New equations for redox and nano-signal transduction

Cells maintain redox potentials (E-h) in intracellular compartments, sometimes referred to as redox environments. These potentials are often very reducing, for example in the cytoplasm, but throughout the cell different potentials are maintained, commensurate with the functionality of that particular part of the cell. Furthermore, within a simple cellular compartment, hot-spots of redox poise may be maintained. However, despite this complexity, the quantification of such redox potentials has been attempted, and there is indeed a need to accurately assess such potentials, and to monitor how they might change with time. Changes in intracellular potentials may control the oxidation or reduction of protein residues, such as cysteine, which would alter the conformation of those proteins and so modulate their function. Although there are several methods for estimating the intracellular redox potential, the most accessible technique is the measurement of intracellular concentrations of GSH and GSSG, and the calculation of E-h using the Nernst equation. However, using this equation shows that the E-h imposed by the glutathione couple is dependent on the total concentration of glutathione present, and therefore values of E-h obtained may be erroneous. Here, we suggest new equations that can be used to calculate the redox environments of cells. (C) 2003 Published by Elsevier Ltd.