Characterization of CuZnSOD model complexes from a redox point of view: Redox properties of copper(II) complexes of imidazole containing ligands

Abstract

The systematic electrochemical studies of the copper complexes of various terminally protected tri-, tetra-, penta- and heptapeptides containing histidine in different location and number in the peptide chain and two histidine derivatives were carried out by cyclic voltammetry. The redox parameters of CuL and CuL 2 complexes coordinating exclusively through imidazole nitrogens were determined. For all studied Cu(II) complexes the characteristic redox reactions are quasi-reversible one electron reduction processes. The obtained formal reduction potential values fall into the 200–400 mV potential range supporting the former results that the CuL and CuL 2 complexes of these multihistidine peptides are not only structural but also good functional models of the Cu–Zn-superoxide dismutase (CuZnSOD) enzyme. These observations are confirmed by the results of SOD activity assay in a representative copper(II)–ligand system.