论文标题
电荷相关性引起的电泳聚合物迁移率反演的理论和计算分析
Theoretical and computational analysis of the electrophoretic polymer mobility inversion induced by charge correlations
论文作者
论文摘要
对于多价盐溶液中强电荷的大分子,通常观察到电泳(EP)迁移率逆转。这种奇怪的效果发生了,例如,当带电的聚合物(例如DNA)吸附过多的柜台时,以使反式面式的表面电荷逆转其符号,从而导致由外部电场驱动的聚合物漂移的反转。为了表征这种看似违反直觉的现象,无法通过静电均值场理论捕获,我们在这里适应了先前开发的强耦合式泊松波尔兹曼方法,以用于聚电解质 - 盐系统的圆柱形几何形状。在这种形式主义的框架内,我们得出了由电荷相关性打扮的分析聚合物迁移率。在与聚合物传输实验的定性一致性中,该迁移率公式预测,单价盐的增加,多价抗衡价的降低以及背景溶剂的介电介电常数的增加,抑制电荷相关性并增加了eP Epmobility逆转所需的多价体积抗衡浓度。这些结果通过粗粒分子动力学模拟来证实,表明多价柜台如何在稀释浓度下诱导迁移率反演并抑制大浓度下的反转效应。以前在类似聚合物溶液的聚集中观察到的这种重点行为要求通过聚合物传输实验进行验证。
Electrophoretic (EP) mobility reversal is commonly observed for strongly charged macromolecules in multivalent salt solutions. This curious effect takes place, e.g., when a charged polymer, such as DNA, adsorbs excess counterions so that the counterion-dressed surface charge reverses its sign, leading to the inversion of the polymer drift driven by an external electric field. In order to characterize this seemingly counterintuitive phenomenon that cannot be captured by electrostatic mean-field theories, we adapt here a previously developed strong-coupling-dressed Poisson-Boltzmann approach to the cylindrical geometry of the polyelectrolyte-salt system. Within the framework of this formalism, we derive an analytical polymer mobility formula dressed by charge correlations. In qualitative agreement with polymer transport experiments, this mobility formula predicts that the increment of the monovalent salt, the decrease of the multivalent counterion valency, and the increase of the dielectric permittivity of the background solvent, suppress charge correlations and increase the multivalent bulk counterion concentration required for EP mobility reversal. These results are corroborated by coarse-grained molecular dynamics simulations showing how multivalent counterions induce mobility inversion at dilute concentrations and suppress the inversion effect at large concentrations. This re-entrant behavior, previously observed in the aggregation of like-charged polymer solutions, calls for verification by polymer transport experiments.