Probing metalloproteins by voltammetry

Abstract

Dynamic electrochemical methods, which have long held an important place among the techniques of the coordination chemist, have generally remained unexploited by those seeking to understand the complex and often elusive chemistry of metal centres in proteins. For a number of reasons, electron transfer between electrodes and proteins' has been regarded as being too slow and irreversible to provide useful information. This article seeks to counter such a view and outlines the advances that have been made towards achieving and interpreting voltammetric responses from metal-containing active sites. The main theme, exploitation, is developed through discussion of several investigations that demonstrate the advantages that are now on offer from electrodes that “talk” to metalloproteins. Far from being restricted to measurements of stable equilibria, voltammetry can address reactive states; species which are thermodynamically inaccessible by normal chemical titration or which display interesting yet complicating dynamic properties such as structural change or catalytic activity. In such cases, the coupled processes are visualised and may be investigated quantitatively and under controlled conditions. The resolution of chemical activity which is thus afforded extends even to multi-site enzyme complexes.