Adsorptive immobilization of cytochrome c on indium/tin oxide (ITO): Electrochemical evidence for electron transfer-induced conformational changes

Asma El Kasmi, Michael C. Leopold, Ryan Galligan, Rebecca T. Robertson, S. Scott Saavedra, Kacem El Kacemi, Edmond F. Bowden

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

The adsorptive immobilization and electrochemistry of horse and yeast cytochrome c on indium/tin oxide (ITO) electrodes is reported. Near-monolayer coverage was achieved in pH 7 phosphate buffers of ionic strength equal to 10 and 50 mM, respectively, for the horse and yeast species. The layers exhibit very well-behaved voltammetry and are stable on the timescale of hours to days. Cyclic voltammetry revealed quasireversible behavior that is a product of both electron transfer (ET) kinetics and ET-induced conformational changes. A square scheme mechanism linking the redox states and the conformational states is proposed. Using a simple ET kinetic model that adequately describes the voltammetry at higher scan rates, a standard ET rate constant of 18 s-1 was determined for adsorbed horse cytochrome c. With decreasing scan rate, we observed a limiting peak separation of approximately 10 mV, an example of unusual quasireversibility (UQR) that we attribute to the effect of conformational changes. Finally we note that the intrinsic cytochrome c ET rate on ITO is some 6 orders of magnitude less than for gold.

Original languageEnglish (US)
Pages (from-to)177-181
Number of pages5
JournalElectrochemistry Communications
Volume4
Issue number2
DOIs
StatePublished - Mar 6 2002

Keywords

  • Cytochrome c monolayers
  • Indium/tin oxide
  • Interfacial electron transfer kinetics
  • Redox-linked conformational changes
  • Unusual quasireversibility

ASJC Scopus subject areas

  • Electrochemistry

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