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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Probing Solvation-Induced Structural Changes in Conformationally Flexible Peptides: IR Spectroscopy of Gly(3)H(+)center dot(H2O)
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Probing Solvation-Induced Structural Changes in Conformationally Flexible Peptides: IR Spectroscopy of Gly(3)H(+)center dot(H2O)

机译：探测溶剂化诱导的构型柔性肽的结构变化：GLY（3）H（+）中心点（H2O）的IR光谱

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摘要

IR predissociation spectroscopy of the Gly(3)H(+)(H2O) complex formed inside of a cryogenic ion trap reveals how the flexible model peptide structurally responds to solvation by a single water molecule. The resulting one-laser spectrum is quite congested, and the spectral analyses were assisted by both H2O/D2O substitution and IR-IR double resonance spectroscopy, revealing the presence of two contributing isomers and extensive anharmonic features. Comparisons to structures found via a systematic computational search identified the geometries of these two isomers. The major isomer, with all trans amide bonds and protonation on the terminal amine, represents similar to 90% of the overall population. It noticeably differs from the unsolvated Gly(3)H(+), which exists in two isomeric forms: one with a cis amide bond and the other with protonation on an amide C=O These results indicate that interactions with just one water molecule can induce significant structural changes, i.e., cis-trans amide bond rotation and proton migration, even as the clustering occurs within an 80 K cryogenic ion trap. Calculations of the isomerization pathways further reveal that the binding energy of the water molecule provides sufficient internal energy to overcome the barriers for the observed structural changes, and the minor solvation isomer results from a small fraction of the ions being kinetically trapped along one of the pathways.
机译：IR预离解的是Gly（3）H（+）（H 2 O）的低温离子阱的复杂内形成的光谱揭示了如何将柔性模型肽结构上由一个单一的水分子响应溶剂化。得到的一次激光光谱是非常拥塞的，并且通过H2O / D2O取代和IR-IR双共振光谱辅助光谱分析，揭示了两种有助于异构体和广泛的无谐波特征。通过系统计算搜索发现的结构的比较识别了这两个异构体的几何形状。主要的异构体，所有反式酰胺键和末端胺上的质子化相似，占总人群的90％。从未转化的GLY（3）H（+）有明显不同，其以两种异构形式存在：一种用CIS酰胺键，另一个在酰胺C = O上的质子化= o这些结果表明与只有一种水分子的相互作用诱导显着的结构变化，即CIS-Trans酰胺键旋转和质子迁移，即使在80k低温离子阱中发生聚类。异构化途径的计算进一步揭示了水分子的结合能提供足够的内部能量以克服观察到的结构变化的屏障，并且少量溶剂化异构体由沿着其中一个途径捕获的离子的一小部分来产生少量的溶剂化异构体。

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