Study on the sorption properties of α₁‐acid glycoprotein (AGP)‐based stationary phase modified by organic solvents

Abstract

An alpha(1)-acid glycoprotein, immobilized on silica (Chiral-AGP) is one of the most widely used chiral stationary phases for the enantiomeric separation of a wide variety of chiral drugs with several applications in the biological and clinical field. The aim of this work was to study the sorption properties of the AGP-based stationary phase, which may have crucial importance for enantioselectivity. New binding data to the mechanism of the chromatographic separation are presented. The sorption of both organic solvents, i.e., acetonitrile and dioxane, shows remarkable pH dependency. A fluorescence quenching study was carried out to elucidate structural changes of AGP in the presence of acetonitrile using 2,2,2-trichloroethanol as fluorescence quencher.

Quantitative determination of the enantiomers of methadone and its metabolite (EDDP) in human saliva by enantioselective liquid chromatography with mass spectrometric detection

“…A reversible conformational change in immobilized AGP has been reported between pH 5.0 and 7.0 in association with the enantioselective separation of the anti-malarial agents chloroquine, mefloquine and enpiroline [38] and between pH 4.0 and 7.0 in association with the sorption of acetonitrile [39]. Thus, results from this study are consistent with pH-induced conformational changes in the AGP molecule, which alter the protein's binding affinity and efficiency.…”

Evaluation of a hydrazide‐linked α1‐acid glycoprotein chiral stationary phase: Separation of R‐ and S‐propranolol

“…This loss of chiral selectivity suggests that hydrophobic interactions play an important role in this separation process; it is also possible that AGP undergoes conformational changes at these higher modifier contents, which could affect its ability to differentiate between R-and S-propranolol. the retention and chiral selectivity of other AGP columns [14,16,18,21,33,38]. For instance, changes in retention and stereoselectivity for agents like propranolol and alprenolol have been seen in the presence of 2-propanol and other organic modifiers on Chiral-AGP columns [16,18,21,33].…”

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

“…In the previous publications , change of protein conformation and chemical environment may take place by varying the eluent pH in the presence of organic additive with a given concentration, further causing the exploration of new chiral‐binding sites. In our work, binding difference of BSA with two DNP‐derived enantiomers under different pH conditions, that is reversal of enantiomer elution order, might be attributed to dramatic change of BSA conformation and binding behavior in the selected mobile phase according to the reported literatures . In addition, there might be different binding mechanisms between BSA‐CSP and the enantiomers of two DNP‐derived compounds .…”

“…Obviously, ACN in mobile phase has played a crucial role in inducing reversal of enantiomer elution order, especially above certain concentration threshold. This phenomenon may be due to nonspecific interaction between ACN and proteins . Increasing ACN in mobile phase may make them partly denature and have significant effect on interactions between proteins and analytes, which finally contributes to reversal of enantiomer elution order.…”