Copper(II) complexes of dipeptides containing aspartyl, glutamyl, and histidyl residues in the side chain.

Copper(II) complexes of various dipeptides containing carboxylate and imidazole-N3 donors (alpha- and gamma-GluVal, alpha- and beta-AspGly, beta-AspHis, gamma-GluHis, and homocarnosine) were studied by potentiometric and spectroscopic methods in solution. It was found that the presence of an alpha-carboxylate group in the N-terminal part of a peptide molecule significantly enhances the metal-binding ability of the ligands as a consequence of stable bis complex formation involving amino acid-like coordination. The interaction of copper(II) with beta-AspHis was characterized by the formation of an imidazole-bridged dimeric species, while the formation of bis complexes was detected in the case of gamma-GluHis. Binding of the imidazole N3 and deprotonated amide nitrogen was presumed in the copper(II)-homocarnosine system.