标题： 蛋白质水合水中的脆弱至强动态交叉观察 显示英文标题

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

摘要： 在低温下，蛋白质处于玻璃态，这是一种没有构象灵活性且没有生物功能的状态。 在水合蛋白质中，在220 K及以上的温度，这种灵活性得以恢复，蛋白质能够采样更多的构象亚状态，因此变得具有生物功能。 这种蛋白质的“动态”转变被认为是由其与水合水的强耦合所触发的，水合水也表现出类似的动态转变。 在这里，我们实验表明，溶菌酶水合物中水动态行为的突然转换 precisely 发生在220 K，并可以描述为一种脆弱到强的动态交叉（FSC）。 在FSC时，水合水的结构从主要的高密度（更流体状态）转变为低密度（更少流体状态），这是由于在高压下存在第二个临界点而产生的。 显示英文摘要

摘要： At low temperatures proteins exist in a glassy state, a state which has no conformational flexibility and shows no biological functions. In a hydrated protein, at and above 220 K, this flexibility is restored and the protein is able to sample more conformational sub-states, thus becomes biologically functional. This 'dynamical' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to low-density (less fluid state) forms derived from existence of the second critical point at an elevated pressure.