BINDING OF PLATINUM(II) INTERCALATION REAGENTS TO DEOXYRIBONUCLEIC-ACID - DEPENDENCE ON BASE-PAIR COMPOSITION, NATURE OF THE INTERCALATOR, AND IONIC-STRENGTH

The DNA binding of three platinum(II) intercalation reagents has been studied and found to depend upon base composition, the nature of the intercalator, and the ionic strength of the solvent medium. In 0.2 M NaCl, binding data for calf thymus DNA show the association constants to be~104 M-1. The binding constants decrease in the order [(o-phen)Pt(en)]2+<[(terpy)Pt(HET)]+≫[(bipy)Pt(en)]2+. The number of available intercalation sites for the doubly charged intercalators is only 70% of the number expected from the nearest-neighbor exclusion model. Binding of [(o-phen)Pt(en)]2+ and [(terpy)Pt(HET)]+ to various DNAs depends linearly on G-C content. Both reagents exhibit essentially the same degree of G-C specificity. Intercalate binding is a function of ionic strength. Increasing the salt concentration minimizes the importance of metallointercalator charge, and extrapolation to 1 M salt reveals the intercalative abilities, as reflected in binding constants, to be equivalent for [(terpy)Pt(HET)]+ and [(o-phen)Pt(en)]2+ and about 1 order of magnitude less than that of ethidium. © 1979, American Chemical Society. All rights reserved.