title: Determination of the surface charge density and temperature dependence of purple membrane by electric force microscopy.
abstract: We report here the measurement of the temperature-dependent surface charge density of purple membrane (PM) by using electrostatic force microscopy (EFM). The surface charge density was measured to be 3.4 × 10(5) e/cm(2) at room temperature and reaches the minimum at around 52 °C. The initial decrease of the surface charge density could be attributed to the reduced dipole alignment because of the thermally induced protein mobility in PM. The increase of charge density at higher temperature could be ascribed to the weakened interaction between proteins and the lipids, which leads to the exposure of the charged amino acids. This work could be a benefit to the direct assessment of the structural stability and electric properties of biological membranes at the nanoscale.
authors.affiliation: National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China.
authors.forename: Huiwen
authors.initials: H
authors.lastname: Du
authors.forename: Denghua
authors.initials: D
authors.lastname: Li
authors.forename: Yibing
authors.initials: Y
authors.lastname: Wang
authors.forename: Chenxuan
authors.initials: C
authors.lastname: Wang
authors.forename: Dongdong
authors.initials: D
authors.lastname: Zhang
authors.forename: Yan-lian
authors.initials: YL
authors.lastname: Yang
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
mesh_terms: D019617:Halobacterium salinarum / Q000378:metabolism; D018625:Microscopy, Atomic Force; D018717:Purple Membrane / Q000737:chemistry* / Q000378:metabolism; D055672:Static Electricity; D013499:Surface Properties; D013696:Temperature