Patent Application
20080076188
The invention relates to compounds based on aromatic and heterocyclic compounds, among others. More particularly, the invention relates to compounds based on aromatic and heterocyclic compounds that are useful as luminescent reporters and long-lifetime labels.
Luminescent compounds may offer researchers the opportunity to use color and light to analyze samples, investigate reactions, and perform assays, either qualitatively or quantitatively. Generally, brighter, more photostable reporters may permit faster, more sensitive and more selective methods to be utilized in such research.
While a calorimetric compound absorbs light, and may be detected by that absorbance, a luminescent compound, or luminophore, is a compound that emits light. A luminescence method, in turn, is a method that involves detecting light emitted by a luminophore, and using properties of that light to understand properties of the luminophore and its environment. Luminescence methods may be based on chemiluminescence and/or photoluminescence, among others, and may be used in spectroscopy, microscopy, immunoassays, and hybridization assays, among others.
Photoluminescence is a particular type of luminescence that involves the absorption and subsequent re-emission of light. In photoluminescence, a luminophore is excited from a low-energy ground state into a higher-energy excited state by the absorption of a photon of light. The energy associated with this transition is subsequently lost through one or more of several mechanisms, including production of a photon through fluorescence or phosphorescence.
Photoluminescence may be characterized by a number of parameters, including extinction coefficient, excitation and emission spectrum, Stokes' shift, luminescence lifetime, and quantum yield. An extinction coefficient is a wavelength-dependent measure of the absorbing power of a luminophore. An excitation spectrum is the dependence of emission intensity upon the excitation wavelength, measured at a single constant emission wavelength. An emission spectrum is the wavelength distribution of the emission, measured after excitation with a single constant excitation wavelength. A Stokes' shift is the difference in wavelengths between the maximum of the emission spectrum and the maximum of the absorption spectrum. A luminescence lifetime is the average time that a luminophore spends in the excited state prior to returning to the ground state. A quantum yield is the ratio of the number of photons emitted to the number of photons absorbed by a luminophore.
Luminescence methods may be influenced by extinction coefficient, excitation and emission spectra, Stokes' shift, and quantum yield, among others, and may involve characterizing fluorescence intensity, fluorescence polarization (FP), fluorescence resonance energy transfer (FRET), fluorescence lifetime (FLT), total internal reflection fluorescence (TIRF), fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), and their phosphorescence analogs, among others.
Luminescence methods have several significant potential strengths. First, luminescence methods may be very sensitive, because modern detectors, such as photomultiplier tubes (PMTs) and charge-coupled devices (CCDs), can detect very low levels of light. Second, luminescence methods may be very selective, because the luminescence signal may come almost exclusively from the luminophore.
Despite these potential strengths, luminescence methods may suffer from a number of shortcomings, at least some of which relate to the nature of the luminescent compound. For example, the luminophore may have an extinction coefficient and/or quantum yield that is too low to permit detection of an adequate amount of light. The luminophore also may have a Stokes' shift that is too small to permit detection of emission light without significant detection of excitation light. The luminophore also may have an excitation spectrum that does not permit it to be excited by wavelength-limited light sources, such as common lasers and arc lamps. The luminophore also may be unstable, so that it is readily bleached and rendered nonluminescent. The luminophore also may have a luminescent lifetime (FLT) that is similar to that of the auto-luminescence of biological and other samples; such autoluminescence is particularly significant at wavelengths below about 600 nm. The luminophore also may be expensive, especially if it is difficult to manufacture.
The invention provides luminescent probes and labels based on aromatic and heterocyclic compounds, among others, reactive intermediates used to synthesize these compounds, and methods of synthesizing and using these reporter compounds, among others. These compounds may have luminescent lifetimes in the order of 4 ns-40 ns.
The luminescent compounds relate generally to the following structure:
wherein
each Ra—Rf is independently selected from the group consisting of H, alkyl, alkoxy, amino, alkylamino, dialkylamino, alkenyl, alkynyl, aryl, halogen, sulfo, carboxy, formyl, acetyl, formylmethyl, sulfate, phosphate, phosphonate, ammonium, alkylammonium, cyano, nitro, azido, heterocyclic, substituted heterocyclic, reactive aliphatic and reactive aromatic groups and
wherein at least one pair of adjacent substituents (Ra, Rb), (Rb, Rc), (Rc, Rd), (Rd, Re), (Re, Rf), (Rf, Ra) is either a substituted cyclic or polycyclic group W1, W2, W3, W4, W5, W6, W7, W8, W9; or
wherein at least one set of three substituents (Ra, Rb, Rc), (Rb, Rc, Rd), (Rc, Rd, Re), (Rd, Re, Rf), (Re, Rf, Ra) is a substituted cyclic or polycyclic group that is represented by the group consisting of W9, W10, W11, W12:
The substituents Ra-Rf, R1-R7, RA-RC, Z1, Z2, X, Y and A− are defined in the Detailed Description below. The disclosed compounds may include a reactive group and/or a carrier. Alternatively, or in addition, the substituents may be chosen so that the compound is photoluminescent and has a luminescent lifetime in the order of 4 ns or higher.
The disclosed methods relate generally to the synthesis and/or use of reporter compounds for fluorescence lifetime or fluorescence polarization based applications especially those compounds described above.
The nature of the invention will be understood more readily after consideration of the drawings, chemical structures, and detailed description that follow.
The following abbreviations, among others, may be used in this application:
The invention relates generally to luminescent compounds having luminescent lifetimes in order of 4 ns and higher and their synthetic precursors, and to methods of synthesizing and using such compounds. These compounds may be useful in both free and conjugated forms, as probes or as labels. This usefulness may reflect in part enhancement of one or more of the following: fluorescence lifetime, fluorescence polarization, quantum yield, Stokes' shift, and photostability.
The remaining discussion includes (1) an overview of structures, (2) an overview of synthetic methods, and (3) a series of illustrative examples.
Overview of Structures
The luminescent reporter compounds may be generally described by the following structure:
Each Ra-Rf substituent is independently selected from the group consisting of H, alkyl, alkoxy, amino, alkylamino, dialkylamino, alkenyl, alkynyl, aryl, halogen, sulfo, carboxy, formyl, acetyl, formylmethyl, sulfate, phosphate, phosphonate, ammonium, alkylammonium, cyano, nitro, azido, heterocyclic, substituted heterocyclic, reactive aliphatic and reactive aromatic groups.
In one aspect of the disclosed compounds, at least one pair of adjacent substituents (Ra, Rb), (Rb, Rc), (Rc, Rd), (Rd, Re), (Re, Rf), (Rf, Ra) is either a substituted cyclic or polycyclic group W1, W2, W3, W4, W5, W6, W7, W8, W9, as defined below.
In another aspect of the disclosed compounds, at least one set of three substituents (Ra, Rb, Rc), (Rb, Rc, Rd), (Rc, Rd, Re), (Rd, Re, Rf), (Re, Rf, Ra) is a substituted cyclic or polycyclic group that is represented by the group consisting of W9, W10, W11, W12, as defined below.
For each of W1—W12, each R1-R7 is independently selected from the group consisting of H, alkyl, alkoxy, amino, alkylamino, dialkylamino, alkenyl, alkynyl, aryl, halogen, sulfo, carboxy, formyl, acetyl, formylmethyl, sulfate, phosphate, phosphonate, ammonium, alkylammonium, cyano, nitro, azido, heterocyclic, substituted heterocyclic, reactive aliphatic and reactive aromatic groups.
The X moiety is selected from the group consisting of C(RB)(RC), O, S, Se, N—RA.
The Y moiety is selected from the group consisting of CRA, N, +N—RA, O+, S+; where RA is selected from H, aliphatic groups, alicyclic groups, alkylaryl groups, aromatic groups, -L-Sc, -L-Rx, and -L-R±, among others.
Each of Z1 and Z2 is independently selected from the group consisting of ═O, ═S, ═Se, ═Te, ═N—RA, and ═C(RB)(RC); where RB and RC are independently selected from H, aliphatic groups, alicyclic groups, alkylaryl groups, aromatic groups, -L-Sc, -L-Rx, -L-R±, among others, or RB and RC, taken in combination, form a cyclic group.
L is a covalent linkage that is linear or branched, cyclic or heterocyclic, saturated or unsaturated, having 1-20 nonhydrogen atoms from the group of C, N, P, O and S, in such a way that the linkage contains any combination of ether, thioether, amine, ester, amide bonds; single, double, triple or aromatic carbon-carbon bonds; or carbon-sulfur bonds, carbon-nitrogen bonds, phosphorus-sulfur, nitrogen-nitrogen, nitrogen-oxygen or nitrogen-platinum bonds, or aromatic or heteroaromatic bonds.
The Rx moiety is a reactive group. The Sc moiety is a conjugated substance. R± is an ionic group, and A− is a biologically compatible and synthetically accessible anion.
In one aspect of the disclosed compounds, the compounds exhibit a luminescence lifetime in the order of 4 nanoseconds (ns) or longer.
