Micellar effect on the kinetics of the base equilibrium of amino acids studied by the ultrasonic absorption method

Abstract

Ultrasonic relaxation absorption has been measured in aqueous solutions of amino acids (tryptophan, leucine, glycine, phenylalanine, asparagine) in the absence and in the presence of micelles of sodium dodecylsulphate. The relaxation absorption was ascribed to the base equilibrium of amino acids, and the rate constants, the base dissociation constant, and the volume change of the reaction were obtained. The smaller micellar catalytic effect for the base equilibrium of amino acids, compared to those of amines and ammonia was ascribed to the electrostatic effect of the carboxylate group. The reaction mechanism, including the interactions of amino acid and the SDS micelles, were discussed.