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The role of cations in uranyl nanocluster association: a molecular dynamics study.
Physical Chemistry Chemical Physics ( IF 3.3 ) Pub Date : 2020-01-06 , DOI: 10.1039/c9cp05138d
Ken Newcomb 1 , Varinia Bernales , Surya Prakash Tiwari , Laura Gagliardi , Edward J Maginn
Affiliation  

Actinyl ions can self-assemble in aqueous solution to form closed cage clusters ranging from 1.5 to 4.0 nm in diameter. The self-assembly, stability, and behavior of the nanoclusters depend on the nature of the aqueous environment, such as the pH and cations present. In this work, a classical force field for [(UO2)20(O2)30]20- (U20) peroxide nanoclusters in aqueous solution was developed from quantum-mechanical calculations. Using molecular dynamics simulations, the preferred binding sites of six cations (Li+, Na+, K+, Rb+, Cs+, and Ca2+) to the nanocluster were determined. Replica exchange molecular dynamics was used to equilibrate the structure and determine the equilibrium distribution of cations and water with respect to the nanocluster cage. In addition, the free energy barriers associated with cations entering the cluster were computed. Finally, the association of two cages was investigated by computing the free energy as a function of intercage distance. The free energy profiles reveal that the nanoclusters prefer to be associated when neutralized with divalent cations, but do not associate when neutralized with monovalent cations. This could explain the formation of tertiary structures observed experimentally.

中文翻译:

阳离子在铀酰纳米簇缔合中的作用:分子动力学研究。

in离子可在水溶液中自组装,形成直径范围为1.5至4.0 nm的封闭笼簇。纳米团簇的自组装,稳定性和行为取决于水性环境的性质,例如所存在的pH和阳离子。在这项工作中,从量子力学计算发展了[(UO2)20(O2)30] 20-(U20)过氧化物纳米团簇在水溶液中的经典力场。使用分子动力学模拟,确定了六个阳离子(Li +,Na +,K +,Rb +,Cs +和Ca2 +)与纳米簇的优选结合位点。复制子交换分子动力学用于平衡结构并确定阳离子和水相对于纳米簇笼的平衡分布。另外,计算了与进入团簇的阳离子相关的自由能垒。最后,通过计算自由能与笼间距离的函数,研究了两个笼的关联。自由能谱显示,纳米团簇在被二价阳离子中和时更倾向于缔合,而在被一价阳离子中和时不缔合。这可以解释实验观察到的三级结构的形成。
更新日期:2020-01-06
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