Department of Chemistry , Indiana University , Bloomington Indiana 47401 , United States.
J Phys Chem B. 2019 Jul 11;123(27):5730-5741. doi: 10.1021/acs.jpcb.9b03803. Epub 2019 Jun 26.
Ion mobility spectrometry-mass spectrometry and quantum chemical calculations are used to determine the structures and stabilities of singly protonated XaaProGlyGly peptides: HDPGG, HNPGG, HEPGG, and HQPGG. The IMS distributions are similar, suggesting the peptides adopt closely related structures in the gas phase. Quantum chemical calculations show that all conformers seen in the experimental spectrum correspond to the configuration about the Xaa-Pro peptide bond, significantly different from the behavior seen previously for HGPGG. Density functional theory and quantum theory of atoms in molecules (QTAIM) investigations uncover a silent drama as a minor conformer not observed in the HDPGG spectrum becomes the preferred conformer in HQPGG, with both conformers being coincident in collision cross section. Investigation of the highly coupled hydrogen bond network, replete with CH···O interactions and bifurcated hydrogen bonds, reveals the cause of this effect as well as the absence of conformers from the spectra. A series of generalized observations are provided to aid in enzyme and ligand design using these coupled hydrogen bond motifs.
采用离子淌度质谱-质谱联用和量子化学计算方法确定了单质子化 XaaProGlyGly 肽：HDPGG、HNPGG、HEPGG 和 HQPGG 的结构和稳定性。IMS 分布相似，表明这些肽在气相中采用密切相关的结构。量子化学计算表明，实验谱中观察到的所有构象都对应于 Xaa-Pro 肽键的 构型，与之前观察到的 HGPGG 行为明显不同。密度泛函理论和原子分子量子理论（QTAIM）研究揭示了一个无声的戏剧，即在 HDPGG 光谱中未观察到的次要构象成为 HQPGG 中的首选构象，这两种构象在碰撞截面中是一致的。对高度耦合氢键网络的研究，充满了 CH···O 相互作用和分叉氢键，揭示了这种效应的原因以及这些构象在光谱中缺失的原因。提供了一系列广义观察结果，以帮助使用这些耦合氢键模体进行酶和配体设计。
