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Electrocatalytic four-electron reduction of oxygen at the cytochrome c 3-adsorbed electrode

Authors
  • Niki, Katsumi
  • Takizawa, Yumiko
  • Kumagai, Hiroaki
  • Fujiwara, Ryoji
  • Yagi, Tatsuhiko
  • Inokuchi, Hiroo
Type
Published Article
Journal
Biochimica et Biophysica Acta (BBA) - Bioenergetics
Publisher
Elsevier
Publication Date
Jan 01, 1981
Volume
636
Issue
2
Pages
136–143
Identifiers
DOI: 10.1016/0005-2728(81)90086-4
Source
Elsevier
Keywords
License
Unknown

Abstract

The electrocatalytic activity of cytochrome c 3 for the reduction of molecular oxygen was characterized from the studies of the adsorption of cytochrome c 3 and the co-adsorption of cytochrome c 3 with cytochrome c on the mercury electrode by the a.c. polarographic technique. The adsorption of cytochrome c 3 on the mercury electrode is irreversible and is diffusion-controlled. The maximum amount of cytochrome c 3 adsorbed was 0.92 · 10 −11 mol · cm −2 at −0.90 V. The amount of cytochrome c 3 in the mixed adsorbed layer with cytochrome c was determined from the differential capacitance measurement. It was shown that the fractional coverage of cytochrome c 3 can be estimated from its bulk concentration and the diffusion coefficient (1.05 · 10 −6 cm 2 · s −1). Cytochrome c 3 catalyzes the electrochemical reduction of molecular oxygen from the two-electron pathways via hydrogen peroxide to the four-electron pathway at the mercury electrode in neutral phosphate buffer solution. The catalytic activity varies with the bulk concentration of cytochrome c 3. The highest catalytic activity for the oxygen reduction (no hydrogen peroxide formation) is attained when one-half of the mercury electrode surface is covered by cytochrome c 3. The addition of cytochrome c or bovine serum albumin to the cytochrome c 3 solution inhibits the catalytic activity of cytochrome c 3. The reversible polarographic behavior of cytochrome c 3 through the mixed adsorbed layer of cytochrome c 3 and cytochrome c was also investigated.

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