单分子拉伸力实验中DNA解链动力学无序效应的介观统计研究  

Dynamic disorder in DNA unzipping from single molecule pulling experiments: an analysis based on generalized Langevin equation

作　　者：边玉坤[1] 赵南蓉[2] 

机构地区：[1]四川大学原子与分子物理研究所,成都610064 [2]四川大学化学学院,成都610064

出　　处：《中国科学：化学》2015年第4期419-426,共8页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(21373141;21173152)资助

摘　　要：单分子拉伸力实验对DNA解链动力学的研究发现了拉断力分布的宽尾特征,意味着解链动力学速率的含时涨落,即动力学无序现象.本文立足一维广义朗之万方程,描述在拉伸力作用下大分子体系构象态转变动力学,结合分数高斯噪声和幂律摩擦记忆内核,引入构型涨落的亚扩散特征;借助Kramers速率理论,推导含时反应速率k(t,F)、非单指数衰减残存概率分布S(t,F)以及恒速拉伸力作用下的拉断力分布p(F)等,揭示动力学无序效应;将理论应用于DNA解链的单分子拉伸力实验研究,采用漏斗势能模型,拟合不同恒速拉伸力作用下的拉断力分布曲线,估算体系的本征反应速率和势能面特征参数;与Bell公式,以及基于马尔可夫近似的介观统计理论进行系统比较.结果表明,本文建立的动力学无序理论能很好地拟合实验结果,解释单分子拉伸力作用下DNA解链拉断力分布的宽尾特征,揭示了该动力学无序效应与DNA构型慢涨落亚扩散机制的内在关联.Recent single molecule pulling experiments on DNA unzipping have revealed a heavy-tailed rupture force distribution, indicating dynamic disorder. Here we present a theoretical framework based on a generalized Langevin equation （GLE） with fractional Gaussian noise （fGn） and power-law memory kernel to study the kinetics of DNA unzipping to address the effects of dynamic disorder on barrier-crossing kinetics under external pulling force. Such a GLE-fGn strategy is associated with the slow conformational fluctuations of macromolecules. By using the Kramers＇ rate theory, we have obtained analytical formulae for the time-dependent rate coefficient k（t,F）, and the distribution of rupture force p（F） which demonstrates a fat tail at high force as functions of time t and force F. In addition, through fitting our results to data from single molecule pulling experiments on DNA unzipping, we estimate the kinetic parameters and qualify the extent of disorder. Our work provides a plausible interpretation for the evidence of dynamic disorder in force-induced DNA unzipping, compared to two other models based on Bell model and Langevin equation （LE） approach.

关 键 词：单分子拉伸力实验 DNA解链 动力学无序 广义郎之万方程 构型涨落亚扩散 

分 类 号：O629.74[理学—有机化学]