Abstract
The fluorescence characteristics of 7-anilino-4-methylcoumarin-3-acetic acid (A MCA) were examined in human serum albumin (HSA) solution. The fluorescence of AMCA was significantly enhanced in the presence of HSA. Scatchard plots and continuous variation plots indicated that one molecule of AMCA binds to HSA. The binding parameters of AMCA were also estimated. Specific binding sites on HSA were examined in connection with Sudlow's classification. The primary binding site of AMCA was found to be site III (digitoxin site) from the results of competitive displacement studies with several drugs. Furthermore, it was suggested from the fluorescence behavior in the presence of tryptophan-, tyrosine-, and lysine-modified HSAs that the binding site of AMCA lies in a region near a tryptophan residue on HSA. The present data indiate that AMCA is useful as a site III marker.
