Li Denghua, Wang Yibing, Du Huiwen, Xu Shiwei, Li Zhemin, Yang Yanlian, Wang Chen
Agricultural Information Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Agricultural Information Service Technology of Ministry of Agriculture, Beijing 100081, China.
CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.
Nanomaterials (Basel). 2016 Nov 2;6(11):197. doi: 10.3390/nano6110197.
Purple membranes (PM) of the bacteria 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 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.
细菌的紫膜（PM）是一种独特的天然膜，其中细菌视紫红质（BR）可以转换光子能量并泵浦质子。阐明生物膜的电子特性对于揭示生物学机制和开发新设备至关重要。我们在此报告通过使用纳米级多功能静电力显微镜（EFM）研究的紫膜的电学性质。同时对紫膜的形貌、表面电位和介电电容进行了成像和定量测量。由于EFM在区分电学特性方面具有高分辨率，因此识别出了紫膜的两种取向。细胞外（EC）侧比细胞质（CP）侧更负8 mV。电位差的方向可能有助于质子跨膜移动，从而在质子泵浦中发挥重要作用。与在紫膜中观察到的依赖于侧面的表面电位不同，EFM电容响应与侧面无关，测量值约为5.25 nF/m。此外，通过基于肽 - 蛋白质相互作用用从头合成肽修饰紫膜，在硅衬底上获得了用于技术设备的定向排列的紫膜组件。这项工作开发了一种研究膜纳米电子学和探索纳米级生物电应用的新方法。
