We use mathematical modeling and computation to investigate how protein friction facilitates contraction of disordered actomyosin networks. We simulate two-dimensional networks using an agent-based model, consisting of a system of force-balance equations for myosin motor proteins and semiflexible actin filaments. A major advantage of our approach is that it enables direct calculation of the network stress tensor, which provides a quantitative measure of contractility. Exploiting this, we use repeated simulations of disordered networks to confirm that both protein friction and actin filament bending are required for contraction. We then use simulations of elementary two-filament systems to show that filament bending flexibility can facilitate contraction on the microscopic scale. Finally, we show that actin filament turnover is necessary to sustain contraction and prevent filament aggregation. Simulations with and without turnover also exhibit contractile pulses. However, these pulses are aperiodic, suggesting that periodic pulsation can only arise because of additional regulatory mechanisms or more complex mechanical behavior.

我们使用数学建模和计算来研究蛋白质摩擦如何促进无序肌动球蛋白网络的收缩。我们使用基于代理的模型模拟二维网络，该模型由肌球蛋白运动蛋白和半柔性肌动蛋白丝的力平衡方程系统组成。我们的方法的一个主要优点是它可以直接计算网络应力张量，这提供了收缩性的定量测量。利用这一点，我们使用无序网络的重复模拟来确认蛋白质摩擦和肌动蛋白丝弯曲都是收缩所必需的。然后，我们使用基本双细丝系统的模拟来表明细丝弯曲柔韧性可以促进微观尺度上的收缩。最后，我们表明，肌动蛋白丝的周转对于维持收缩和防止丝聚集是必要的。有和没有营业额的模拟也表现出收缩脉冲。然而，这些脉冲是非周期性的，这表明周期性脉动只能由于额外的调节机制或更复杂的机械行为而产生。