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DNA单分子弹性理论

Elastic theory of single DNA molecules

  • 摘要: 随着单分子操纵技术的发明与发展,人们已经可以对单个生物大分子施以力或力矩,并测量它们的物理性质.DNA单分子的力学实验表明,在分子尺度上理解生物大分子的生化过程,力与能量是同等重要的结构与功能参数.一个梯子模型被用来描述双链DNA的外力拉伸曲线,在这个模型中,DNA是由许多碱基对(梯子的横杆,横杆之间存在吸引势)连接两条聚核苷酸虫链(梯子的两侧)形成的高分子.利用路径积分法得出的理论曲线与实验曲线吻合得很好.对于单链DNA,用分立的杂化高分子链统计理论的母函数方法来计算其弹性行为,得出与实验相符合的外力引起的解链相变结果.此外,对于抑瘤蛋白p53识别序列DNA微环弹性进行分析,发现其弹性模量只是通常随机序列的三分之一.

     

    Abstract: With the development of single molecule manipulation, the properties of single biological macro-molecules can be tested by applying a force or torque to it. Mechanical experiments suggest that both force and energy are equally important structural and functional elements for the understanding of bio-chemical processes in biological macro-molecules. A ladder model where the double strand DNA consists of a number of base pairs (parallel rungs of the ladder with attractions between them) linking to two worm-like nucleotide chains (two long sides of the ladder) is presented to describe the force-extension curve of DNA. The theoretical curve obtained by the path integral method agrees well with experimental results. The generated function method in the hybridized statistics theory of polymer chains is used to calculate the elastic behavior of single strand DNA, and the theoretical results are consistent with the force-induced unzipping phase transition observed in experiments. Moreover, it is found that the elastic modulus for DNA sequences determined by p53 (the tumor-suppressor protein) is about one-third of the value for random-sequence DNA.

     

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