Department of Computer Science, Aalto University, P. O. Box 15400, FI-00076 Aalto, Finland.
Phys Rev E. 2017 May;95(5-1):052418. doi: 10.1103/PhysRevE.95.052418. Epub 2017 May 26.
We use stochastic rotation dynamics (SRD) to examine the dynamics of the ejection of an initially strongly confined flexible polymer from a spherical capsid with and without hydrodynamics. The results obtained using stochastic rotation dynamics (SRD) are compared to similar Langevin simulations. Inclusion of hydrodynamic modes speeds up the ejection but also allows the part of the polymer outside the capsid to expand closer to equilibrium. This shows as higher values of radius of gyration when hydrodynamics are enabled. By examining the waiting times of individual polymer beads, we find that the waiting time t_{w} grows with the number of ejected monomers s as a sum of two exponents. When ≈63% of the polymer has ejected, the ejection enters the regime of slower dynamics. The functional form of t_{w} versus s is universal for all ejection processes starting from the same initial monomer densities. Inclusion of hydrodynamics only reduces its magnitude. Consequently, we define a universal scaling function h such that the cumulative waiting time t=N_{0}h(s/N_{0}) for large N_{0}. Our unprecedentedly precise measurements of force indicate that this form for t_{w}(s) originates from the corresponding force toward the pore decreasing superexponentially at the end of the ejection. Our measured t_{w}(s) explains the apparent superlinear scaling of the ejection time with the polymer length for short polymers. However, for asymptotically long polymers, t_{w}(s) predicts linear scaling.
我们使用随机旋转动力学(SRD)来研究在存在和不存在流体力学的情况下,最初被强约束的柔性聚合物从球形衣壳中射出的动力学。使用随机旋转动力学(SRD)获得的结果与类似的 Langevin 模拟进行了比较。包含流体力学模式会加快射出速度,但也允许衣壳外的聚合物部分更接近平衡膨胀。这表现为在启用流体力学时转动惯量半径值更高。通过检查单个聚合物珠的等待时间,我们发现等待时间 t_{w} 随射出的单体数 s 增长为两个指数的和。当约 63%的聚合物射出时,射出进入较慢动力学的区域。从相同的初始单体密度开始的所有射出过程中,t_{w} 与 s 的函数形式都是通用的。包含流体力学只会降低其幅度。因此,我们定义了一个通用的标度函数 h,使得对于大的 N_{0},累积等待时间 t=N_{0}h(s/N_{0})。我们对力的前所未有的精确测量表明,这种形式的 t_{w}(s)源于射出结束时朝向孔的力呈超指数减小。我们测量的 t_{w}(s)解释了短聚合物的射出时间与聚合物长度之间的明显超线性标度关系。然而,对于渐近长的聚合物,t_{w}(s)预测线性标度。