Conjugated Cofactor Enables Efficient Temperature-Independent Electronic Transport Across 鈭? nm Long Halorhodopsin

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• 作者：Sabyasachi Mukhopadhyay ; Sansa Dutta ; Israel Pecht ; Mordechai Sheves ; David Cahen
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：September 9, 2015
• 年：2015
• 卷：137
• 期：35
• 页码：11226-11229
• 全文大小：267K
• ISSN：1520-5126

文摘

We observe temperature-independent electron transport, characteristic of tunneling across a 鈭? nm thick Halorhodopsin (phR) monolayer. phR contains both retinal and a carotenoid, bacterioruberin, as cofactors, in a trimeric protein-chromophore complex. This finding is unusual because for conjugated oligo-imine molecular wires a transition from temperature-independent to -dependent electron transport, ETp, was reported at 鈭? nm wire length. In the 鈭? nm long phR, the 鈭? nm 50-carbon conjugated bacterioruberin is bound parallel to the 伪-helices of the peptide backbone. This places bacterioruberin鈥檚 ends proximal to the two electrodes that contact the protein; thus, coupling to these electrodes may facilitate the activation-less current across the contacts. Oxidation of bacterioruberin eliminates its conjugation, causing the ETp to become temperature dependent (>180 K). Remarkably, even elimination of the retinal-protein covalent bond, with the fully conjugated bacterioruberin still present, leads to temperature-dependent ETp (>180 K). These results suggest that ETp via phR is cooperatively affected by both retinal and bacterioruberin cofactors.