The particular substituents on the substituted rings may be chosen quite broadly, and may include any of the various components listed above, in various combinations, among other configurations and substituents.
Reporter Compounds
The compounds disclosed herein may be particularly useful for fluorescence lifetime and fluorescence polarization based applications and methods, as discussed below.
Reactive Groups (Rx).
The substituents on the disclosed compounds may include one or more reactive groups, where a reactive group generally is a group capable of forming a covalent attachment with another molecule or substrate. Such other molecules or substrates may include proteins, carbohydrates, nucleic acids, and plastics, among others. Reactive groups (Rx) vary in their specificity, and may preferentially react with particular functional groups and molecule types. Thus, reactive compounds generally include reactive groups chosen preferentially to react with functional groups found on the molecule or substrate with which the reactive compound is intended to react.
The compounds of the invention are optionally substituted, either directly or via a substituent, by one or more chemically reactive functional groups that may be useful for covalently attaching the compound to a desired substance. Each reactive group Rx, may be bound to the compound directly by a single covalent bond (—Rx), or may be attached via a covalent spacer or linkage, -L-, and may be depicted as -L-Rx.
The reactive group (—Rx) of the invention may be selected from the following functional groups, among others: activated carboxylic esters, acyl azides, acyl halides, acyl halides, acyl nitrites, acyl nitriles, aldehydes, ketones, alkyl halides, alkyl sulfonates, anhydrides, aryl halides, azindines, boronates, carboxylic acids, carbodiimides, diazoalkanes, epoxides, haloacetamides, halotriazines, imido esters, isocyanates, isothiocyanates, maleimides, phosphoramidites, silyl halides, sulfonate esters, and sulfonyl halides.
The following reactive functional groups (—Rx), among others, are particularly useful for the preparation of labeled molecules or substances, and are therefore suitable reactive functional groups for the purposes of the reporter compounds:
The R moieties associated with the various substituents of Z may include any of a number of groups, as described above, including but not limited to aliphatic groups, alicyclic groups, aromatic groups, and heterocyclic rings, as well as substituted versions thereof.
Aliphatic groups may include groups of organic compounds characterized by straight- or branched-chain arrangement of the constituent carbon atoms. Aliphatic hydrocarbons comprise three subgroups: (1) paraffins (alkanes), which are saturated and comparatively unreactive; (2) olefins (alkenes or alkadienes), which are unsaturated and quite reactive; and (3) acetylenes (alkynes), which contain a triple bond and are highly reactive. In complex structures, the chains may be branched or cross-linked and may contain one or more heteroatoms (such as polyethers and polyamines, among others).
As used herein, “alicyclic groups” include hydrocarbon substituents that incorporate closed rings. Alicyclic substituents may include rings in boat conformations, chair conformations, or resemble bird cages. Most alicyclic groups are derived from petroleum or coal tar, and many can be synthesized by various methods. Alicyclic groups may optionally include heteroalicyclic groups, that include one or more heteroatoms, typically nitrogen, oxygen, or sulfur. These compounds have properties resembling those of aliphatics and should not be confused with aromatic compounds having the hexagonal benzene ring. Alicyclics may comprise three subgroups: (1) cycloparaffins (saturated), (2) cycloolefins (unsaturated with two or more double bonds), and (3) cycloacetylenes (cyclynes) with a triple bond. The best-known cycloparaffins (sometimes called naphthenes) are cyclopropane, cyclohexane, and cyclopentane; typical of the cycloolefins are cyclopentadiene and cyclooctatetraene. Most alicyclics are derived from petroleum or coal tar, and many can be synthesized by various methods.
Aromatic groups may include groups of unsaturated cyclic hydrocarbons containing one or more rings. A typical aromatic group is benzene, which has a 6-carbon ring formally containing three double bonds in a delocalized ring system. Aromatic groups may be highly reactive and chemically versatile. Most aromatics are derived from petroleum and coal tar. Heterocyclic rings include closed-ring structures, usually of either 5 or 6 members, in which one or more of the atoms in the ring is an element other than carbon, e.g., sulfur, nitrogen, etc. Examples include pyridine, pyrole, furan, thiophene, and purine. Some 5-membered heterocyclic compounds exhibit aromaticity, such as furans and thiophenes, among others, and are analogous to aromatic compounds in reactivity and properties.
Any substituent of the compounds of the invention, including any aliphatic, alicyclic, or aromatic group, may be further substituted one or more times by any of a variety of substituents, including without limitation, F, Cl, Br, I, carboxylic acid, sulfonic acid, CN, nitro, hydroxy, phosphate, phosphonate, sulfate, cyano, azido, amine, alkyl, alkoxy, trialkylammonium or aryl. Aliphatic residues can incorporate up to six heteroatoms selected from N, O, S. Alkyl substituents include hydrocarbon chains having 1-22 carbons, more typically having 1-6 carbons, sometimes called “lower alkyl”.
As described in International Publication No. WO01/11370, the substitution of sulfonamide groups such as —(CH2)n—SO2—NH—SO2—R, —(CH2)n—CONH—SO2—R, —(CH2)n—SO2—NH—CO—R, and —(CH2)n—SO2NH—SO3H, where R is aryl or alkyl and n=1-6, may be used to reduce the aggregation tendency of some compounds, and have some positive effects on their photophysical properties.
Where a compound substituent is further substituted by a functional group R± that is ionically charged, such as for example a carboxylic acid, sulfonic acid, phosphoric acid, phosphonate or a quaternary ammonium group, the ionic substituent R± may serve to increase the overall hydrophilicity of the compound.
As used herein, functional groups such as “carboxylic acid,” “sulfonic acid,” and “phosphoric acid” include the free acid moiety as well as the corresponding metal salts of the acid moiety, and any of a variety of esters or amides of the acid moiety, including without limitation alkyl esters, aryl esters, and esters that are cleavable by intracellular esterase enzymes, such as alpha-acyloxyalkyl ester (for example acetoxymethyl esters, among others).
The compounds of the invention are optionally further substituted by a reactive functional group Rx, or a conjugated substance Sc, as described below.
The compounds of the invention may be depicted in structural descriptions as possessing an overall charge, it is to be understood that the compounds depicted include an appropriate counter ion or counter ions to balance the formal charge present on the compound. Further, the exchange of counter ions is well known in the art and readily accomplished by a variety of methods, including ion-exchange chromatography and selective precipitation, among others.
Carriers and Conjugated Substances Sc
The reporter compounds of the invention, including synthetic precursor compounds, may be covalently or noncovalently associated with one or more substances. Covalent association may occur through various mechanisms, including a reactive functional group as described above, and may involve a covalent linkage, -L-, separating the compound or precursor from the associated substance (which may therefore be referred to as -L-Sc).
A covalent linkage binds the reactive group Rx, the conjugated substance Sc or the ionic group R± to the dye molecule, either directly via a single covalent bond which is depicted in the text as —Rx, —R±, —Sc, or with a combination of stable chemical bonds (-L-), that include single, double, triple or aromatic carbon-carbon bonds; carbon-sulfur bonds, carbon-nitrogen bonds, phosphorus-sulfur bonds, nitrogen-nitrogen bonds, nitrogen-oxygen or nitrogen-platinum bonds, or aromatic or heteroaromatic bonds; -L- includes ether, thioether, carboxamide, sulfonamide, urea, urethane or hydrazine moieties. Preferably, -L- includes a combination of single carbon-carbon bonds and carboxamide or thioether bonds.
Where the substance is associated noncovalently, the association may occur through various mechanisms, including incorporation of the compound or precursor into or onto a solid or semisolid matrix, such as a bead or a surface, or by nonspecific interactions, such as hydrogen bonding, ionic bonding, or hydrophobic interactions (such as Van der Waals forces). The associated carrier may be selected from the group consisting of polypeptides, polynucleotides, polysaccharides, beads, microplate well surfaces, metal surfaces, semiconductor and non-conducting surfaces, nanoparticles, and other solid surfaces.
The associated or conjugated substance may be associated with or conjugated to more than one reporter compound, which may be the same or different. Generally, methods for the preparation of dye-conjugates of biological substances are well-known in the art. See, for example, Haugland et al., MOLECULAR PROBES HANDBOOK OF FLUORESCENT PROBES AND RESEARCH CHEMICALS, Eighth Edition (1996), or G. T. Hermanson, Bioconjugate Techniques, Academic Press, London, (1996), which is hereby incorporated by reference. Typically, the association or conjugation of a chromophore or luminophore to a substance imparts the spectral properties of the chromophore or luminophore to that substance.
Useful substances for preparing conjugates according to the present invention include, but are not limited to, amino acids, peptides, proteins, phycobiliproteins, nucleosides, nucleotides, nucleic acids, carbohydrates, lipids, ion-chelators, biotin, pharmaceutical compounds, nonbiological polymers, cells, and cellular components. The substance to be conjugated may be protected on one or more functional groups in order to facilitate the conjugation, or to insure subsequent reactivity.
