Date/Time
Date(s) - 29/10/2014
3:30 pm - 4:30 pm
Title: Collagen Fibrils and Plastic Damage
Speaker: Dr. Laurent Kreplak
Institute: Dalhousie University-Department of Physics and Atmospheric Science
Location: ABB 102
Description:
Collagen fibrils are the main constituent of connective tissues and the main load bearing element in tendons and ligaments. One of the open question in these tissues is how mechanical failure and plastic damage develop. One way of approaching this complex problem is to look at the failure modes and plastic deformation mechanisms at the single fibril level. To achieve this goal we combine atomic force microscopy (AFM) based nanomechanical testing of single fibrils extracted of damaged and undamaged tendons with tensile testing of single fibrils using AFM based micromanipulation. Using both techniques we have observed that broken and plastically deformed fibrils show discrete deformations in the form of kinks that have been reported previously [1] as well as a loss of lateral cohesion between the molecules within the fibrils. The loss of lateral cohesion does not affect the axial packing of the molecules and the fibrils retain their characteristic 67 nm banding pattern between kinks. We propose that the loss of lateral cohesion can be explained in term of a glass to rubber transition within the fibril. This idea is supported by nanomechanical testing of fibrils exposed to temperature close to the denaturation temperature of connective tissues, 65 degrees celsius [2]. If time permits I will also present a molecular model of collagen fibril radial architecture [3] that may be used as a framework to explain some of our experimental findings.
[1] Veres, SP, Lee JM, Designed to fail: a novel mode of collagen fibril disruption and its relevance to tissue toughness, Biophys J, 2012, 102:2876-84
[2] Baldwin, SJ, Quigley, AS, Clegg, C, Kreplak, L. Nanomechanical mapping of hydrated rat tail tendon collagen I fibrils, Biophys J, 2014, 107:1794-1801
[3] Brown, AI, Kreplak, L, Rutenberg, AD. An equilibrium double-twist model for the radial structure of collagen fibrils. Soft Matter, 2014, 10:8500-11