圆DNA拓扑态的温度依赖性
Temperature dependence of circular DNA topological states
摘要：
环状双链DNA具有不同的拓扑状态，这些拓扑状态由它们的连接数定义。通过连接酶将线性DNA闭合成环状，可以获得连接数的平衡分布。利用Monte Carlo模拟，我们预测了小的圆形DNA的连接数分布的温度依赖性。我们的预测是基于灵活的缺陷激发导致局部熔化或unstacking的DNA碱基对。我们发现，降低弯曲刚度单独可以导致可测量的变化的短圆形DNA的连接数分布的方差。如果缺陷伴随着局部解旋，则影响变得更加突出。这些预测结果易于在实验中进行验证，为研究急剧弯曲DNA的微观力学和特定DNA序列的热稳定性提供了一种新的方法。此外，预测是直接适用于结合的DNA扭曲蛋白，可以局部降低DNA刚性，形成DNA扭结，或引入本地解旋的研究。
英文摘要：
Circular double stranded DNA has different topological states which are defined by their linking numbers. Equilibrium distribution of linking numbers can be obtained by closing a linear DNA into a circle by ligase. Using Monte Carlo simulation, we predict the temperature dependence of the linking number distribution of small circular DNAs. Our predictions are based on flexible defect excitations resulted from local melting or unstacking of DNA base pairs. We found that the reduced bending rigidity alone can lead to measurable changes of the variance of linking number distribution of short circular DNAs. If the defect is accompanied by local unwinding, the effect becomes much more prominent. The predictions can be easily investigated in experiments, providing a new method to study the micromechanics of sharply bent DNAs and the thermal stability of specific DNA sequences. Furthermore, the predictions are directly applicable to the studies of binding of DNA distorting proteins that can locally reduce DNA rigidity, form DNA kinks, or introduce local unwinding.
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