Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany.
J Chem Phys. 2019 Feb 14;150(6):064913. doi: 10.1063/1.5082723.
The conformational and dynamical properties of semiflexible active Brownian ring polymers are investigated analytically. A ring is described by the Gaussian semiflexible polymer model accounting for the finite contour length. Activity is implemented by a Gaussian, non-Markovian stochastic process resembling either an external nonthermal force or a local self-propulsion velocity as for an active Ornstein-Uhlenbeck particle. Specifically, the fluctuation spectrum of normal-mode amplitudes is analyzed. At elevated activities, flexible (tension) modes dominate over bending modes even for semiflexible rings, corresponding to enhanced conformational fluctuations. The fluctuation spectrum exhibits a crossover from a quadratic to a quartic dependence on the mode number with increasing mode number, originating from intramolecular tension, but the relaxation behavior is either dominated by intra-polymer processes or the active stochastic process. A further increase in activity enhances fluctuations at large length scales at the expense of reduced fluctuations at small scales. Conformationally, the mean square ring diameter exhibits swelling qualitatively comparable to liner polymers. The ring's diffusive dynamics is enhanced, and the mean square displacement shows distinct activity-determined regimes, consecutively, a ballistic, a subdiffusive, and a diffusive regime. The subdiffusive regime disappears gradually with increasing activity.
半刚性活性布朗环聚合物的构象和动力学性质得到了分析研究。环由高斯半刚性聚合物模型描述，该模型考虑了有限的轮廓长度。活性通过高斯非马尔可夫随机过程来实现，该过程类似于外部非热力或局部自推进速度，适用于活性奥恩斯坦-乌伦贝克粒子。具体来说，分析了正常模式振幅的涨落谱。在较高的活性下，即使对于半刚性环，柔性（张力）模式也会主导弯曲模式，从而导致构象波动增强。随着模式数的增加，涨落谱从二次依赖转变为四次依赖，这源于分子内张力，但松弛行为要么由聚合物内过程主导，要么由活性随机过程主导。进一步增加活性会增加大尺度上的波动，而减少小尺度上的波动。在构象上，均方环直径表现出与线性聚合物相当的肿胀。环的扩散动力学得到增强，均方位移显示出明显的活性确定的区域，依次为弹道、亚扩散和扩散区域。随着活性的增加，亚扩散区域逐渐消失。
