The expression mechanism of permselectivity through a gramicidin A (gA) channel between two aqueous phases (W1 and W2) was investigated. When the concentration of CsCl or CsBr in W1 was equivalent to that in W2, the single‐channel current was proportional to the absolute value of the applied membrane potential. Although the single‐channel current linearly increased with increasing electrolyte concentration in W1 and W2 until about 0.1 M (mol dm⁻³), it began to level off around 0.1 M, indicating that ion permeation across the channel pore is the rate‐determining step and that the saturation of the transporting ion within the channel pore provokes the leveling off. In the case of asymmetric composition of the electrolyte in W1 and W2, the monovalent cation and the counter anion were transported in the opposite direction through the gA channel pore or the bilayer lipid membrane around the gA channel. Finally, the experimental data was fitted using the Goldman‐Hodgkin‐Katz equation based on the relationship between the membrane potential and the single‐channel current to define the ratio of the diffusion coefficients of Cs⁺, Cl⁻, and Br⁻ as 5.7 : 1.0 : 0.26.

中文翻译：

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基于单通道记录的Gramicidin A通道的渗透选择性

研究了通过两个水相（W1和W2）之间的短杆菌素A（gA）通道进行渗透选择性的表达机理。当W1中的CsCl或CsBr浓度与W2中的浓度相等时，单通道电流与施加的膜电位的绝对值成比例。尽管单通道电流随着W1和W2中电解质浓度的增加而线性增加，直到约0.1 M（mol dm ^-3），它开始在约0.1 M处趋于稳定，这表明离子在通道孔中的渗透是决定速率的步骤，并且通道孔中传输离子的饱和会促使其趋于平稳。在W1和W2中电解质组成不对称的情况下，单价阳离子和抗衡阴离子以相反的方向穿过gA通道孔或gA通道周围的双层脂质膜。最后，实验数据是使用基于膜电位和单通道电流之间的关系的戈德曼霍奇金卡茨方程来定义Cs的扩散系数比嵌合⁺，氯^-和Br ^- 5.7： 1.0：0.26。