Where the substance is a peptide, the peptide may be a dipeptide or larger, and typically includes 5 to 36 amino acids. Where the conjugated substance is a protein, it may be an enzyme, an antibody, lectin, protein A, protein G, hormones, or a phycobiliprotein. The conjugated substance may be a nucleic acid polymer, such as for example DNA oligonucleotides, RNA oligonucleotides (or hybrids thereof), or single-stranded, double-stranded, triple-stranded, or quadruple-stranded DNA, or single-stranded or double-stranded RNA.
Another class of carriers includes carbohydrates that are polysaccharides, such as dextran, heparin, glycogen, starch and cellulose.
Where the substance is an ion chelator, the resulting conjugate may be useful as an ion indicator (calcium, sodium, magnesium, zinc, potassium and other important metal ions) particularly where the optical properties of the reporter-conjugate are altered by binding a target ion. Preferred ion-complexing moieties are crown ethers (U.S. Pat. No. 5,405,957) and BAPTA chelators (U.S. Pat. No. 5,453,517).
The associated or conjugated substance may be a member of a specific binding pair, and therefore useful as a probe for the complementary member of that specific binding pair, each specific binding pair member having an area on the surface or in a cavity which specifically binds to and is complementary with a particular spatial and polar organization of the other. The conjugate of a specific binding pair member may be useful for detecting and optionally quantifying the presence of the complementary specific binding pair member in a sample, by methods that are well known in the art.
Representative specific binding pairs may include ligands and receptors, and may include but are not limited to the following pairs: antigen-antibody, biotin-avidin, biotin-streptavidin, IgG-protein A, IgG-protein G, carbohydrate-lectin, enzyme-enzyme substrate; ion-ion-chelator, hormone-hormone receptor, protein-protein receptor, drug-drug receptor, DNA-antisense DNA, and RNA-antisense RNA.
Preferably, the associated or conjugated substance includes proteins, carbohydrates, nucleic acids, drugs, and nonbiological polymers such as plastics, metallic nanoparticles such as gold, silver and carbon nanostructures among others. Further carrier systems include cellular systems (animal cells, plant cells, bacteria). Reactive dyes can be used to label groups at the cell surface, in cell membranes, organelles, or the cytoplasm.
The compounds of the disclosure may also be linked to small molecules such as amino acids, vitamins, drugs, haptens, toxins, and environmental pollutants, among others. Another important ligand is tyramine, where the conjugate is useful as a substrate for horseradish peroxidase.
Synthesis and Characterization
The synthesis of the disclosed reporter compounds typically, but not exclusively, is achieved in a multi-step reaction. The synthesis of representative dyes and reactive labels are provided in the Examples below. While the syntheses of non-reactive dyes have been previously described, reactive version and conjugates of the present compounds have not been described. The fluorescent properties of representative dyes are given in Table 1.
The lifetime and fluorescent properties of the presently disclosed dyes may be tuned by selection of the substituents present on the ring systems. For example, the naphtalimide ring system with a dimethylamino substituent has a luminescent lifetime of 4.7 ns when the imide nitrogen is substituted with an aromatic phenyl ring (Table 1, 2a) but becomes twice as long when substituted with a hexanoic acid group (Table 1, compound 2b).
This section describes the synthesis of representative dyes of this disclosure. The spectral properties as well as the luminescent lifetimes of representative dyes in various solvents are provided in Table 1 below. The syntheses of selected protein-conjugates and reactive versions (e.g. NHS esters) for the purpose of covalently labeling biomolecules has also been provided.
Phenylimide (1) and 4-carboxyphenylimide of 4-dimethylaminonaphthalic acid (2a) were synthesized according to the method described in USSR Patent No. 1262911.
1: Yield 59%. M.P. 269-271° C.
2a: Yield 70%. M.P. 315-318° C.
2b: Yield 20%. M.P. 125-128° C.
2.45 g (0.01 mmol) of 5-nitro-1H,3H-benzo[de]isochromene-1,3-dione and 1.23 g (0.01 mmol) of 6-aminohexanoic acid was alloyed with at 210-220° C. for 35 min. The obtained crude 6-(5-nitro-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoic acid was recrystallized from ethanol. Yield 1.7 g (48%). The product was dissolved in 50 mL of ethanol and was added dropwise to the hot solution of 8 g of tin chloride in 9 mL of hydrochloric acid at boiling. The reaction mixture was boiled for 4 h, then poured with water and neutralized with 5% solution of sodium hydrate. Yellow sediment was filtered and purified by a column chromatography (Silica gel, chloroform). Yield 1.1 g of ethyl 6-(5-amino-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoate (31.5% counting on 5-nitro-1H,3H-benzo[de]isochromene-1,3-dione). M.p. 108-110° C.
A mixture of 1.8 g (5.08 mmol) of ethyl 6-(5-amino-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoate in 9 mL of chloroform was added at 40° C. to a solution of 1.35 g (13.2 mmol) of sodium hydrocarbonate in 6 mL of water. Then 1.3 mL (17.6 mmol) of dimethyl sulfate was added and heated under stirring at 40° C. for 1 h. The reaction mixture was heated at 55-60° C. for 20 min, cooled to RT and dilute with chloroform. The solvent was removed and the residue was suspended in 20 mL of acetic anhydride and heated on the water bath for 40 min. The reaction mixture was poured into water, neutralized with ammonia and extracted with chloroform. The product was column purified (Silica gel, chloroform). The obtained 0.6 g (30%) of ethyl 6-(5-dimethylamino-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoate was treated with 0.1 M solution of HCl to yield 0.42 g (75%) of 6-(5-dimethylamino-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoic acid. M.p. 111-114° C. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 8.21-7.42 (5H, arom), 3.99 t (2H, α-CH2, J 7.3 Hz), 3.11 (6H, N(CH3)2), 2.21 t (2H, ε-CH2, J 7.3 Hz), 1.56 m (4H, β,γ-CH2 J 7.3 Hz), 1.36 m (2H, δ-CH2, J 7.3 Hz).
Dyes 3, 4 and 5 were synthesized according to procedures described by Patsenker et al. (L. D. Patsenker et al., Tetrahedron, 2000, V. 56, No. 37, P. 7319-7323).
Compound 3 was obtained by the same procedure as 5 using 1.44 g (4 mmol) of phenylimide instead of carboxyphenylimide. Yield 0.92 g (51%), yellow solid. M.P. 255-258° C. Found: C, 63.9; H, 4.8; Cl, 7.8; N, 9.4, C24H21ClN3O4. Calculated: C, 63.93; H, 4.69; Cl, 7.86; N, 9.32%; IR, νmax(KBr) 1715, 1695, 1660, 1600, 1570, 1465, 1404, 1380, 1350, 1280, 1240 cm−1; 1H-NMR (300 MHz, DMSO-d6, δ, ppm) 3.32 (6H, s, +N(CH3)2), 3.73 (3H, s, 4-NCH3), 5.01 (2H, s, CH2), 5.25 (2H, s, CH2), 7.38-8.67 (8H, m, arom H).
To a solution of 90 mg (0.25 mmol) of 6-(5-dimethylamino-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)hexanoic acid in 0.4 mL of DMF 0.09 ml of POCl3 were added dropwise at 40° C. The mixture was heated under stirring at 80° C. for 1.5 h, cooled to RT and poured into ice water. The product was precipitated with isopropyl alcohol and purified by column chromatography on reverse phase (PR-18, H2O-acetonitrile 5:1, v/v). Yield: 45 mg (40%). M.p. 186-188° C. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 8.39-7.82 (5H, arom), 5.17 s (2H, CH2), 4.85 s (2H, CH2), 4.04 t (2H, α-CH2, J 7.3 Hz), 3.65 s (3H, NCH3), 3.19 s (6H, +N(CH3)2), 1.94 t (2H, ε-CH2, J 7.3 Hz), 1.54 m (4H, β,γ-CH2 J 7.3 Hz), 1.26 m (2H, δ-CH2, J 7.3 Hz).
To a mixture of 0.177 g (0.5 mmol) of 2b and 0.5 mL (6.5 mmol) of DMF 0.18 mL (2 mmol) of POCl3. The mixture was heated at 80° C. for 1.5 h, treated with ice, and acetone was added to precipitate the oily product, which was treated with ether to give yellow crystals.
1.26 g (4 mmol) of 4-carboxyphenylimide of 4-dimethylaminonaphthalic acid (2) were dissolved in 5 mL (65 mmol) of DMF, and then 1.7 mL (18 mmol) of POCl3 were added dropwise at 60-70° C. The mixture was heated with stirring at 100° C. for 25 min, cooled to RT and poured into ice water. The crude product was recrystallized from ethanol to give the 5 (0.86 g, 53%) as a yellow solid, M.P. 235° C. Found: C, 66.3; H, 5.5; Cl, 8.7; N, 10.4, C23H22ClN3O2.0.5H2O. Calculated: C, 66.26; H, 5.56; Cl, 8.50; N, 10.08%. IR, νmax(KBr) 1695, 1650, 1600, 1565, 1450, 1400, 1375, 1340 cm−1. 1H-NMR (300 MHz, DMSO-d6, δ, ppm) 3.42 (6H, s, +N(CH3)2), 3.88 (3H, s, 4-NCH3), 5.00 (2H, s, CH2), 5.16 (2H, s, CH2), 7.42-8.86 (9H, m, arom H).
