Cocco Simona, Monasson Rémi, Marko John F
Laboratoire de Dynamique des Fluides Complexes, 3 rue de l'Université, 67000 Strasbourg, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Nov;66(5 Pt 1):051914. doi: 10.1103/PhysRevE.66.051914. Epub 2002 Nov 22.
The two strands of the DNA double helix can be "unzipped" by the application of approximately 15 pN force. We analyze the dynamics of unzipping and rezipping for the case where the molecule ends are separated and reapproached at constant velocity. For unzipping of 50-kilobase DNAs at less than about 1000 bases per second, thermal-equilibrium-based theory applies. However, for higher unzipping velocities, rotational viscous drag creates a buildup of elastic torque to levels above k(B)T in the double-stranded DNA region, causing the unzipping force to be well above or well below the equilibrium unzipping force during, respectively, unzipping and rezipping, in accord with recent experimental results of Thomen et al. [Phys. Rev. Lett. 88, 248102 (2002)]. Our analysis includes the effect of sequence on unzipping and rezipping, and the transient delay in buildup of the unzipping force due to the approach to the steady state.
通过施加约15皮牛的力，DNA双螺旋的两条链可以被“拉开”。我们分析了在分子末端以恒定速度分离和重新靠近的情况下拉开和重新闭合的动力学过程。对于每秒拉开少于约1000个碱基的50千碱基DNA的拉开过程，基于热平衡的理论适用。然而，对于更高的拉开速度，旋转粘性阻力会在双链DNA区域产生弹性扭矩积累，使其高于玻尔兹曼常数乘以温度（k(B)T）的水平，导致在拉开和重新闭合过程中，拉开力分别远高于或远低于平衡拉开力，这与托门等人[《物理评论快报》88, 248102 (2002)]最近的实验结果一致。我们的分析包括序列对拉开和重新闭合的影响，以及由于接近稳态而导致拉开力积累的瞬态延迟。
