尿嘧啶核苷酸阴离子液相中的过电子附着和电离

本文采用QM/MM方法研究液相尿嘧啶核苷酸阴离子的过电子附着和电离过程. 从分子动力学模拟的轨线抽取了40个采样结构，并计算了在这些采样点的垂直电子亲合势、绝热电子亲合势、垂直电子剥离能、垂直电离能和绝热电离能，分析了过电子附着和电离过程中的过电子及空穴分布. 模拟的垂直电子亲合势和绝热电子亲合势的平均值分别为-0.31 eV和2.13 eV，表明过电子很容易附着到尿嘧啶核苷酸阴离子上. 在尿嘧啶碱基上，垂直和绝热过电子分布的平均值分别为-0.50 eV和-0.62 eV，证明大多数的过电子局域在尿嘧啶碱基上. 双阴离子结构弛豫后，在几个抽样中发现过电子分布也可能会在碱基/糖环或者糖环/磷酸根上非局域化. 2.78 eV的垂直电子剥离能平均值表明，过电子附着后形成的尿嘧啶核苷酸双阴离子非常稳定. 液相尿嘧啶核苷酸阴离子的垂直电离能平均值为8.13 eV，与以前采用溶剂模型模拟的结果一致. 电离中，空穴主要分布在尿嘧啶碱基上，表明其最容易被电离. 在垂直电离中，几个抽样下的空穴会非局域分布在尿嘧啶碱基和糖环上. 绝热的空穴分布表明，在特定结构下，电离后的结构弛豫会导致磷酸根上电子和碱基上空穴转移到糖环上.

Excess-Electron Attachment and Ionization of Aqueous Uridine Monophosphate Anion

We applied quantum mechanics/classical mechanics simulations to study excess-electron attachment and ionization of uridine monophosphate anion (dUMP^-) in explicit aqueous solutions. We calculated vertical electron affinities (VEAs), adiabatic electron affinities (AEAs), vertical detachment energies (VDEs), vertical ionization energies (VIEs), and adiabatic ionization energies (AIEs) of the 40 structures obtained from molecular dynamic trajectory. The excess-electron and hole distributions were analyzed in electron attachment and ionization of aqueous dUMP^-. The converged mean VEA (-0.31 eV) and AEA (2.13 eV) suggest that excess-electron can easily attach to dUMP^-. The mean vertical (-0.50 e) and adiabatic (-0.62 e) excess-electron on uracil reveal that main excesselectrons are localized on nucleobases at the most snapshots. The distributions at several special snapshots demonstrate the excess-electron delocalization over nucleobases/ribose or ribose/phosphate group after the structural relaxations of dUMP^2- dianion. The VDE value (2.78 eV) indicates that dUMP^2- dianion could be very stable. Moreover, the mean VIE is 8.13 eV which is in agreement with the previous calculation using solvation model. The hole distributions on uracil suggest that the nucleobases are easily ionized after the irradiation of high-energy rays. In vertical ionizations, the holes would be delocalized over uracil and ribose at several snapshots. Observing the adiabatic hole distributions, it can be found that electrons on phosphate group and holes on nucleobases can be transferred to ribose at the special snapshots in the structural relaxation of neutral species.