磷酸盐骨架振动激发下RNA熔融过程中水化模式的变化
Change of Hydration Patterns upon RNA Melting Probed by Excitations of Phosphate Backbone Vibrations
摘要：
水化壳层对RNA的结构和功能性质具有决定性的影响。RNA结构在融化和生化过程中的变化伴随着水合模式的变化，这是一个几乎没有特征的过程。为了在分子水平上辨别RNA双螺旋的骨架磷酸基团周围的水合几何形状，我们将磷酸振动的二维红外光谱与理论模拟相结合。RNA A-螺旋有三种不同的共存水化基序，一种有序的链状排列的水分子与相邻的磷酸基团之间的联系，多达六个水分子的单独的局部水化壳，和水合磷酸/反式接触对。RNA在融化时的无序与从主要有序的水结构到磷酸盐单元周围的局部水化壳的过渡有关。结构波动主要由librational水运动发生在300 fs的时间尺度上，没有水合图案之间的交换。
英文摘要：
The water hydration shell has decisive impact on the structural and functional properties of RNA. Changes of RNA structure upon melting and in biochemical processes are accompanied by a change of hydration patterns, a process which is barely characterized. To discern hydration geometries around the backbone phosphate groups of an RNA double helix at the molecular level, we combine two-dimensional infrared spectroscopy of phosphate vibrations with theoretical simulations. There are three distinct coexisting hydration motifs of the RNA A-helix, an ordered chain-like arrangement of water molecules with links between neighboring phosphate groups, separate local hydration shells of up to six water molecules, and hydrated phosphate/counterion contact pairs. RNA disordering upon melting is connected with a transition from predominant ordered water structures to local hydration shells around phosphate units. Structural fluctuations are dominated by librational water motions occurring on a 300 fs time scale, without exchange between hydration motifs.
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