EVALUATIONS OF REDUCTION POTENTIAL DATA IN RELATION TO COUPLING, KINETICS AND FUNCTION

This commentary addresses the effect and measurement of time-dependent contributions to reduction potentials. Reduction potentials form the basis for many quantitative or semi-quantitative judgements in biologi cal redox chemistry. However, since data are obtained under an assumpt ion of equilibrium being established, their relevance to biological fu nctions requires consideration of the kinetics of the subprocesses tha t contribute to or influence the overall free energy change. Initial a nd final states effective in rapid and complex biological functions ma y differ considerably from those analysed after slow equilibration in a sample tube. A shortcoming of traditional potentiometric measurement s is that the time domain is not probed. Voltammetry, a technique that has been much less widely applied in biological chemistry than in che mistry, examines redox transformations in both potential and time doma ins, and may enable a more realistic picture to be derived.