Simple voltammetric approach for characterization of two-step surface electrode mechanism in protein-film voltammetry
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ORIGINAL PAPER
Simple voltammetric approach for characterization of two-step surface electrode mechanism in protein-film voltammetry Rubin Gulaboski 1 & Valentin Mirceski 2,3 Received: 13 March 2020 / Revised: 18 March 2020 / Accepted: 18 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Many enzymes embedding multivalent metal ions or quinone moieties as redox-active centres undergo electrochemical transformation via two successive electron transfer steps. If electrochemical features of such redox enzymes are analyzed with “protein-film voltammetry”, one frequently meets a challenging reaction scenario where the two electron transfers take place at the same formal potential. Under such conditions, one observes voltammogram with a single oxidation-reduction pattern hiding voltammetric features of both redox reactions. By exploring some aspects of the two-step surface EECrev mechanism one can develop simple methodology under conditions of square-wave voltammetry to enable recognizing and characterizing each electron transfer step. The method relies on the voltammetric features of the second electron transfer, which is coupled to a follow-up chemical reaction. The response of the second electron transfer step shifts to more positive potentials by increasing the rate of the chemical reaction. The proposed methodology can be experimentally applied by modifying the concentration of an electrochemically inactive substrate, which affects the rate of the follow-up chemical reaction. The final voltammetric output is represented by two well-separated square-wave voltammetric peaks that can be further exploited for complete thermodynamic and kinetic analysis of the EECrev mechanism. Keywords Square-wave voltammetry . Two-step electrode mechanism . Kinetics of electron transfer . Protein-film voltammetry
Introduction Protein-film voltammetry is a valuable methodology introduced about two decades ago that enables an insight into important electrochemical and chemical features of many enzymes [1–5]. By adsorption of a given lipophilic enzyme on the surface of a working electrode one prepares an enzymemodified electrode, which is suitable for exploration of protein We dedicate this work on the occasion of the 65th birthday of our supervisor and great friend, professor Fritz Scholz. * Rubin Gulaboski [email protected] 1
Faculty of Medical Sciences, Goce Delcev University, Stip, Macedonia
2
Department of Chemistry, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University, Skopje, Macedonia
3
Department of Inorganic and Analytical Chemistry, University of Lodz, Tamka 12, Łódź, Poland
redox chemistry by means of a common three-electrode setup. Valuable data about mechanisms of action of many proteins, as well as important thermodynamic and kinetic parameters of the redox transformations of many enzymes, have been obtained in the last 20 years [1–5]. Many of the analyzed enzymes, in particular those featuring multivalent redox centres, exhibit rather complex electr
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