Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1596;
Institute for Computational Mechanics, Technical University of Munich, 80333 Munich, Germany.
Proc Natl Acad Sci U S A. 2021 Apr 13;118(15). doi: 10.1073/pnas.2024362118.
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.
僵硬的细丝束在生物世界中无处不在，存在于细胞骨架和细胞外基质中。这些束通常由较小的交联分子固定在一起。我们通过分析、数值模拟和实验证明，这样的束可以发生扭结，即存在具有长寿命亚稳态的局部高曲率区域。我们提出了三种可能的扭结稳定机制：两个交联之间的细丝段被困长度的差异、细丝端点出现在束内的位错以及束内细丝的编织。在交联浓度较高的情况下，后两种效应导致拓扑保护的扭结状态。最后，我们通过数值模拟和分析研究了亚稳态扭结状态到稳定直束的转变。
