Steered Molecular Dynamics Study of Mechanical Response of Full Length and Short Collagen Molecules

Abstract

Collagen is a fibrous protein that is responsible for structural integrity of various connective tissues such as bone, tendon, and skin. The mechanical properties of these hierarchical tissue structures are greatly influenced by presence of long and slender (~300 long and ~1.5 nm in diameter) collagen molecules that impart strength and elasticity. The current molecular dynamics studies of collagen are limited to the use of short collagen molecules that are approximately 8.5 nm in length. This study investigates the mechanical behavior of the full-length collagen molecule and the short collagen by using steered molecular dynamics. The simulations were carried out at various loading conditions corresponding to different rates of pulling and springs of different stiffness were used to pull collagen molecules. The underlying mechanisms with respect to unfolding of collagen molecules differ significantly between short and full-length molecules when stretched in molecular dynamics simulations. These differences affect the mechanical properties of the short and full-length collagen molecules. In addition, the elastic modulus values are also affected by the pulling rate and the stiffness of the spring used by varying amounts for small and full-length collagen molecules. From this study, one may decipher the nuances of mechanical response of collagen in greater detail and recognize the similarities and differences in deformation mechanism of short and long collagen.