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

The protein binding of ketoprofen has been studied using circular dich roism titration method as well as the new algorithm proposed by the au thors for the treatment of data obtained. The quantitative parameters association constants (k) and number of binding sites (N) have been de termined. It is proved that the protein binding of Ketoprofen is going through separate stages and the number of binding sites probably aris es. It is acceptable that a high affinity binding takes place primaril y (k(I) = 3.8 . 10(6) I . mol-1). Later, due to the conformational cha nges in the protein molecule the binding areas are modified and the nu mber of binding sites considerably arises (N(I) = 3.5 and N(II) = 14), while the binding affinity reduces 100-fold (k(II) = 5 . 10(4) I . mo l-1). The number of binding sites has been studied and an identificati on of the chromophore taking part in the drug-protein interaction has been performed on the base of UV- and CD spectra. A mechanism of the i nteraction is proposed which coincides with the stepwise binding model .