Patent Application
20200010383
The field of the invention generally relates to the use of shear flows to perform separation and analysis of chiral molecules, and more particularly, to a method and device for the separation and analysis of enantiomeric compounds using fluid shear flow and the molecular propeller effect.
A chiral object is any object or system that differs from its mirror image in such a way that its mirror image cannot be superimposed on the original object. One type of chiral object is a chiral molecule, also called an enantiomer. A common feature of chiral molecules is their “handedness” (i.e., right-handed or left-handed). Enantiomers are a subset of chiral objects called stereoisomers, which are a set of isomeric molecules whose atoms have similar connectivity but differ in the way the atoms are arranged in space. Chirality is important in chemistry, especially for biological and drug applications. Separation and analysis of chiral molecules plays an important role in the pharmaceutical industry.
A mixture of molecules is called racemic when it contains equal amounts of right-handed and left-handed enantiomers. The mixture is called enantiopure when only one type of enantiomer dominates. In the follow text, a racemic mixture is defined more broadly to include any non-pure mixture of stereoisomers that are not enantiopure whatever the ratio of counterpart enantiomers.
Each enantiomer has a unique connectivity and arrangement of atoms in the space, which is called an absolute configuration of the molecule. For example, for a chiral molecule with one chiral center there are two possible arrangement of atoms around the chiral center, typically referred to as S and R absolute configurations.
Many conventional molecular separation techniques are not effective for chiral molecules, because two counterpart enantiomers (i.e. S or R) generally share identical physical properties, including size, charge, chemical composition, electric or magnetic dipole moments and interact identically with other achiral substances.
Enantiomers can be identified by their interaction with a circularly polarized light or with other chiral substances. Accordingly, the currently used chiral separation methods utilize interactions with chiral selectors as in e.g. chiral chromatography or rely on recrystallization from solutions. Absolute configuration is typically determined using x-ray crystallography or chiroptical spectroscopy (including vibrational circular dichroism (VCD)). However these methods are time consuming, require large amount of sample and development of specific separation protocol for each newly synthesized chiral molecule. Other more recently proposed chiral separation/analysis methods include chiral gratings and NMR in the presence of static electric field. Very recently, molecular handedness has been detected using microwaves and Coulomb explosion imaging, however these new methods are applicable to molecules that can be sampled in the gas phase and have not been demonstrated for large molecules with high degrees of conformational freedom.
Another relevant chiral separation and analysis method includes a method and device described by Kibar et al. (U.S. Pat. Nos. 7,935,906 and 8,698,031), wherein chiral molecules are exposed to rotating electric fields to utilize the molecular propeller effect that leads to separation of counterpart enantiomers. This method and device require use of very strong rotating electric fields and a few days to achieve partial enantiomer separation for typical chiral molecules. In this method the interaction of the electric field with the dipole moment is used to induce a torque on the chiral molecule and cause it to rotate; the further improvement of this method is limited, among other factors, by available materials that can withstand even stronger electric fields required to accelerate the separation process. Moreover the method requires the chiral molecule to have a large dipole moment and preferential use of non-polar solvents (to increase the electric field magnitude within the chamber) which limits utility of the method.
The disclosure described herein generally relates to a method and device for separation of enantiomers. An exemplary form of a device comprises an approximately cylindrical inner member and an outer member, which can be rotated with respect of each other.
In brief, the inner and outer members are configured to form a contiguous channel or channels (i.e., gap or gaps) between them, which is filled with a solution of enantiomers. The relative rotation of the inner and outer members induces a fluid shear in the contiguous channel between them.
In an embodiment, the overall shape of the inner member is that of an inverted cylinder, e.g., a cup, which can be attached to an axel that can be rotated manually or by a suitable motor. The outer member is also of a cylindrical shape and contains an extruded cylindrical or cup-shaped inner part that is of a smaller diameter than the inner member. The channel between the outer wall of the outer member and the inner member, and the channel between the extruded wall of the outer member and the inner member are approximately the same. The inner member is positioned within the outer member by leaving a small gap at the bottom to enable molecules in solution to diffuse freely between the inner and outer channel areas. The inner member can be moved up or down to form a contact with the bottom of the outer member and seal the solution in the two cylindrical channels. The outer member can also be attached to an axel and rotated in the opposite direction to the rotation of the inner member.
Contained within the device, depending on the overall configuration, are necessary power sources, electronic circuitry and sensors configured to maintain specified rotation frequency, temperature and monitor separation efficiency. In certain instances, one or more functions, e.g., data analysis circuitry, power, data display light sources and sensors, and other components and devices, may be located in a separate portion of the device connected to the device portion by means of electrical wires and/or fiber optics.
