The ultrastructure of fibronectin fibers pulled from a protein monolayer at the air-liquid interface and the mechanism of the sheet-to-fiber transition
OPEN ACCESS
Loading...
Author / Producer
Date
2015-01
Publication Type
Journal Article
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Abstract
Fibronectin is a globular protein that circulates in the blood and undergoes fibrillogenesis if stretched or under other partially denaturing conditions, even in the absence of cells. Stretch assays made by pulling fibers from droplets of solutions containing high concentrations of fibronectin have previously been introduced in mechanobiology, particularly to ask how bacteria and cells exploit the stretching of fibronectin fibers within extracellular matrix to mechano-regulate its chemical display. Our electron microscopy analysis of their ultrastructure now reveals that the manually pulled fibronectin fibers are composed of densely packed lamellar spirals, whose interlamellar distances are dictated by ion-tunable electrostatic interactions. Our findings suggest that fibrillogenesis proceeds via an irreversible sheet-to-fiber transition as the fibronectin sheet formed at the air-liquid interface of the droplet is pulled off by a sharp tip. This far from equilibrium process is driven by the externally applied force, interfacial surface tension, shear-induced fibronectin self-association, and capillary force-induced buffer drainage. The ultrastructural characterization is then contrasted with previous FRET studies that characterized the molecular strain within these manually pulled fibers. Particularly relevant for stretch-dependent binding studies is the finding that the interior fiber surfaces are accessible to nanoparticles smaller than 10 nm. In summary, our study discovers the underpinning mechanism by which highly hierarchically structured fibers can be generated with unique mechanical and mechano-chemical properties, a concept that might be extended to other bio- or biomimetic polymers.
Permanent link
Publication status
published
Editor
Book title
Journal / series
Volume
36
Pages / Article No.
66 - 79
Publisher
Elsevier
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Fibronectin; Fibrillogenesis; Sheet-to-fiber transition; Monolayer-to-lamella transition; Electron microscopy; Kinetically trapped supramolecular system
Organisational unit
03640 - Vogel, Viola (emeritus) / Vogel, Viola (emeritus)
Notes
Funding
133122 - Towards simulating a cell adhesion site at angstrom resolution (SNF)