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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Infrared multiphoton dissociation spectroscopy of cationized serine: Effects of alkali-metal cation size on gas-phase conformation
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Infrared multiphoton dissociation spectroscopy of cationized serine: Effects of alkali-metal cation size on gas-phase conformation

机译：阳离子化丝氨酸的红外多光子离解光谱：碱金属阳离子尺寸对气相构象的影响

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摘要

The gas-phase structures of alkali-metal cation complexes of serine (Ser) are examined using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. Spectra of Li+(Ser) and Na+(Ser) are similar and relatively simple, whereas Cs+(Ser) includes distinctive new IR bands, and K+(Ser) and Rb+(Ser) exhibit intermediate behavior. Measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level to identify the structures present in the experimental studies. On the basis of these experiments and calculations, the only conformations accessed for the complexes to the smaller alkali-metal cations, Li+ and Na+, are charge-solvated structures involving tridentate coordination to the amine and carbonyl groups of the amino acid backbone and to the hydroxyl group of the side chain, M1[N,CO,OH]. For the cesiated complex, a band corresponding to a zwitterionic structure, ZW[CO2-], is clearly visible. K+(Ser) and Rb+(Ser) exhibit evidence of the charge-solvated analogue of the zwitterions, M3[COOH], in which the metal cation binds to the carboxylic acid group. Calculations indicate that the relative stability of the M3[COOH] structure is very strongly dependent on the size of the metal cation, consistent with the range of conformations observed experimentally.
机译：丝氨酸（Ser）的碱金属阳离子配合物的气相结构使用红外多光子离解（IRMPD）光谱，利用自由电子激光产生的光结合从头算来进行检查。 Li +（Ser）和Na +（Ser）的光谱相似且相对简单，而Cs +（Ser）包含独特的新IR波段，而K +（Ser）和Rb +（Ser）表现出中间行为。将测得的IRMPD光谱与在B3LYP / 6-311 + G（d，p）水平计算的光谱进行比较，以鉴定实验研究中存在的结构。在这些实验和计算的基础上，对于较小的碱金属阳离子Li +和Na +的配合物，唯一获得的构象是电荷溶剂化的结构，涉及与氨基酸骨架的胺和羰基以及与氨基酸骨架的三齿配位。侧链的羟基，M1 [N，CO，OH]。对于该铯复合物，与两性离子结构ZW [CO2-]相对应的谱带清晰可见。 K +（Ser）和Rb +（Ser）显示出两性离子的电荷溶剂化类似物M3 [COOH]的证据，其中金属阳离子与羧酸基团结合。计算表明，M3 [COOH]结构的相对稳定性非常强烈地取决于金属阳离子的大小，这与实验观察到的构象范围一致。

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