ELECTROCHEMISTRY OF CU(II)-PEPTIDE COMPLEXES CONTAINING HISTIDINE-RESIDUES .2. ANOMALOUS CURRENT FLUCTUATION IN THE REDUCTION PROCESS OF CU(II)-GGH

The electrochemical behavior of a Cu(II)-GGH solution with a mercury electrode has been investigated. Cu(II)-GGH showed anomalous current-potential and current-time characteristics in the electrode processes at the mercury electrode, which are described as follows. (i) Periodical current fluctuations and subsequent sudden cessation of the fluctuation were observed in the potential step measurement. (ii) Periodical current fluctuations were observed in the drop-life of a dropping mercury electrode in the potential region where the polarographic maximum appeared. (iii) Cyclic voltammogram showed irregular current fluctuations and a reversed current peak in the cathodic and the anodic runs, respectively. (iv) The half-wave potential of Cu(II)-GGH was fairly negative in comparison with that of other Cu(II)-oligopeptide complexes. All of these phenomena were proposed to relate to the adsorption and desorption behaviors of the reduction product of Cu(II)-GGH. The differential equation was presented to simulate the periodicity observed in the potential step measurement and it is found that a relatively simplified equation well simulated the periodical phenomena.