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首页> 外文期刊>The Journal of Chemical Physics >Predominance of short range Coulomb forces in phosphate-water interactions-a theoretical analysis
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Predominance of short range Coulomb forces in phosphate-water interactions-a theoretical analysis

机译：短程库仑力在磷酸盐-水相互作用中的优势-理论分析

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摘要

Electric forces play a key role in the interaction of negatively charged phosphate groups with the dipolar water molecules of an aqueous environment. Both fluctuation amplitudes and effective spatial range of the electric fields that fluctuate on a multitude of time scales have remained highly controversial. We employ the dimethylphosphate anion (DMP) as a fundamental building block of the phosphodiester backbone in DNA to model electric fields at the phosphate-water interface. DMP is considered to be solvated in bulk water and the fluctuating electric forces exerted on the (PO2)(-) moiety are calculated by combining the ab initio based effective fragment potential approach that accounts for electric fields due to static multipoles and polarization contributions due to induced dipoles, with molecular dynamics. We demonstrate that the total time-averaged electric field generated by water molecules arises to a large extent from the first water layer. The second layer contributes some 18% with noticeable contributions from induction. We further show that the solvent electric field experienced by the phosphate group is the dominant contribution to the pronounced solvatochromism of the asymmetric (PO2)(-) stretch vibration. Accounting for a field expansion up to quadrupoles and polarization due to induced dipoles allows us to simulate solvent induced frequency shifts and lineshapes in almost quantitative agreement to experiment. Our theoretical model strongly supports the picture of short-range electric forces that arise locally from the first and second hydration shell. Published by AIP Publishing.
机译：电动势在带负电荷的磷酸基团与水性环境的偶极水分子的相互作用中起关键作用。在多个时间尺度上波动的电场的振幅和有效空间范围都一直存在很大争议。我们采用磷酸二甲酯阴离子（DMP）作为DNA中磷酸二酯主链的基本构件，以模拟磷酸盐-水界面的电场。 DMP被认为是在大量水中溶解的，作用在（PO2）（-）部分上的波动电势是通过结合基于从头算的有效碎片电势方法计算的，该方法解决了由于静态多极而产生的电场以及由于极化引起的极化感应偶极子，具有分子动力学。我们证明了由水分子产生的总时间平均电场在很大程度上来自第一水层。第二层贡献了约18％的归纳贡献。我们进一步表明，磷酸根所经历的溶剂电场是对不对称（PO2）（-）拉伸振动的明显溶剂变色现象的主要贡献。考虑到场扩展到四极子和归因于偶极子引起的极化，使我们能够以几乎定量的协议模拟溶剂诱导的频移和线形，以进行实验。我们的理论模型有力地支持了由第一和第二水化壳局部产生的短程电力的图景。由AIP Publishing发布。

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