Collagen's Triple Helix Reduces the Susceptibility to Base-Catalyzed Hydrolysis.

Collagen is the most abundant structural protein in mammals. As the primary component of tendons, ligaments, and other connective tissues, it has to withstand extreme forces. Base-catalyzed peptide hydrolysis was recently shown to be greatly accelerated by mechanical force. This puts collagen at risk of degradation under physiological loads, yet collagen is known to be remarkably stable. Using hybrid quantum mechanics/molecular mechanics (QM/MM) simulations, we investigated the hydrolysis reaction within the complex chemical environment of a collagen triple helix. We demonstrate that the unique triple-helical structure increases the reaction barrier for base-catalyzed hydrolysis compared to a single peptide chain. Our results can explain why collagen mechanical failure proceeds through homolytic bond rupture and mechanoradical formation.