关键词: 色氨酸, 牛血清白蛋白, 立体专一性结合

Abstract: The binding of two enantiomeric tryptophans(D-,L-Trp) to bovine serum albumin (BSA) has been studied using centrifugal ultrafiltration and circular dichroism spectroscopy.The binding data are analyzed according to the model of specific and non-specific sites, and the hinding constants are obtained.The primary binding site is shown to have higher affinity for L--Trp(1gK,=5.14 L/mol), as compared to that for D-Trp(K,- 0).CDspectrum measurements also provide evidence for this stereospecificity.The pHdependence of K, indicates that the affinity increase with increasing of pHand reaches maximum near pH 9.0, this finding is explained by the N-Bconformational transition model of albumin.The results are discussed in terms of an allosteric domain model where in the indole ring embedded in the hydrophobic interior of domain Ⅱ as a strong point of attachment at the binding site, the carboxyl and amino groups are still exposed in the hydrophilic exterior and interact electrostatically with the basic and acidic side chains of the protein placed around the opening of domain Ⅱ.

Key words: Tryptophan, Bovine serum albumin, Stereospecif ic binding