Abstract: The interactions between human erythrocyte spectrin(SP) and Pt(II) complexes with different composition and configuration were studied by fluorescence and circular dichroism spectra. The results showed that there are 4.7×10² binding sites of cisplatin(CDDP) in a spectrin tetramer(SPT). Among them, about 70 sites with apparent binding constant K1>3.47×10⁶ were of highest affinity, 1.8×10² sites with K2 = 3.47×10⁶ were of high affinity, and other 2.2×10² sites with K3 = 8.77×10⁵ were of low affinity. The conformation change of spectrin, depending on the concentration of Pt(II) complex and molar ratio (R) of Pt(II) complex to spectrin, was induced by the binding of Pt(II) complexes. It indicated that the interaction of both CDDP and cis-diaquodiamine platinum (DADP) with SP followed a twostep first order kinetic process in the first stage (1 h), and the kinetic constants were determined. In the second stage, the induced conformation change, polymerization and depolymerization of SP were probably involved. It was noticed that in the reaction of SP and Pt(II) complexes with 1,2-cyclohexanediammine isomers as chiral carrier ligand, stereo-matching played a more important role than the affinity of Pt(II) to thiol groups of SP.

Key words: Pt(II) complex, Spectrin, Conformation, Binding sites, Kinetic, Chiral