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首页> 外文期刊>Chemistry: A European journal >Competition between pi and Non-pi Cation-Binding Sites in Aromatic Amino Acids:A Theoretical Study of Alkali Metal Cation(Li~+,Na~+,K~+)-Phenylalanine Complexes
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Competition between pi and Non-pi Cation-Binding Sites in Aromatic Amino Acids:A Theoretical Study of Alkali Metal Cation(Li~+,Na~+,K~+)-Phenylalanine Complexes

机译：芳香氨基酸中pi和非pi阳离子结合位点之间的竞争：碱金属阳离子（Li〜+，Na〜+，K〜+）-苯丙氨酸配合物的理论研究

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摘要

To understand the cation-pi interaction in aromatic amino acids and peptides,the binding of M~+(where M~+=Li~+,Na~+,and K~+)to phenylalanine(Phe)is studied at the best level of density functional theory reported so far.The different modes of M~+ binding show the same order of binding affinity(Li~+>Na~+>K~+),in the approximate ratio of 2.2:1.5:1.0.The most stable binding mode is one in which the M~+ is stabilized by a triden-tate interaction between the cation and the carbonyl oxygen(O=C),amino nitrogen(-NH_2),and aromatic pi ring;the absolute Li~+,Na~+,and K~+ affinities are estimated theoretically to be 275,201,and 141 kJ mol~-1,respectively.Factors affecting the relative stabilities of various M~+-Phe binding modes and conformers have been identified,with ion-dipole interaction playing an important role.We found that the trend of pi and non-pi cation bonding distances(Na~+-pi>Na~+-N>Na~+-O and K~+-pi>K~+-N>K~+-O)in our theoretical Na~+/K~+-Phe structures are in agreement with the reported X-ray crystal structures of model synthetic receptors(sodium and potassium bound lariat ether complexes),even though the average alkali metal cation-pi distance found in the crystal structures is longer.This difference between the solid and the gas-phase structures can be reconciled by taking the higher coordination number of the cations in the lariat ether complexes into account.
机译：为了了解芳香族氨基酸和肽中的阳离子-pi相互作用，以最佳水平研究了M〜+（其中M〜+ = Li〜+，Na〜+和K〜+）与苯丙氨酸（Phe）的结合。迄今为止，有关密度泛函理论的报道。不同的M〜+结合方式表现出相同的结合亲和力（Li〜+> Na〜+> K〜+），比例约为2.2：1.5：1.0。稳定的结合方式是通过阳离子与羰基氧（O = C），氨基氮（-NH_2）和芳香族pi环之间的Triden-tate相互作用来稳定M〜+的方式;绝对Li〜+理论上估计Na〜+和K〜+亲和力分别为275,201和141 kJ mol〜-1。已经确定了影响各种M〜+ -Phe结合模式和构象异构体相对稳定性的因素，采用离子偶极子我们发现pi和非pi阳离子键合距离的趋势（Na〜+ -pi> Na〜+ -N> Na〜+ -O和K〜+ -pi> K〜+ -N > K〜+ -O）在我们的理论Na〜+ / K〜+ -Phe结构中与即使在晶体结构中发现的平均碱金属阳离子-π距离更长，模型合成受体（钠和钾结合的套索状醚络合物）的有序X射线晶体结构也可以。固相和气相结构之间的这种差异可以通过考虑套索醚络合物中阳离子的较高配位数来进行调节。

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