To a mixture of 3.16 g (0.01 mol) of phenylimide 3-dimethylaminonaphthalic acid and 13.8 mL (0.18 mol) of DMF at 30-35° C. 4.1 mL (0.045 mol) of POCl3 were added dropwise. The mixture was stirred at 80° C. for 30 min, cooled down to RT, and treated with ice. Then LiPF6 was added and the obtained precipitate was filtered off and dried. Yield 3.10 g (60%). M.P. 259-260° C. 1H-NMR (300 MHz, δ, ppm,): 8.36 d (1H, H7, J 7.3 Hz), 8.18 s (1H, H5), 8.14 d (1H, H2, J 8.4 Hz), 7.93 dd (1H, H6, J1 8.3, J2 7.4 Hz), 7.59-7.34 m (5H, phenyl), 5.22 s (2H, CH2), 4.87 s (2H, CH2), 3.39 s (3H, N—CH3), 3.22 s (6H, +N(CH3)2). Found, %: C, 53.35; H, 4.30; N, 10.99, C23H22F6N3O2P. Calculated, %: C, 53.39; H, 4.26; N, 11.25.
Dyes 7a, 7b, and 8 were synthesized according to Lyubenko et al. (O. N. Lyubenko, et al., Chem. Heterocycl. Compd., Engl. Transl., 2003, No. 4, P. 594).
A mixture of 5 mmol of 2-amino-6-dimethylamino-2,3-dihydro-1H-benzo[de]isoquinoline-1,3-dione (O. N. Lyubenko, et al., Chem. Heterocycl. Compd., Engl. Transl., 2003, No. 4, P. 594), 4.5 mL (35 mmol) of acetoacetic acid diethyl ester and 0.01 g (0.057 mmol) p-toluenesulfonic acid was stirred at 130° C. for 4 h under nitrogen atmosphere. The obtained precipitate of hydrazone was filtered off, washed with methanol, water, and dried. Then the hydrazone was refluxed for 1 h in 2.5 mL of DMF and 0.01 g (0.12 mmol) of NaOAc. The precipitate was filtered off, washed with methanol, water, and dried. Isomeric dyes 1a and 1b were separated using a column chromatography (Al2O3, benzene). 1a. Yield 18%. M.P. 204-205° C. 1H-NMR, (200 MHz, DMSO-d6, δ, ppm): 9.28 (1H, d, J=7.6, 7-H), 8.52 (1H, d, J=8.5, 2-H), 8.38 (1H, d, J=8.5, 5-H), 7.68 (1H, t, J=8.0, 6-H), 7.24 (1H, d, J=8.5, 3-H), 7.2; COOCH2CH3), 4.42 (2H, q, J=14.1), 3.19 (6H, s, N(CH3)2), 2.50 (3H, s, CH3), 1.39 (3H, t, J=7.2, COOCH2CH3). Found, %: C, 68.70; H, 5.38; N, 11.60, C20H19N3O3. Calculated, %: C, 68.77; H, 5.44; N, 12.03. IR (ν, cm−1, KBr): 1680 (C═O carbonyl), 1710 (C═O ester). 1b. Yield 12%. M.P. 194-195° C. 1H-NMR, (200 MHz, DMSO-d6, δ, ppm): 9.26 (1H, d, J=8.4, 7-H), 8.68 (1H, d, J=7.3, 2-H), 8.62 (1H, dd., J=8.4; 0.7; 4-H), 7.83 (1H, t, J=7.9, 3-H), 7.18 (1H, d, J=8.5, 6-H), 4.38 (2H, q, J=14.2; 7.1; COOCH2CH3), 3.07 (6H, s, N(CH3)2), 2.48 (3H, s, CH3), 1.39 (3H, t, J=7.1, COOCH2CH3). Found, %: C 68.71; H, 5.40; N, 11.79, C20H19N3O3. Calculated, %: C, 68.77; H, 5.44; N, 12.03. IR (ν, cm−1, KBr): 1680 (C═O carbonyl), 1710 (C═O ester).
General Procedure for the Synthesis of Dyes 7a, 7b, and 8.
To a mixture of 1 mmol of pyrazole 1a or 1b in 2 mL (26 mmol) of DMF at 60° C. 0.37 mL (4 mmol) of POCl3 was added dropwise. The mixture was stirred at 100° C. for 3 h in case of 1a and 4 h in case of 1b, cooled down and poured into ice. 13-Acetyl-4,6,6,12-tetramethyl-9-oxo-4,6,7,9-tetrahydro-5H-pyrazolo[5′, 1′: 1,2]isoquino[4,5-gh]quinazoline-6-ium chloride (7a) and 12-acetyl-2,2,4,11-tetramethyl-8-oxo-2,3,4,8-tetrahydro-1H-pyrazolo[1′,5′:2,3]isoquino[4,5-gh]quinazoline-2-ium chloride (8) were precipitated by isopropanol. Chlorides 7a and 13 were recrystallized from ethanol. Crystalline 13-acetyl-4,6,6,12-tetramethyl-9-oxo-4,6,7,9-tetrahydro-5H-pyrazolo-[5′,1′:1,2]isoquino[4,5-gh]quinazoline-6-ium hexafluorophosphate 7b was obtained using 0.15 g (1 mmol) of LiPF6, and then was column purified (Silochrom C-120, acetonitrile). 7a: Yield 30%. M.P. 251-252° C. (ethanol). 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 9.27 (1H, d, J=7.6, 7-H), 8.39 (1H, d J=8.6, 5-H), 8.32 (1H, s 2-H), 7.75 (1H, t J=8.2, 6-H), 5.17 (2H, s CH2), 5.02 (2H, s CH2), 4.42 (2H, q, J=14.0; 7.0; COOCH2CH3), 3.72 (3H, s, NCH3), 3.31 (6H, s, N+(CH3)2), 2.49 (3H, s, CH3), 1.41 (3H, t, J=7.2, COOCH2CH3). Found, %: C, 62.59; H, 5.73; N, 12.23; Cl 7.89. C23H25N4O3Cl. Calculated, %: C, 62.65; H, 5.67; N, 12.71; Cl 8.06. IR (ν, cm−1, KBr): 1680 (C═O carbonyl), 1700 (C═O ester). 7b: Yield 45%. M.P. 315-318° C. (acetonitrile). 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 1.41 (3H, t, J=7.1, COOCH2CH3); 2.52 (3H, s, CH3); 3.24 (6H, s, N+(CH3)2); 3.69 (3H, s, NCH3); 4.44 (2H, q, J=14.1; 7.0; COOCH2CH3); 4.93 (2H, s, CH2); 5.06 (2H, s, CH2); 7.84 (1H, t, J=8.1, 6-H); 8.45 (1H, s, 2-H); 8.46 (1H, d, J=7.9, 5-H); 9.36 (1H, d, J=7.6, 7-H). Found, %: C, 50.11; H, 4.46; N, 10.54, C23H25N4O3 PF6. Calculated, %: C, 50.18; H, 4.54; N, 10.18. IR (ν, cm−1, KBr): 1700 (C═O carbonyl), 1680 (C═O ester). 8: Yield 34%. M.P. 242-245° C. (ethanol). 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 1.41 (3H, t, J=7.2, COOCH2CH3); 2.54 (3H, s, CH3); 3.30 (6H, s, N+(CH3)2); 3.68 (3H, s, NCH3); 4.41 (2H, q, J=14.1; 7.2; COOCH2CH3); 4.92 (2H, s, CH2); 5.11 (2H, s, CH2); 7.91 (1H, t, J=7.9, 3-H); 8.65 (1H, d, J=6.3, 2-H); 8.68 (1H, d, J=8.2, 4-H); 9.16 (1H, s, 7-H). Found, %: C, 62.59; H, 5.72; N, 12.66; Cl 8.23, C23H25N4O3Cl. Calculated, %: C, 62.65; H, 5.67; N, 12.71; Cl 8.06. IR (ν, cm−1, KBr): 1650 (C═O carbonyl), 1700 (C═O ester).
13-ethyl-7-oxo-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-13-ium 4-methyl-1-benzenesulfonate (9) was synthesized according to (USSR Patent 493-496).
A mixture of 3 g of 1,8-naphthoilene-1′,2′-benzimidazole and 10 g of ethyl p-toluenesulfonate was heated at 200° C. for 15 min, cooled down to 20-30° C. and treated with 70 mL of toluene. The obtained crystalline product was washed with 10 mL of toluene, dried at 70-80° C., and recrystallized from ethanol. M.P. 215-217° C. Found, %: N 5.85; S 6.33. C27H22N2O4S. Calculated, %: N 5.95; 6.81.
