Key role of the anchoring PEI layer on the electrochemistry of redox proteins at carbon electrodes: Consequences on assemblies involving proteins and clay

The key role of positively charged anchoring films on the electroactivity of various bacterial proteins at a pyrolytic graphite electrode is discussed. Several iron-containing low redox potential proteins, either negatively charged or positively charged were considered. Using quartz crystal microgravimetry (QCM) and electrochemical techniques, it is demonstrated that electron transfer on these proteins can be inhibited or promoted essentially depending on the electrostatic interactions with the positive PEI layer. Consequences of this interaction on the electroactivity of proteins involved in assemblies with clays are discussed. In particular, although bacterial polyhemic cytochrome c3 is able to form stable LBL assemblies with intercalated clay layers, electroactivity of the so-mounted construction is highly dependant on the structure of the anchoring layer.