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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.

Original publication

DOI

10.1021/nl203965w

Type

Journal article

Journal

Nano Lett

Publication Date

08/02/2012

Volume

12

Pages

899 - 903

Keywords

Bacteriorhodopsins, Electric Conductivity, Electrodes, Gold, Halobacterium salinarum, Microscopy, Atomic Force, Models, Molecular, Nanotechnology, Photochemical Processes, Protein Engineering, Surface Plasmon Resonance