Department of Physics, Clarkson University, Potsdam, New York 13699, USA.
J Chem Phys. 2019 Mar 21;150(11):115103. doi: 10.1063/1.5080944.
The ability to separate proteins is desirable for many fields of study, and nanoporous membranes may offer a method for rapid protein filtration at high throughput volume, provided there is an understanding of the protein dynamics involved. In this work, we use Brownian dynamics simulations to study the motion of coarse-grained proteins insulin and ubiquitin in an electrically biased membrane. In our model, the protein is subjected to various biases applied to the silicon membrane equipped with a nanopore of different radii. The time each protein takes to find a cylindrical nanopore embedded in a thin silicon membrane, attempt to translocate it (waiting time), and successfully translocate it in a single attempt (translocation time) is calculated. We observe insulin finding the nanopore and translocating it faster than the electrically neutral ubiquitin due to insulin's slightly smaller size and net negative charge. While ubiquitin's dynamics is also affected by the size of the pore, surprisingly, its translocation process is also noticeably changed by the membrane bias. By investigating the protein's multipole moments, we demonstrate that this behavior is largely due to the protein's dipole and quadrupole interactions with the membrane potential.
蛋白质的分离能力在许多研究领域都是理想的，而纳米多孔膜可能为高通量体积的快速蛋白质过滤提供了一种方法，前提是对所涉及的蛋白质动力学有一定的了解。在这项工作中，我们使用布朗动力学模拟来研究在偏置电场的膜中粗粒化蛋白质胰岛素和泛素的运动。在我们的模型中，蛋白质受到施加在硅膜上的各种偏置的影响，硅膜上配备了不同半径的纳米孔。计算了每种蛋白质找到嵌入在薄硅膜中的圆柱形纳米孔、尝试穿过它（等待时间）以及一次成功穿过它（迁移时间）所需的时间。我们观察到胰岛素比电中性的泛素更快地找到纳米孔并穿过它，这是由于胰岛素的尺寸略小且带净负电荷。虽然泛素的动力学也受到孔尺寸的影响，但令人惊讶的是，膜偏置也明显改变了其迁移过程。通过研究蛋白质的多极矩，我们证明这种行为主要是由于蛋白质的偶极子和四极子与膜势的相互作用。
