Frankfurt Institute for Advanced Studies, Goethe University, Ruth-Moufang-Str. 1, 60438 Frankfurt/Main, Germany.
Faraday Discuss. 2010;144:57-70; discussion 93-110, 467-81. doi: 10.1039/b902011j.
The electrophoretic behaviour of flexible polyelectrolyte chains ranging from single monomers up to long fragments of a hundred repeat units is studied by a mesoscopic simulation approach. Abstracting from the atomistic details of the polyelectrolyte and the fluid, a coarse-grained molecular dynamics model connected to a mesoscopic fluid described by the Lattice-Boltzmann approach is used to investigate free-solution electrophoresis. Our study demonstrates the importance of hydrodynamic interactions for the electrophoretic motion of polyelectrolytes and quantifies the influence of surrounding ions. The length-dependence of the electrophoretic mobility can be understood by evaluating the scaling behavior of the effective charge and the effective friction. The perfect agreement of our results with experimental measurements shows that all chemical details and fluid structure can be safely neglected, and a suitable coarse-grained approach can yield an accurate description of the physics of the problem, provided that electrostatic and hydrodynamic interactions between all entities in the system, i.e., the polyelectrolyte, dissociated counterions, additional salt and the solvent, are properly accounted for. Our model is able to bridge the single molecule regime of a few nm up to macromolecules with contour lengths of more than 100 nm, a length scale that is currently not accessible to atomistic simulations.
通过介观模拟方法研究了从单个单体到数百个重复单元的长链柔性聚电解质的电泳行为。通过将聚电解质和流体的原子细节抽象化，使用连接到由格子玻尔兹曼方法描述的介观流体的粗粒度分子动力学模型来研究自由溶液电泳。我们的研究表明，流体动力学相互作用对聚电解质的电泳运动很重要，并量化了周围离子的影响。通过评估有效电荷和有效摩擦的标度行为，可以理解电泳迁移率的长度依赖性。我们的结果与实验测量的完美吻合表明，可以安全地忽略所有化学细节和流体结构，并且合适的粗粒度方法可以提供对问题物理的准确描述，前提是系统中的所有实体（即聚电解质、离解抗衡离子、额外盐和溶剂）之间的静电和流体动力学相互作用得到适当考虑。我们的模型能够连接几个纳米的单分子范围到超过 100nm 的大分子，这是目前原子模拟无法达到的长度尺度。
