Bundles of stiff filaments are ubiquitous in the living world, found both in the cytoskeleton and in the extracellular medium. These bundles are typically held together by smaller cross-linking molecules. We demonstrate, analytically, numerically, and experimentally, that such bundles can be kinked, that is, have localized regions of high curvature that are long-lived metastable states. We propose three possible mechanisms of kink stabilization: a difference in trapped length of the filament segments between two cross-links, a dislocation where the endpoint of a filament occurs within the bundle, and the braiding of the filaments in the bundle. At a high concentration of cross-links, the last two effects lead to the topologically protected kinked states. Finally, we explore, numerically and analytically, the transition of the metastable kinked state to the stable straight bundle.

硬丝束在生物世界中无处不在，在细胞骨架和细胞外介质中均有发现。这些束通常由较小的交联分子固定在一起。我们通过分析、数值和实验证明，这种束可以扭结，即具有高曲率的局部区域，这些区域是长期存在的亚稳态。我们提出了三种可能的扭结稳定机制：两个交联之间长丝段的捕获长度的差异、长丝端点发生在束内的错位以及束中长丝的编织。在高浓度交联时，后两种效应导致拓扑保护的扭结状态。最后，我们探索，数值和分析，