Formation and dissociation of protonated cytosine–cytosine base pairs in i-motifs by ab initio quantum chemical calculations  

作　　者：张小虎 黎明 王延颋 欧阳钟灿 

机构地区：[1]State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences [2]Department of Physical Science,University of Chinese Academy of Sciences

出　　处：《Chinese Physics B》2014年第2期189-192,共4页中国物理B（英文版）

基　　金：Project supported by the National Basic Research Program of China (973 Program,Grant No.2013CB932804);the National Natural Science Foundation of China (Grant Nos.91227115 and 11121403);the Hundred Talent Program of the Chinese Academy of Sciences (CAS)

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.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.

关 键 词：ab initio quantum chemical calculation I-MOTIF protonated cytosine-cytosine base pair 

分 类 号：O469[理学—凝聚态物理]