20 g (0.1 mol) of 1H,3H-benzo[de]isochromene-1,3-dione and 9 g (0.129 mol) of hydroxylamine hydrochloride in 500 mL of 2% solution of sodium carbonate were boiled for 3 h. Then 500 mL of 10% sodium carbonate solution were added and heated to boiling. After cooling 17 g of 2-hydroxy-2,3-dihydro-1H-benzo[de]isoquinoline-1,3-dione sodium salt were obtained.
16 g (0.084 mol) of p-toluenesulfonic acid was added to a mixture of 17 g (72 mmol) of 2-hydroxy-2,3-dihydro-1H-benzo[de]isoquinoline-1,3-dione sodium salt in 400 mL of dry benzene, refluxed for 6 h, and the hot mixture was filtered. The obtained 2-(4-methylphenylsulfonyloxy)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinoline (12.85 g, 50%) was suspended in 600 mL of methanol. Then 91 mL of 0.5 N solution of sodium hydroxide in methanol were added. After stirring at RT for 1 h the mixture was neutralized with HCl. The solvent was removed on a rotary evaporator and residue was washed several times with water. Yield: 5.6 g (95%). M.p. 170-172° C. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 10.70 s (1H, NH), 8.17 d (1H, H3, J 8.1 Hz), 8.02 d (1H, H3, J 7.2 Hz), 7.79 t (1H, H3, J 7.8 Hz), 8.17 d (1H, H3, J 8.1 Hz) 8.17 d (1H, H3, J 8.1 Hz).
3-methoxybenzanthrone (10) was synthesized according to USSR Patent No. 194828; and Krasovitskii, et al. (B. M. Krasovitskii, et al., Zhurn. Vsesojuz. Khim. Obshchestva [in Russ.], 1967, V. 12, P. 713).
A mixture of 2.4 g (0.01 mol) of 3-aminobenzanthrone and 10 mL (0.1 mol) of dimethylsulphate was heated at 130° C. for 2 h. Then the mixture was diluted with water, neutralized, and the crude product was filtered off, dried, and column purified (benzene, Silica Gel). Yield 1.8 g (67%). M.P. 125-127° C. Red crystals.
2.73 g (0.1 mol) of 2-dimethylamino benzanthrone was dissolved in 4.6 mL (0.06 mol) of DMF and 3.66 mL (0.04 mol) of POCl3 were added dropwise at 35-40° C. The mixture was heated with stirring at 80° C. for 1.5 h, cooled down to RT and treated with ice. Then NH4 PF6 was added and the obtained precipitate was recrystallized from a water-ethanol (1:1, v/v) mixture. Yield 3.18 g (67%). M.P. 295-297° C. 1H-NMR, (200 MHz, DMSO-d6, δ, ppm): 8.79 d (1H, H6, J 8.2 Hz), 8.47 d (1H, H7, J 7.6 Hz), 8.45 s (1H, H1), 8.33 d (1H, H10, J 7.5 Hz), 8.11 d (1H, H4, J 8.3 Hz), 7.90 t (2H, H8, H9, J 7.6 Hz), 7.68 t (1H, H5, J 8.0 Hz), 5.15 s (2H, CH2), 4.86 s (2H, CH2), 3.51 s (3H, NCH3), 3.22 s (6H, +N(CH3)2). Found, %: C, 55.58; H, 4.62; N, 5.39, C22H21N2OPF6. Calculated, %: C, 55.70; H, 4.46; N, 5.91.
0.5 g (1.92 mmol) of 3-methoxy-7H-benzo[de]anthracen-7-one (10) and 1.5 ml of 9% oleum (fuming sulfuric acid) were mixed and heated at 50° C. with stirring for 8 hours. After cooling reaction mixture was poured into ice and then triturated with concentrated HCl. The obtained red-brown precipitate was filtered off and washed with concentrated HCl. The product was dried in a vacuum desiccator to yield 200 mg (31%) of the product 13.
2.21 g (10 mmol) of 2-dimethylaminoanthracene was added at 0-5° C. to a mixture of 4.2 mL (55 mmol) DMF and 1.83 mL (20 mmol) of POCl3. The mixture was heated with stirring at 80° C. for 3 h, cooled down to RT, treated with ice, neutralized with AcONa, and NH4 PF6 was added. The obtained precipitate was recrystallized from aqueous ethanol. Yield 2.74 g (65%). M.P. 255-256° C. 1H-NMR, (200 MHz, DMSO-d6, δ, ppm): 8.57 s (1H, H9), 8.14 s (1H, H10), 8.11 d (1H, H4, J 9.4 Hz), 8.06 d (2H, H5, H8, J 8.3 Hz), 7.60 m (2H, H6, H7, J 8.3 Hz), 7.49 d (1H, H3, J 9.3 Hz), 5.08 s (2H, CH2), 4.83 s (2H, CH2), 3.25 s (3H, NCH3), 3.22 s (6H, +N(CH3)2). Found, %: C, 54.22; H, 5.17; N, 6.81, C19H21N2 PF6. Calculated, %: C, 54.03; H, 5.01; N, 6.63.
3-Sulfopyrene (18) was synthesized according to Vollmann, et al. (Vollmann, et al, Ann. Chem., 1937, Bd. 531, S. 106).
3-Aminopyrene (19a) was synthesized according to Vollman et al. (Vollmann, et al, Ann. Chem., 1937, Bd. 531, S. 109).
0.2 g (0.63 mmol) of sodium 6-amino-1-pyrenesulfonate was added to a mixture of 0.14 g (0.70 mmol) 6-bromohexanoic acid and 20% solution of sodium hydroxide. The mixture was heated with stirred at 90-95° C. for 2 h, cooled down to RT, neutralized with hydrochloric acid to pH=1, and green fine dust was filtered. The obtained precipitate was twice column purified (Silica gel PR-18, water). Yield 11%. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 8.92 d (1H, arom, J 9.7 Hz), 8.39 d (1H, arom, J 9.7 Hz), 8.32 d (1H, arom, J 7.9 Hz), 8.06 d (1H, arom, J 7.1 Hz), 7.90 d (1H, arom, J 7.9 Hz), 7.89 d (1H, arom, J 8.8 Hz), 7.68 d (1H, arom, J 8.8 Hz), 7.31 d (1H, arom, J 8.3 Hz), 3.48 m (2H, CH2), 2.25 t (2H, CH2, J 7.1 Hz), 1.77 t (2H, CH2, J 7.1 Hz), 1.66-1.37 m (4H, 2CH2).
0.72 g (2.93 mmol) of 1-pyrenecarboxylic acid was added to 12.6 g (130 mmol) of sulfuric acid and the mixture was stirred at RT for 3 h, mixed up with ice, neutralized with sodium hydroxide, and obtained yellowish precipitate was twice column purified (Silica gel PR-18, water). Yield 13%. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 9.32 d (1H, arom, J 9.9 Hz), 9.05 d (1H, arom, J 7.9 Hz), 8.46 d (1H, arom, J 8.0 Hz), 8.33 t (1H, arom, J 7.9 Hz), 8.18 (1H, arom, J 7.9 Hz), 8.15 m (1H, arom, J 8.1 Hz), 8.105 s (1H, arom), 8.098 s (1H, arom).
1.2 g (3.64 mmol) of ethyl 4-oxo-4-(1-pyrenyl)butanoate was added to a mixture of 2.54 g (21.82 mmol) of chlorosulfonic acid and 20 mL of chloroform. The mixture was stirred at RT for 5 h. Then the product was extracted with 50 mL of water and hydrolyzed with 0.15 ml of HCl (d=1.19). Green solution was column purified (Silica gel PR-18, water). Yield 13%. 1H-NMR (200 MHz, DMSO-d6, δ, ppm): 9.30 d (1H, arom, J 9.5 Hz), 8.72 d (1H, arom, J 9.5 Hz), 8.57 d (1H, arom, J 9.7 Hz), 8.40 d (1H, arom, J 8.2 Hz), 8.30 (1H, arom, J 8.0 Hz), 8.28 m (1H, arom, J 9.4 Hz), 3.49 t (2H, CH2, J 6.1 Hz), 2.75 t (2H, CH2, J 6.1 Hz).
6-amino-1,3-naphthalenedisulfonic acid disodium salt (22) was purchased from TCI (Product No A0340).
