Molecular Scale Conductance Photoswitching in Engineered Bacteriorhodopsin

• Published in: Nano letters 2012-02, Vol.12 (2), p.899-903
• Main Authors: Berthoumieu, Olivia, Patil, Amol V, Xi, Wang, Aslimovska, Lubica, Davis, Jason J, Watts, Anthony
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Bacteria; Bacteriorhodopsin; Bacteriorhodopsins - chemistry; Bacteriorhodopsins - isolation & purification; Chemisorption; Conductance; Cysteine; Electric Conductivity; Electrodes; Exact sciences and technology; Gold; Gold - chemistry; Group theory; Halobacterium; Halobacterium salinarum - chemistry; Mathematics; Microscopy, Atomic Force; Models, Molecular; Nanostructure; Nanotechnology; Photochemical Processes; Protein Engineering; Sciences and techniques of general use; Surface chemistry; Surface Plasmon Resonance; Topological groups, lie groups
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl203965w

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.