Electrochemical studies of ternary complexes of copper (II) with dipeptide or histidine and an amino acid

424-427The reduction steps of ternary complexes of Cu(II) with dipeptide, glycylglycine (gg) and amino acids ɑ-alanine (ala); tyrosine (tyr); and histidine and the amino acids ɑ-alanine (ala), tyrosine (tyr), phenylalanine (phe) and tryptophan (trp) have been studied by cyclic voltammetry in aqueous medium. The reduction proceeds through a one electron process resulting in the formation of copper(I) ternary complexes. The copper(I) - dipeptide - amino acid species are found to be unstable and undergo disproportionation yielding Cu0 and Cu(II) complex at the mercury electrode. The imidazole coordination of histidine in binary and ternary complexes stabilizes the Cu(I) species due to which there is no disproportionation and hence there is no formation of (Cu0) complex. This emphasises the significance of imidazole coordination in stabilizing Cu(I) state in biological redox processes