The effect of the N-B transition of bovine and human serum albumins on the binding sites of fluorescent probes

Abstract

The N(neutral)-B(alkaline) transition of bovine serum albumin (BSA) and human serum albumin (HSA) was investigated with three anionic and one cationic dansyl (dimethylamino-naphthalenesulfonyl, DNS) probes. The N-B transition of the HSA-probe complex was characterized by a large enhancement of the fluorescence intensity of the dansyl group, accompanied by a blue-shift of the maximum wavelength in the emission spectra, and large changes in the thermodynamic parameters of the binding process. Contrary to this, such changes were not observed for the BSA-probe complex. It is suggested that the conformational adaptability of HSA to the probes at the binding site increases in the B conformation, although the nature of the site on BSA is hardly affected by the transition.