The process by which actin polymerization generates pulling forces in cellular processes such as endocytosis is less well understood than pushing-force generation. To clarify the basic mechanisms of pulling-force generation, we perform stochastic polymerization simulations for a square array of polymerizing semiflexible actin filaments, having different interactions with the membrane. The filaments near the array center have a strong attractive component. Filament bending and actin-network elasticity are treated explicitly. We find that the outer filaments push on the membrane and the inner filaments pull, with a net balance of forces. The total calculated pulling force is maximized when the central filaments have a very deep potential well, and the outer filaments have no well. The steady-state force is unaffected by the gel rigidity, but equilibration takes longer for softer gels. The force distributions are flat over the pulling and pushing regions. Actin polymerization is enhanced by softening the gel or reducing the filament binding to the membrane. Filament-membrane detachment can occur for softer gels, even if the total binding energy of the filaments to the membrane is 100 [Formula: see text] or more. It propagates via a stress-concentration mechanism similar to that of a brittle crack in a solid, and the breaking stress is determined by a criterion similar to that of the 'Griffith' theory of crack propagation.

中文翻译：

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通过聚合肌动蛋白丝的集合产生拉力。

肌动蛋白聚合在细胞过程（例如胞吞作用）中产生拉力的过程比推力产生的了解还少。为了阐明拉力产生的基本机理，我们对聚合的半柔性肌动蛋白丝的正方形阵列进行了随机聚合模拟，该阵列与膜的相互作用不同。靠近阵列中心的细丝具有很强的吸引力。细丝弯曲和肌动蛋白网络弹性得到明确处理。我们发现外部细丝在膜上推动而内部细丝在力的净平衡下拉动。当中心细丝具有非常深的势阱，而外部细丝却没有势阱时，计算出的总拉力将最大化。稳态力不受凝胶硬度的影响，但平衡需要更长的时间才能形成更柔软的凝胶。力分布在拉动和推动区域上是平坦的。通过软化凝胶或减少长丝与膜的结合来增强肌动蛋白的聚合。对于较软的凝胶，即使细丝与膜的总结合能为100或更高，也会发生细丝-膜的分离。它通过类似于固体中脆性裂纹的应力集中机制进行传播，断裂应力由类似于裂纹扩展的“格里菲斯”理论的准则确定。对于较软的凝胶，即使细丝与膜的总结合能为100或更高，也会发生细丝-膜的分离。它通过类似于固体中脆性裂纹的应力集中机制进行传播，断裂应力由类似于裂纹扩展的“格里菲斯”理论的准则确定。对于较软的凝胶，即使细丝与膜的总结合能为100或更高，也会发生细丝-膜的分离。它通过类似于固体中脆性裂纹的应力集中机制进行传播，断裂应力由类似于裂纹扩展的“格里菲斯”理论的准则确定。