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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Cation [M = H~+,Li~+,Na~+,K~+,Ca~(2+),Mg~(2+),NH_4~+,and NMe_4~+] Interactions with the Aromatic Motifs of Naturally Occurring Amino Acids:A Theoretical Study
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Cation [M = H~+,Li~+,Na~+,K~+,Ca~(2+),Mg~(2+),NH_4~+,and NMe_4~+] Interactions with the Aromatic Motifs of Naturally Occurring Amino Acids:A Theoretical Study

机译：阳离子[M = H〜+，Li〜+，Na〜+，K〜+，Ca〜（2 +），Mg〜（2 +），NH_4〜+和NMe_4〜+]与天然芳香基团的相互作用氨基酸的发生：理论研究

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Ab initio(HF,MP2,and CCSD(T))and DFT(B3LYP)calculations were done in modeling the cation(H~+,Li~+,Na~+,K~+,Ca~(2+),Mg~(2+),NH_4~+,and NMe_4~+)interaction with aromatic side chain motifs of four amino acids(viz.,phenylalanine,tyrosine,tryptophan and histidine).As the metal ion approaches the pi-framework of the model systems,they form strongly bound cation-pi complexes,where the metal ion is symmetrically disposed with respect to all ring atoms.In contrast,proton prefers to bind covalently to one of the ring carbons.The NH_4~+ and NMe_4~+ ions have shown N-H...pi interaction and C-H...pi interaction with the aromatic motifs.The interaction energies of N-H...pi and C-H...pi complexes are higher than hydrogen bonding interactions;thus,the orientation of aromatic side chains in protein is effected in the presence of ammonium ions.However,the regioselectivity of metal ion complexation is controlled by the affinity of the site of attack.In the imidazole unit of histidine the ring nitrogen has much higher metal ion(as well as proton)affinity as compared to the jr-face,facilitating the in-plane complexation of the metal ions.The interaction energies increase in the order of 1-M < 2-M < 3-M < 4-M < 5-M for all the metal ion considered.Similarly,the complexation energies with the model systems decrease in the following order:Mg~(2+)> Ca~(2+)> Li~+ > Na~+ > K~+ approx= NH_4~+ > NMe_4~+.The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.
机译：在模拟阳离子H〜+，Li〜+，Na〜+，K〜+，Ca〜（2 +），Mg时进行了从头算（HF，MP2和CCSD（T））和DFT（B3LYP）计算〜（2 +），NH_4〜+和NMe_4〜+与四个氨基酸（即苯丙氨酸，酪氨酸，色氨酸和组氨酸）的芳香族侧链基序相互作用。当金属离子接近模型的pi框架时质子体系形成牢固结合的阳离子-π络合物，其中金属离子相对于所有环原子对称排列。相反，质子更倾向于与其中一个环碳共价结合。NH_4〜+和NMe_4〜+离子具有NH ... pi和CH ... pi配合物的相互作用能高于氢键相互作用;因此，芳香族侧链的取向蛋白质的存在是在铵离子存在的情况下实现的。但是，金属离子络合的区域选择性是由进攻位点的亲和力控制的。在组氨酸的咪唑单元中，环氮原子与jr面相比，具有更高的金属离子（以及质子）亲和力，有利于金属离子的面内络合。相互作用能按1-M <2-M <3-M的顺序增加<4-M <5-M对于所有考虑的金属离子。同样，模型系统的络合能按以下顺序降低：Mg〜（2 +）> Ca〜（2 +）> Li〜+> Na〜 +> K〜+大约= NH_4〜+> NMe_4〜+。配位时键长的变化和电荷转移的程度与计算出的相互作用能密切相关。

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