Iorio A, Camisasca G, Rovere M, Gallo P
Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy.
Department of Physics, AlbaNova University Center, Stockholm University, S-106 91 Stockholm, Sweden.
J Chem Phys. 2019 Jul 28;151(4):044507. doi: 10.1063/1.5108579.
The structural and dynamical properties of hydration water in aqueous solutions of trehalose are studied with molecular dynamics simulation. We simulate the systems in the supercooled region to investigate how the interaction with the trehalose molecules modifies the hydrogen bond network, the structural relaxation, and the diffusion properties of hydration water. The analysis is performed by considering the radial distribution functions, the residence time of water molecules in the hydration shell, the two body excess entropy, and the hydrogen bond water-water and water-trehalose correlations of the hydration water. The study of the two body excess entropy shows the presence of a fragile to strong crossover in supercooled hydration water also found in the relaxation time of the water-water hydrogen bond correlation function, and this is in agreement with predictions of the mode coupling theory and of previous studies of the oxygen-oxygen density correlators [A. Iorio et al., J. Mol. Liq. 282, 617 (2019); Sci. China: Phys., Mech. Astron. 62, 107011 (2019)]. The water-trehalose hydrogen bond correlation function instead evidences a strong to strong crossover in the relaxation time, and this crossover is related to a trehalose dynamical transition. This signals the role that the strong interplay between the soluted molecules and the surrounding solvent has in determining the dynamical transition common to both components of the system that happens upon cooling and that is similar to the well known protein dynamical transition. We connect our results with the cryoprotecting role of trehalose molecules.
利用分子动力学模拟研究了海藻糖水溶液中水合水的结构和动力学性质。我们在过冷区域模拟这些系统，以研究与海藻糖分子的相互作用如何改变氢键网络、结构弛豫以及水合水的扩散性质。通过考虑径向分布函数、水分子在水合壳层中的停留时间、两体过量熵以及水合水的水 - 水和水 - 海藻糖氢键相关性来进行分析。对两体过量熵的研究表明，在过冷水合水中存在从脆弱到强的转变，这也在水 - 水氢键相关函数的弛豫时间中发现，这与模式耦合理论的预测以及先前对氧 - 氧密度相关器的研究一致 [A. Iorio 等人，《分子液体杂志》282, 617 (2019); 《中国科学：物理学、力学、天文学》62, 107011 (2019)]。相反，水 - 海藻糖氢键相关函数在弛豫时间上显示出从强到强的转变，并且这种转变与海藻糖的动力学转变有关。这表明溶质分子与周围溶剂之间的强相互作用在决定系统两个组分在冷却时共同发生的动力学转变中所起的作用，这种转变类似于众所周知的蛋白质动力学转变。我们将我们的结果与海藻糖分子的冷冻保护作用联系起来。
