USING CAPILLARY ELECTROPHORESIS FRONTAL ANALYSIS TO SCREEN DRUGS INTERACTING WITH HUMAN SERUM-PROTEINS

We have used capillary electrophoresis in the frontal analysis mode (C E/FA) to determine the binding capacity of beta-adrenoceptor blocking drugs to individual serum proteins, serum protein mixtures and human s erum. The free drug concentration was directly measured from the heigh t of the frontal peak and used to calculate the bound drug concentrati on. From the bound drug concentration, the percentage of drug bound to the serum proteins alpha(1)-acid glycoprotein (AGP) and human serum a lbumin (PISA) was then determined. In addition to determining the perc ent of a drug bound to a protein, the drug-protein association constan t (K-a) was determined for AGP binding to beta-blockers. The data-esti mated association constants were consistent with literature values. Th e CE/FA studies on the beta-adrenoceptor blocking drugs and the serum proteins indicated that PISA, AGP, high density lipoprotein (HDL), and low density lipoprotein (LDL) were the main contributors to serum bin ding for this series of compounds. The serum-drug binding data sorted the beta-adrenoceptor blocking drugs into high and low binding categor ies. The protein mixture (AGP + HSA + HDL + LDL) resulted in dividing the beta-blockers into the same high/low rankings. The protein mixture (AGP + HSA + HDL + LDL) was amenable to automation, did not autoaggre gate, and had constant concentrations for the proteins.