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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Experimental and Theoretical Investigation of the Aromatic-Aromatic Interaction in Isolated Capped Dipeptides
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Experimental and Theoretical Investigation of the Aromatic-Aromatic Interaction in Isolated Capped Dipeptides

机译：分离的封端二肽中芳香-芳香相互作用的实验和理论研究

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Among the forces responsible for shaping proteins, interactions between side chains of aromatic residues play an important role as they are involved in the secondary and the tertiary structures of proteins contributing to the formation of hydrophobic domains. The purpose of this paper is to document this interaction in two capped dipeptides modeling a segment of a protein chain having two consecutive Phe residues, Ac-Phe-Phe- NH2 and Ac-Phe-D-Phe-NH2. These two molecules have been investigated in the gas phase by IR/UV double resonance spectroscopy, and the assignment of the observed conformers has been done by comparison with quantum chemistry calculations. Both peptides are found to adopt a -turn type I conformation stabilized by an edge-to-face interaction between the two aromatic rings. Comparison with other dipeptides in the literature demonstrates the impact of this aromatic-aromatic interaction on the shape adopted by the peptide chain, and its role among the other shaping forces (H-bonds, NH-π interactions) is discussed. As an illustration, the H-bond strength is found to be significantly lower in the -turn type I conformer, in which the two rings interact, as compared to the similar conformer where such an interaction does not exist. This structural feature due to the backbone distortion induced by the interaction between the aromatic rings makes this system a good test for evaluating the ability of computational methods to correctly account for the competition between these forces. MP2, SCS-MP2, DFT, and DFT-D methods have been assessed in this respect. Comparison between geometries, energies, and frequency calculations illustrate their respective limitations in describing conformations resulting from a subtle equilibrium between the several interactions at play.
机译：在形成蛋白质的力中，芳族残基侧链之间的相互作用起着重要的作用，因为它们参与蛋白质的二级和三级结构，从而有助于形成疏水域。本文的目的是在两个带帽的二肽中证明这种相互作用，该二肽模拟了具有两个连续的Phe残基Ac-Phe-Phe-NH2和Ac-Phe-D-Phe-NH2的蛋白质链段。这两个分子已经在气相中通过红外/紫外双共振光谱法进行了研究，观察到的构象异构体的分配已通过与量子化学计算进行了比较。发现两种肽都具有通过两个芳环之间的边对面相互作用而稳定的I型转角构象。与文献中其他二肽的比较表明，这种芳香族-芳香族相互作用对肽链所采用的形状有影响，并讨论了其在其他赋形力（H键，NH-π相互作用）中的作用。作为说明，与不存在这种相互作用的相似构象异构体相比，发现在两个环相互作用的I型转角I构象异构体中，H键强度明显更低。由于芳环之间相互作用引起的骨架扭曲，这种结构特征使该系统成为评估计算方法正确考虑这些力之间竞争能力的良好测试。在这方面，已经对MP2，SCS-MP2，DFT和DFT-D方法进行了评估。几何，能量和频率计算之间的比较说明了在描述构象时它们各自的局限性，这些构象是由多个相互作用之间的微妙平衡引起的。

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