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

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 CuL2 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 CuL2 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.