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Abstract
High-performance affinity chromatography (HPAC) was used to study various drug-protein interactions. The binding studies of phenytoin to human serum albumin (HSA) was first investigated by zonal elution using four probes for specific sites on HSA. It was found that phenytoin had interactions with major and minor sites on HSA, with the interactions between two probes, (i.e. R-warfarin and cis-clomiphene) with phenytoin showing a complicated phenomenon involving both allosteric and competitive interactions. A theory was proposed to study allosteric interactions by HPAC and was used to analyze the data in two previous papers plus new experiments including phenytoin-L-tryptophan interactions. The results was consistent with those obtained by other methods.
Due to the low solubility of some drugs, to increase their solubility without affecting protein binding, beta-cyclodextrin was used as a mobile phase additive. A theory to obtain binding constants for drugs with beta-cyclodextrin by HPAC was proposed. Warfarin, tamoxifen and phenytoin binding were studied by this approach. The binding constants for beta-cyclodextrin with these drugs were then used to study the allosteric interactions of nonpolar drugs. A theory for studying these allosteric interactions was developed to include the use of beta-cyclodextrin as a mobile phase additive. This theory was then used to study warfarin-tamoxifen interactions.
