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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Echoes Of A Salty Exchange
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Echoes Of A Salty Exchange

机译：咸交换的回声

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摘要

In aqueous solution, the water molecules in the layer surrounding an ion rearrange through exchange reactions, in which the attractive hydrogen (H) bond between a water molecule and this ion switches to a new H bond between that water and another water molecule. This exchange and its time scale are critical in a wide range of chemical and biochemical processes. For aqueous reactions such as substitution processes (1) or acid-base mechanisms (2) or for reactions at aqueous interfaces (3), it can be the rate-determining step. It is also key for transport of ionic solutes in water; ionic mobility, for example, depends not only on the ion size but also on the hydration shell lability, which determines whether the ion travels alone or accompanied by its hydration layer (4). Further, this H-bond exchange plays a central role in several physiological contexts. One example is nerve signal transmission, which involves numerous ion transports across cell membranes, where the ions' hydration shells reorganize in the initial and final stages of the membrane-crossing mechanism (5). However, a direct experimental measurement of this ultrafast (picosecond) H-bond exchange has been lacking. In a recent issue of PNAS, Moilanen et al. (6) reported a breakthrough in capturing this exchange reaction with ultrafast infrared (IR) laser pulses.
机译：在水溶液中，围绕离子的层中的水分子通过交换反应重新排列，在交换反应中，一个水分子与该离子之间的有吸引力的氢键（H）切换为该水与另一个水分子之间的新H键。这种交换及其时间尺度在广泛的化学和生化过程中至关重要。对于诸如取代过程（1）或酸碱机理（2）之类的水性反应，或对于水性界面处的反应（3），它可以是决定速率的步骤。这也是水中离子溶质运输的关键。例如，离子迁移率不仅取决于离子的大小，还取决于水合壳的不稳定性，后者决定了离子是单独传播还是伴随其水化层（4）传播。此外，这种氢键交换在几种生理环境中起着核心作用。一个例子是神经信号传递，它涉及许多跨细胞膜的离子传输，其中离子的水合壳在跨膜机制的初始阶段和最后阶段进行重组（5）。然而，这种超快速（皮秒）氢键交换的直接实验测量一直缺乏。在最近一期的PNAS中，Moilanen等人。 （6）报道了在利用超快红外（IR）激光脉冲捕获这种交换反应方面的突破。

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