Cooperativity during binding of a ligand to a multidentate oligomer

A matrix method to describe the equilibrium binding of a ligand by a multidentate oligomer with a system of binding centers differing in the affinity for the binding ligand has been proposed. The example of a complexation process simulating the formation of a complex between an oligonucleotide and zinc phthalocyanine ZnPc is considered. With the use of the proposed method, diagrams of the relative contents of different forms of DNA-ligand complexes have been constructed and analyzed. It is shown that the cooperativity of complexation has a considerable effect on the equilibrium of the ligand with the system of nonequivalent centers of binding. The experimental data on changes in the intensity of luminescence in the course of binding between zinc tetrakis(diisopropylguanidinio)phthalocyanine and a DNA molecule with the nucleotide sequence GTTA(GAGTTA)4GG have been analyzed.