A mixture of 5.0 g (14 mmol) of 6-hydrazino-1,3-naphthalenedisulfonic acid (S. R. Mujumdar, R. B. Mujumdar, C. M. Grant, et al., Bioconjugate Chem., 1996, V. 7, P. 356-362), 2.8 g (15 mmol) of 7-methyl-8-oxononanoic acid, 2.7 g (28 mmol) of potassium acetate and 40 ml of acetic acid was refluxed for 24 hours. The residue was treated with ether, filtered off and washed three times with 20 ml of isopropanol. The product was dried in vacuum desiccator and purified by column chromatography (Li Chroper RP-18, 0.05% trifluoroacetic acid—water) to yield 2.3 g (35%) of the product 24. 1H-NMR (200 MHz, DMSO-d6, δH) 8.90 (1H, d, arom. H), 8.24 (1H, s, arom. H), 8.22 (1H, s, arom. H), 7.69 (1H, d, arom. H), 2.27 (3H, s, 2-CH3), 2.3-2.1 (2H, m, CH2), 2.10 (2H, t, CH2COOH), 1.43 (3H, s, 3-CH3), 1.35-0.95 (4H, m, (CH2)2), 0.6-0.15 (2H, m, —CH2). UV: λmax (abs)=217, 228, 254, 263, 271 nm (methanol).
1.25 g (2.7 mmol) of 6-(1,2-dimethyl-6,8-disulfo-1H-benzo[e]indol-1-yl)hexanoic acid (24) were dissolved in 10 ml of methanol and then 450 mg (8 mmol) of potassium hydroxide in 30 ml of isopropanol was added slowly under stirring at RT. The obtained mixture was stirred for 30 minutes at RT. The residue was filtered off, washed with isopropanol, and dried in a vacuum desiccator. Yield 2.26 g (80%). UV: λmax(abs)=216, 229, 254, 262.5, 271 nm (water).
1.26 g (2.2 mmol) of tripotassium 6-(1,2-dimethyl-6,8-disulfonato-1H-benzo[e]indol-1-yl)hexanoate and 1.58 g (13 mmol) of 1,3-propane sultone was melted at 140-150° C. for 12 hours. After cooling the solid formed was treated with acetone. The residue obtained was filtered, washed several times with 10 ml of isopropanol and acetone. The product was dried in a vacuum desiccator. Yield: 1.6 g (99%) of raw product 25. UV: λmax (abs)=228 nm, 263 nm, 272 nm, 281 nm (water).
1,3,8,10-tetraoxo-1,3,8,10-tetrahydroisochromeno[6′,5′,4′:10,5,6]anthra-[2,1,9-def]isochromene-5,12-disulfonic acid (27) was synthesized according to Zhubanov, et al. (B. A. Zhubanov, et al. Zhurn. Organ. Khim. [in Russ], 1992, V. 28, P. 1486-1488).
6-amino-3-methyl-2,7-dihydro-3H-naphtho[1,2,3-de]quinoline-2,7-dione (38) was synthesized according to Kazankov (M. V. Kazankov, Zhurn. Vsesojuz. Khim. Obshchestva [in Russ.], 1974, V. 19, P. 64-71).
4-dimethylamino-6,11-dihydroanthra[1,2-c][1,2,5]thiadiazole-6,11-dione (39) was synthesized according to (M. V. Gorelik, et al, Khimiya Geterotsykl. Soed. [in Russ.], 1968, No. 3, P. 447-452; M. V. Gorelik, et al, Khimiya Geterotsykl. Soed. [in Russ.], 1971, No. 2, P. 238-243).
Protein labeling reactions were carried out using a 50 mM bicarbonate buffer (pH 9.1). A stock solution of 1 mg of dye in 100 μL of anhydrous DMF was prepared. 10 mg of protein were dissolved in 1 mL of 100 mM bicarbonate buffer (pH 9.1). Dye from the stock solution was added, and the mixture was stirred for 24 h at room temperature.
Unconjugated dye was separated from labelled proteins using gel permeation chromatography with SEPHADEX G50 (0.5 cm×20 cm column) and a 22 mM phosphate buffer solution (pH 7.3) as the eluent. The first colored or/and fluorescent band contained the dye-protein conjugate. A later colored or/and fluorescent band with a much higher retention time contained the separated free dye. A series of labeling reactions as described above were set up to obtain different dye-to-protein ratios. Compared to the free forms, the protein-bound forms of the dyes show distinct changes in their spectral properties.
The dye-to-protein ratio (D/P) gives the number of dye molecules covalently bound to the protein. The D/P ratio was determined according to Mujumdar et al. (R. B. Mujumdar, L. A. Ernst, S. R. Mujumdar, C. J. Lewis, A. S. Waggoner, Bioconjugate Chem., 4 (1993) 105-111). Each dye—BSA conjugate was diluted with phosphate buffer (PB) pH 7.4 to provide the absorbance (Aconj(λmax)) in a 5-cm quartz cuvette in the range of 0.15-0.20 at the long-wavelength absorption maximum of the dye—BSA conjugate. For these solutions the absorbances Aconj(λmax) at the long-wavelength maximum of the dye and Aconj(278) at 278 nm were measured. Then the absorbances of the free dye at 278 nm (Adye(278)) and at the long-wavelength maximum (Adye(λmax)) were taken from the dye absorption spectrum. The dye-to-protein ratio (DIP) were calculated using the following formula:
where εdye is the extinction coefficient of the dye at the long-wavelength maximum, and εBSA=45540 M−1 cm−1 is the extinction coefficient of BSA at 278 nm, and x=Adye(278)/Adye(λmax).
Covalent Attachment of NHS-Esters to BSA
A stock solution of 1 mg of NHS-ester in 100 μL of anhydrous DMF was prepared. Then 5 mg of BSA was dissolved in 1 mL of a 50 mM bicarbonate buffer, pH 9.0, and a relevant amount of the dye stock solution was added. The mixture was allowed to stir for 3 h at 25° C. Separation of the dye-BSA conjugate from non-conjugated dye was achieved using gel permeation chromatography on a 1.5 cm×25 cm column (stationary phase: SEPHADEX G25; eluent: 67 mM PB, pH 7.4). The fraction with the lowest retention time containing the dye-BSA conjugate was collected.
Covalent Attachment of NHS-Esters to Polyclonal Anti-HSA
385 μL (5.2 mg/mL) of anti-HSA were dissolved in a 750 μL bicarbonate buffer (0.1 M, pH 9.0). 1 mg of NHS-ester is dissolved in 50 μL of DMF and slowly added to the above-prepared protein solution with stirring. After 20 h of stirring, the protein-conjugate was separated from the free dye using SEPHADEX G50 and a phosphate buffer (22 mM, pH 7.2). The first colored or/and fluorescent fraction that is isolated contains the labeled conjugate.
100 mg (0.22 mmol) of 3, 100 mg (0.33 mmol) TSTU, and 76 μL (0.44 mmol) of DIPEA were dissolved in 20 mL of acetonitrile. The obtained solution was stirred at room temperature for 2 h. The reaction was monitored by TLC (RP-18, acetonitrile/water=5/1). After completion, the solvent was removed under reduced pressure and the residue was washed several times with ether, dried and stored in a vacuum desiccator to give NHS ester of 3 with quantitative yield.
0.8 mg of NHS ester of 3 were dissolved in 80 μL of anhydrous DMF and 17 μL of this solution were added to a solution of 5 mg of BSA in 1 mL of a 50 mM bicarbonate buffer, pH 9.0. The mixture was allowed to stir for 3 h at 25° C. Separation of the dye 3-BSA conjugate from non-conjugated dye was done using a gel permeation chromatography on the 1.5 cm×25 cm column (stationary phase SEPHADEX G25, eluent 67 mM PB of pH 7.4). The fluorescent fraction of yellow color with the lowest retention time containing the dye-BSA conjugate was collected. The obtained D/P ratio was 3.
Using 60 μL of the above dye-NHS stock solution the dye-BSA conjugate with D/P ratio 8 was obtained.
A mixture of 1 mg (2.4 μmol) of 23, 1.1 mg (3.7 μmol) of TSTU, 1 μL (5.7 μmol) of DIPEA, and 100 μL of anhydrous DMF was stirred at room temperature for 2 h. The obtained 23-NHS solution in DMF was used for covalent labeling to protein without additional purification.
11 mg of BSA were dissolved in 1 mL of a 50 mM of bicarbonate buffer pH 9.0, and 35 μL of the described above 23-NHS solution in DMF were added. The mixture was allowed to stir for 3 h at 25° C. Separation of the dye 23-BSA conjugate from non-conjugated dye was achieved using a gel permeation chromatography on a 1.5 cm×25 cm column (stationary phase SEPHADEX G25, eluent 67 mM PB of pH 7.4). The lowest retention time fluorescent fraction containing the dye-BSA conjugate was collected.
A mixture of 1.2 mg (2.0 μmol) of 25, 1.0 mg (3.3 μmol) of TSTU, 1 μL (5.7 μmol) of DIPEA, and 120 μL of anhydrous DMF was stirred at room temperature for 2 h. The obtained 25-NHS solution in DMF was used for the covalent attachment to protein without additional purification.
