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Abstract

Collagen, the most abundant protein in the human body, must withstand high mechanical loads due to its structural role in tendons, skin, bones, and other connective tissue. It was recently found that tensed collagen creates mechanoradicals by homolytic bond scission in the sub-failure regime. The locations and types 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 employ hybrid scale-bridging simulations to determine these first breakage points in collagen, combining existing and newly developed methods tailored towards collagen’s hierarchical structure. We improved our Kinetic Monte Carlo/Molecular Dynamics scheme to simulate bond scissions at the all-atom level, and also developed a mesoscopic ultra coarse-grained description of a collagen fibril. We find collagen crosslinks to rupture first, and identify individual sacrificial bonds in trivalent crosslinks that break preferentially, without compromising structural integrity. Collagen’s weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our simulations further suggest the length of helices between pairs of crosslinks to determine the trade-off between overall strength and breakage specificity. The combined results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing.