Investigation on the binding of tryptophan enantiomers to human serum albumin.

The binding of radiolabelled tryptophan enantiomers to human serum albumin was investigated by ultrafiltration and by the microparticle technique. L-Trp was found to exhibit a high degree of secondary binding. D-Trp showed increased degree of binding when the HSA concentration was decreased. Stereoselective binding has also been detected in stereoselectively labelled racemic mixtures. Both L- and D-Trp were found to compete for the primary binding site with specific benzodiazepine markers. All the experiments indicate that stereoselectivity of binding is much lower than generally believed.