In an alternate embodiment of the device, the overall shape of the device is that of a rectangular or trapezoidal fluidic channel, in which the channel height is significantly smaller than the channel width in order to maintain a higher shear rate. The channel height can be lower on one side than the other to enable faster flow of the fluid on one side versus another side of the channel. A non-pure solution of enantiomers can be injected near the center bottom of the channel. The effect of shear flow conditions causes the chiral molecules to rotate leading to propulsion of counterpart enantiomers into opposite directions along the direction perpendicular to the flow and to the shear plane. If channel heights are chosen to be different on the left and right sides of the channel, then enantiomers are not only separated in the direction perpendicular to the flow but also separated along the direction of the flow because flow velocity is different on the left and right sides of the channel. To prevent molecules diffusing away from the bottom of the channel where the shear rate is highest, two different, immiscible fluids can be used wherein, the solvent injected near bottom contains dissolved chiral molecules while the solvent injected above the bottom has low solubility with respected to the chiral molecules of interest thereby preventing the diffusion of the chiral molecules away from the bottom of the channel.
Data and analysis from the device may be displayed on a small screen located on the outside of the member in an embodiment. In other embodiments, such data may be transmitted either wirelessly or via electrical connection to adjacent data receiving devices for display and further analysis.
Thus, in one aspect the disclosure provides a method to separate enantiomers using fluid shear and molecular propeller effect, the method including (a) injecting non-pure enantiomer solution into the channel(s) between the inner and the outer members; (b) rotating the inner and outer member with respect to each other to create fluid shear; (c) waiting for an amount of time until the counterpart enantiomers become enriched in the inner and outer channels or, in the case, when only one channel is used in the upper and the lower sides of the channel; and (d) collecting the separated enantiomers. In some embodiments, two or more injection and collection ports may be included in the inner and outer members to facilitate the injection of the non-pure solution and collections of enriched or separated enantiomer solutions.
In other embodiments, the method can further include (a) performing theoretical simulation to determine direction of motion of an enantiomer in the specific absolute configuration; (b) using the described device on the solution of a pure or enriched enantiomer with unknown absolute configuration to determine its direction of motion; and (c) using the comparison between the theoretical and experimental directions to determine the absolute configuration of the enantiomer.
The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
Provided herein, in various aspects, are methods and devices for the separation of chiral molecules, i.e. counterpart enantiomeric compounds, and the determination of their absolute configuration.
The methods and devices described herein overcome the shortcoming of the existing chiral separation and analysis methods by eliminating the need for a chiral selectors, strong electric fields and dipole moments, recrystallization challenges, solvent restrictions and enabling a priori prediction of separation performance and determination of absolute configuration on minute amounts of the enantiomer within short time.
Pasteur showed that dissymmetry generated by a rotation coupled with linear motion is similar to chirality in chemical structures. Similarly the macroscopic propeller effect is a known hydrodynamic phenomenon which manifests itself through rotational-translational coupling in left-right dissymmetrical bodies. Thus enantiomers can be envisaged as tiny propellers with their “handedness” and propulsion direction being determined by absolute configuration of the molecule. It has been proposed by Baranova et al., that the radio frequency electric field with rotating polarization could be used to separate enantiomers. However, using electric field to rotate molecules is not an optimal approach due to reasons listed above.
It has been proposed that a particle placed in the fluid shear flow will experience a torque causing it to rotate. For example the rotation frequency, v, of a spherical particle placed in the shear flow can be calculated as follows:
v=¼π{dot over (γ)} (eq. 1)
where γ is a shear rate. Notably, the rotation frequency does not depend on the diameter of the particle.
As shown in
The propulsion velocity due to propeller effect in shear flows can be calculated according to the following formula:
v=C
ave
L
r
v (eq. 2)
where v is the molecular rotation frequency given by eq. 1, Lr is the rotational-translation coupling constant (i.e. the amount of translation displacement per one revolution of the molecule) and Cave is the orientational factor, which accounts for the random orientation of the most efficient molecular “propeller axis” with respect to the shear plane, its expected value is ˜0.5. Equation 2 indicates that molecular propulsion due to molecular propeller effect is linearly proportional to the shear rate magnitude.
