[Albumin-drug binding study by capillary electrophoresis. II. Determination of drug enantiomeric binding constants].
A capillary electrophoresis (CE) method was applied to determine the binding constants of the basic racemic drug, verapamil (VER) to human serum albumin (HSA) under drug-HSA binding equilibrium (in phosphae buffer pH 7.4, ionic strength = 0.17). In coated capillary, the unbound basic drug eluted as two zonal plateau peaks due to enantiomers separated by chiral selector (45 mmol/L trimethyl-beta-cyclodextrin dissolved in pH 2.5 phosphate buffer) at 15 kV, and their concentrations can be determined from the peak heights. To avoid disturbing the VER-HSA equilibrium, the pH 7.4 solution was used as the inlet vial buffer, and a plug(about 3 cm long) of this buffer was introduced to the capillary before injection of analyte. The binding constants were obtained from linear regression plots. The unbound concentration of S-VER was 1.67 times higher than that of the antipode for the solution 300 mumol/L (+/-) VER-500 mumol/L HSA, while 1.13 for 100 mumol/L (+/-) VER-100 mumol/L HSA. The study confidently provides the binding constants of VER enantiomers to HSA, which are KR = 2.7 x 10(3) (+/- 4.4 x 10(2)) and Ks = 8.5 x 10(3) (+/- 1.0 x 10(2)).
Ding
Y
Y
Dalian Institute of Chemical Physics, Chinese Acedemy of Sciences, Dalian, 116023.
Lin
B
B
D001667:Binding, Competitive; D004347:Drug Interactions; D019075:Electrophoresis, Capillary; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011485:Protein Binding; D012709:Serum Albumin / Q000032:analysis* / Q000378:metabolism; D013237:Stereoisomerism; D014700:Verapamil / Q000032:analysis*
D012709:Serum Albumin; D014700:Verapamil