Collective motion of driven semiflexible filaments tuned by soft repulsion and stiffness
Collective motion of driven semiflexible filaments tuned by soft repulsion and stiffness
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DOI：
10.1039/d0sm01036g
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发表时间：
2020-11-07
期刊：
影响因子：
3.4
通讯作者：
Betterton, Meredith D.
中科院分区：
文献类型：
--
作者：
Moore, Jeffrey M.;Thompson, Tyler N.;Betterton, Meredith D.
在活性物质系统中，自推进粒子可以自组织进行集体运动，导致持续的动力学行为失去平衡。在细胞中，细胞骨架细丝和马达蛋白形成对细胞力学、运动性和分裂重要的复杂结构。细胞骨架系统的集体动力学可以通过细丝滑动实验来重建，在该实验中，细胞骨架细丝由表面结合的马达蛋白推动。这些实验观察到了不同的动力学状态，包括集群、极流、旋涡和单丝螺旋。最近对微管和运动蛋白的实验发现，通过改变拥挤的大分子甲基纤维素在溶液中的浓度，可以调节滑动细丝的集体行为。增加甲基纤维素浓度减少了细丝交叉，促进了取向，并导致了从活跃的、各向同性取向的细丝向局部排列的极流的转变。这种集体运动的出现通常被解释为活性极性粒子的维塞克型模型增加了排列相互作用。然而，目前尚不清楚空间相互作用和弯曲刚性如何改变活性半柔性纤维的集体行为。在这里，我们使用具有可调软排斥力和刚性的驱动灯丝的模拟，以便更好地理解灯丝柔性和空间效应之间的相互作用如何导致不同的活跃动态。我们发现，与Vicsek型模型的假设相反，增加灯丝刚度降低了灯丝排列的几率，但增加了集体运动和长程有序度。我们识别了漩涡群、极流、弯曲带和螺旋，并描述了支配这些状态之间转变的物理。除了排斥力和驱动力之外，调谐细丝硬度还可以促进集体行为，并控制活跃的各向同性细丝、局部排列的细丝和极流之间的过渡。
In active matter systems, self-propelled particles can self-organize to undergo collective motion, leading to persistent dynamical behavior out of equilibrium. In cells, cytoskeletal filaments and motor proteins form complex structures important for cell mechanics, motility, and division. Collective dynamics of cytoskeletal systems can be reconstituted using filament gliding experiments, in which cytoskeletal filaments are propelled by surface-bound motor proteins. These experiments have observed diverse dynamical states, including flocks, polar streams, swirling vortices, and single-filament spirals. Recent experiments with microtubules and kinesin motor proteins found that the collective behavior of gliding filaments can be tuned by altering the concentration of the crowding macromolecule methylcellulose in solution. Increasing the methylcellulose concentration reduced filament crossing, promoted alignment, and led to a transition from active, isotropically oriented filaments to locally aligned polar streams. This emergence of collective motion is typically explained as an increase in alignment interactions by Vicsek-type models of active polar particles. However, it is not yet understood how steric interactions and bending stiffness modify the collective behavior of active semiflexible filaments. Here we use simulations of driven filaments with tunable soft repulsion and rigidity in order to better understand how the interplay between filament flexibility and steric effects can lead to different active dynamic states. We find that increasing filament stiffness decreases the probability of filament alignment, yet increases collective motion and long-range order, in contrast to the assumptions of a Vicsek-type model. We identify swirling flocks, polar streams, buckling bands, and spirals, and describe the physics that govern transitions between these states. In addition to repulsion and driving, tuning filament stiffness can promote collective behavior, and controls the transition between active isotropic filaments, locally aligned flocks, and polar streams.