11 mg of BSA were dissolved in 1 mL of a 100 mM of bicarbonate buffer of pH 8.4 and 35 μL of the described above 23-NHS solution in DMF was added. The mixture was allowed to stir for 4 h at 25° C. Separation of the dye 25-BSA conjugate from non-conjugated dye was done using a gel permeation chromatography on the 1.5 cm×25 cm column (stationary phase SEPHADEX G25, eluent 67 mM PB of pH 7.4). The fluorescent fraction with the lowest retention time containing the dye-BSA conjugate was collected.
Reactive functional groups other than NHS have been described in the literature and can be synthesized according to previously described procedures. The syntheses of selective reactive functional groups are described in International Publication no. WO 02/26891 A1.
Spectral Properties of Representative Dyes:
Compounds of the present disclosure invention may have particularly long luminescence lifetimes. For example, selected compounds may exhibit a luminescence lifetime on the order of 4 ns or greater. Such compounds may therefore be particularly useful in lifetime- and polarization-based assays, Fluorescence Lifetime Imaging (FLIM) and other applications where the luminescence lifetime is a parameter of use. In one aspect of the disclosed compounds, they have a luminescence lifetime of 10 ns or longer. In another aspect of the disclosed compounds, they have a luminescence lifetime of between 4 and 30 ns.
The synthesis of selected long-lifetime probes and labels are described in the following Examples. The structures, absorption and emission data as well as the luminescent lifetime in different solvents of specific dyes are given in Table 1.
In one embodiment of the disclosure, the long-lifetime probes and labels are based on naphthalic acid derivatives which have lifetimes in the range of 5 to 23 ns or higher. Representative dyes are listed in Table 1 (compounds 1 to 9) and the synthesis of these dyes is described in the Examples Section (Examples 1 to 5). This class of dyes is perfectly suited for excitation with the blue 404 nm or 436 nm diode lasers and some of these compounds were labeled to BSA to demonstrate that these dyes do maintain long lifetimes in presence of proteins. The data in Table 1 also indicate that the luminescent lifetimes of these compounds is not strongly dependent on the solvent system (see compounds 5 and 6). Compound 6 having a long luminescent lifetime of around 23 ns is a probe and potential label that could have wide-spread use for the development of luminescent assays and sensors for clinical applications and high-throughput screening.
Benzanthrone dyes 10-13 of this invention have longer absorption and emission wavelength (up to 700 nm in water) with lifetimes in the range of 5 to 10 ns in presence of protein.
In another embodiment the lifetime probes and labels are based on anthracene derivatives (Table 1, compounds 14-17). These derivatives have absorption and emission in the blue region of the spectrum with lifetime of 8 ns and higher. In particular reactive derivatives of compound 16 which has a lifetime of 20 ns in water would be very suitable as labels for lifetime based applications.
Pyrenes are known to have long luminescence lifetimes. The sulfo-pyrene compound (Table 1, compound 18) has a lifetime of around 40 ns in water. The sulfonate functional group of this compound can easily be converted into a sulfonyl chloride for covalent labeling to biomolecules. The synthesis is described in Example 11.
Acridine derivatives as shown in Table 1, compounds 20 and 21 have long lifetimes in water which makes them very suitable candidates as labels for lifetime and polarization based assays.
Naphthalene derivatives as shown in Table 1, compounds 22 and 23 have great potential as lifetime probes and labels due to long lifetimes in water and when labeled to proteins. From the data in Table 1 (compounds 23 and 23-BSA) it can be seen that covalent attachment of the naphthalene derivative 23 to proteins does not have a strong effect on the lifetime, which is an important criterion for a label that is used in polarization based assays. Surprisingly the fluorescence lifetime of the disulfo-benzoindole derivative 25 (Table 1) increases more than 3 times from 4.5 ns to 15 ns upon covalent labeling to BSA. This is a very important and unexpected feature and this compound could be used as a lifetime-sensitive tracer in assays and for sensing applications.
Reporter compounds including a 1,3,3-trimethyl-1,2,3,4-tetrahydro pyrimidin-3-ium moiety, where each of the RA, RB and RC substituents are methyl, may demonstrate a particularly enhanced luminescence lifetime. In one embodiment, these compounds may exhibit a luminescence lifetime of greater than 10 ns.
Fused aromatic ring systems are an additional group of lifetime compounds. Some of these derivatives have lifetime in the order of 10 to 20 ns. Importantly the absorption and emission maxima of these compounds are shifted towards longer wavelengths (around 500-600 nm). Reactive versions of these compounds could also be used for labeling and development of luminescence lifetime- and polarization-based assays and sensors.
Table 1. Spectral properties and luminescent lifetimes of representative dyes of this invention
Description of Applications of the Invention
The reporter compounds disclosed above exhibit utility for any assay that utilizes colorimetric or luminescent labeling. In general, a variety of useful assay formats exist that may be improved by the use of the presently disclosed compounds.
For example, the assay may be a competitive assay that includes a recognition moiety, a binding partner, and an analyte. Binding partners and analytes may be selected from the group consisting of biomolecules, drugs, and polymers, among others. In some competitive assay formats, one or more components are labeled with photoluminescent compounds in accordance with the invention. For example, the binding partner may be labeled with such a photoluminescent compound, and the displacement of the compound from an immobilized recognition moiety may be detected by the appearance of fluorescence in a liquid phase of the assay. In other competitive assay formats, an immobilized enzyme may be used to form a complex with the fluorophore-conjugated substrate.
Some of the present reporter molecules include specific moieties for specific labeling of protein tyrosine phosphatases, as well as other phosphatases as described by Zhu, Q., et al. (Tetrahedron Letters, 44, 2669 (2003).
The binding of antagonists to a receptor can be assayed by a competitive binding method in so-called ligand/receptor assays. In such assays, a labeled antagonist competes with an unlabeled ligand for the receptor binding site. One of the binding partners can be, but not necessarily has to be, immobilized. Such assays may also be performed in microplates. Immobilization can be achieved via covalent attachment to the well wall or to the surface of beads.
Other preferred assay formats are immunological assays. There are several such assay formats, including competitive binding assays, in which labeled and unlabeled antigens compete for the binding sites on the surface of an antibody (binding material). Typically, there are incubation times required to provide sufficient time for equilibration. Such assays can be performed in a heterogeneous or homogeneous fashion.
Sandwich assays may use secondary antibodies and excess binding material may be removed from the analyte by a washing step.
Other types of reactions include binding between avidin and biotin, protein A and immunoglobulins, lectins and sugars (e.g., concanavalin A and glucose).
Certain dyes of the invention are charged due to the presence sulfonic or a quarternary nitrogen atoms in a ring structure (see compounds 3-9, 12, 16 in Table 1). These compounds are typically impermeant to membranes of biological cells. In this case treatments such as electroporation and shock osmosis can be used to introduce the dye into the cell. Alternatively, such dyes can be physically inserted into the cells by pressure microinjection, scrape loading etc.
The reporter compounds described here also may be used in sequencing nucleic acids and peptides. For example, fluorescently-labeled oligonucleotides may be used to trace DNA fragments. Other applications of labeled DNA primers include fluorescence in-situ hybridization methods (FISH) and for single nucleotide polymorphism (SNIPS) applications, among others.
Multicolor labeling experiments may permit different biochemical parameters to be monitored simultaneously. For this purpose, two or more reporter compounds are introduced into the biological system to report on different biochemical functions. The technique can be applied to fluorescence in-situ hybridization (FISH), DNA sequencing, fluorescence microscopy, and flow cytometry among others. One way to achieve multicolor analysis is to label biomolecules such as nucleotides, proteins or DNA primers with different luminescent reporters having distinct luminescence properties (e.g. excitation or emission maxima). Multi-lifetime analysis on the other hand is based on labeling with reporters that have the same excitation and emission maxima but differ due to their distinct luminescence lifetimes. Compounds of this invention have lifetimes in the range from 4 ns to 40 ns and higher and can therefore be easily differentiated by measuring the luminescence lifetime or a relevant parameter (e.g. phase angle).
Phosphoramidites are useful functionalities for the covalent attachment of dyes to oligos in automated oligonucleotide synthesizers. They are easily obtained by reacting the hydroxyalkyl-modified dyes of the invention with 2-cyanoethyl-tetraisopropyl-phosphorodiamidite and 1-H tetrazole in methylene chloride.
The simultaneous use of FISH (fluorescence in-situ hybridization) probes in combination with different fluorophores is useful for the detection of chromosomal translocations, for gene mapping on chromosomes, and for tumor diagnosis, to name only a few applications. One way to achieve simultaneous detection of multiple sequences is to use combinatorial labeling. The second way is to label each nucleic acid probe with a luminophore with distinct properties (e.g lifetime). Conjugates can be synthesized from this invention and can be used in a multicolor-multilifetime multisequence analysis approach.
In another approach the dyes of the invention might be used to directly stain or label a sample so that the sample can be identified and or quantitated. Such dyes might be added/labeled to a target analyte as a tracer. Such tracers could be used e.g. in photodynamic therapy where the labeled compound is irradiated with a light source and thus producing singlet oxygen that helps to destroy tumor cells and diseased tissue samples.
