Translocation of closed polymers through a nanopore under an applied external field

The dynamic behaviours of the translocations of closed circular polymers and closed knotted polymers through a nanopore, under the driving of an applied field, are studied by three-dimensional Langevin dynamics simulations. The power-law scaling of the translocation time τ with the chain length N and the distribution of translocation time are investigated separately. For closed circular polymers, a crossover scaling of translocation time with chain length is found to be τ～ N α , with the exponent α varying from α = 0.71 for relatively short chains to α = 1.29 for longer chains under driving force F = 5. The scaling behaviour for longer chains is in good agreement with experimental results, in which the exponent α = 1.27 for the translocation of double-strand DNA. The distribution of translocation time D(τ) is close to a Gaussian function for duration time τ < τ p and follows a falling exponential function for duration time τ > τ p . For closed knotted polymers, the scaling exponent α is 1.27 for small field force (F = 5) and 1.38 for large field force (F = 10). The distribution of translocation time D(τ) remarkably features two peaks appearing in the case of large driving force. The interesting result of multiple peaks can conduce to the understanding of the influence of the number of strands of polymers in the pore at the same time on translocation dynamic process and scaling property.     

脱氧核糖核酸单链序列的预测

利用Langevin动力学方法模拟了脱氧核糖核酸(DNA)单链在电场力作用下穿越纳米孔道的动力学过程.研究表明,不同种类的单体对应着不同的居留时间,相邻单体的居留时间随着孔道长度的增大而减小.在简化模型的基础上,可以从居留时间图中一次性地推测出一条DNA链的嘌呤和嘧啶的分布.应用该方法对17条不同序列的DNA链进行了预测,平均准确率为951%.在此方法的基础上做一些改进,可以为DNA链的测序提供一种高效的低成本方法. 关键词： Langevin动力学 脱氧核糖核酸单链 序列预测