Mechano-chemical selections of two competitive unfolding pathways of a single DNA i-motif  

作　　者：徐悦 陈虎 璩玉杰 Artem K.Efremov 黎明 欧阳钟灿 刘冬生 严洁 

机构地区：[1]State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics [2]Mechanobiology Institute, National University of Singapore [3]Department of Physics, National University of Singapore [4]School of Physics, University of Chinese Academy of Sciences [5]Department of Physics, Xiamen University [6]Key Laboratory of Organic Optoelectronics & Molecular Engineering of the Ministry of Education,Department of Chemistry, Tsinghua University

出　　处：《Chinese Physics B》2014年第6期621-628,共8页中国物理B（英文版）

基　　金：supported by Grants from the National Research Foundation through the Mechanobiology Institute Singapore and the Ministry of Education of Singapore(Grant No.MOE2012-T3-1-001)[to Yan J];the National Basic Research Program of China(Grant No.2013CB932800);the Major Research Plan of the National Natural Science Foundation of China(Grant Nos.91027046 and 91027045);the Fundamental Research Funds for the Central Universities(Grant No.2013121005)

摘　　要：The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.

关 键 词：single-molecule techniques I-MOTIF folding/structure of biomolecules mechanical proper-ties/biomolecules 

分 类 号：O561[理学—原子与分子物理]