Chiral discrimination and interaction mechanism between enantiomers and serum albumins.

The chiral discrimination studies of biological system are theoretically and practically significant for the development of chiral drugs and life science. Our work has embarked upon the interaction between serum albumin (SA) (including human SA and bovine SA), R,S-1-(4-methoxyphenyl)ethylamine, and R,S-1-(3-methoxyphenyl)ethylamine. The formation of intermediate transition state, binding sites, and chiral discrimination ability can be investigated by ultraviolet-visible spectra and fluorescence spectra. Moreover, both the changes of hydrophobic microenvironment and energy transfer can be detected by synchronous fluorescence spectra and fluorescence lifetime.

Effect of chromatographic conditions on enantioseparation of bovine serum albumin chiral stationary phase in HPLC and thermodynamic studies.

Twelve chiral compounds were enantiomerically resolved on bovine serum albumin chiral stationary phase (BSA-CSP) by high-performance liquid chromatography (HPLC) in reversed-phase modes. Chromatographic conditions such as mobile phase pH, the percentage of organic modifier, and concentration of analyte were optimized for separation of enantiomers. For N-(2, 4-dinitrophenyl)-serine (DNP-ser), the retention factors (k) greatly increase from 0.81 to 6.23 as the pH decreasing from 7.21 to 5.14, and the resolution factor (R(s)) exhibited a similar increasing trend (from 0 to 1.34). More interestingly, the retention factors for N-(2, 4-dinitrophenyl)-proline (DNP-pro) decrease along with increasing 1-propanol in mobile phase (3%, 5%, 7% and 9% by volume), whereas the resolution factor shows an upward trend (from 0.96 to 2.04). Moreover, chiral recognition mechanisms for chiral analytes were further investigated through thermodynamic methods.

Reversal of elution order of N-(2,4-dinitrophenyl)-proline and N-(2,4-dinitrophenyl)-serine in HPLC by BSA chiral stationary phase.

N-(2,4-dinitrophenyl)-proline and N-(2,4-dinitrophenyl)-serine were enantiomerically resolved on the BSA chiral stationary phase by HPLC in reversed-phase mode. Effects of chromatographic conditions on enantioseparation and elution order have been investigated in detail. For these two samples, reversal of enantiomer elution order was observed by changing buffer pH, the content of acetonitrile, or alcohol modifiers in mobile phase, which is firstly reported in the BSA chiral stationary phase studies. More interestingly, combined effect between buffer pH and the content of acetonitrile was also observed. In addition, coelution range of enantiomers varied along with the content of acetonitrile in mobile phase.

The impact of silica gel pore and particle sizes on HPLC column efficiency and resolution for an immobilized, cyclodextrin-based, chiral stationary phase.

In this study, the CD derivative, mono (6(A)-azido-6(A)-deoxy)-per(p-chlorophenylcarbamonylated) ß-CD was chemically immobilized onto the surface of an amino-functionalized silica gel with different pore (100, 300, and 500Å) and particle (3, 5, and 10 µm) sizes to obtain novel chiral stationary phases. The impact of pore and particle size on the amount of immobilized Ph-ß-CD, column performance, and enantioselectivity was investigated by evaluating the separation of a variety of racemates in both the normal- and the reversed-phase modes. Experimental results revealed that the retention factor and resolution of racemates generally decreased with increasing pore size; the column prepared with the smallest (3 µm) silica gel particle size gave the best column performance and enantioselectivity in both the normal- and the reversed-phase modes.