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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Thermochemistry of alkali metal cation interactions with histidine: Influence of the side chain
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Thermochemistry of alkali metal cation interactions with histidine: Influence of the side chain

机译：碱金属阳离子与组氨酸相互作用的热化学：侧链的影响

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摘要

The interactions of alkali metal cations (M+ = Na+, K+, Rb+, Cs+) with the amino acid histidine (His) are examined in detail. Experimentally, bond energies are determined using threshold collision-induced dissociation of the M+(His) complexes with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy dependent cross sections provide 0 K bond energies of 2.31 ± 0.11, 1.70 ± 0.08, 1.42 ± 0.06, and 1.22 ± 0.06 eV for complexes of His with Na+, K+, Rb+, and Cs+, respectively. All bond dissociation energy (BDE) determinations include consideration of unimolecular decay rates, internal energy of reactant ions, and multiple ion-neutral collisions. These experimental results are compared to values obtained from quantum chemical calculations conducted previously at the MP2(full)/6-311+G(2d,2p), B3LYP/6-311+G(2d,2p), and B3P86/6-311+G(2d,2p) levels with geometries and zero point energies calculated at the B3LYP/6-311+G(d,p) level where Rb and Cs use the Hay-Wadt effective core potential and basis set augmented with additional polarization functions (HW*). Additional calculations using the def2-TZVPPD basis set with B3LYP geometries were conducted here at all three levels of theory. Either basis set yields similar results for Na+(His) and K+(His), which are in reasonable agreement with the experimental BDEs. For Rb+(His) and Cs +(His), the HW* basis set and ECP underestimate the experimental BDEs, whereas the def2-TZVPPD basis set yields results in good agreement. The effect of the imidazole side chain on the BDEs is examined by comparing the present results with previous thermochemistry for other amino acids. Both polarizability and the local dipole moment of the side chain are influential in the energetics.
机译：详细检查了碱金属阳离子（M + = Na +，K +，Rb +，Cs +）与氨基酸组氨酸（His）的相互作用。实验上，在导向离子束串联质谱仪中，使用阈值碰撞诱导的M +（His）配合物与氙的离解来确定键能。对于His与Na +，K +，Rb +和Cs +的络合物，能量依赖性截面的分析分别提供了2.31±0.11、1.70±0.08、1.42±0.06和1.22±0.06 eV的0 K键能。所有键离解能（BDE）的确定都包括单分子衰减率，反应物离子的内能以及多次离子-中性碰撞的考虑。将这些实验结果与先前在MP2（full）/ 6-311 + G（2d，2p），B3LYP / 6-311 + G（2d，2p）和B3P86 / 6-进行的量子化学计算所得的值进行比较311 + G（2d，2p）能级，具有在B3LYP / 6-311 + G（d，p）能级下计算出的几何形状和零点能量，其中Rb和Cs使用Hay-Wadt有效磁芯电势，并且基集增加了附加极化功能（HW *）。在这里，在所有三个理论水平上都使用了带有B3LYP几何形状的def2-TZVPPD基础集进行了其他计算。任一基集对Na +（His）和K +（His）都产生相似的结果，与实验的BDE合理地吻合。对于Rb +（His）和Cs +（His），HW *基础集和ECP低估了实验性BDE，而def2-TZVPPD基础集产生的结果吻合良好。通过将本结果与先前对其他氨基酸的热化学比较，可以检查咪唑侧链对BDE的影响。极化率和侧链的局部偶极矩都对能量学有影响。

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