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钾离子通道作为细胞中阳离子浓度的调节器之一, 在神经细胞动作电位去极化及复极化过程中起着重要作用. KcsA(K +conduction and selectivity architecture)通道结构简单又具有钾离子通道的共性, 常作为钾通道研究的模板. 本文采用布朗动力学数值方法, 系统地对KcsA钾通道的电学特性进行模拟. 得到静电场作用下通道内离子的平均势能分布、均匀与非均匀溶液的电流-电压特性曲线、通道轴向的离子浓度分布曲线以及电导-浓度曲线. 研究结果发现, KcsA钾离子通道选择性过滤区域几乎完全阻隔了Cl –通过, 呈现倾向于K +通过的特异选择特性; 其电流-电压曲线基本呈线性分布, 电导-浓度曲线呈现先增大后平缓的趋势, 基本规律与实验现象一致. 另外, 还模拟分析了太赫兹场对通道K +电流的影响, 相比于仅施加同幅值静电场, 选定的0.6 THz, 1.2 THz, 5 THz的太赫兹场可通过影响离子对之间的相互作用势能, 降低通道平均力势, 从而增大K +电流. 本文的研究不但加深了对于KcsA钾离子通道的规律性认识, 还为其他类型离子通道以及太赫兹场对离子通道特性影响的研究提供了新思路.As one of the regulators of cationic concentration in cells, potassium channels play an important role in the depolarization and repolarization of nerve cell. KcsA (K +conduction and selectivity architecture) channel is simple and has the commonness of potassium ion channel, which is often used as a template for potassium channel research. In this paper, Brownian dynamics (BD) method is used to simulate the electrical characteristics of the actual KcsA potassium channel systematically. The potential mean force (PMF) of ions in the channel under electrostatic field, the current-voltage characteristic curve of symmetric solution and asymmetric solution, the ion concentration distribution curve in the axial direction of the channel, and the conduction-concentration curve are obtained. The results show that the selectivity filter region of KcsA potassium channel blocks the passage of Cl –basically, showing a special selection characteristic of the passage of K +, that its current-voltage curve presents a basically linear distribution, and that the conductivity-concentration curve presents a trend of first increasing and then flattening. The basic characteristic is consistent with the experimental phenomenon. In addition, the influence of the THz field on the channel K +current is also simulated and analyzed. Compared with applying only the same amplitude electrostatic field, the selected terahertz field of 0.6 THz, 1.2 THz, and 5 THz can reduce the PMF by affecting the interaction potential energy between ion pairs, thereby increasing the K +current. The research in this paper not only deepens the understanding of the regularity of KcsA potassium ion channels, but also provides a new idea for studying other types of ion channels and the influence of terahertz field on the characteristics of ion channels.
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