摘要
在SMD/MP2/6-311++G(3df,2pd)//SMD/WB97X-D/6-311++G(d,p)双理论水平,对水液相环境下氢氧根(OH-)催化苯丙氨酸(phenylalanine,Phe)分子手性对映体转变及质子的作用进行研究。研究发现:水液相环境下OH-催化Phe手性转变有OH-抽α-氢和氢氧根水分子簇(OH-·H2O)抽α-氢两种情况。氢氧根水分子簇抽氢时有两个通道a和b,a通道是氢氧根水分子簇与Phe的α-氢和氨基氮氢键作用形成的底物异构;b通道是氢氧根水分子簇与Phe的α-氢和羰基氧氢键作用形成的底物异构。a通道又分为两个路径a1和a2,a1是羧基异构后氢氧根水分子簇抽氢;a2是氢氧根水分子簇直接抽氢。当OH-抽氢时,Phe的手性转变只能通过氢氧根水分子簇抽氢的a通道上两个路径a1和a2实现。势能面计算结果显示:氢氧根(水分子簇)抽α-氢结合Phe碳负离子抽取水分子(簇)中的质子,很容易使Phe实现手性对映体转变,只是OH-抽α-氢时决速步能垒更低,路径a2更具优势。质子攻击Phe碳负离子是无势垒放热过程。结果表明,水液相环境下OH-可以催化Phe的手性对映体转变,质子的存在会进一步加速此反应。
The chiral enantiomer transition of phenylalanin(Phe) catalyzed by hydroxyl and the proton effects on this transition in water liquid environment was studied by means of SMD/MP2/6-311++G(3 df, 2 pd)//SMD/WB97 X-D/6-311++G(d, p)methods. The study reveals that the chiral enantiomer transition of Phe catalyzed by hydroxyl can be divided into two cases, which are α-H abstraction of hydroxyl ion(OH-) and α-H abstraction of hydroxyl water clusters(OH-·H2O). For the second case, two channels(a and b) are discovered, which are substrate isomerism caused by a hydrogen bond formed between the hydroxyl water clusters and Phe’s α-H and amino nitrogen or carbonyl oxygen, respectively. As for Channel a, it can also be divided into two paths(a1 and a2), which are the α-H abstraction of hydroxyl water clusters after carboxy isomerism or the direct α-H abstraction of hydroxyl water clusters, respectively. However, when α-H abstraction of hydroxyl, the chiral enantiomer transition of Phe can only be realized in the two paths a1 and a2 of Channel a with α-H abstraction of hydroxyl water clusters. The potential energy surface shows that it is easy for Phe to realize chiral enantiomer transition by α-H abstraction of hydroxyl(water clusters) and protons abstraction of carbon anion of Phe from water(clusters). However, the energy barrier of the rate-determining step is lower when α-H abstraction of hydroxyl, and the Path a2 is more advantageous. The proton attack on carbon anion of Phe is a barrierfree exothermic process. The results show that chiral enantiomer transition of Phe can be catalyzed by hydroxyl ions in water liquid environment, and the presence of protons will further accelerate the reaction.
作者
王野
庄严
姜春旭
潘宇
王佐成
WANG Ye;ZHUANG Yan;JIANG Chunxu;PAN Yu;WANG Zuocheng(College of Physics,Baicheng Normal University,Baicheng 137000,Jilin,China;Computer Science College,Baicheng Normal University,Baicheng 137000,Jilin,China)
出处
《武汉大学学报（理学版）》
CAS
CSCD
北大核心
2020年第1期32-42,共11页
Journal of Wuhan University:Natural Science Edition
基金
吉林省科技发展计划自然科学基金(20130101308JC)
吉林省教育厅“十三五”科学技术研究项目(JJKH20190618KJ).
关键词
苯丙氨酸
手性对映体
氢氧根
质子
能垒
phenylalanine
chiral enantiomer
hydroxyl
proton
energy barrier
