蛋白质水化水的表观脆强转变的起源

蛋白质水化水中脆-强动力学交叉的观察

Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water

在低温下，蛋白质以玻璃态存在，这种状态没有构象灵活性，也没有生物学功能。在水合蛋白质中，在220 K及以上，这种柔性恢复，并且蛋白质能够采样更多的构象亚状态，从而变得具有生物学功能。蛋白质的这种“动态”转变被认为是由其与水合水的强耦合触发的，这也显示出类似的动态转变。在这里，我们实验证明，这种突然切换的动态行为的水化溶菌酶发生在220 K，可以被描述为一个脆弱的强动态交叉（FSC）。在FSC中，水化水的结构从主要的高密度（更多的流体状态）转变为低密度（更少的流体状态）形式，这是由于在升高的压力下存在第二临界点。

蛋白质水化动力学的温度依赖机制：分子动力学模拟研究

Temperature-dependent mechanisms for the dynamics of protein-hydration waters: a molecular dynamics simulation study

利用分子动力学模拟研究了弹性蛋白样肽和胶原蛋白样肽水化壳的温度依赖性动力学和结构。对于这两个模型肽，它是一致的观察到，在冷却时，水动力学的机制不断变化，从小步扩散运动到大步跳跃运动，水动力学的温度依赖性表现出弱交叉从脆弱的行为到强的行为，和氢键网络的顺序增加。从脆弱到强大的行为的弱交叉的温度被发现与达到氢键网络的最大可能的顺序，使结构变得与温度无关的温度相一致。在强区，水的平移和旋转动力学的温度依赖性的特征在于由一个激活能ca。E_a=0.43 eV，与以前对蛋白质水化水的介电谱和核磁共振研究结果一致。在这些温度下，围绕双重分子对称轴的扭曲π翻转运动，即，水特异性β过程是水动力学的一个重要方面，至少在水-肽界面处是如此。此外，它示出的水合水表现出明显的动力学不均匀性，这可以追溯到一个强烈的放缓水运动的肽分子附近，由于形成水-肽氢键。

Influence of Surface Hydrophilicity and Hydration on the Rotational Relaxation of Supercooled Water on Graphene Oxide Surfaces

Hydration or interfacial water present in biomolecules and inorganic solids have been shown to exhibit a dynamical transition upon supercooling. However, an understanding of the extent of the underlying surface hydrophilicity as well as the local distribution of hydrophilic/hydrophobic patches on the dynamical transition is unexplored. Here, we use molecular dynamics simulations with a TIP4P/2005 water model to study translational and rotational relaxation dynamics of interfacial water on graphene surfaces. The purpose of this study is to investigate the influence of both surface chemistry as …

Dynamics of Protein Hydration Water

We present the frequency- and temperature-dependent dielectric properties of lysozyme solutions in a broad concentration regime, measured at subzero temperatures and compare the results with measurements above the freezing point of water and on hydrated lysozyme powder. Our experiments allow examining the dynamics of unfreezable hydration water in a broad temperature range including the so-called No Man's Land (160 - 235 K). The obtained results prove the bimodality of the hydration shell dynamics and are discussed in the context of the highly-debated fragile-to-strong transition of water.

Curvature Dependence of Hydrophobic Hydration Dynamics

We investigate the curvature-dependence of water dynamics in the vicinity of hydrophobic spherical solutes using molecular dynamics simulations. For both, the lateral and perpendicular diffusivity as well as for H-bond kinetics of water in the first hydration shell, we find a non-monotonic solute-size dependence, exhibiting extrema close to the well-known structural crossover length scale for hydrophobic hydration. Additionally, we find an apparently anomalous diffusion for water moving parallel to the surface of small solutes, which, however, can be explained by topology effects. The intimate…

蛋白质水化水的动态转变

The Dynamic Transition of Protein Hydration Water

生物分子和其他纳米结构表面上的薄层水可以过冷到本体水无法达到的温度。Chen等人[PNAS 103，9012（2006）]提出，通过准弹性中子散射观察到的220 K附近的异常可以用大量水的隐藏临界点来解释。基于更灵敏的测量水的全氘藻蓝蛋白，使用新的中子背散射光谱仪SPHERES，和改进的数据分析，我们目前的结果表明，没有迹象表明这样一个脆弱的强过渡。在220 K下的弹性强度的拐点具有与在170 K下的量热玻璃化转变相容的动力学起源。弛豫时间的温度依赖性对数据评估高度敏感;它可以与其他技术的结果完全一致，没有任何异常。