DNA发夹在拉力作用下的热力学和动力学性质

发布时间：2018-03-30 02:30

本文选题：DNA发夹　切入点：拉力　出处：《中国科学技术大学》2017年硕士论文

【摘要】：本论文利用二维朗之万动力学模拟方法和理论分析研究了 DNA发夹在拉力作用下的相转变行为。研究发现DNA发夹处于展开状态的概率与所施加的拉力大小有关,在拉力比较小时(f=1.5),DNA发夹几乎全部都处在折叠状态,展开状态只会偶尔出现。随着拉力的增加,由拉力导致的展开状态出现的频率会增加,直到拉力增加到f=2.0时,DNA发夹几乎全部处在展开状态。展开状态的概率与施加的拉力有定量关系,并且可以通过统计力学的角度进行解释。通过选取不同的参数组合,并进行大量的模拟实验,我们分别得到了 DNA发夹的拉力-碱基配对强度和拉力-温度相图。所得相图表明碱基配对强度增强或温度降低都有利于DNA发夹处于折叠状态。DNA发夹在拉力作用下不会一直处在完全折叠或者是完全展开状态。DNA发夹可能只打开了一个或者几个碱基对。半打开状态是亚稳状态,在半打开状态时的自由能是局部最小值。模拟所得到的这些相图非常有益于加深人们对DNA发夹在拉力作用下的热力学性质的理解。另外通过朗之万动力学还得到了 DNA发夹打开所需要的力与拉力速率的关系,以及DNA发夹打开时间和拉力之间的关系,此外还研究了 DNA发夹打开概率与最大拉力和时间的关系。这些可以很好地帮助我们理解DNA发夹在拉力作用下的动力学性质。
[Abstract]:In this paper, the phase transition behavior of DNA hairpin under tension is studied by using two-dimensional Langevin dynamics simulation method and theoretical analysis. It is found that the probability of DNA hairpin being in an unfolded state is related to the magnitude of the applied pull. Almost all of the DNA hairpins are in a folding state, but only occasionally in the unfolded state. As the tension increases, the frequency of the unfolded state increases with the increase of the tensile force. The DNA hairpins are almost all in the unfolded state until the tensile force increases to fen 2.0. The probability of the unfolding state is quantitatively related to the tension applied, and can be explained by statistical mechanics. By selecting different parameter combinations, And carried out a lot of simulation experiments, We obtained the tension-base pairing strength and the tension-temperature phase diagram of the DNA hairpin respectively. The results show that the increase of the base pair strength or the decrease of the temperature are beneficial to the DNA hairpin in the folding state. The DNA hairpin may only open one or more base pairs. The semi-open state is metastable. The free energy in the semi-open state is the local minimum. These phase diagrams obtained from the simulation are very helpful to deepen the understanding of the thermodynamic properties of the DNA hairpin under the action of tension. In addition, the Langevin dynamics has also been obtained. The relationship between the force required for the opening of the DNA hairpin and the rate of tension, The relationship between the opening time of DNA hairpin and the pull force is also studied. The relationship between the opening probability of DNA hairpin and the maximum pull and time can help us to understand the dynamic properties of DNA hairpin under the action of pull force.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q751

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