Screen-printed graphite macroelectrodes for the direct electron transfer of cytochrome c: a deeper study of the effect of pH on the conformational states, immobilization and peroxidase activity

Analyst. 2014 Mar 21;139(6):1442-8. doi: 10.1039/c3an02137h.

Abstract

The direct electron transfer of cytochrome c has been studied at screen-printed graphite macroelectrodes without recourse to mediators or the need for any electrode pre-treatment as is commonly employed within the literature. A wide range of pH values from 2.0 to 11.0 have been explored upon the electrochemical response of cytochrome c and different voltammetric signatures have been observed. The direct electron transfer of the alkaline transition of cytochrome c was found impeded within alkaline media leading to either an irreversible redox process or even no voltammetric responses. In acidic aqueous media the electrochemical process is observed to undergo a mixed diffusion and adsorption controlled process rather than a purely diffusional process of the native conformation as observed at pH 7.0. Interestingly, at pH 3.5 a new conformational state is revealed in cooperation with the native conformation. The immobilization of the protein was satisfactorily obtained using a simple method by cycling the protein at specific solution pH values allowing amperometric responses to be obtained and gives rise to useful pseudo-peroxidase activity for sensing H2O2. Apparent Michaelis-Menten constant values (Km) were calculated via the Lineweaver-Burk method with deduced values of 25 ± 4, 98 ± 12 and 230 ± 30 mM, respectively for pH values of 2.0, 3.0 and 7.0. Such work is important for those utilising cytochrome c in bio-electrochemical and related applications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biosensing Techniques
  • Cytochromes c / chemistry*
  • Cytochromes c / metabolism
  • Electrochemical Techniques
  • Electron Transport
  • Enzymes, Immobilized / chemistry*
  • Enzymes, Immobilized / metabolism
  • Graphite / chemistry*
  • Horses
  • Hydrogen Peroxide / analysis*
  • Hydrogen Peroxide / metabolism
  • Hydrogen-Ion Concentration
  • Models, Molecular
  • Peroxidases / metabolism*
  • Protein Conformation

Substances

  • Enzymes, Immobilized
  • Graphite
  • Cytochromes c
  • Hydrogen Peroxide
  • Peroxidases