Rationalizing the diversity of amide–amide H-bonding in peptides using the natural bond orbital method†,Physical Chemistry Chemical Physics

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Rationalizing the diversity of amide–amide H-bonding in peptides using the natural bond orbital method†
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2019-10-07 , DOI: 10.1039/c9cp03825f
Valérie Brenner _{1,

2,

3,

4,

5} , Eric Gloaguen _{1,

2,

3,

4,

5} , Michel Mons _{1,

2,

3,

4,

5}

Affiliation

Natural bond orbital (NBO) analysis of electron delocalization in a series of capped isolated peptides is used to diagnose amide–amide H-bonding and backbone-induced hyperconjugative interactions, and to rationalize their spectral effects. The sum of the stabilization energies corresponding to the interactions between NBOs that are involved in the H-bonding is demonstrated as an insightful indicator for the H-bond strength. It is then used to decouple the effect of the H-bond distance from that, intrinsic, of the donor/acceptor relative orientation, i.e., the geometrical approach. The diversity of the approaches given by the series of peptides studied enables us to illustrate the crucial importance of the approach when the acceptor is a carbonyl group, and emphasizes that efficient approaches can be achieved despite not matching the usual picture of a proton donor directly facing a lone pair of the proton acceptor, i.e., that encountered in intermolecular H-bonds. The study also illustrates the role of backbone flexibility, partly controlled by backbone–amide hyperconjugative interactions, in influencing the equilibrium structures, in particular by frustrating or enhancing the HB for a given geometrical approach. Finally, the presently used NBO-based HB strength indicator enables a fair prediction of the frequency of the proton donor amide NH stretching mode, but this simple picture is blurred by ubiquitous hyperconjugative effects between the backbone and amide groups, whose magnitude can be comparable to that of the weakest H-bonds.

中文翻译：

使用自然键轨道方法合理化肽中酰胺-酰胺H键的多样性†

一系列带帽分离肽中电子离域的自然键轨道（NBO）分析用于诊断酰胺-酰胺H键和主链诱导的超共轭相互作用，并使它们的光谱效应合理化。对应于氢键作用的NBO之间相互作用的稳定能的总和被证明是氢键强度的有见地的指标。然后，它被用来从是，本征的，供体/受体的相对取向，解耦氢键距离的效果即，几何方法。研究的一系列肽提供的方法的多样性使我们能够说明当受体为羰基时该方法的至关重要性，并强调尽管与直接面对质子供体的通常情况不符，但仍可实现有效的方法一对孤对的质子受体，即，在分子间氢键中遇到。这项研究还说明了骨架柔性的作用，该骨架部分受骨架-酰胺超共轭相互作用的控制，在影响平衡结构方面，特别是通过挫败或增强给定几何方法的HB的作用。最后，目前使用的基于NBO的HB强度指示器可以合理预测质子供体酰胺NH拉伸模式的频率，但是由于骨架和酰胺基团之间普遍存在的超共轭作用，这种简单的画面变得模糊了，其幅值可与最弱的H债券。

更新日期：2019-11-01

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