中山大学学报自然科学版 ›› 2018, Vol. 57 ›› Issue (5): 88-97.

• 论文 • 上一篇    下一篇

水环境下氢氧根水分子团簇催化赖氨酸旋光异构及羟自由基致损伤的机理

赵晓波1,佟华2,杨晓翠2,王佐成2   

  1. 1. 白城师范学院化学学院,吉林 白城 137000;
    2. 白城师范学院物理学院,吉林 白城 137000  
  • 收稿日期:2018-01-12 出版日期:2018-09-25 发布日期:2018-09-25
  • 通讯作者: 杨晓翠(1965年生),女;研究方向:物理化学;E-mail: yxc0622@163.com 王佐成(1963年生),男;研究方向:单分子反应机理;E-mail: wangzc188@163.com

Mechanism of optical isomerism of lysine catalyzed by hydroxide  ion-water clusters and the damage induced by hydroxy radicals in water environment

ZHAO Xiaobo1, TONG Hua2, YANG Xiaocui2, WANG Zuocheng2   

  1. 1. The College of Chemistry, Baicheng Normal College, Baicheng 137000, China;
    2. The College of Physics, Baicheng Normal College, Baicheng 137000, China
  • Received:2018-01-12 Online:2018-09-25 Published:2018-09-25

摘要:

在MP2/6-311++G(2df, pd)∥B3LYP/6-31+G(d, p)双理论水平,研究了氢氧根水分子团簇催化2种稳定构象的赖氨酸分子旋光异构及羟基自由基致其损伤的机理。反应通道研究发现:赖氨酸旋光异构有2个通道a与b,a是氢氧根水分子团簇与α-氢和氨基氮通过氢键作用形成底物,氢氧根拔α--氢,然后α-碳再拔另一侧2个水分子簇的氢;b是氢氧根水分子团簇与〖WTBX〗α〖WTBZ〗-氢和羰基氧通过氢键作用形成底物,氢氧根拔α-氢,而后α-碳再拔另一侧2个水分子簇的氢。羟自由基拔氢致赖氨酸损伤可在b通道实现。势能面计算表明:水液相环境下,构象1(氨基羧基间为单氢键)和构象2(氨基羧基间为双氢键)旋光异构的优势通道均为b,决速步能垒分别是49.94和60.41 kJ·mol-1,羟自由基在b通道致构象1和2赖氨酸分子的损伤为低或无势垒放热反应。

关键词: 赖氨酸, 密度泛函理论, 过渡态, 微扰理论, 吉布斯自由能, 氢氧根, 羟自由基, 旋光异构, 损伤

Abstract:

The study investigated the mechanism of optical isomerism of two stable conformations of lysine catalyzed by hydroxide ion groupwater clusters and the damage induced by hydroxy radicals in water environment of two conformations of valine molecules by using MP2/6-311++G(2df, pd)∥B3LYP/6-31+G(d, p) dualtheory. The result of reaction channels showed that there are two channels a and b in the optical isomer reaction of lysine. In channel a, the substrate was formed by hydrogen bonds of hydroxide ionwater clusters with α-H and N of amino groups; hydroxide ion abstracted α-H, and then α-C abstracted the hydrogen of two water clusters at the other side. And in channel b, the substrate was formed by hydrogen bonds of hydroxide ion-water clusters with α-H and O of carbonyl groups; hydroxide ion abstracted α-H, and then α-C abstracted the hydrogen of two water clusters at the other side. Lysine can be damaged by hydroxy radicals abstracting hydrogen in channel b. The potential energy surface calculation showed that the dominant optical isomerism reaction channels are channel b both in conformation 1(monohydrogen bond between amino- and carboxyl-group) and 2(dual-hydrogen bond between amino- and carboxyl-group), and the energy barriers of rate-limiting steps are 49.94, 60.41 kJ/mol, relatively. So the damage by hydroxy radical of conformation 1 and conformation 2 in channel b was low or non-barrier exothermic reactions.

Key words: lysine, density functional theory, transition state, perturbation theory, Gibbs free energy, hydroxide ion, hydroxy radical, optical isomers, damage

中图分类号: