Site I on human albumin: Differences in the binding of (R)- and (S)-warfarin

The binding of drugs known to interact with area I on human serum albumin ( HSA) was investigated using a chiral stationary phase obtained by anchoring HSA to a silica matrix. In particular, this high-pressure affinity chromat ography selector was employed to study the binding properties of the indivi dual enantiomers of warfarin. The pH and composition of the mobile phase mo dulate the enantioselective binding of warfarin. Displacement chromatograph y experiments evidenced significant differences in the binding of the warfa rin enantiomers to site L The (S)-enantiomer was shown to be a direct compe titor for (R)-warfarin, while (R)-warfarin was an indirect competitor for t he (S)-enantiomer. Salicylate directly competed with (R)-warfarin and indir ectly with (S)warfarin. This behavior was confirmed by difference CD experi ments, carried out with the same [HSA]/[drug] system in solution. (C) 1999 Wiley-Liss, Inc.