STRUCTURE AND MECHANICS OF STRETCHED COLLAGEN FIBRILS

Abstract

Collagen fibril are the smallest repeating units in load-bearing collagenous tissues such as tendon and bone, functioning as a microscopic stress mediators in mammalian bodies. These fibrils are twisted self-assembled aggregates of triple-helical polypeptides, forming with a characteristic 67nm density striation known as the D-band. Although the stress-strain curve of individual collagen fibrils has been studied, changes in the fibrillar structure with strain have typically been investigated through tissue-level measurements using X-ray scattering. In this thesis I address the need to mechanically and structurally assess individual collagen fibrils under tension by capturing atomic force images of collagen fibrils adsorbed to an elastomeric film (PDMS), which is strained using a house-build stretching stage. Results from this experiment show that the fibrillar structure responds inhomogeneously to applied tension through tautening and sliding of its constituent polypeptides, restructuring mechanisms that have been suggested in previous studies but never directly observed.