Reaction path optimization and vibrational frequency analysis via ab initio QM/MM free energy gradient (FEG) method: application to isomerization process of glycine in aqueous solution
Reaction path optimization and vibrational frequency analysis via ab initio QM/MM free energy gradient (FEG) method: application to isomerization process of glycine in aqueous solution
复制标题
通过从头开始 QM/MM 自由能梯度 (FEG) 方法的反应路径优化和振动频率分析：在水溶液中甘氨酸异构化过程中的应用
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M. Nagaoka
中科院分区：
文献类型：
--
作者：
N. Takenaka;Y. Kitamura;Yoshiyuki Koyano;T. Asada;M. Nagaoka
为了准确探索溶液中化学反应体系的反应路径，我们提出了结合从头算QM/ MM-MD计算的自由能梯度（FEG）方法，即从头算QM/ MM-MD方法。为了证明该方法的有效性，我们将该方法应用于甘氨酸在水溶液中的异构化反应，即分子内质子从两性离子（ZW）转移到中性形式（NF）的反应。通过从头算QM/ MM-FEG方法明确考虑溶剂效应，在相同从头算QM水平下，这些稳态结构与气相和隐式介质连续介质模型得到的稳态结构不同。另外，利用溶液中的“自由能（FE）”矩阵进行振动频率分析，计算得到的振动频率与实验得到的振动频率在ZW的低至中频范围内吻合较好。此外，从ZW到NF的活化FE不仅与Car-Parrinello MD方法的估计吻合，而且与先前的实验结果吻合得很好。结果表明，从头算QM/ MM-FEG方法与许多传统的平均场近似方法相比，能够更好地描述溶液中的化学反应体系，具有较好的应用前景。
For the purpose to explore reaction paths accurately for chemical reaction systems in solution, we have proposed the free energy gradient (FEG) method combined with ab initio QM/MM–MD calculation, i.e., the ab initio QM/MM–FEG method. For demonstration, the method has been applied to the isomerization reaction of glycine in aqueous solution, i.e., the intramolecular proton transfer reaction from zwitterion (ZW) to the neutral form (NF). Including the solvent effect explicitly by the ab initio QM/MM–FEG method, those stable-state structures were found different from those obtained in gas phase and by an implicit dielectric continuum model at the same ab initio QM level. Additionally, by the vibration frequency analysis with the “free energy (FE)” hessian in solution, the calculated vibrational frequencies were in good agreement with the experimental ones in the range from low to middle frequency of ZW. Furthermore, the FE of activation from ZW to NF was found in very good agreement with not only the estimation by the Car-Parrinello MD method but also by the previous experimental one. It is concluded that the ab initio QM/MM–FEG method is promising and should provide a better description of chemical reaction systems in solution in comparison with a number of conventional approaches by using the mean field approximations.
影响因子：
5.5
作者：
Zhenyu Lu;Yingkai Zhang
通讯作者：
Zhenyu Lu;Yingkai Zhang