title: On the steady-state assumption and its application to the rotating disk voltammetry of adsorbed enzymes.
abstract: Rotating disk voltammetry is routinely used to study electrochemically driven enzyme catalysis because of the assumption that the method produces a steady-state system. This assumption is based on the sigmoidal shape of the voltammograms. We have introduced an electrochemical adaptation of the King-Altman method to simulate voltammograms in which the enzyme catalysis, within an immobilized enzyme layer, is steady-state. This method is readily adaptable to any mechanism and provides a readily programmable means of obtaining closed form analytical equations for a steady-state system. The steady-state simulations are compared to fully implicit finite difference (FIFD) simulations carried out without any steady-state assumptions. On the basis of our simulations, we conclude that, under typical experimental conditions, steady-state enzyme catalysis is unlikely to occur within electrode-immobilized enzyme layers and that typically sigmoidal rotating disk voltammograms merely reflect a mass transfer steady state as opposed to a true steady state of enzyme intermediates at each potential.
authors.affiliation: Centre for Metals in Biology, Department of Chemistry, University of Queensland, Brisbane 4072, Australia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Honeychurch
authors.forename: Paul V
authors.initials: PV
authors.lastname: Bernhardt
mesh_terms: D000327:Adsorption; D002384:Catalysis; D004563:Electrochemistry; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D008433:Mathematics; D008962:Models, Theoretical
chemical_list: D004800:Enzymes, Immobilized