Abstract

The mechanism of the binding of several sulfonamides to bovine serum albumin has been investigated by relaxation time measurements on their high resolution proton magnetic resonance spectra. Upon addition of albumin to the sulfonamide solutions generally a larger increment in the relaxation rate was found for the p-aminobenzenesulfonamide moiety than for any of the substituents on N-1, indicating that the parent molecule is the primary binding site. The three-ring compound sulfaphenazole was found to be an exception. Two of the three rings, the p-aminobenzene sulfonamide and the phenyl portion of the N-1 substituent, bind independently. The two binding sites can be clearly distinguished since phenylpropanol interferes with the binding of the p-aminobenzenesulfonamide moiety and slightly enhances the binding of the phenyl group.