Dagdug Leonardo, Berezhkovskii Alexander M, Bezrukov Sergey M
Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, 09340 Mexico City, Mexico.
Section of Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20819, United States.
J Phys Chem B. 2023 Aug 24;127(33):7291-7298. doi: 10.1021/acs.jpcb.3c04520. Epub 2023 Aug 11.
The geometry of ion and metabolite channels in membranes of biological cells and organelles is usually far from that of a regular right cylinder. Rather, the channels have complex shapes that are characterized by the so-called vestibules and constriction zones which play roles of molecular filters determining the channel selectivity. In the present paper we discuss several channel structures with varying radius that approximate most of the cases found in nature, specifically, channels of smoothly varying radius and channels composed of multiple cylindrical sections of different lengths and radii including channels containing very thin circular constrictions. We consider diffusive transport of electrically neutral molecules driven by the concentration gradient and derive analytical expressions for the diffusion resistance - the integral parameter that describes steady-state transport properties of membrane channels.
生物细胞和细胞器膜中离子通道和代谢物通道的几何形状通常与规则的直圆柱体相差甚远。相反，这些通道具有复杂的形状，其特征在于所谓的前庭和收缩区，它们起着分子过滤器的作用，决定了通道的选择性。在本文中，我们讨论了几种半径不同的通道结构，这些结构近似于自然界中发现的大多数情况，具体来说，包括半径平滑变化的通道以及由不同长度和半径的多个圆柱形部分组成的通道，其中包括含有非常细的圆形收缩区的通道。我们考虑由浓度梯度驱动的电中性分子的扩散传输，并推导扩散阻力的解析表达式——这是一个描述膜通道稳态传输特性的积分参数。
