BINDING OF SULINDAC TO HUMAN SERUM-ALBUMIN STUDIED BY CIRCULAR-DICHROISM

The protein binding of sulindac (CAS 38194-50-2) was studied using cir cular dichroism (CD). By the new algorithm for the analysis of propose d data the association constants (k) and number of binding sites (N) w ere determined. The binding was found to go through separate stages, w here the binding affinity tends to become lower: the first step charac terized by k(I) = 7.6 x 10(6) l . mol(-1) and N-I = 1.4; while for the second step k(II) = 1.7 x 10(6) l . mol(-1) and N-II = 6.6. On the ba sis of the CD-data and using UV-spectra the nature of binding sites wa s studied. It may be stated that the binding sites are situated in the region of asymmetrically perturbed chromophore of the drug, which mad e a positive contribution to the Cotton effect. The results obtained s uggest a mechanism of interaction which is consistent with the stepwis e binding model.