Mechanical Properties of Type I Collagen: Insights From Molecular Dynamics Simulations

Abstract

Fibrous collagens are present in all mammalian species where they form the structural basis for connective tissue, including those in the heart, vasculature, skin, cornea, bones, and tendons. While the general features of the structure of type I collagen have been known for a long time, the specific packing arrangement of collagen molecules was identified only recently (Orgel et al., PNAS, 103:9001, 2006). Each collagen molecule is approximately 300 nm long and 1.5 nm in diameter. It is made up of three polypeptide chains, called alpha chains, each containing about 1000 amino acids. These alpha helices are twisted together into a right-handed triple helix, a cooperative quaternary structure presumably stabilized by inter-chain hydrogen bonding and other non-bonded interactions. The individual collagen molecules are then arranged to form a super twisted (discontinuous) right-handed microfibril that interdigitates with neighboring microfibrils. In order to better understand the nature of the intermolecular interactions in collagen at an atomic level, and to understand how observed mechanical properties of collagen emerge from these interactions, we have run a series of molecular dynamics simulations. Our calculations are the first set of atomistic simulations of individual collagen molecules. The data from the simulations provide valuable insights into the origin of the mechanical properties of collagen fibrils, that in some ways are different from those obtained using simulations and experiments of collagen analogues.