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首页> 外文期刊>Journal of theoretical & computational chemistry >ESTIMATION ON THE INTRAMOLECULAR 8- AND 12-MEMBERED RING N-H...O=C HYDROGEN BONDING ENERGIES IN ,_-PEPTIDES
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ESTIMATION ON THE INTRAMOLECULAR 8- AND 12-MEMBERED RING N-H...O=C HYDROGEN BONDING ENERGIES IN ,_-PEPTIDES

机译：，_-肽中的分子内8和12元环N-H ... O = C氢键能的估计

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摘要

Computation of accurate hydrogen bonding energies in peptides is of great importance in understanding the conformational stabilities of peptides. In this paper, the intramolecu_lar 8- and 12-membered ring N_H...O=C hydrogen bonding energies in β-peptide struc_tures were evaluated. The optimal structures of the β-peptide conformers were obtained using MP2/6-31G(d) method. The MP2/6-311++G(d,p) calculations were then car_ried out to evaluate the single-point energies. The results show that the intramolecular 8-membered ring N-H...O=C hydrogen bonding energies in the five β-dipeptide struc_tures ,_-di, β-di-R1, _-di-R2, β-di-R3, and β-di-R4 are -5.50, -5.40, -7.28, -4.94, and _6.84 kcal/mol with BSSE correction, respectively; the intramolecular 12-membered ring N_H...O=C hydrogen bonding energies in the nine β-tripeptide structures β-tri, _-tri_Rl, β-tri-R2, β-tri-R3, β-tri-R4, β-tri-R1', β-tri-R2', β-tri-R3' and β-tri-R4' are -10.23, _10.32, -9.53, -10.30, -10.32, -10.55, -10.09, -10.51, and -9.60 kcal/mol with BSSE correction, respectively. Our calculation results further indicate that for the intramolecu_lar 8-membered ring hydrogen bondings, the structures where the orientation of the side chain methyl group is "a_a" have stronger intramolecular hydrogen bondings than those where the orientation of the side chain methyl group is "e_e" , while for the intramolecu_lar 12-membered ring hydrogen bondings, the structures where the orientation of the side chain methyl group is "e_e" have stronger intramolecular hydrogen bondings than those where the orientation of the side chain methyl group is "a_a". The method is also applied to estimate the individual intermolecular hydrogen bonding energies in the dimers of amino-acetaldehyde, 2-amino-acetamide, 2-oxo-acetamide, and oxalamide, each dimer having two identical intermolecular hydrogen bonds. According to our method, the indi_vidual intermolecular hydrogen bonding energies in the four dimers are calculated to be _1.71, _1.50, _4.67, and _3.22 kcal/mol at the MP2/6-311++G(d,p) level, which are in good agreement with the values of _1.84, _1.72, _4.93, and _3.26 kcal/mol predicted by the supermolecular method.
机译：肽中准确的氢键能的计算对于理解肽的构象稳定性非常重要。本文评估了β-肽结构中的分子内8和12元环N_H ... O = C氢键能。使用MP2 / 6-31G（d）方法获得了β肽构象体的最佳结构。然后进行MP2 / 6-311 ++ G（d，p）计算以评估单点能量。结果表明，在五个β-二肽结构，_- di，β-di-R1，_-di-R2，β-di-R3，...中，分子内8元环NH ... O = C氢键能通过BSSE校正，β-di-R4和-di-R4分别为-5.50，-5.40，-7.28，-4.94和_6.84 kcal / mol;九个β-三肽结构中的分子内12元环N_H ... O = C氢键能β-tri，_-tri_Rl，β-tri-R2，β-tri-R3，β-tri-R4，β -tri-R1'，β-tri-R2'，β-tri-R3'和β-tri-R4'为-10.23，_10.32，-9.53，-10.30，-10.32，-10.55，-10.09，- BSSE校正分别为10.51和-9.60 kcal / mol。我们的计算结果进一步表明，对于分子内的8元环氢键，侧链甲基的取向为“ a_a”的结构比侧链甲基的取向为“ e_e”的结构具有更强的分子内氢键对于分子内12元环氢键而言，侧链甲基的取向为“ e_e”的结构比侧链甲基的取向为“ a_a”的结构具有更强的分子内氢键。该方法还适用于估计氨基乙醛，2-氨基乙酰胺，2-氧代乙酰胺和草酰胺中的各个分子间氢键能，每个二聚体具有两个相同的分子间氢键。根据我们的方法，在MP2 / 6-311 ++ G（d处）计算出四个二聚体中的单个分子间氢键能分别为_1.71，_1.50，_4.67和_3.22 kcal / mol。 ，p）水平，与通过超分子方法预测的_1.84，_1.72，_4.93和_3.26 kcal / mol值非常吻合。

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