucleotide under vacuum. Ethanol precipitate the dried QSY-dye labeled oligonucleotide 51 by diluting oligonucleotide in nuclease free water in Eppendorf tube and vortexing. Add 50 mM sodium acetate in ethanol and vortex. Put oligonucleotide in freezer to cool. Centrifuge tube at 2500 rpm for 5 minutes to pellet crude Remove supernatant out of oligonucleotide tube into waste beaker. Repeat three times and dry down oligonucleotide pellet in vacuum savant.
The dried amino QSY oligonucleotide 52 is removed from the savant and suspended in 0.25M sodium bicarbonate in water (pH 8.5) with vortexing and mild heating. A solution of Dye NHS ester Alexa Fluor 647 (53) solution is prepared in DMSO at 60 mM. The dye DMSO solution (5 equivalents) is added to the oligonucleotide and the solution is vortexed. The reaction is run for 1-2 hours at room temperature with intermittent agitation. The reaction is monitored by collecting a mass spectrum of the reaction mixture and when the labeled product reaches 80% conversion the reaction is stopped ethanol precipitated by adding 50 mM sodium acetate in ethanol, cooling and collecting the pelleted material by centrifugation and drying the pellet under vacuum. The pure QSY labeled probe 53 is isolated by reverse phase HPLC employing 0.1M TEAA and 0.1M TEAA in 50/50 acetonitrile/water.
The procedure of Scheme 13 can be implemented with other types of dyes provided in phosphoramidite form in place of FAM, such as, e.g., VIC, NED, and HEX. Other dyes that can be utilized instead of AF647 in Scheme 13 include NHS derivatives of cyanine dyes, such as, e.g., AF660, and AF680 or rhodamine dyes, such as, TAMRA or ROX.
Preparation of fluorescein-rhodamine energy transfer dyes using the L2 linker with rhodamine dyes such as ROX rhodamine were performed by reaction of 4-aminomethylbenzoic acid with 4-aminomethyl-5-carboxyfluorescein and subsequent conjugation to the rhodamine HNS ester (Scheme 14) (see,
Synthesis of ROX-L2-NHS
A mixture of 5-ROX-NHS 54 (5 mg, 9 □mol) 4-aminomethylbenzoic acid 55 (3 mg, 19 □mol), and triethylamine (20 □l) was suspended in dimethylformamide (DMF, 200 □l) in a 1.5 ml Eppendorf tube (Scheme 14). The mixture was heated to 60° C. for 10 min. Reaction progress was monitored by TLC on silica gel with elution with a 400/30/10 mixture of dichloromethane, methanol and acetic acid. The insoluble 4-aminomethylbenzoic acid was separated by centrifugation and the DMF solution was decanted into 5% HCl (1 ml). The insoluble 4-aminomethylbenzoic acid -5-ROX 56 was separated by centrifugation, washed with 5% HCl (2×1 m1) and dried in a vacuum centrifuge.
A solution of crude 4-aminomethylbenzoic acid -ROX 56 in DMF (125 ul), diisopropylethylamine (10 □1) and disuccinimidylcarbonate (10 mg) was combined in a 1.5 ml Eppendorf tube and heated to 60° C. Reaction progress was monitored by TLC on silica gel with elution with a 600/60/16 mixture of dichloromethane, methanol and acetic acid. After 5 min the reaction appeared to be complete. The solution was diluted into methylene chloride (3 ml) and washed with 250 mM carbonate/bicarbonate buffer, pH 9 (4×1 ml), the organic layer dried (Na2SO4) and concentrated to dryness in a vacuum centrifuge to give 57. The solid was dissolved in DMF (100 ul). The yield was determined by diluting an aliquot into pH 9 buffer and measuring the absorbance at 552 nm. Using an extinction coefficient of 50,000/cm/M, the concentration of 4-aminomethylbenzoic acid -5-ROX-NHS 57 was 4.8 mM for an 8% yield from 54.
Synthesis of FAM-ROX ET Dye
A solution of 4-aminomethylbenzoic acid -5ROX NHS 57 (1 □mol in 250 □l DMF) was combined with a solution of 4-aminomethyl-5-carboxyfluorescein 58 (19, 2.2 □mol in 100 □l DMSO) and triethylamine (20 □l) in a 1.5 ml Eppendorf tube (Scheme 15). The reaction was monitored by HPLC using a C8 reverse phase column with an elution gradient of 15-35% acetonitrile versus 0.1 M TEAA. HPLC analysis indicated that 57 was consumed, leaving the excess, unreacted 58. The reaction was diluted with 5% HCl (1 ml) and the FAM-ROX ET Dye acid product 59 separated by centrifugation, leaving the unreacted 58 in the aqueous phase. The solid was washed with 5% HCl (4×1 ml), dried in a vacuum centrifuge and taken up in DMF (300 □l). The yield was quantitative.
