This study builds upon our prior researches and seeks to investigate and clarify the influences of various characteristics of hydrogen bonds (H-bonds) and charge transfer (CT) interactions, which were detected within the inhibitor binding pockets (labeled as the QM models I–IV) of MraY–capuramycin, MraY–carbacaprazamycin, MraY–3′-hydroxymureidomycin A, and MraY–muraymycin D2 complexes by QTAIM and NBO analyses from DFT QM/MM MD calculations, on the O chemical shielding (CS) and electric field gradient (EFG) tensors of carboxylate (Oδ), carbonyl (C═O), and hydroxyl (O–H) oxygens in these models. The O CS and EFG tensors of these three types of oxygens in QM models I–IV were calculated at the M06-2X/6-31G** level by including the solvent effects using the polarizable continuum model. From the computed O CS and EFG tensors in these models, it was found that the nuclear shielding, σ, for carboxylate or carbonyl oxygen increases (shielding effect) as the H-bond length decreases and the percentage p-character of / lone pair partner in the CT interaction enhances. In contrast, the σ (O–H) decreases (deshielding effect) with a reduction in the H-bond length as well as with an enhancement in percentage s-character of the lone pair/σ* antibond. By reducing the H-bond length or by increasing p-character of the / lone pair, the Oδ/O═C quadrupole coupling constant smoothly decreases, while the Oδ/O═C asymmetry parameter smoothly increases. Moreover, these calculated parameters are in a good agreement with the experimental values. The information garnered here is valuable particularly for further understanding of empirical correlations between O NMR spectroscopic and H-bonding characteristics in the protein–ligand complexes.

中文翻译：

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不同氢键特性对与核苷类抗生素卡普拉霉素、卡巴卡唑霉素、3′-羟基尿霉素 A 和穆拉霉素 D2 结合的 MraYAA 活性位点内 17O 化学屏蔽和电场梯度张量影响的理论研究


本研究建立在我们先前研究的基础上，旨在研究和阐明氢键（H 键）和电荷转移 （CT） 相互作用的各种特性的影响，这些特性是在 MraY-卡普拉霉素、MraY-卡帕拉霉素、MraY-3′-羟基鼠霉素 A 和 MraY-穆拉霉素 D2 复合物的抑制剂结合口袋（标记为 QM 模型 I-IV）中检测到的，通过 QTAIM 和 DFT QM/MM MD 计算的 NBO 分析， 在这些模型中，羧酸盐 （Oδ）、羰基 （C═O） 和羟基 （O-H） 氧的 O 化学屏蔽 （CS） 和电场梯度 （EFG） 张量上。QM 模型 I-IV 中这三种氧的 O CS 和 EFG 张量是使用可极化连续介质模型包括溶剂效应，在 M06-2X/6-31G** 水平上计算的。从这些模型中计算的 O CS 和 EFG 张量中，发现羧酸盐或羰基氧的核屏蔽 σ 随着 H 键长度的减少而增加（屏蔽效应），并且 CT 相互作用中/孤对伙伴的百分比 p 字符增加。相比之下，σ （O-H） 随着 H 键长度的减少以及孤对/σ* 反键百分比 s 字符的增加而降低（脱屏蔽效应）。通过减小 H 键长度或增加 / 孤对电子的 p 字符，Oδ/O═C 四极子耦合常数平滑减小，而 Oδ/O═C 不对称参数平滑增加。此外，这些计算的参数与实验值吻合较好。这里获得的信息特别有价值，特别是对于进一步理解蛋白质-配体复合物中 O NMR 波谱和 H 键特性之间的经验相关性。