凝聚相中的互变异构平衡
Tautomeric equilibrium in condensed phases
摘要：
本文采用从头算分子动力学方法研究了甘氨酸和丙酮水溶液中的互变异构平衡。互变异构用于加速质子在互变异构中心之间的迁移。由于在水环境中形成复杂的水离子结构涉及质子动力学，标准的增强采样方法可能面临严重的限制，在提供一个一般的描述的现象。最近，我们开发了一组集体变量（CV），旨在研究复杂凝聚体系中的质子转移反应[Grifoni et al. PNAS，2019，116（10），4054-4057]。在这项工作中，我们采用这种方法来研究质子解离动力学导致生物和化学相关的原型系统，即甘氨酸和丙酮在水中的互变异构体相互转化。虽然从化学的角度来看相对简单，但结果表明，即使对于这些小系统，也观察到复杂的反应途径和非平凡的转化动力学。我们的方法的一般性允许获得这些结果，而不提供任何先验信息的解离动力学，但只有原子物种，可以交换质子的过程中。我们的结果与文献估计一致，并证明了该方法在互变异构反应研究中的普遍适用性。
英文摘要：
We present an ab initio molecular dynamics (MD) investigation of the tautomeric equilibrium for aqueous solutions of glycine and acetone at realistic experimental conditions. Metadynamics is used to accelerate proton migration among tautomeric centers. Due to the formation of complex water-ion structures involved the proton dynamics in the aqueous environment, standard enhanced sampling approaches may face severe limitations in providing a general description of the phenomenon. Recently, we developed a set of Collective Variables (CVs) designed to study protons transfer reactions in complex condensed systems [Grifoni et al. PNAS, 2019, 116(10), 4054-4057]. In this work we applied this approach to study proton dissociation dynamics leading to tautomeric interconversion of biologically and chemically relevant prototypical systems, namely glycine and acetone in water. Although relatively simple from a chemical point of view, the results show that even for these small systems complex reaction pathways and non-trivial conversion dynamics are observed. The generality of our method allows obtaining these results without providing any prior information on the dissociation dynamics but only the atomic species that can exchange protons in the process. Our results agree with literature estimates and demonstrate the general applicability of this method in the study of tautomeric reactions.
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