Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Chem Phys. 2020 Mar 14;152(10):104713. doi: 10.1063/1.5141346.
Over the past few decades, the experimental literature has consistently reported observations of attraction between like-charged colloidal particles and macromolecules in aqueous solution. Examples include nucleic acids and colloidal particles in the bulk solution and under confinement, and biological liquid-liquid phase separation. This observation is at odds with the intuitive expectation of an interparticle repulsion that decays monotonically with distance. Although attraction between like-charged particles can be rationalized theoretically in the strong-coupling regime, e.g., in the presence of multivalent counterions, recurring accounts of long-range attraction in aqueous solution containing monovalent ions at low ionic strength have posed an open conundrum. Here, we show that the behavior of molecular water at an interface-traditionally disregarded in the continuum electrostatics picture-provides a mechanism to explain the attraction between like-charged objects in a broad spectrum of experiments. This basic principle will have important ramifications in the ongoing quest to better understand intermolecular interactions in solution.
在过去的几十年中，实验文献一直报告在水溶液中观察到带相同电荷的胶体颗粒和大分子之间的吸引力。例如，包括在本体溶液中和受限条件下的核酸和胶体颗粒，以及生物液-液相分离。这种观察结果与颗粒间排斥的直观预期不一致，后者随着距离的增加而单调衰减。尽管在强耦合（例如，存在多价抗衡离子的情况下）的情况下，可以从理论上合理地解释带相同电荷的颗粒之间的吸引力，但在含有单价离子的低离子强度的水溶液中经常出现长程吸引力的报道，这仍然是一个悬而未决的难题。在这里，我们表明，界面处的分子水的行为——传统上在连续体静电学图像中被忽略——为解释在广泛的实验中带相同电荷的物体之间的吸引力提供了一种机制。这一基本原理将对正在进行的更好地理解溶液中分子间相互作用的研究产生重要影响。
