Bradshaw R W, Robertson C R
J Membr Biol. 1975 Dec 4;25(1-2):93-114. doi: 10.1007/BF01868570.
Ion-carrier complexes and organic ions of similar size and shape have mobilities in lipid bilayer membranes which span several orders of magnitude. In this communication, an examination is made of the hypothesis that the basis for this unusually wide range of ionic mobilities is the potential energy barrier arising from image forces which selectively act on ions according to their polarizability. Using Poisson's equation to evaluate the electrostatic interaction between an ion and its surroundings, the potential energy barrier to ion transport due to image effects is computed, with the result that the potential energy barrier height depends strongly on ionic polarizability. Theoretical membrane potential energy profile calculations are used in conjunction with Nernst-Planck electrodiffusion equation to analyze the available mobility data for several ion-carrier complexes and lipid-soluble ions in lipid bilayer membranes. The variation among the mobilities of different ions is shown to be in agreement with theoretical predictions based on ionic polarizability and size. Furthermore, the important influence exerted by image forces on ion transport in lipid bilayer membranes compared to the frictional effect of membrane viscosity is established by contrasting available data on the activation energy of ionic conductivity with that for membrane fluidity.
离子载体复合物以及大小和形状相似的有机离子在脂质双分子层膜中的迁移率跨越了几个数量级。在本通讯中，对以下假设进行了检验：这种异常广泛的离子迁移率范围的基础是由镜像力产生的势能垒，该镜像力根据离子的极化率选择性地作用于离子。使用泊松方程评估离子与其周围环境之间的静电相互作用，计算了由于镜像效应导致的离子传输的势能垒，结果表明势能垒高度强烈依赖于离子极化率。理论膜势能分布计算与能斯特 - 普朗克电扩散方程结合使用，以分析脂质双分子层膜中几种离子载体复合物和脂溶性离子的可用迁移率数据。不同离子迁移率之间的变化与基于离子极化率和大小的理论预测一致。此外，通过将离子电导率的活化能与膜流动性的可用数据进行对比，确定了与膜粘度的摩擦效应相比，镜像力对脂质双分子层膜中离子传输的重要影响。
