Department of Biological Structure, University of Washington, Seattle, Washington 98195, USA.
Annu Rev Biochem. 2012;81:615-35. doi: 10.1146/annurev-biochem-070110-123033. Epub 2012 Mar 12.
There are three kinds of membrane potentials: the surface potentials, resulting from the accumulation of charges at the membrane surfaces; the transmembrane potential, determined by imbalance of charge in the aqueous solutions; and the dipole potential, a membrane-internal potential from the dipolar components of the phospholipids and interface water. The absolute value of the dipole potential has been very difficult to measure, although its value has been estimated to be in the range of 200-1,000 mV from ion translocation rates (determined by the planar lipid bilayer method), the surface potential of lipid monolayers (determined by the lipid monolayer method), molecular-dynamics calculations, and electron scattering using cryoelectron microscopy (cryo-EM). Spectroscopy methods have also been used to monitor the dipole potential changes on the basis of the observed fluorescence changes of voltage-sensitive probes. The dipole potential accounts for the much larger permeability of a bare phospholipid membrane to anions than cations and affects the conformation and function of membrane proteins.
表面电位，由膜表面电荷积累引起；跨膜电位，由水相溶液中电荷不平衡决定；以及偶极电位，一种由磷脂和界面水中的偶极分量产生的膜内电位。尽管已经从离子迁移率（通过平面脂质双层方法确定）、脂质单层的表面电位（通过脂质单层方法确定）、分子动力学计算和使用冷冻电子显微镜（cryo-EM）的电子散射中估计偶极电位的值在 200-1000 mV 范围内，但偶极电位的绝对值非常难以测量。光谱法也已被用于监测基于电压敏感探针观察到的荧光变化的偶极电位变化。偶极电位解释了裸露的磷脂膜对阴离子的通透性比阳离子大得多，并影响膜蛋白的构象和功能。
