Head D A, Briels W J, Gompper Gerhard
School of Computing, Leeds University, Leeds LS2 9JT, United Kingdom.
Computational Biophysics, University of Twente, 7500 AE Enschede, The Netherlands.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Mar;89(3):032705. doi: 10.1103/PhysRevE.89.032705. Epub 2014 Mar 10.
In the presence of adenosine triphosphate, molecular motors generate active force dipoles that drive suspensions of protein filaments far from thermodynamic equilibrium, leading to exotic dynamics and pattern formation. Microscopic modeling can help to quantify the relationship between individual motors plus filaments to organization and dynamics on molecular and supramolecular length scales. Here, we present results of extensive numerical simulations of active gels where the motors and filaments are confined between two infinite parallel plates. Thermal fluctuations and excluded-volume interactions between filaments are included. A systematic variation of rates for motor motion, attachment, and detachment, including a differential detachment rate from filament ends, reveals a range of nonequilibrium behavior. Strong motor binding produces structured filament aggregates that we refer to as asters, bundles, or layers, whose stability depends on motor speed and differential end detachment. The gross features of the dependence of the observed structures on the motor rate and the filament concentration can be captured by a simple one-filament model. Loosely bound aggregates exhibit superdiffusive mass transport, where filament translocation scales with lag time with nonunique exponents that depend on motor kinetics. An empirical data collapse of filament speed as a function of motor speed and end detachment is found, suggesting a dimensional reduction of the relevant parameter space. We conclude by discussing the perspectives of microscopic modeling in the field of active gels.
在三磷酸腺苷存在的情况下，分子马达产生主动力偶极子，驱动蛋白质丝悬浮液远离热力学平衡，从而导致奇异的动力学和图案形成。微观建模有助于量化单个马达与细丝之间的关系，以及分子和超分子长度尺度上的组织与动力学之间的关系。在这里，我们展示了活性凝胶的大量数值模拟结果，其中马达和细丝被限制在两个无限平行板之间。模拟中考虑了热涨落以及细丝之间的排阻体积相互作用。对马达运动、附着和脱离速率进行系统变化，包括细丝末端的差异脱离速率，揭示了一系列非平衡行为。强马达结合产生我们称为星状体、束状或层状的结构化细丝聚集体，其稳定性取决于马达速度和差异末端脱离。通过一个简单的单细丝模型可以捕捉到观察到的结构对马达速率和细丝浓度依赖性的总体特征。松散结合的聚集体表现出超扩散质量传输，其中细丝易位与滞后时间成比例，具有取决于马达动力学的非唯一指数。发现细丝速度作为马达速度和末端脱离函数的经验数据塌缩，这表明相关参数空间的维度约化。我们通过讨论活性凝胶领域微观建模的前景来结束本文。
