Nanoscale Electron Transport and Photodynamics Enhancement in Lipid-Depleted Bacteriorhodopsin Monomers
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- 作者：Sabyasachi Mukhopadhyay ; Sidney R. Cohen ; Debora Marchak ; Noga Friedman ; Israel Pecht ; Mordechai Sheves ; David Cahen
- 刊名：ACS Nano
- 出版年：2014
- 出版时间：August 26, 2014
- 年：2014
- 卷：8
- 期：8
- 页码：7714-7722
- 全文大小：440K
- ISSN：1936-086X
文摘
Potential future use of bacteriorhodopsin (bR) as a solid-state electron transport (ETp) material requires the highest possible active protein concentration. To that end we prepared stable monolayers of protein-enriched bR on a conducting HOPG substrate by lipid depletion of the native bR. The ETp properties of this construct were then investigated using conducting probe atomic force microscopy at low bias, both in the ground dark state and in the M-like intermediate configuration, formed upon excitation by green light. Photoconductance modulation was observed upon green and blue light excitation, demonstrating the potential of these monolayers as optoelectronic building blocks. To correlate protein structural changes with the observed behavior, measurements were made as a function of pressure under the AFM tip, as well as humidity. The junction conductance is reversible under pressure changes up to 鈭?00 MPa, but above this pressure the conductance drops irreversibly. ETp efficiency is enhanced significantly at >60% relative humidity, without changing the relative photoactivity significantly. These observations are ascribed to changes in protein conformation and flexibility and suggest that improved electron transport pathways can be generated through formation of a hydrogen-bonding network.