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Entropic Elasticity Controls Nanomechanics of Single Tropocollagen Molecules

Published online by Cambridge University Press:  26 February 2011

Markus J. Buehler  and
Sophie Wong
Markus J. Buehler
Affiliation:
mbuehler@MIT.EDU, MIT, Civil and Environmental Engrg, 77 Mass Ave, Cambridge, MA, 02139, United States, mbuehler@MIT.EDU
Sophie Wong
Affiliation:
slokwong@MIT.EDU, Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 77 Massachusetts Ave., Cambridge, MA, 02139, United States
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Abstract

We report molecular modeling of stretching single molecules of tropocollagen, the building block of collagen fibrils and fibers that provide mechanical support in connective tissues. For small deformation, we observe a dominance of entropic elasticity. At larger deformation, we find a transition to energetic elasticity, which is characterized by first stretching and breaking of hydrogen bonds, followed by deformation of covalent bonds in the protein backbone, eventually leading to molecular fracture. Our force-displacement curves show excellent quantitative agreement with optical tweezer experiments, suggesting a persistence length of approximately 16 nm. We demonstrate that assembly of single TC molecules into fibrils significantly decreases their flexibility, leading to decreased contributions of entropic effects during deformation. We develop a simple continuum model capable of describing entire deformation range of TC molecules.

Keywords

biologicalelastic propertiesfracture
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 975: Symposium DD – Mechanics of Biological and Bio-Inspired Materials , 2006 , 0975-DD02-04
Copyright
Copyright © Materials Research Society 2007

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