Acid-Base and Metal-Ion-Binding Properties of the Quaternary [cis-(NH3)2Pt(dGuo)(dGMP)] Complex Formed Betweencis-Diammineplatinum(II), 2′-Deoxyguanosine (dGuo), and 2′-Deoxyguanosine 5′-Monophosphate (dGMP2−) in Aqueous Solution

Abstract

For the first time the acid–base and metal-ion-binding properties of a quaternary PtII complex (right) were studied (potentiometric pH titrations). The release of the protons from the two H(N1) sites is facilitated by the N7-coordinated PtII on average by ΔpKa≈0.8, and from the -P(O)2(OH)− residue by ΔpKa = 0.44. Formation of the quinternary [M{cis-(NH3)2Pt(dGuo)(dGMP)}]2+ complexes (M2+ = Mg2+, Cu2+, Zn2+) via the -PO32− group is only slightly inhibited compared with the coordination tendency expected from its basicity. Several conclusions regarding DNA and the participation of nucleotides as substrates in enzymic reactions are presented.