title: Molecular scale conductance photoswitching in engineered bacteriorhodopsin.
abstract: Bacteriorhodopsin (BR) is a robust light-driven proton pump embedded in the purple membrane of the extremophilic archae Halobacterium salinarium . Its photoactivity remains in the dry state, making BR of significant interest for nanotechnological use. Here, in a novel configuration, BR was depleted from most of its endogenous lipids and covalently and asymmetrically anchored onto a gold electrode through a strategically located and highly responsive cysteine mutation; BR has no indigenous cysteines. Chemisorption on gold was characterized by surface plasmon resonance, reductive striping voltammetry, ellipsometry, and atomic force microscopy (AFM). For the first time, the conductance of isolated protein trimers, intimately probed by conducting AFM, was reproducibly and reversibly switched under wavelength-specific conditions (mean resistance of 39 ± 12 MΩ under illumination, 137 ± 18 MΩ in the dark), demonstrating a surface stability that is relevant to potential nanodevice applications.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
authors.forename: Olivia
authors.initials: O
authors.lastname: Berthoumieu
authors.forename: Amol V
authors.initials: AV
authors.lastname: Patil
authors.forename: Wang
authors.initials: W
authors.lastname: Xi
authors.forename: Lubica
authors.initials: L
authors.lastname: Aslimovska
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Davis
authors.forename: Anthony
authors.initials: A
authors.lastname: Watts
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000302:isolation & purification; D004553:Electric Conductivity; D004566:Electrodes; D006046:Gold / Q000737:chemistry; D019617:Halobacterium salinarum / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D036103:Nanotechnology; D055668:Photochemical Processes; D015202:Protein Engineering; D020349:Surface Plasmon Resonance
chemical_list: D001436:Bacteriorhodopsins; D006046:Gold