Synthesis of FAM-ROX ET-NHS
A solution of FAM-ROX ET Dye 59 (0.6 □mol in 100 □l DMF), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (DEC, 2 mg) and N-hydroxysuccinimide (4 mg) were combined in a 1.5 ml Eppendorf tube (Scheme 16). The mixture was sonicated briefly and heated to 60° C. The reaction was monitored by TLC on silica gel with elution with a 600/60/16 mixture of dichloromethane, methanol and acetic acid. The reaction was complete in 30 min and diluted with 5% HCl. The precipitated product 60 was separated by centrifugation and dried in a vacuum centrifuge. The activated FAM-ROX ET Dye NHS 60 was dissolved in DMF (20 □l).
Preparation of ET Dye-Labeled Oligonucleotides
A representative preparation of L2 ET ROX-labeled oligonucleotide is described below (Scheme 17). A solution of 5-aminohexyl-functionalized oligonucleotide (10 □l, 1 mM) in carbonate/bicarbonate buffer (2 □l, 1 M) and ET ROX-NHS 60 (10 □l, 12 mM in dimethylsulfoxide) were combined. After 10 min at room temperature the solution was subjected to gel filtration on Sephadex G-25 to separate free dye. The fraction containing dye-labeled oligonucleotide and unlabeled oligonucleotide was collected and subjected to HPLC purification on a reverse phase column. The unlabeled oligonucleotide and each dye isomer of dye-labeled oligonucleotide were separated using an elution gradient of 10-30% acetonitrile versus 0.1 M TEAA. The solutions containing dye-labeled oligonucleotide were concentrated in a vacuum centrifuge and redissolved in TE buffer.
It is to be understood that, while the foregoing embodiments have been described in detail by way of illustration and example, numerous modifications, substitutions, and alterations are possible without departing from the spirit and scope of the invention as described in the following clauses and claims.
1. A fluorescent energy transfer dye conjugate comprising:
wherein L1 is a first linker, wherein L1 is attached to D1, D2 and A through a covalent bond or through a spacer comprising one or more intervening atoms;
wherein L2 is a second linker, wherein L2 is attached to each of D2 and D3 through a covalent bond or through a spacer comprising one or more intervening atoms;
wherein L3 is a third linker, wherein L3 is attached to each PO4H and D1 through a covalent bond or through a spacer comprising one or more intervening atoms;
wherein L4 is a fourth linker, wherein L4 is attached to PO4H and D2 through a covalent bond or through a spacer comprising one or more intervening atoms;
wherein A is the analyte;
wherein each of D1, D2, and D3 is interchangeably a donor dye or an acceptor dye;
wherein the combination of D1 and D2 in LI and LIII and D2 and D3 in LII forms an energy transfer dye pair.
7. The energy transfer dye conjugate of clause 6, wherein the L1 linker comprises an arylene portion of the formula
wherein
wherein
wherein each R2, m and * is as defined above.
11. The energy transfer dye conjugate of clause 6, wherein the L3 linker comprises a fragment of the formula.
wherein
wherein
wherein
one of the dyes FAM-TAMRA, FAM-ABY, or FAM-NED;
330. The method of any of clauses 316-329, wherein the second dye comprises a fluorophore selected from the group consisting of a fluorescein dye, a rhodamine dye, a pyronine dye, and a cyanine dye.
331. The method of any of clauses 316-330, wherein the first dye is covalently attached to a first probe, and the second dye is covalently attached to a second probe, wherein the first and second probes are configured to bind to a first and a second target molecule, respectively.
332. The method of clause 331, wherein the first and second probes are oligonucleotide probes and the second probe is according to any of clauses 18-36.
333. The method of any of clauses 316-332, wherein the first and second target molecules are nucleic acid molecules.
334. The method of any of clauses 316-333, wherein the first dye comprises a maximum absorption wavelength that is equal to or substantially equal to a maximum absorption wavelength of the second dye.
335. he method of clause 334, wherein one or more of the first maximum absorption wavelength or second maximum absorption wavelength is an absolute maximum over an entirety of the respective spectrum.
336. The method of any of clauses 316-335, wherein the first dye is an on-axis dye and the second dye is an off-axis dye.
337. The method of any of clauses 316-336, wherein the first dye is configured to bind to a first target molecule and the second dye is configured to bind to a second target molecule, the method further comprising determining an amount of any target molecules present in the sample based on the measured emissions.
338. A method, comprising:
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/705,935, filed Jul. 23, 2020, the disclosure of which is hereby incorporated by reference as if set forth in full
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/043000 | 7/23/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62705935 | Jul 2020 | US |
