Microhydration of cytosine and its radical anion:: Cytosine•(H2O)n (n=1-5)
Microhydration of cytosine and its radical anion:: Cytosine•(H2O)n (n=1-5)
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DOI：
10.1063/1.2432123
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发表时间：
2007-02-14
影响因子：
4.4
通讯作者：
Schaefer, Henry F., III
中科院分区：
文献类型：
--
作者：
Kim, Sunghwan;Schaefer, Henry F., III
通过显式考虑最多5个水分子的胞嘧啶络合物的不同结构，从理论上研究了微水化对胞嘧啶及其自由基阴离子的影响。每个连续的水分子(通过n=5)以7-10千卡的摩尔(-1)结合到相应的胞嘧啶复合体。对于相似的阴离子体系，水化能均匀较高。分离的胞嘧啶的垂直分离能(VDE)预计仅为0.48 eV，而最低位置的五水胞嘧啶的垂直分离能(VDE)预计将增加到1.27 eV。胞嘧啶的绝热电子亲和势(AEA)也从0.03 eV增加到0.61 eV，这意味着胞嘧啶阴离子虽然在气相中是可疑的，但在水溶液中是结合的。对于给定的水化数，胞嘧啶的VDE和AEA值均小于尿嘧啶和胸腺嘧啶。这些结果与Schiedt等人的光剥离-光电子能谱研究的实验结果定性一致。
Microhydration effects on cytosine and its radical anion have been investigated theoretically, by explicitly considering various structures of cytosine complexes with up to five water molecules. Each successive water molecule (through n=5) is bound by 7-10 kcal mol(-1) to the relevant cytosine complex. The hydration energies are uniformly higher for the analogous anion systems. While the predicted vertical detachment energy (VDE) of the isolated cytosine is only 0.48 eV, it is predicted to increase to 1.27 eV for the lowest-lying pentahydrate of cytosine. The adiabatic electron affinity (AEA) of cytosine was also found to increase from 0.03 to 0.61 eV for the pentahydrate, implying that the cytosine anion, while questionable in the gas phase, is bound in aqueous solution. Both the VDE and AEA values for cytosine are smaller than those of uracil and thymine for a given hydration number. These results are in qualitative agreement with available experimental results from photodetachment-photoelectron spectroscopy studies of Schiedt et al.