Study of the reactions between platinum(II) complexes and L-methionine in the presence and absence of 5'-GMP

The reactions of the platinum(II) complexes, [Pt(dien)(H(2)O)](2+), [PtCl(dien)](+) and [PtBr(dien)](+) (dien is diethylenetriamine) with some biologically relevant ligands such as inosine (INO), inosine-5'-monophosphate (5'-IMP), guanosine-5'-monophosphate (5'-GMP), glutathione (GSH) and l-methionine (S-meth), have been studied by UV-Visible spectrophotometry and (1)H NMR spectroscopy. Kinetic and thermodynamic parameters of these reactions were determined. Competitive reactions of [PtCl(dien)](+) with l-methionine and 5'-GMP demonstrated initially rapid formation of [Pt(dien)(S-meth)](2+) followed by displacement of l-methionine by 5'-GMP. In the later stages the concentration of [Pt(dien)(N7-GMP)](2+) is predominant. The results are analyzed in reference to the anti-tumour activity of Pt(II) complexes.