The Péclet number, Pe, is given by a ratio of shear rate to the rotational friction coefficient of the chiral molecule. For typical chiral molecules and practically achievable shear rates (˜1×106 s−1) the Pe<<1. For such low Pe numbers previous theoretical reports predicted that migration velocity of macroscopic helical particles should be proportional to the cube of the shear rate thus making chiral separation of enantiomers (with size around 1 nm) not possible under practically achievable shear rates. Previous reports of molecular dynamics in shear flows did not consider molecular propeller effect which, as we show above, has linear dependence on the shear rate, suggesting that chiral separation of small molecules can be achieved under realistic conditions. Moreover our approach, based on using the concept of molecular propeller effect, offers a straightforward approach to calculate the magnitude and direction of the propulsion velocity in the shear flow which enables application of the method to absolute configuration determination.
As shown in
The outer member (201) can also be attached to an axel (210) and rotated in the opposite direction to the rotation of the inner member (202). Both inner and outer members can be rotated in opposite directions to create opposite shear flows in the outer channel (205) and inner channel (211). Alternatively, only the inner member (202) can be rotated while outer member (201) is kept stationary. Both the inner member (201) and the outer members (202) may contain ports, e.g., (208) and (209), respectively, for injection and collection of a solution containing chiral molecules.
For example, if the channels between the inner and outer members are filled with a racemic solution of enantiomers, the shear flow created by the relative rotation of the inner and outer members will cause the molecules to rotate and then propel up or down along the channels with their direction being dependent on the absolute configuration of the enantiomers. That is, a specific enantiomer (e.g. S), located in the outer channel (205) may propel downward as indicated by the dashed arrows (207) towards the bottom of the device, then diffuse over into the inner channel (211) where the inverse direction of shear flow will drive it upwards. Similar processes will happen for the counterpart enantiomer (e.g. R) i.e. the enantiomer with different absolute configuration, initially located in the inner channel (211) except it will be propelled downwards in the inner channel (211), then diffuse into outer channel (205) at the bottom of the device and be propelled upwards (as indicated by solid arrows 206) along outer channel (205). After sufficient time, the outer channel (205) will contain only the R enantiomers while the inner channel (211) will contain only the S enantiomers. At this time, the inner member (202) can be lowered to seal outer channel (205) and inner channel (211) from each other, and the solutions can be collected with the separated enantiomers.
In other alternate embodiments, the inner member (202) may contain more cylindrical surfaces and the outer member (201) could contain more extruded cylindrical surfaces arranged in such a way that the surfaces of the inner and outer members are interdigitated to form a series of gaps (i.e. more than two) thereby increasing a distance over which the chiral separation can proceed, i.e., an increased separation distance or the amount of effective theoretical plates, which would be advantageous for some chiral molecules requiring more time for separation.
Thus, in an embodiment the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, the device including a) a rotatable inner member containing one or more surfaces; b) an outer member containing one or more surfaces; and c) a contiguous channel between the inner member and the outer member for containing the solution of enantiomers, wherein the inner member can be lowered to separate and seal the mixture of the solution of enantiomers in the contiguous channel into an inner chamber and an outer chamber for collecting the separated enantiomers.
In one aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the outer member is rotatable during operation.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the inner member or the outer member is stationary during operation.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the inner member and the outer member are cooled to maintain a stable temperature during operation.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the inner member and the outer member includes one or more ports for loading and removing the solution containing the mixture of enantiomers from the inner chamber and the outer chamber.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein a relative enrichment of enantiomers in the inner chamber or the outer chamber is used to determine an absolute configuration of the enantiomers.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein a solution of a pure enantiomer is placed in the device and a relative enrichment of the enantiomer in the inner chamber or the outer chamber is used to determine an absolute configuration of the enantiomer.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the inner member and the outer member each contain two or more rotating surfaces exposed to the solution of enantiomers.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein a rotation frequency of the enantiomers is between about 1-5000 rpm, or between about 5000-10000 rpm, or between about 10000-20000 rpm, or between about 20000-50000 rpm, or between about 50000-10000 rpm, or more than 100000 rpm.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the outer member has an inner diameter in the range of less than about 0.1 cm, or from about 0.1 cm to about 1 cm, or from about 1 cm to about 5 cm, or from about 5 cm to about 10 cm, or from about 10 cm to about 20 cm, or more than 20 cm.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the contiguous channel between the one or more surfaces of the inner member and the one or more surfaces of the outer member are each independently in the range of about less than 0.1 μm, or from about 0.1 μm to about 1 μm, or from about 1 μm to about 10 μm, or from about 10 inn to about 1 mm, or from about 1 mm to about 10 mm, or more than 10 mm.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein shear rate is between: less than 10 s−1, 10 s−1-100 s−1, 100 s−1-1000 s−1, 1000 s−1-10000 s−1, 10000 s−1-100000 s−1, 100000 s−1-1000000 s−1, 106 s−1-107 s−1, more than 107 s−1.
