Evidence for the fatty acid-induced heterogeneity of the N and B conformations of human serum albumin.

The influence of oleic acid on the interaction between albumin and warfarin, oxyphenbutazone or diazepam has been studied by circular dichroism and equilibrium dialysis. The pH dependences of the molar ellipticity of the drug-albumin complexes and of the free fraction of drug are completely changed by the presence of oleic acid. This phenomenon is attributed to an oleic acid-induced conformational change in both the neutral (N) and the basic (B) conformation of albumin, a change to which the warfarin-oxyphenbutazone binding area and the diazepam binding site is sensitive. The oleic acid-induced conformational states of albumin, the so-called N* and B* conformations, show binding properties that are different from the binding properties of the N and B conformations.