第一篇：停流-圓二色譜法研究DNA i-motif的折疊與解折疊動力學

停流-圓二色譜法研究DNA i-motif的折疊與解折疊動力學

陳春1，黎明2,*，楊忠強1，劉冬生

21,* 清華大學化學系，北京市，100084 中科院研究生院，北京市，100190

*Email: liudongsheng@tsinghua.edu.cn, liming@gucas.ac.cn

利用停流-圓二色譜法，本文研究了DNA i-motif的折疊與解折疊動力學。結(jié)果表明，DNA i-motif的折疊與解折疊過程具有pH依賴性，并且時間尺度在100毫秒左右。此外，根據(jù)定量數(shù)據(jù)所構(gòu)建的模型表明，質(zhì)子的協(xié)同作用對于折疊與解折疊過程非常重要。在解折疊過程中，唯一的限速步驟是兩個質(zhì)子（而非全部六個）被中和掉；而在折疊過程中，卻是三個質(zhì)子協(xié)同地結(jié)合在DNA i-motif上。這些研究結(jié)果有助于理解DNA i-motif的折疊與解折疊動力學，并進一步指導分子機器的構(gòu)建。[1]

關(guān)鍵詞：DNA i-motif；kinetics；folding；unfolding

參考文獻

[1] Gehring, K.;Leroy, J.L.;Gueron, M.Nature 1993, 363, 561.The Folding and Unfolding Kinetics of DNA i-motif Studied by

Stopped-flow Circular Dichroism 1, M.Li 2,*, Z.Q.Yang1, D.S.Liu1,*

1Department of Chemistry, Tsinghua University, Beijing, 100084

2College of Physical Sciences, Graduate University of Chinese Academy of Sciences, Beijing,100190

Using the stopped-flow circular dichroism(SFCD)technique, we investigate the kinetics of pH-induced folding and unfolding processes of DNA i-motif.It is found that the molecule can fold or unfold at a timescale of 100 ms when the solution pH is changed and that the folding and unfolding rates strongly depend on the solution pH.Based on quantitative data, we propose a model to decipher the folding and unfolding kinetics.Our model suggests that cooperativity of protons is crucial for either folding or unfolding process.In the unfolding pathway, cooperative neutralization of two protons is the only rate-limiting step.In the folding process, there are three protons cooperatively binding to the DNA strand in the rate-limiting step.These results offer in-depth understanding of the folding and unfolding kinetics of the DNA i-motif and may give precise guidance to construct novel nanostructures.