Infrared multiphoton dissociation spectroscopy of cationized serine: effects of alkali-metal cation size on gas-phase conformation.
Infrared multiphoton dissociation spectroscopy of cationized serine: effects of alkali-metal cation size on gas-phase conformation.
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DOI：
10.1021/jp710885a
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发表时间：
2008
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影响因子：
--
通讯作者：
P. Armentrout;M. Rodgers;J. Oomens;J. Steill
中科院分区：
文献类型：
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作者：
P. Armentrout;M. Rodgers;J. Oomens;J. Steill
利用自由电子激光产生的光，结合从头计算，用红外多光子解离(IRMPD)光谱研究了丝氨酸(Ser)碱金属阳离子络合物的气相结构。Li+(Ser)和Na+(Ser)的光谱相似且相对简单，而Cs+(Ser)包含独特的新红外光谱，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)水平上计算的光谱进行比较，以确定实验研究中存在的结构。在这些实验和计算的基础上，配合物对较小的碱金属阳离子Li+和Na+的唯一构象是电荷溶剂化结构，包括与氨基酸主链的胺和羰基以及侧链的羟基M1[N，CO，OH]的三齿配位。对于硫化的络合物，可以清楚地看到与两性离子结构ZW[CO2-]相对应的带。K+(Ser)和Rb+(Ser)显示了两性离子的电荷溶剂化类似物M3[COOH]，其中金属阳离子与羧酸基结合。计算表明，M3[COOH]结构的相对稳定性强烈依赖于金属阳离子的大小，这与实验观察到的构象范围是一致的。
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.