A Unified Theory of All Mechanisms in Protein-Film Voltammetry

Protein-film voltammetry provides direct access to the thermodynamics and kinetics of redox-active proteins and enzymes immobilized on electrode surfaces. This work introduces a unified theoretical framework that integrates the principal electrochemical and chemical pathways encountered in protein-film voltammetry, including sequential electron transfers, reversible and irreversible chemical transformations, and regenerative mechanism as well. The proposed model demonstrates how these mechanisms emerge as interconnected limiting cases of a generalized reaction scheme. Simulated voltammetric responses reveal characteristic effects of electron-transfer kinetics, chemical equilibrium, catalytic rate, and experimental time scale on peak position, current, shape, and reversibility. The framework provides a systematic basis for mechanistic discrimination and kinetic analysis of complex protein-film processes and supports the interpretation and design of voltammetric experiments involving redox enzymes and other surface-confined biomolecules. A full simulation protocol given in Mathcad format in this work allows everyone to simulate various protein-film voltammetric scenarios of all common mechanisms in which redox proteins might be involved.