The temperature dependence and thermal denaturation of the cytochrome c/cytochrome c oxidase/dioxygen system: an electrochemical investigation

Abstract

Cyclic voltammetry (CV) and differential scanning calorimetry (DSC) have been used to study the thermal denaturation of the coupled cytochrome c/cytochrome c oxidase/dioxygen system in solution. CV has also been used to determine the rates of homogeneous electron transfer between cytochrome c and cytochrome c oxidase over a temperature range from 10 to 45°C. These electron transfer reactions have been initiated by direct reduction of cytochrome c at indium oxide electrodes. Denaturation mechanisms have been characterized by both CV and DSC demonstrating the complementary nature of the information provided from these different methods. Cytochrome c oxidase denaturation resulted in a large decrease in the thermal stability of cytochrome c while the presence of cytochrome c had no measurable effect on the thermal stability of cytochrome c oxidase. The kinetics of denaturation have been followed by CV following the rapid increase in sample temperature and mechanisms for denaturation have been suggested.