Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
J Phys Chem Lett. 2022 Apr 7;13(13):2901-2907. doi: 10.1021/acs.jpclett.2c00227. Epub 2022 Mar 25.
The facilitated surface diffusion of transiently adsorbing molecules in a planar confined microenvironment (i.e., slit-like confinement) is highly relevant to biological phenomena, such as extracellular signaling, as well as numerous biotechnology systems. Here, we studied the surface diffusion of individual proteins confined between two symmetric lipid bilayer membranes, under a continuum of confinement heights, using single-molecule tracking and convex lens-induced confinement as well as hybrid, kinetic Monte Carlo simulations of a generalized continuous time random walk process. Surface diffusion was observed to vary non-monotonically with confinement height, exhibiting a maximum at a height of ∼750 nm, where diffusion was nearly 40% greater than that for a semi-infinite system. This demonstrated that planar confinement can, in fact, increase surface diffusion, qualitatively validating previous theoretical predictions. Simulations reproduced the experimental results and suggested that confinement enhancement of surface diffusion for symmetric systems is limited to cases where the adsorbate exhibits weak surface sticking.
在平面受限微环境（即狭缝状限制）中，瞬态吸附分子的促进表面扩散与生物现象密切相关，如细胞外信号传递以及许多生物技术系统。在这里，我们使用单分子跟踪和凸面镜诱导限制以及广义连续时间随机行走过程的混合动力学蒙特卡罗模拟，研究了在连续的限制高度下，夹在两个对称脂质双层膜之间的单个蛋白质的表面扩散。表面扩散随限制高度的变化是非单调的，在约 750nm 的高度处表现出最大值，扩散速度比半无限系统快近 40%。这表明平面限制实际上可以增加表面扩散，定性地验证了先前的理论预测。模拟再现了实验结果，并表明对称系统中表面扩散的限制增强仅限于吸附剂表现出较弱表面粘性的情况。
