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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Investigation of intermolecular hydrogen bond interactions in crystalline l-Cysteine by DFT calculations of the oxygen-17, nitrogen-14, and hydrogen-2 EFG tensors and AIM analysis.
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Investigation of intermolecular hydrogen bond interactions in crystalline l-Cysteine by DFT calculations of the oxygen-17, nitrogen-14, and hydrogen-2 EFG tensors and AIM analysis.

机译：通过对氧17，氮14和氢2 EFG张量的DFT计算和AIM分析，研究结晶I-半胱氨酸中的分子间氢键相互作用。

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摘要

A systematic computational study is carried out to investigate hydrogen bond (HB) interactions in the real crystalline structures of l-Cysteine at 30 and 298 K by density functional theory (DFT) calculations of electric field gradient (EFG) tensors at the sites of O-17, N-14, and H-2 nuclei. One-molecule (monomer) and nine-molecule (cluster) models of l-Cysteine are created by available crystal coordinates at both temperatures and the EFG tensors are calculated for both models to indicate the effect of HB interactions on the tensors. The calculated EFG tensors at the level of B3LYP and B3PW91 DFT methods and 6-311++G** and cc-pVTZ basis sets are converted to those experimentally measurable nuclear quadrupole resonance (NQR) parameters i.e. quadrupole coupling constants (qcc) and asymmetry parameters (eta(Q)). The evaluated NQR parameters reveal that the EFG tensors of (17)O, (14)N, and (2)H are influenced and show particular trends from monomer to the target molecule in the cluster due to the contribution of target molecule to classic N-H...O, and non-classic S-H...O and S-H...S types of HB interactions. On the other hand, atoms in molecules (AIM) analyses confirm the presence of HB interactions and rationalize the observed EFG trends. The results indicate different contribution of various nuclei to HB interactions in the cluster where O2 and N1 have major contributions. The EFG tensors as well as AIM analysis at the H6 site show that the N1-H6...O2 HB undergoes a significant change from 30 to 298 K where changes in other N-H...O interactions are almost negligible. There is a good agreement between the calculated (14)N NQR parameters and reported experimental data.
机译：通过密度泛函理论（DFT）计算O位点处的电场梯度（EFG）张量，进行了系统的计算研究，以研究30和298 K下半胱氨酸的真实晶体结构中的氢键（HB）相互作用。 -17，N-14和H-2核。半胱氨酸的单分子（单体）和九分子（簇）模型是通过在两个温度下的可用晶体坐标创建的，并针对这两个模型计算了EFG张量，以表明HB相互作用对张量的影响。将在B3LYP和B3PW91 DFT方法以及6-311 ++ G **和cc-pVTZ基组级别上计算的EFG张量转换为实验上可测量的核四极共振（NQR）参数，即四极耦合常数（qcc）和不对称性参数（eta（Q））。评估的NQR参数揭示（17）O，（14）N和（2）H的EFG张量受到影响，并且由于目标分子对经典NH的贡献，因此显示了从单体到目标分子的特定趋势... O和非经典的SH ... O和SH ... S类型的HB相互作用。另一方面，分子中的原子（AIM）分析证实了HB相互作用的存在，并使观察到的EFG趋势合理化。结果表明，在O2和N1具有主要贡献的簇中，各个核对HB相互作用的贡献不同。 EFG张量以及H6站点的AIM分析表明，N1-H6 ... O2 HB从30 K到298 K发生了显着变化，而其他N-H ... O相互作用的变化几乎可以忽略不计。在计算的（14）N NQR参数与报告的实验数据之间有很好的一致性。

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