In another embodiment, the disclosure provides a method for separating and analyzing counterpart enantiomers from a mixture of a solution of enantiomers, the method including a) inducing fluid shear flow conditions in the solution of enantiomers; b) rotating each of the enantiomers independently due to the shear flow, wherein each counterpart enantiomer rotates in the same direction; c) propelling each of the enantiomers independently due to a molecular propeller effect along a direction perpendicular to a plane of shear flow, wherein each counterpart enantiomer moves in opposite directions; and d) waiting for an amount of time until a specified degree of enantiomer separation is achieved.
In one aspect, the disclosure provides a method for separating and analyzing counterpart enantiomers from a mixture of a solution of enantiomers, wherein the shear flow is induced by relative motion of multiple surfaces in contact with the solution of enantiomers.
In another aspect, the disclosure provides a method for separating and analyzing counterpart enantiomers from a mixture of a solution of enantiomers, wherein the shear flow is induced by pressure-induced flow of the solution of enantiomers through a channel containing multiple surfaces.
In another aspect, the disclosure provides a method for separating and analyzing counterpart enantiomers from a mixture of a solution of enantiomers, wherein the direction of motion of the enantiomer is dependent on the absolute configuration of the enantiomer.
In another aspect, the disclosure provides a method for separating and analyzing counterpart enantiomers from a mixture of a solution of enantiomers, wherein an experimentally determined direction of a pure enantiomer is used to determine its absolute configuration.
In one embodiment the channel (301) is split using Y-junction which divides the flow of the left and the right sides of the channel and sends it into two different collections ports, 310 and 309, respectively, thereby enabling separation and collections of S and R enantiomers. When Y-junction is used a rectangular channel can be used since separation of enantiomers only in the direction perpendicular to the channel is required. Using Y-junction is a preferred embodiment as a shorter channel is required to achieve separation as compared to trapezoidal channel which enables separation along the direction parallel to the flow but is expected to require significantly longer channel.
In another embodiment, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, the device including a) a fluidic channel having a proximal portion and a distal portion; b) an injection port near the proximal portion of the channel for injecting the solution of enantiomers; c) one or more injections ports near the proximal portion of the channel for injecting solvents at different heights of the channel; d) a pump to drive a flow in the channel; and e) two or more ports on the distal side of the channel for collecting the separated enantiomers.
In one aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the channel has trapezoidal form and a height of the channel on one side is different than a height of the channel on the other side.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein two or more different solvents are used to confine the solution of enantiomers near the proximal portion of the channel.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein one of the two or more different solvents dissolves enantiomers and the other of the two or more different solvents does not.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein one of the two or more different solvents has larger viscosity than the other of the two or more different solvents in order to increase shear rate and/or to decrease diffusion.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein an aspect ratio of a width to a height of the channel is less than about 1, or from about 1 to about 5, or from about 5 to about 10, or from about 10 to about 50, or from about 50 to about 100, or from about 100 to about 1000, or more than 1000.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein the height of the channel is less than about 10 nm, or from about 10 nm to about 100 nm, or from about 100 nm to about 500 nm, or from about 500 nm to about 1 μm, or from about 1 μm to about 2 μm, or from about 2 μm to about 10 μm, or from about 10 μm to about 50 inn, or from about 50 μm to about 100 μm, or from about 100 μm to about 500 μm, or from about 500 μm to about 1 mm, or from about 1 mm to about 5 mm, or from about 5 mm to about 10 mm, or more than 10 mm.
In another aspect, the disclosure provides a device for separating counterpart enantiomers from a mixture of a solution of enantiomers, wherein shear rate is less than 10 s−1, or from about 10 s−1 to about 100 s−1, or from about 100 s−1 to about 1000 s−1, or from about 1000 s−1 to about 10000 s−1, or from about 10000 s−1 to about 100000 s−1, or from about 100000 s−1 to about 1000000 s−1, or from about 106 s−1 to about 107 s−1, or more than 107 s−1.
The method can further comprise performing a theoretical simulation to determine the direction of motion of an enantiomer in the specific absolute configuration. In the theoretical analysis method, a molecular dynamics simulation is performed on the molecular model of the enantiomer with given absolute configuration in an explicit solvent to produce molecular dynamics trajectory. The trajectory is analyzed to determine correlations between the random rotational and translation motions of the enantiomer to determine (a) a preferred axis of rotation; (b) the axis with maximal rotational translation coupling; and (c) the average rotational-translational coupling for the enantiomer and the expected direction of propulsion for the given absolute configuration of the enantiomer.
