Heyden Matthias, Matyushov Dmitry V
School of Molecular Sciences, Arizona State University, P.O. Box 871604, Tempe, Arizona 85287-1604, United States.
Department of Physics and School of Molecular Sciences, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287-1504, United States.
J Phys Chem B. 2020 Dec 24;124(51):11634-11647. doi: 10.1021/acs.jpcb.0c09007. Epub 2020 Dec 13.
A nonionic particle placed in the gradient of an electric field experiences the dielectrophoretic force which scales linearly with the gradient of the electric field squared. The proportionality constant is the dielectrophoretic susceptibility, that is, a linear transport coefficient. For proteins in solution, it is mostly affected by the following two parameters: the squared dipole moment and the cavity susceptibility accounting for cross-correlations of the protein dipole with the hydration shell (protein-water Kirkwood factor). Both of these parameters enter the dielectric increment of the solution which fully specifies the dielectrophoretic susceptibility. The link between these two measurable properties is proven here to hold using molecular dynamics simulations of solvated proteins. The dielectrophoretic susceptibility for proteins is in the range of 10, significantly exceeding traditional estimates limiting it to values below unity. Part of this large magnitude of the dielectrophoretic response is the cavity susceptibility of the protein-water interface, which significantly exceeds dielectric estimates. The study analyzes local fields inside the protein in terms of the reaction-field and directing-field components. We find that the local field exceeds the external field by a substantial factor described by the local field susceptibility. The electric field produced by water inside the protein is retarded by 3-4 orders of magnitude compared to the bulk.
置于电场梯度中的非离子粒子会受到介电泳力的作用，该力与电场平方的梯度呈线性关系。比例常数即为介电泳敏感性，也就是一个线性输运系数。对于溶液中的蛋白质而言，它主要受以下两个参数影响：平方偶极矩以及考虑蛋白质偶极与水化层交叉相关性的空穴敏感性（蛋白质 - 水柯克伍德因子）。这两个参数都进入了溶液的介电增量中，而该介电增量完全决定了介电泳敏感性。本文通过对溶剂化蛋白质的分子动力学模拟证明了这两个可测量性质之间的联系成立。蛋白质的介电泳敏感性在10的范围内，显著超过了传统估计中限制其值低于1的范围。这种介电泳响应的大幅值部分是由于蛋白质 - 水界面的空穴敏感性，其显著超过了介电估计值。该研究从反应场和导向场分量的角度分析了蛋白质内部的局部场。我们发现局部场比外部场大一个由局部场敏感性描述的可观因子。蛋白质内部水产生的电场与本体相比滞后3 - 4个数量级。
