Smith G R, Sansom M S
Laboratory of Molecular Biophysics, University of Oxford, Oxford OX1 3QU, United Kingdom.
Biophys J. 1998 Dec;75(6):2767-82. doi: 10.1016/S0006-3495(98)77720-3.
We present simulation results for the effective diffusion coefficients of a sodium ion in a series of model ion channels of different diameters and hydrophobicities, including models of alamethicin, a leucine-serine peptide, and the M2 helix bundle of the nicotinic acetylcholine receptor. The diffusion coefficient, which in the simulations has a value of 0.15(2) A2ps-1 in bulk water, is found to be reduced to as little as 0.02(1) A2ps-1 in the narrower channels, and to about 0.10(5) A2ps-1 in wider channels such as the nicotinic acetylcholine receptor. It is anticipated that this work will be useful in connection with calculations of channel conductivity using such techniques as the Poisson-Nernst-Planck equation, Eyring rate theory, or Brownian dynamics.
我们展示了钠离子在一系列不同直径和疏水性的模型离子通道中的有效扩散系数的模拟结果，这些模型包括丙甲菌素（一种亮氨酸 - 丝氨酸肽）模型以及烟碱型乙酰胆碱受体的M2螺旋束模型。在模拟中，扩散系数在体相水中的值为0.15(2) Ųps⁻¹，发现在较窄的通道中会降低至低至0.02(1) Ųps⁻¹，而在较宽的通道如烟碱型乙酰胆碱受体中约为0.10(5) Ųps⁻¹。预计这项工作将有助于使用诸如泊松 - 能斯特 - 普朗克方程、艾林速率理论或布朗动力学等技术来计算通道电导率。
