National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China.
J Phys Chem B. 2013 Aug 29;117(34):9895-9. doi: 10.1021/jp403075w. Epub 2013 Aug 16.
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.
我们通过静电原子力显微镜（EFM）报告了紫色膜（PM）表面电荷密度随温度变化的测量结果。室温下表面电荷密度为 3.4×10(5) e/cm(2)，在 52°C 左右达到最小值。表面电荷密度的初始下降可归因于 PM 中热诱导的蛋白质流动性导致偶极子排列减少。较高温度下电荷密度的增加可归因于蛋白质与脂质之间相互作用的减弱，这导致带电氨基酸暴露。这项工作有助于直接评估纳米尺度生物膜的结构稳定性和电特性。
