Nanoscale Electric Characteristics and Oriented Assembly of Halobacterium salinarum Membrane Revealed by Electric Force Microscopy.
Purple membranes (PM) of the bacteriaHalobacterium salinarumare 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 adC/dzvalue 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.
Agricultural Information Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Information Service Technology of Ministry of Agriculture, Beijing 100081, China. lidenghua@caas.cn.|CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. lidenghua@caas.cn.
Denghua
D
Li
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. ybwang@ecust.edu.cn.
Yibing
Y
Wang
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. duhw@nanoctr.cn.
Huiwen
H
Du
Agricultural Information Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Information Service Technology of Ministry of Agriculture, Beijing 100081, China. xushiwei@caas.cn.
Shiwei
S
Xu
Agricultural Information Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Information Service Technology of Ministry of Agriculture, Beijing 100081, China. lizhemin@caas.cn.
Zhemin
Z
Li
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. yangyl@nanoctr.cn.
Yanlian
Y
Yang
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. wangch@nanoctr.cn.
Chen
C
Wang
electrostatic force microscopy (EFM); oriented assembly; peptides; purple membrane (PM); surface potential