Potentiometric and spectroscopic studies on the ternary complexes of copper(II) with dipeptides and nucleobases.

Ternary complexes of copper(II) with dipeptides (GlyGly, GlyAsp, and MetVal) and nucleobases (MeC, MeA, MeUH, MeTH, EtGH, uridine, and thymidine) or derivatives of amino acids (Ac-Lys and Ac-Hm) were studied by potentiometric, UV-visible, and EPR spectroscopic methods. It was found that all ligands form stable adducts with the CuAH-1 species of dipeptides, and the ternary complexes formed by the coordination of imidazole nitrogen donor atom are the most favored in the physiological pH range. The formation of a dimeric species Cu2A2H-2B was detected in the case of EtGH supporting that both N1 and N7 nitrogens of purine take part in metal ion coordination. The data of spectroscopic measurements supported the equatorial coordination of nitrogen donors in CuABH-1 ternary complexes.