The combined hydrodynamic and thermodynamic effects of immobilized proteins on the diffusion of mobile transmembrane proteins
The combined hydrodynamic and thermodynamic effects of immobilized proteins on the diffusion of mobile transmembrane proteins
复制标题
固定化蛋白质对移动跨膜蛋白质扩散的综合流体力学和热力学效应
DOI：
10.1017/jfm.2019.592
复制
发表时间：
2019
影响因子：
3.7
通讯作者：
Koch, Donald L.
中科院分区：
文献类型：
--
作者：
Singh, Rohit R.;Sangani, Ashok S.;Daniel, Susan;Koch, Donald L.
细胞的质膜是薄的粘性片，其中一些跨膜蛋白具有二维移动性，而另一些则是固定的。先前的研究表明，固定蛋白质通过流体动力学相互作用延迟了移动颗粒的短时扩散性，并且固定蛋白质的空间效应降低了忽略流体动力学相互作用的模型中的长期扩散性。我们提出了单个移动蛋白质与一系列固定蛋白质在周期性边界条件下进行流体动力学和热力学相互作用的长期扩散率的严格推导。该方法基于移动蛋白质扩散的概率密度的有限元法 (FEM) 解，其具有通过斯托克斯方程的多极解确定的位置依赖性迁移率。随着阵列中的间距以与润滑分析一致的方式接近颗粒尺寸，方形阵列中模拟的长时间扩散率降低。在随机阵列中，空间效应导致渗滤阈值体积分数，高于该阈值则长时间扩散被阻止。 FEM/多极方法用于计算远离该阈值的长时间扩散率。然后，对通过由键连接的孔网络的移动蛋白质扩散进行近似分析，电阻由有限元/多极计算确定，以探索更高的固定面积分数，并评估渗滤阈值附近扩散的有限模拟细胞尺寸缩放行为。令人惊讶的是，这些二维固定阵列中的长期扩散率与空间平均短时扩散率的比率在存在流体动力相互作用的情况下比在不存在流体动力相互作用的情况下更高。最后，讨论了这项工作的意义，包括使用此处开发的方法来研究在细胞膜中观察到的更复杂的扩散现象的可能性。
The plasma membranes of cells are thin viscous sheets in which some transmembrane proteins have two-dimensional mobility and some are immobilized. Previous studies have shown that immobile proteins retard the short-time diffusivity of mobile particles through hydrodynamic interactions and that steric effects of immobile proteins reduce the long-time diffusivity in a model that neglects hydrodynamic interactions. We present a rigorous derivation of the long-time diffusivity of a single mobile protein interacting hydrodynamically and thermodynamically with an array of immobile proteins subject to periodic boundary conditions. This method is based on a finite element method (FEM) solution of the probability density of the mobile protein diffusing with a position-dependent mobility determined through a multipole solution of Stokes equations. The simulated long-time diffusivity in square arrays decreases as the spacing in the array approaches the particle size in a manner consistent with a lubrication analysis. In random arrays, steric effects lead to a percolation threshold volume fraction above which long-time diffusion is arrested. The FEM/multipole approach is used to compute the long-time diffusivity far away from this threshold. An approximate analysis of mobile protein diffusion through a network of pores connected by bonds with resistances determined by the FEM/multipole calculations is then used to explore higher immobile area fractions and to evaluate the finite simulation cell size scaling behaviour of diffusion near the percolation threshold. Surprisingly, the ratio of the long-time diffusivity to the spatially averaged short-time diffusivity in these two-dimensional fixed arrays is higher in the presence of hydrodynamic interactions than in their absence. Finally, the implications of this work are discussed, including the possibility of using the methods developed here to investigate more complex diffusive phenomena observed in cell membranes.