ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
J Phys Chem B. 2020 Dec 3;124(48):10983-10993. doi: 10.1021/acs.jpcb.0c07780. Epub 2020 Nov 17.
Liquid water is known as the "universal" solvent, capable of dissolving a wide variety of different solutes. While much is now understood about the impact of solutes on the water structure in binary solutions, it is much more challenging to deconvolute the potentially competing effects of more complex solutions. Here, we present a correlative NMR and neutron diffraction study to examine the solute induced perturbation of water structure and dynamics in a tertiary solution containing the naturally occurring osmolyte trimethylamine N-oxide (TMAO) and magnesium perchlorate (Mg(ClO)). We show that while TMAO and Mg(ClO) perturb the water structure in an opposing manner, the two solutes slow water dynamics in an additive manner. We quantify the relative ability of each solute to perturb water by introducing a weighting parameter and show that TMAO is 1.54 times more effective at perturbing water structure and dynamics than Mg(ClO). The combination of NMR, neutron diffraction, and computational modelling offers unprecedented access to the structure and dynamics of more complex aqueous solutions, permitting the deconvolution of solute specific perturbation of water. Such insight provides a new route to understand this universal solvent in the context of important and relevant aqueous environments.
液态水是众所周知的“通用”溶剂，能够溶解多种不同的溶质。虽然现在已经了解了溶质对二元溶液中水分子结构的影响，但要分解更复杂溶液中可能存在的竞争效应则更加具有挑战性。在这里，我们进行了一项相关的 NMR 和中子衍射研究，以检查在含有天然渗透调节剂三甲胺 N-氧化物 (TMAO) 和高氯酸镁 (Mg(ClO))的三元溶液中，溶质对水分子结构和动力学的影响。结果表明，尽管 TMAO 和 Mg(ClO)以相反的方式干扰水分子结构，但这两种溶质以加和的方式使水分子的动力学变慢。我们通过引入加权参数来量化每种溶质干扰水分子的相对能力，并表明 TMAO 比 Mg(ClO)更有效地干扰水分子结构和动力学，其效率是后者的 1.54 倍。NMR、中子衍射和计算模型的组合为更复杂水溶液的结构和动力学提供了前所未有的研究途径，使得能够分解水分子的特定溶质干扰。这种见解为在重要且相关的水相环境中理解这种通用溶剂提供了新的途径。
