Protein Bindings. I. Binding of 2-(4'-Hydroxyphenylazo) benzoic Acid to Bovine Serum Albumin

Abstract

Binding of anionic dye 2-(4'-hydroxyphenylazo) benzoic acid (HABA) to bovine serum albumin at pH 7.4 was studied spectrophotometrically. The relationship between albuminbound ratio of HABA and concentration of the unbound dye was expressed by a modified Langmuir-type equation involving a repulsing interaction. The binding becomes more difficult with the increasing bonds. The binding constant and the number of binding sites on albumin were evaluated in 0.05 M phosphate buffer solution and in 0.15 M tris. buffer solution at 25°and 37°.