Electron Transfer in Complex Two-cofactor-containing Enzymes at Alkanethiol-modified Gold Electrodes

Lo Gorton ,  Elena E. Ferapontova ,  Tautgirdas Ruzgas ,  Leonard Stoica 

Lund University, Centre for Chemistry and Chemical Engineering (KC), Lund SE-221 00, Sweden

Abstract

In biological redox catalysis, energy transduction, and many aspects of regulation, electron transfer (ET) is linked directly to conformational change, ligand/substrate binding, ion/proton transfer etc., and the ways in which these events occur and how the system as a whole is optimised and harmonised are still not well understood. Studies of biological electron transfer (ET) within multi-cofactor redox enzymes under conditions when the electrode replaces the natural redox partner of the enzyme can contribute to understanding intramolecular ET within the biomolecules followed by ET coupling of the active sites. The obligatory condition for the bioelectrocatalytic event in this case is the existence of a direct communication between the electrode and at least one of the active sites present in the enzyme, which is difficult to attain in some cases. Mimicking the natural partner/environment of protein by the modified electrode is then of particular interest to achieve an efficient ET reaction through the enzyme. To provide a biomembrane-like microenvironment of the membrane/intermembrane enzymes at the electrode surface self-assembled monolayers (SAM) of synthetic terminally functionalised alkanethiols can be used. Therewith, a successful simulation of the molecular surfaces of enzyme biological partners, e.g. cytochrome c, by the SAM of alkanethiols on gold may provide the necessary amount/orientation of the enzyme molecules for direct ET reaction with the electrode, as well as a conformation appropriate for efficient intramolecular ET, including electrostatic compatibility of the docking sites and the aspect of mobility in achieving a proper orientation for fast ET. We report how the choice of alkanethiols of different polarity/hydrophobicity and charge provides the surface properties of the Au electrode necessary for the proper adsorption/orientation of sulphite oxidase, theophylline oxidase, or fructose dehydrogenase.

 

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Presentation: Tutorial lecture at SMCBS 2003 Workshop, by Lo Gorton
See On-line Journal of SMCBS 2003 Workshop

Submitted: 2003-08-28 13:45
Revised:   2009-06-08 12:55