Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin, (LJP), F-75005 Paris, France.
Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, CY Cergy Paris, Université, F-95302 Cergy-Pontoise Cedex, France.
Soft Matter. 2022 May 18;18(19):3793-3800. doi: 10.1039/d2sm00130f.
Active gels made of cytoskeletal proteins are valuable materials with attractive non-equilibrium properties such as spatial self-organization and self-propulsion. At least four typical routes to spatial patterning have been reported to date in different types of cytoskeletal active gels: bending and buckling instabilities in extensile systems, and global and local contraction instabilities in contractile gels. Here we report the observation of these four instabilities in a single type of active gel and we show that they are controlled by two parameters: the concentrations of ATP and depletion agent. We demonstrate that as the ATP concentration decreases, the concentration of passive motors increases until the gel undergoes a gelation transition. At this point, buckling is selected against bending, while global contraction is favored over local ones. Our observations are coherent with a hydrodynamic model of a viscoelastic active gel where the filaments are crosslinked with a characteristic time that diverges as the ATP concentration decreases. Our work thus provides a unified view of spatial instabilities in cytoskeletal active matter.
由细胞骨架蛋白组成的活性凝胶是具有吸引力的非平衡性质的有价值材料，例如空间自组织和自推进。迄今为止，已经在不同类型的细胞骨架活性凝胶中报道了至少四种典型的空间图案形成途径：伸展系统中的弯曲和屈曲不稳定性，以及收缩性凝胶中的全局和局部收缩不稳定性。在这里，我们在一种单一类型的活性凝胶中观察到了这四种不稳定性，并表明它们由两个参数控制：ATP 和耗竭剂的浓度。我们证明，随着 ATP 浓度的降低，被动马达的浓度增加，直到凝胶经历胶凝转变。此时，弯曲被压弯，而全局收缩则优于局部收缩。我们的观察结果与粘弹性活性凝胶的流体动力学模型一致，其中纤维通过具有特征时间的交联，随着 ATP 浓度的降低而发散。因此，我们的工作为细胞骨架活性物质中的空间不稳定性提供了统一的观点。
