Using Monte Carlo simulations, we study the hysteresis in unzipping of a double-stranded block copolymer DNA with $-A_n{B}_n-$ repeat units. Here $A$ and $B$ represent two different types of base pairs having two and three bonds, respectively, and $2n$ represents the number of such base pairs in a unit. The end of the DNA are subjected to a time-dependent periodic force with frequency ($\omega$) and amplitude ($g_0$) keeping the other end fixed. We find that the equilibrium force-temperature phase diagram for the static force is independent of the DNA sequence. For a periodic force case, the results are found to be dependent on the block copolymer DNA sequence and on the base pair type on which the periodic force is acting. We observe hysteresis loops of various shapes and sizes and obtain the scaling of loop area both at low- and high-frequency regimes.

中文翻译：

---

通过周期性力解开双链嵌段共聚物 DNA

使用蒙特卡罗模拟，我们研究了双链嵌段共聚物 DNA 解链的滞后性 $-{\mathrm{一种}}_n{乙}_n-$重复单位。这里$\mathrm{一种}$ 和 $乙$ 分别代表具有两个和三个键的两种不同类型的碱基对，并且 $2n$表示一个单位中此类碱基对的数量。DNA 的末端受到频率随时间变化的周期性力（$\omega$) 和振幅 ($G_0$) 保持另一端固定。我们发现静力的平衡力-温度相图与 DNA 序列无关。对于周期性力的情况，发现结果取决于嵌段共聚物 DNA 序列和周期性力作用的碱基对类型。我们观察了各种形状和大小的磁滞回线，并获得了低频和高频区域的回线面积比例。