How electrolyte shielding influences the electrical potential in transmembrane ion channels.
How electrolyte shielding influences the electrical potential in transmembrane ion channels.
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DOI：
10.1016/s0006-3495(89)82903-0
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发表时间：
1989-06
影响因子：
3.4
通讯作者：
Peter C. Jordan;R. Bacquet;J. McCammon;P. Tran
中科院分区：
文献类型：
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作者：
Peter C. Jordan;R. Bacquet;J. McCammon;P. Tran
由于固定电荷分布的电势在膜附近强烈地改变，并且显著地依赖于电解质水溶液浓度。提出了一种求解非线性Poisson-Boltzmann方程的有效方法，该方法适用于一般的圆柱对称介质几何。它将Gouy-Chapman理论推广到含有跨膜通道的系统。该方法适用于三个通道系统：短杆菌肽，缝隙连接，和孔蛋白。我们发现，对于一个长，窄的通道，如短杆菌肽浓度的变化对离子渗透的电图像势垒的影响不大。然而，电解质屏蔽减少了图像诱导的贡献，所需的多个占用的能量。此外，电解质的存在由于施加的电势而显著影响电压分布，基本上将电场压缩到紧邻孔本身。在大直径通道中，其中可以假设本体电解质进入孔，电解质大大降低了对离子渗透的图像屏障。在生理离子强度下，这种屏障可以忽略不计，并且通道可以容易地被多次占据。在所有考虑的离子强度（1大于0.005 M）的图像屏障饱和迅速，基本上是恒定的一个以上的通道半径从入口到孔。在较低的离子强度（1小于0.016 M），有明显的（大于20 mV）的能量损失与多个占用。
The electrical potential due to fixed charge distributions is strongly altered in the vicinity of a membrane and notably dependent on aqueous electrolyte concentration. We present an efficient way to solve the nonlinear Poisson-Boltzmann equation applicable to general cylindrically symmetric dielectric geometries. It generalizes Gouy-Chapman theory to systems containing transmembrane channels. The method is applied to three channel systems: gramicidin, gap junction, and porin. We find that for a long, narrow channel such as gramicidin concentration variation has little influence on the electrical image barrier to ion permeation. However, electrolyte shielding reduces the image induced contribution to the energy required for multiple occupancy. In addition, the presence of electrolyte significantly affects the voltage profile due to an applied potential, substantially compressing the electric field to the immediate vicinity of the pore itself. In the large diameter channels, where bulk electrolyte may be assumed to enter the pore, the electrolyte greatly reduces the image barrier to ion permeation. At physiological ionic strengths this barrier is negligible and the channel may be readily multiply occupied. At all ionic strengths considered (l greater than 0.005 M) the image barrier saturates rapidly and is essentially constant more than one channel radius from the entrance to the pore. At lower ionic strengths (l less than 0.016 M) there are noticeable (greater than 20 mV) energy penalties associated with multiple occupancy.