An equilibrium double-twist model for the radial structure of collagen fibrils

Aidan I. Brown, Laurent Kreplak, Andrew D. Rutenberg

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)

Abstract

Mammalian tissues contain networks and ordered arrays of collagen fibrils originating from the periodic self-assembly of helical 300 nm long tropocollagen complexes. The fibril radius is typically between 25 to 250 nm, and tropocollagen at the surface appears to exhibit a characteristic twist-angle with respect to the fibril axis. Similar fibril radii and twist-angles at the surface are observed in vitro, suggesting that these features are controlled by a similar self-assembly process. In this work, we propose a physical mechanism of equilibrium radius control for collagen fibrils based on a radially varying double-twist alignment of tropocollagen within a collagen fibril. The free-energy of alignment is similar to that of liquid crystalline blue phases, and we employ an analytic Euler-Lagrange and numerical free energy minimization to determine the twist-angle between the molecular axis and the fibril axis along the radial direction. Competition between the different elastic energy components, together with a surface energy, determines the equilibrium radius and twist-angle at the fibril surface. A simplified model with a twist-angle that is linear with radius is a reasonable approximation in some parameter regimes, and explains a power-law dependence of radius and twist-angle at the surface as parameters are varied. Fibril radius and twist-angle at the surface corresponding to an equilibrium free-energy minimum are consistent with existing experimental measurements of collagen fibrils. Remarkably, in the experimental regime, all of our model parameters are important for controlling equilibrium structural parameters of collagen fibrils. This journal is

Original languageEnglish
Pages (from-to)8500-8511
Number of pages12
JournalSoft Matter
Volume10
Issue number42
DOIs
Publication statusPublished - Nov 14 2014

Bibliographical note

Publisher Copyright:
© the Partner Organisations 2014.

ASJC Scopus Subject Areas

  • General Chemistry
  • Condensed Matter Physics

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't

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