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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Density Functional Study of Intradimer Proton Transfers in Hydrated Adenine Dimer Ions, A2~+(H2O)_n (n=0-2)
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Density Functional Study of Intradimer Proton Transfers in Hydrated Adenine Dimer Ions, A2~+(H2O)_n (n=0-2)

机译：水合腺嘌呤二聚体离子，A2〜+（H2O）_n（n = 0-2）内质子转移的密度泛函研究

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Structures of mono- and dihydrated adenine dimers and their cations were calculated using B3LYP density functional theory with the 6-31+G(d,p) basis set, in order to help understand photofragmentation experiments of hydrated adenine dimers from the energetics point of view. Several important pathways leading to the major fragmentation product, protonated adenine ion (AH~+), thermodynamically at minimum costs were investigated at the ground-state electronic potential surface of hydrated adenine dimer cations. Our calculations suggest that the proton transfer from one adenine moiety to the other in hydrated dimer ions readily occurs with negligible barriers in normal hydration conditions. In asymmetrically hydrated ions, however, the proton transfer to more hydrated adenine moieties is kinetically hindered due to heightened transition-state barriers, while the other way is still barrierless. Such directional preference in proton transfer may be characterized as a unique dimer ion property, stemming from the difference in basicity of the two nitrogen atoms involved in the double hydrogen bond that would be equivalent without hydration. We also found that dimer cleavage requires about 4 times larger energy than evaporation of individual water molecules, so it is likely that most solvent molecules evaporate before the eventual dimer cleavage when available internal energy is limited.
机译：使用B3LYP密度泛函理论和6-31 + G（d，p）基集计算一水合和二水合腺嘌呤二聚体的结构及其阳离子，以帮助从能量学角度理解水合腺嘌呤二聚体的光致碎裂实验。 。在水合腺嘌呤二聚体阳离子的基态电子势能表面上，以最小的成本热力学地研究了导致主要片段化产物质子化腺嘌呤离子（AH〜+）的几种重要途径。我们的计算表明，在水合二聚离子中，质子从一个腺嘌呤部分转移到另一个腺苷部分很容易发生，在正常水合作用条件下可以忽略不计。但是，在不对称水合离子中，由于过渡态势垒的提高，在动力学上阻碍了质子向水合腺嘌呤部分的转移，而另一种方法仍然是无障碍的。质子转移中的这种方向性偏好可以表征为独特的二聚离子性质，这是由于参与双氢键的两个氮原子的碱性不同而没有水合而引起的。我们还发现，二聚体裂解所需的能量大约是单个水分子蒸发量的4倍，因此，当可用内部能量受到限制时，大多数溶剂分子可能会在最终的二聚体裂解之前蒸发。

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