Fujitani Y, Bedeaux D
Department of Physical and Macromolecular Chemistry, Leiden University, The Netherlands.
Biophys J. 1997 Oct;73(4):1805-14. doi: 10.1016/S0006-3495(97)78211-0.
The current-voltage relationship of ion leak (i.e., ion transport involving neither special channels nor carriers) across the lipid-bilayer membrane has been observed to be log-linear above the ohmic regime. The coefficient of the linear term has been found to be universal for membranes and penetrants examined. This universality has been explained in terms of diffusion in an external field, where the ion position is described as a Markovian process. Such a diffusion picture can be questioned, however. It is also probable that a leaking ion gets over the potential barrier before experiencing sufficient random collision in the membrane, considering that each ion is surrounded with long lipid molecules aligned almost unidirectionally. As an alternative, we discuss this ion leak in terms of velocity distribution of the ions entering the membrane and density fluctuation of the lipids. We conclude that we can explain the universality without resorting to the diffusion picture.
已观察到，在高于欧姆区的情况下，离子泄漏（即既不涉及特殊通道也不涉及载体的离子运输）跨脂质双分子层膜的电流 - 电压关系呈对数线性。已发现线性项的系数对于所研究的膜和渗透剂而言是通用的。这种通用性已根据外部场中的扩散来解释，其中离子位置被描述为马尔可夫过程。然而，这样的扩散图景可能受到质疑。考虑到每个离子都被几乎单向排列的长脂质分子包围，一个泄漏的离子在膜中经历足够的随机碰撞之前越过势垒也是有可能的。作为一种替代方法，我们根据进入膜的离子的速度分布和脂质的密度涨落来讨论这种离子泄漏。我们得出结论，无需借助扩散图景就能解释这种通用性。
