Kinetic Isotope Effects from QM/MM Subset Hessians: "Cut-Off" Analysis for SN2 Methyl Transfer in Solution.
Kinetic Isotope Effects from QM/MM Subset Hessians: "Cut-Off" Analysis for SN2 Methyl Transfer in Solution.
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DOI：
10.1021/ct200771t
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发表时间：
2012-01
影响因子：
5.5
通讯作者：
I. H. Williams
中科院分区：
文献类型：
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作者：
I. H. Williams
同位素分配功能比和动力学同位素效应的反应S-腺苷甲硫氨酸与儿茶酚在水中进行评估，使用一个子集的324个原子在其周围的水环境中的AM 1/TIP 3 P水平。两种不同的方法治疗运动的子集原子相对于其环境的六个自由度的librational进行了比较。通过从初始的972 × 972 Hessian中累积删除行和列，生成一系列连续较小的Hessian子集。我们发现，它是更好地处理这些振动比平移和旋转，并没有必要调用泰勒-Redlich产品规则。对截断原子子集的同位素效应计算的“截断”方法的有效性进行了评估：为了保证所有考虑的同位素取代的ln（KIE）误差< 1%（或量子校正KIE误差<2%），有必要使用比熟悉的双键截断规则所建议的限制性更小的方法。
Isotopic partition-function ratios and kinetic isotope effects for reaction of S-adenosylmethionine with catecholate in water are evaluated using a subset of 324 atoms within its surrounding aqueous environment at the AM1/TIP3P level. Two alternative methods for treating motion in the six librational degrees of freedom of the subset atoms relative to their environment are compared. A series of successively smaller subset Hessians are generated by cumulative deletion of rows and columns from the initial 972 × 972 Hessian. We find that it is better to treat these librations as vibrations than as translations and rotations and that there is no need to invoke the Teller-Redlich product rule. The validity of "cut-off" procedures for computation of isotope effects with truncated atomic subsets is assessed: to ensure errors in ln(KIE) < 1% (or 2% for the quantum-corrected KIE) for all isotopic substitutions considered, it is necessary to use a less-restrictive procedure than is suggested by the familiar two-bond cutoff rule.