Binding of Acid and Basic Dyes by Wool Keratin Derivatives

Abstract

Wool keratin derivatives such as S-carboxymethylated, S-cyanoethylated, S-sulfo nated, and regenerated keratin derivatives have been prepared to study the binding of acid and basic dyes (methyl orange, chrome violet, and acridine orange) by the derivatives in aqueous solution. The first binding constants and the thermodynamic parameters accompanying the binding were evaluated. The first binding constants of the proteins for the dyes were on the order of 105-106, which is similar to or higher than that of serum albumin. The favorable free energy of the binding of chrome violet and acridine orange observed for the formation of the dye-protein complex seems to be a result of a favorable enthalpy change rather than any favorable entropy change. The binding of methyl orange by the regenerated keratin derivative is accompanied by an entropy gain and an exothermic enthalpy change. The nature and phenomena of dyes binding with the keratin derivatives are discussed.