Initial quality assessment and qualitative interpretation of protein film electrochemistry catalytic data
Miriam Malagnini, Anna Aldinio-Colbachini, Laura V. Opdam, Andrea di Giuliantonio, Andrea Fasano, Vincent Fourmond, Christophe Léger
Abstract
When a redox enzyme is wired to an electrode under conditions of direct electron transfer (DET), its activity can be simply detected as a current. This approach has been reviewed extensively, but here we address a gap in the literature by discussing the initial qualitative interpretation and assessment of catalytic DET electrochemical data. Topics addressed here include electroactive coverage, turnover frequencies, mass transport limitations, film loss, redox-driven (in)activation, signal corrections, distinction between steady-state and transient responses, and identification of non-ideal behaviors. Based on our group's expertise, we provide explanations, general advice, and prescriptive guidance to help readers understand experimental issues. • In protein film electrochemistry, a redox enzyme undergoes direct electron transfer with an electrode, and its activity is measured as a current. • The interpretation of the signal is often simple, since under most conditions the current is proportional to the turnover frequency. • The electroactive coverage being often unknown, the value of the turnover frequency cannot be measured, and the relative changes in current matter more than its absolute intensity. • Complications due to mass transport limitations and heterogeneity deserve special attention.