The disclosure further describes a method to determine an absolute configuration of the enantiomer. The method includes (a) performing theoretical simulation to determine direction of motion of an enantiomer in the specific absolute configuration; (b) using described device on the solution of a pure or enriched enantiomer with unknown absolute configuration to determine its direction of motion; and (c) using comparison between the theoretical and experimental directions to determine the absolute configuration of the enantiomer.
Thus, in another embodiment, the disclosure provides an analysis method to determine the direction of motion of an enantiomer having specific absolute configuration, the method including a) performing molecular dynamics simulations on the enantiomer in explicit solvent to obtain molecular dynamics trajectory; and b) using on molecular dynamics trajectory to correlate rotational and translational motions of the enantiomer to determine direction of propulsion due to molecular propeller effect.
In one aspect, the disclosure provides an analysis method to determine the direction of motion of an enantiomer having specific absolute configuration, wherein propulsion direction is determined by using hydrodynamic calculation of rotational to translation coupling.
In another aspect, the disclosure provides an analysis method to determine the direction of motion of an enantiomer having specific absolute configuration, wherein the size of the chiral molecule is less than about 0.5 nm, or from about 0.5 nm to about 1 nm, or from about 1 nm to about 2 nm, or from about 2 nm to about 3 nm, or from about 3 nm to about 5 nm, or from about 5 nm to about 10 nm, or from about 10 nm to about 100 nm, or more than 100 nm.
In another aspect, the disclosure provides an analysis method to determine the direction of motion of an enantiomer having specific absolute configuration, wherein the chiral molecule is any microscopic or macroscopic chiral object.
Contained within the devices, depending on the overall configuration, are necessary power sources, electronic circuitry and sensors configured to maintain specified rotation frequency or pressure, temperature and monitor separation efficiency. In certain instances, one or more functions, e.g., data analysis circuitry, power, data display light sources and sensors, and other components and devices, may be located in a separate portion of the device connected to the device portion by means of electrical wires or fiber optics.
The described method and device can be used for the purification/isolation of majority of chiral molecules both currently known as well as those yet to be discovered.
The described method and device separates racemic mixtures of biologically active substances into their purified enantiomeric constituents which may have distinct biological and/or toxicological attributes (“an active agent”).
When the active agent is a compound, then salts, solvates (including hydrates) of the free compound or salt, crystalline forms, non-crystalline forms, and any polymorphs of the compound are included. All forms are contemplated herein regardless of the methods used to obtain them.
The described method/apparatus can be used in the purification of chiral chemical intermediates in addition to the purification of chiral biologically active substances.
Non-limiting examples of chiral molecules that can be purified into their enantiopure form by a process employing the described method and device are listed in Tables I and II.
Chiral molecule examples contained herein are meant to be offered merely by way of illustration but are not meant to limit the scope of the invention both in terms of currently known as well as currently unknown chiral molecules which can be purified into enantiopure form by the process employing the described method and apparatus.
The application may be better understood by reference to the following non-limiting examples, which are provided as exemplary embodiments of the application. The following examples are presented in order to more fully illustrate embodiments and should in no way be construed, however, as limiting the broad scope of the application.
The methods and devices disclosed herein may be employed for a variety of uses and applications. Such applications include but are not limited to:
In this example, a device as disclosed herein may be employed to separate enantiomers from a racemic mixture.
In this example, a device as disclosed herein may be employed to separate enantiomers from a racemic mixture. In order to separate enantiomers of a chiral molecule, a racemic mixture of chiral molecules is dissolved in a suitable solvent and injected into separation device shown in
In this example, a device as disclosed herein may be employed by a chemist to determine absolute configuration of the enantiomer purified using other means e.g. chiral HPLC. In order to determine absolute configuration of an enantiomer of a chiral molecule, the pure enantiomer (or a mixture enriched in one enantiomer) is dissolved in a suitable solvent and injected into separation device shown in
In this example, a device as disclosed herein may be employed to separate enantiomers from a racemic mixture. In order to separate enantiomers of a chiral molecule, a racemic mixture of chiral molecules is dissolved in a suitable solvent (selected as described above) and injected into separation device shown in
This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 62/185,891, titled: “CHIRAL SEPARATION AND ANALYSIS BY MOLECULAR PROPELLER EFFECT,” filed on Jun. 29, 2015, the entire disclosure of which is hereby incorporated by reference in its entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US16/39505 | 6/27/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62185891 | Jun 2015 | US |
