In this study, we report a computational investigation on how the mechanochemical characteristics of crosslinking molecules influence the viscoelasticity of three dimensional F-actin networks, an issue of key interest in analyzing the behavior of living cells and biological gels. In particular, it was found that the continuous breakage and rebinding of cross-linkers result in a locally peaked loss modulus in the rheology spectrum of the network, reflecting the fact that maximum energy dissipation is achieved when the driving frequency of the applied oscillating shear becomes comparable to the dissociation/association rate of crosslinking molecules. In addition, we showed that when subjected to constant rate of shear, an actin network can exhibit either strain hardening or softening depending on the ratio between the loading rate and unbinding speed of cross-linkers. A criterion for predicting the transition from softening to hardening was also obtained, in agreement with recent experiments. Finally, significant structural evolution was found to occur in random networks undergoing mechanical “training” (i.e. under a constant applied shear stress over a period of time), eventually leading to a pronounced anisotropic response of the network afterward which again is consistent with experimental observations.

中文翻译：

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由交联剂的机械化学特性决定的 3D 肌动蛋白网络的粘弹性

在这项研究中，我们报告了关于交联分子的机械化学特性如何影响三维 F-肌动蛋白网络的粘弹性的计算研究，这是分析活细胞和生物凝胶行为的关键问题。特别是，发现交联剂的连续断裂和重新结合导致网络流变谱中的局部峰值损耗模量，反映了当施加的振荡剪切的驱动频率变为最大时实现最大能量耗散的事实与交联分子的解离/缔合速率相当。此外，我们表明，当受到恒定剪切速率时，肌动蛋白网络可以表现出应变硬化或软化，这取决于交联剂的加载速率和解结合速度之间的比率。与最近的实验一致，还获得了预测从软化到硬化的转变的标准。最后，在接受机械“训练”的随机网络中发现了显着的结构演化（即在一段时间内施加恒定的剪切应力下），最终导致网络出现明显的各向异性响应，这再次与实验观察一致。