Examination of n = 2 reaction mechanisms that reproduce pH-dependent reduction potentials

Flavo- and quinoproteins often exhibit trends in reduction potentials that approximate −30 mV per pH unit. At least five different reaction mechanisms can model the behavior described by the following Nernst equation: Eobserved=E0′+(0.059/2) log [H+]Eobserved=E0′+(0.059/2) log [H+]. The pH-reduction potential profile described by this equation can be reproduced by various models using different reaction mechanisms, and these mechanisms yield different reduction potentials and acid dissociation constants. In order to understand these discrepancies, this article discusses how the various methods reproduce this pH-dependent Nernst equation.