质子从非活性气相尼古丁结构转移到生物活性水相结构
Marie-Pierre Gaigeot1, Alvaro Cimas, Mahamadou Seydou
1Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, LAMBE UMR8587 CNRS, Université d'Evry val d'Essonne, boulevard F. Mitterrand, Bat. Maupertuis, 91025 Evry Cedex, France. mgaigeot@univ-evry.fr
Journal of the American Chemical Society
|December 15, 2010
概括
水分子促进尼古丁的产生.
科学领域:
- 计算化学计算化学
- 物理化学 物理化学
- 分子动力学分子动力学
背景情况:
- 尼古丁存在于气相中的无活性形式和水溶液中的生物活性形式.
- 这些形式之间的结构转变对其生物活动至关重要.
- 水在这种转变中的作用在分子水平上还没有完全理解.
研究的目的:
- 研究水在尼古丁从无活性形式转化为生物活性形式的结构变化中的作用.
- 在水溶液中确定质子转移分化自由能量障碍.
- 阐明由水分子介导的质子转移机制.
主要方法:
- 尼古丁H ((+) - ((H ((2) O) ((n) 复合物的几何优化.
- 分子动力学 (MD) 模拟,包括 Car-Parrinello MD (CPMD) 使用明确的水分子.
- 有偏差的CPMD模拟来测量质子转移的自由能量概况.
主要成果:
- 水分子在尼古丁的质子化位点之间形成桥梁链 (pyridine和pyrrolidine环).
- 质子转移的自由能量屏障随着水分子的增加而减少,但在较小的中仍然显著 (16kJ/mol与4个水分子).
- CPMD模拟显示在散装水中极快的质子转移 (在0.5 ps内),通过水桥而没有能量屏障发生.
结论:
- 水在促进水溶液中尼古丁的分离中起着关键作用.
- 质子转移在小水群中是一个罕见的事件,但在散装水中变得容易.
- 水桥对于水性尼古丁中的快速质子转移机制至关重要.
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