Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany.
Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany.
Nat Commun. 2023 Apr 12;14(1):2075. doi: 10.1038/s41467-023-37726-z.
Collagen is a force-bearing, hierarchical structural protein important to all connective tissue. In tendon collagen, high load even below macroscopic failure level creates mechanoradicals by homolytic bond scission, similar to polymers. The location and type of initial rupture sites critically decide on both the mechanical and chemical impact of these micro-ruptures on the tissue, but are yet to be explored. We here use scale-bridging simulations supported by gel electrophoresis and mass spectrometry to determine breakage points in collagen. We find collagen crosslinks, as opposed to the backbone, to harbor the weakest bonds, with one particular bond in trivalent crosslinks as the most dominant rupture site. We identify this bond as sacrificial, rupturing prior to other bonds while maintaining the material's integrity. Also, collagen's weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing.
胶原蛋白是一种承重的、层次结构的蛋白质，对所有结缔组织都很重要。在肌腱胶原中，即使在宏观失效水平以下，高负荷也会通过均裂键断裂产生机械自由基，类似于聚合物。初始断裂部位的位置和类型对这些微断裂对组织的机械和化学影响至关重要，但尚未得到探索。我们在这里使用凝胶电泳和质谱支持的跨尺度模拟来确定胶原蛋白中的断裂点。我们发现，交联键而不是骨干，具有最薄弱的键，三价交联中的一个特定键是最主要的断裂部位。我们将该键确定为牺牲键，在其他键断裂之前断裂，同时保持材料的完整性。此外，胶原蛋白的弱键使断裂集中，从而使潜在有害的机械自由基很容易得到稳定。我们的结果表明，胶原蛋白的这种独特的失效模式是为了对抗宏观失效和材料老化的早期发生而量身定制的。
