Hey John C, Smeeton Lewis C, Oakley Mark T, Johnston Roy L
School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K.
J Phys Chem A. 2016 Jun 16;120(23):4008-15. doi: 10.1021/acs.jpca.6b01495. Epub 2016 Jun 3.
Hydrated ions are crucially important in a wide array of environments, from biology to the atmosphere, and the presence and concentration of ions in a system can drastically alter its behavior. One way in which ions can affect systems is in their interactions with proteins. The Hofmeister series ranks ions by their ability to salt-out proteins, with kosmotropes, such as sulfate, increasing their stability and chaotropes, such as perchlorate, decreasing their stability. We study hydrated perchlorate clusters as they are strongly chaotropic and thus exhibit different properties than sulfate. In this study we simulate small hydrated perchlorate clusters using a basin-hopping geometry optimization search with empirical potentials. We compare topological features of these clusters to data from both computational and experimental studies of hydrated sulfate ions and draw some conclusions about ion effects in the Hofmeister series. We observe a patterning conferred to the water molecules within the cluster by the presence of the perchlorate ion and compare the magnitude of this effect to that observed in previous studies involving sulfate. We also investigate the influence of the overall ionic charge on the low-energy structures adopted by these clusters.
水合离子在从生物学到大气的广泛环境中至关重要，系统中离子的存在和浓度会极大地改变其行为。离子影响系统的一种方式是它们与蛋白质的相互作用。霍夫迈斯特序列根据离子使蛋白质盐析的能力对离子进行排序，盐析剂（如硫酸根）会增加蛋白质的稳定性，而离液剂（如高氯酸根）则会降低其稳定性。我们研究水合高氯酸根簇，因为它们具有很强的离液性，因此表现出与硫酸根不同的性质。在本研究中，我们使用基于经验势的盆地跳跃几何优化搜索来模拟小的水合高氯酸根簇。我们将这些簇的拓扑特征与水合硫酸根离子的计算和实验研究数据进行比较，并就霍夫迈斯特序列中的离子效应得出一些结论。我们观察到高氯酸根离子的存在赋予簇内水分子一种模式，并将这种效应的大小与先前涉及硫酸根的研究中观察到的效应进行比较。我们还研究了总离子电荷对这些簇所采用的低能量结构的影响。
