Atomistic and continuum modeling of mechanical properties of collagen: Elasticity, fracture, and self-assembly

We report studies of the mechanical properties of tropocollagen molecules under different types of mechanical loading including tension, compression, shear, and bending. Our modeling yields predictions of the fracture strength of single tropocollagen molecules and polypeptides, and also allows for quantification of the interactions between tropocollagen molecules. Atomistic modeling predicts a persistence length of tropocollagen molecules ξ ≈ 23.4 nm, close to experimental measurements. Our studies suggest that to describe large-strain or hyperelastic properties, it is critical to include a correct description of the bond behavior and breaking processes at large bond stretch, information that stems from the quantum chemical details of bonding. We use full atomistic calculations to derive parameters for a mesoscopic bead-spring model of tropocollagen molecules. We demonstrate that the mesoscopic model enables one to study the finite temperature, long-time scale behavior of tropocollagen fibers, illustrating the dynamics of solvated tropocollagen molecules for different molecular lengths.