Formation and Dissociation of Protonated Cytosine-Cytosine Base Pairs in I-Motifs by Ab Initio Quantum Chemical Calculations

分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2016-05-04

Xiaohu Zhang Ming Li Yanting Wang Zhong-can Ou-Yang

摘要： Formation and dissociation mechanisms of C-C+ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C+ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C+ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.

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