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Formation and Dissociation of Protonated Cytosine-Cytosine Base Pairs in I-Motifs by Ab Initio Quantum Chemical Calculations |
1. 中国科学院理论物理研究所
2. 中国科学院大学
3. Institute of Theoretical Physics
4.
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Abstract I-motif is a cytosine-rich DNA oligomer with a tetrameric structure formed in an acidic environment. It is a four-stranded complex consisting two base-paired parallel-stranded duplexes, each of which is held together by protonated cytosine-cytosine (C-C+) base pairs. This work employs ab initio quantum chemical calculations to investigate the formation and dissociation mechanisms of C-C+ base pairs in acidic and alkaline environments, respectively. Our calculations suggest that, in an acidic environment, a cytosine monomer is firstly protonated and then dimerize with an unprotonated cytosine monomer to form a C-C+ base pair; in an alkaline environment, a protonated cytosine dimer is firstly unprotonated and then dissociate 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. Those results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.
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Received: 22 September 2013
Published: 31 October 2013
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Corresponding Authors:
Yanting Wang
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Cite this article:
Formation and Dissociation of Protonated Cytosine-Cytosine Base Pairs in I-Motifs by Ab Initio Quantum Chemical Calculations Chin. Phys. B 0
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