The reporter compounds of the invention can also be used in screening assays for a combinatorial library of compounds. The compounds can be screened for a number of characteristics, including their specificity and avidity for a particular recognition moiety.
Assays for screening a library of compounds are well known. A screening assay is used to determine compounds that bind to a target molecule, and thereby create a signal change which is generated by a labeled ligand bound to the target molecule. Such assays allow screening of compounds that act as agonists or antagonists of a receptor, or that disrupt a protein-protein interaction. It also can be used to detect hybridization or binding of DNA and/or RNA.
Other screening assays are based on compounds that affect the enzyme activity. For such purposes, quenched enzyme substrates of the invention could be used to trace the interaction with the substrate. In this approach, the cleavage of the fluorescent substrate leads to a change in the spectral properties such as the excitation and emission maxima, intensity, polarization and/or lifetime, which allows to distinguish between the free and the bound luminophore.
The dye compounds are also useful for use as biological stains. There may be limitations in some instances to the use of the above compounds as labels. For example, typically only a limited number of dyes may be attached to a biomolecules without altering the fluorescence properties of the dyes (e.g. quantum yields, lifetime, emission characteristics, etc.) and/or the biological activity of the bioconjugate. Typically quantum yields may be reduced at higher degrees of labeling. Encapsulation into beads offers a means to overcome the above limitation for the use of such compounds as fluorescent markers. Fluorescent beads and polymeric materials are becoming increasingly attractive as labels and materials for bioanalytical and sensing applications. Various companies offer particles with defined sizes ranging from nanometers to micrometers. Noncovalent encapsulation in beads may be achieved by swelling the polymer in an organic solvent, such as toluene or chloroform, containing the dye. Covalent encapsulation may be achieved using appropriate reactive functional groups on both the polymer and the dyes.
In general, hydrophobic versions of the invention may be used for non-covalent encapsulation in polymers, and one or more dyes could be introduced at the same time. Surface-reactive fluorescent particles allow covalent attachment to molecules of biological interest, such as antigens, antibodies, receptors etc. Hydrophobic versions of the invention such as dye having lipophilic substituents such as phospholipids will non-covalently associate with lipids, liposomes, lipoproteins. They are also useful for probing membrane structure and membrane potentials.
Compounds of this invention may also be attached to the surface of metallic nanoparticles such as gold or silver nanoparticles or metal-coated surfaces. It has recently been demonstrated that fluorescent molecules may show increased quantum yields near metallic nanostructures e.g. gold or silver nanoparticles (O. Kulakovich et al. Nanoletters 2 (12) 1449-52, 2002). This enhanced fluorescence may be attributable to the presence of a locally enhanced electromagnetic field around metal nanostructures. The changes in the photophysical properties of a fluorophore in the vicinity of the metal surface may be used to develop novel assays and sensors. In one example the nanoparticle may be labeled with one member of a specific binding pair (antibody, protein, receptor etc) and the complementary member (antigen, ligand) may be labeled with a fluorescent molecule in such a way that the interaction of both binding partners leads to an detectable change in one or more fluorescence properties (such as intensity, polarization, quantum yield, lifetime, phase angle among others). Replacement of the labeled binding partner from the metal surface may lead to a change in fluorescence, which can then be used to detect and/or quantify an analyte.
Conventional fluorophores have lifetimes in the range of 100 ps to 4 ns. It is known that the luminescence lifetime of a fluorophore near a metallic nanostructure exhibits shorter lifetimes thus the lifetime of conventional labels will be shortened to an extend that measurement with inexpensive instrumentation is not possible. Dyes of this invention have in average 10 times longer lifetimes than conventional dyes and will therefore allow the use of inexpensive instrumentation even in presence of metallic nanostructures.
Gold colloids can be synthesized by citrate reduction of a diluted aqueous HAuCl4 solution. These gold nanoparticles are negatively charged due to chemisorption of citrate ions. Surface functionalization may be achieved by reacting the nanoparticles with thiolated linker groups containing amino or carboxy functions. In another approach, thiolated biomolecules are used directly for coupling to these particles.
Analytes
The invention may be used to detect an analyte that interacts with a recognition moiety in a detectable manner. As such, the invention can be attached to a recognition moiety which is known to those of skill in the art. Such recognition moieties allow the detection of specific analytes. Examples are pH-, or potassium sensing molecules, e.g., synthesized by introduction of potassium chelators such as crown-ethers (aza crowns, thia crowns etc). Dyes with N—H substitution in the heterocyclic rings are known to exhibit pH-sensitive absorption and emission (S. Miltsov et al., Tetrahedron Lett. 40: 4067-68, (1999), M. E. Cooper et al., J. Chem. Soc. Chem. Commun. 2000, 2323-2324), Calcium-sensors based on the BAPTA (1,2-Bis(2-aminophenoxy)ethan-N,N,N′,N′-tetra-aceticacic) chelating moiety are frequently used to trace intracellular ion concentrations. The combination of a compound of the invention and the calcium-binding moiety BAPTA may lead to new long-wavelength absorbing and emitting Ca-sensors which could be used for determination of intra- and extracellular calcium concentrations (Akkaya et al. Tetrahedron Lett. 38:4513-4516 (1997). Additionally, or in the alternative, reporter compounds already having a plurality of carboxyl functional groups may be directly used for sensing and/or quantifying physiologically and environmentally relevant ions.
Fluorescence Methods
Dyes of this disclosure may be useful in particular because of their long luminescent lifetimes up to 40 ns and higher. The long nanosecond lifetime of the dyes and dye-protein conjugates may allow the use of relatively inexpensive instrumentation that employs laser diodes for excitation. Typical assays based on the measurement of the fluorescence lifetime as a parameter include for example FRET (fluorescence resonance energy transfer) assays. The binding between a fluorescent donor labeled species (typically an antigen, or a ligand) and a fluorescent acceptor labeled species may be accompanied by a change in the intensity and/or the fluorescence lifetime. The lifetime can be measured using intensity-based (Time-correlated single photon counting TCSPC) or phase-modulation-based methods (J. R. LAKOWICZ, PRINCIPLES OF FLUORESCENCE SPECTROSCOPY (2nd Ed. 1999)). Due to the broad range of lifetimes exhibited by these dyes they can be used simultaneously in multi-lifetime multi-analyte assays (see above).
Dyes of this disclosure may also exhibit high intrinsic polarization in the absence of rotational motion, making them useful as tracers in fluorescence polarization (FP) assays. Fluorescence polarization immunoassays (FPI) are widely applied to quantify low molecular weight antigens. The assays are based on polarization measurements of antigens labeled with fluorescent probes. The requirement for polarization probes used in FPIs is that emission from the unbound labeled antigen be depolarized and increase upon binding to the antibody. Low molecular weight species labeled with the compounds of the invention can be used in such binding assays, and the unknown analyte concentration can be determined by the change in polarized emission from the fluorescent tracer molecule. The longer luminescent lifetimes of the present labels permit the measurement of higher molecular weight antigens in a fluorescence polarization assay because the MW of the labeled analyte that can be measured in such a polarization assay is directly dependent on the luminescence lifetime of the label (E. Terpetschnig et al. Biophys J. 68(1):342-50, 1995).
Compositions and Kits
The invention also provides compositions, kits and integrated systems for practicing the various aspects and embodiments of the invention, including producing the novel compounds and practicing of assays. Such kits and systems may include a reporter compound as described above, and may optionally include one or more of solvents, buffers, calibration standards, enzymes, enzyme substrates, and additional reporter compounds having similar or distinctly different optical properties.
Although the invention has been disclosed in preferred forms, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense, because numerous variations are possible. Applicant regards the subject matter of his invention to include all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. No single element, feature, function, or property of the disclosed embodiments is essential. The following claims define certain combinations and subcombinations of elements, features, functions, and/or properties that are regarded as novel and nonobvious. Other combinations and subcombinations may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such claims, whether they are broader, narrower, or equal in scope to the original claims, also are regarded as included within the subject matter of applicant's invention.
This application is based upon and claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 60/814,972, filed Jun. 19, 2006, which is incorporated herein by reference in its entirety for all purposes. This application incorporates by reference in their entirety for all purposes all patents, patent applications (published, pending, and/or abandoned), and other patent and nonpatent references cited anywhere in this application. The cross-referenced materials include but are not limited to the following publications: Richard P. Haugland, HANDBOOK OF FLUORESCENT PROBES AND RESEARCH CHEMICALS (6th ed. 1996); JOSEPH R. LAKOWICZ, PRINCIPLES OF FLUORESCENCE SPECTROSCOPY (2nd Ed. 1999); RICHARD J. LEWIS, SR., HAWLEY'S CONDENSED CHEMICAL DICTIONARY (12th ed. 1993).
| Number | Date | Country | |
|---|---|---|---|
| 60814972 | Jun 2006 | US |
