Adsorption of a laccase from fusarium proliferatum on Au(111) and HOPG electrodes: A scanning probe microscopy and electrochemical approach

A laccase enzyme produced by Fusarium proliferatum was successfully adsorbed as a laccase submonolayer (SML) on a bare Au(111) single-crystal electrode (Au), the same electrode modified with a hexadecanethiol self-assembled monolayer (SAM-Au) then treated with the SML, and also on a highly-ordered pyrolytic graphite electrode (HOPG). The three treated electrode surfaces were scanned by AFM and STM, and their electrochemical and catalytic responses studied. The SML clearly established electrical contact with Au, but did not retain either electrochemical response or catalytic activity. However, the SML on SAM-Au and HOPG surfaces showed a direct electron transfer (DET) process, retaining catalytic activity. The arrangement and electrochemical and catalytic behavior of the SML on the different surfaces are clearly linked with their interactions with the surfaces, without evidence of dependence on any specific molecular orientation. Alternative explanations for this are provided, given the possible conformational differences resulting from these interactions, which would alter the internal electron transfer mechanism at the laccase active centers. © 2012 by ESG.