Nanoscale Electric Characteristics and Oriented Assembly of Halobacterium salinarum Membrane Revealed by Electric Force Microscopy
by
Denghua Li 1,2, Yibing Wang 2, Huiwen Du 2, Shiwei Xu 1, Zhemin Li 1, Yanlian Yang 2,* and Chen Wang 2,*
Denghua Li 1,2, Yibing Wang 2, Huiwen Du 2, Shiwei Xu 1, Zhemin Li 1, Yanlian Yang 2,* and Chen Wang 2,*
1
Agricultural Information Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Information Service Technology of Ministry of Agriculture, Beijing 100081, China
2
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Lital Alfonta
Nanomaterials 2016, 6(11), 197; https://doi.org/10.3390/nano6110197
Received: 15 July 2016 / Revised: 28 September 2016 / Accepted: 8 October 2016 / Published: 2 November 2016
(This article belongs to the Special Issue Nanostructured Biofuel Cells)
Purple membranes (PM) of the bacteria Halobacterium salinarum are a unique natural membrane where bacteriorhodopsin (BR) can convert photon energy and pump protons. Elucidating the electronic properties of biomembranes is critical for revealing biological mechanisms and developing new devices. We report here the electric properties of PMs studied by using multi-functional electric force microscopy (EFM) at the nanoscale. The topography, surface potential, and dielectric capacity of PMs were imaged and quantitatively measured in parallel. Two orientations of PMs were identified by EFM because of its high resolution in differentiating electrical characteristics. The extracellular (EC) sides were more negative than the cytoplasmic (CP) side by 8 mV. The direction of potential difference may facilitate movement of protons across the membrane and thus play important roles in proton pumping. Unlike the side-dependent surface potentials observed in PM, the EFM capacitive response was independent of the side and was measured to be at a dC/dz value of ~5.25 nF/m. Furthermore, by modification of PM with de novo peptides based on peptide-protein interaction, directional oriented PM assembly on silicon substrate was obtained for technical devices. This work develops a new method for studying membrane nanoelectronics and exploring the bioelectric application at the nanoscale.
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Keywords:
electrostatic force microscopy (EFM); purple membrane (PM); surface potential; peptides; oriented assembly
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MDPI and ACS Style
Li, D.; Wang, Y.; Du, H.; Xu, S.; Li, Z.; Yang, Y.; Wang, C. Nanoscale Electric Characteristics and Oriented Assembly of Halobacterium salinarum Membrane Revealed by Electric Force Microscopy. Nanomaterials 2016, 6, 197.
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