Electrochemical behavior of c-type cytochromes at clay-modified carbon electrodes: a model for the interaction between proteins and soils

Voltammetric studies-of c-type cytochromes at clay-modified pyrolytic graph ite electrodes have been undertaken as providing a good model for investiga ting interactions of proteins with soils. Different clays have been investi gated according to their global charge, composition and hydrophobicity. The electrochemical behavior of either mitochondrial or bacterial cytochromes at these modified electrodes has been used to define a general rule for the nature of interactions between cytochromes and clays. The influence of var ious parameters such as pi values of proteins, pH, ionic strength, composit ion of the clay coating, on the electrochemical response is reported. It is demonstrated that while electrostatic interactions are responsible for the electrochemical promotion of cytochrome c, hydrophobic factors play a key role in the electron transfer process on multiheme cytochromes at clay-modi fied electrodes. Finally, the consequences of these interactions on the met al reductase activity developed by bacterial polyheme c-type cytochromes ha ve been discussed. (C) 2000 Elsevier Science B.V. All rights reserved.