The Center for Modeling & Simulation Chemistry, Institute of Theoretical Chemistry, Shandong University, Jinan, 250100, People's Republic of China.
J Chem Phys. 2012 Mar 14;136(10):105101. doi: 10.1063/1.3685606.
We present a combined first-principles calculation and molecular dynamics simulation study of an excess electron (EE) in condensed phase of a microhydrated protonated amino group in proteins in this work. The protonated amino group, -NH(3)(+), is modeled by a CH(3)NH(3)(+) and an amount of water molecules are included to form various microhydrated CH(3)NH(3)(+) clusters, and the states and the dynamics of the trapped EE are analyzed. In addition to the localized and delocalized states observed, the N-H/O-H bond cleavage phenomena followed by escape of a H atom are also observed for some hydrated clusters in which the -NH(3)(+) group exposes on the surface of the cluster and directly participates in binding an EE. The state-to-state conversion is controlled by thermal motion of molecules in the clusters, and the cleavage of the N-H or the O-H bond and the H escape are determined by the binding modes of the EE. The H-escape nature could be attributed to the dissociation of the N-H or O-H bond induced by the trapped EE which transfers to their antibonding orbitals. This work provides a microscopical picture of the EE trapping at a microhydrated hydrophilic group in proteins, long-range electron migration, and the H-evolving mechanisms relevant for the lesions or damages of proteins or DNA. This is the first step in considering increasingly larger peptide fragments for further investigation of the detailed lesion/damage or charge migration mechanisms. Further work about this topic is underway.
在这项工作中，我们提出了一种组合的第一性原理计算和分子动力学模拟研究，研究了凝聚相中质子化氨基基团中多余电子（EE）的状态和动力学。质子化氨基基团-NH(3)(+)由-CH(3)NH(3)(+)模拟，并包含一定数量的水分子以形成各种微水合-CH(3)NH(3)(+)簇，分析了捕获 EE 的状态和动力学。除了观察到的局域态和离域态外，对于一些 -NH(3)(+)基团暴露在簇表面并直接参与结合 EE 的水合簇，也观察到 N-H/O-H 键断裂现象以及 H 原子的逃逸。状态到状态的转换由簇中分子的热运动控制，N-H 或 O-H 键的断裂和 H 逃逸由 EE 的结合模式决定。H 逃逸的性质可以归因于被捕获的 EE 转移到它们的反键轨道，从而导致 N-H 或 O-H 键的解离。这项工作提供了一个蛋白质中微水合亲水性基团中 EE 捕获、长程电子迁移以及与蛋白质或 DNA 的损伤相关的 H 演化机制的微观图景。这是考虑进一步研究详细的损伤/迁移机制时，对越来越大的肽片段进行研究的第一步。关于这个主题的进一步工作正在进行中。
