title: Orientation-dependent electron transport in a single redox protein.
abstract: The redox-active protein cytochrome b(562) has been engineered to introduce pairs of thiol groups in the form of cysteine residues at specified sites. Successful STM imaging of the molecules adsorbed on a gold surface indicated that one thiol group controls the orientation of the molecule and that the protein maintains its native form under the experimental conditions. Stable protein-gold STM tip electrical contact was directly observed to form via the second free thiol group in current-voltage and current-distance measurements. Proteins with thiol contacts positioned across the protein's short axis displayed a conductance of (3.48 ± 0.05) × 10(-5)G(0). However proteins with thiol groups placed along the long axis reproducibly yielded two distinct values of (1.95 ± 0.03) × 10(-5)G(0) and (3.57 ± 0.11) × 10(-5)G(0), suggesting that the placement of the asymmetrically located haem within the protein influences electron transfer. In contrast, the unengineered wild-type cytochrome b(562) had conductance values at least 1 order of magnitude less. Here we show that an electron transfer protein engineered to bind gold surfaces can be controllably oriented and electrically contacted to metallic electrodes, a prerequisite for potential integration into electronic circuits.
authors.affiliation: School of Physics and Astronomy, Cardiff University, Cardiff Wales CF10 3XQ, United Kingdom.
authors.forename: Eduardo Antonio
authors.initials: EA
authors.lastname: Della Pia
authors.forename: Martin
authors.initials: M
authors.lastname: Elliott
authors.forename: D Dafydd
authors.initials: DD
authors.lastname: Jones
authors.forename: J Emyr
authors.initials: JE
authors.lastname: Macdonald
mesh_terms: D045303:Cytochromes b / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D004579:Electron Transport; D009154:Mutation; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods*
chemical_list: D045303:Cytochromes b