The Entropic and Enthalpic Contributions to Force-Dependent Dissociation Kinetics of the Pyrophosphate Bond
The Entropic and Enthalpic Contributions to Force-Dependent Dissociation Kinetics of the Pyrophosphate Bond
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DOI：
10.1021/ja207421v
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发表时间：
2011-12-21
影响因子：
15
通讯作者：
Boulatov, Roman
中科院分区：
文献类型：
--
作者：
Hermes, Matthew;Boulatov, Roman
我们报告了与约束势耦合的构象柔性反应物中焦磷酸键溶剂解的活化自由能的量子化学计算。结果表明，即使是相当小的反应物，构象熵对力依赖性动力学也有显着贡献，这表明拉伸聚合物中局部反应动力学的准确预测或分子解释可能需要明确考虑其力依赖性构象异质性。我们进一步表明，将反应物的构象空间和过渡态建模为重叠谐波阱的集合，可以准确预测高达 2 nN 的力相关激活自由能，而无需详细的量子化学计算。使用所有亲核置换反应共有的局部坐标从最小（Eyring Bell Evans）模型获得活化能的估计。
We report quantum-chemical calculations of the activation free energy of solvolysis of the pyrophosphate bond in a conformationally flexible reactant coupled to a constraining potential. The results reveal a significant contribution of conformational entropy to the force-dependent kinetics of even a fairly small reactant, suggesting that accurate predictions or molecular interpretation of localized reaction kinetics in stretched polymers may require explicit consideration of their force-dependent conformational heterogeneity. We further show that modeling the conformational space of the reactant and the transition state as collections of overlapping harmonic wells accurately predicts the force-dependent activation free energy up to 2 nN without detailed quantum-chemical computations. An estimate of the activation energies is obtained from the minimal (Eyring Bell Evans) model using the local coordinate common to all nucleophilic displacement reactions.