The interplay between viscoelastic and thermodynamic properties determines the birefringence of F-actin gels
The interplay between viscoelastic and thermodynamic properties determines the birefringence of F-actin gels
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? 2006 Elsevier Inc
Accession number: 8599994
Title: The interplay between viscoelastic and thermodynamic properties determines the birefringence of F-actin gels
Authors: Helfer, E.1 ; Panine, P.; Carlier, M.-F.; Davidson, P.
Author affiliation: 1 Dynamique du Cytosquelette, CNRS, Gif-sur-Yvette, France
Serial title: Biophysical Journal
Abbreviated serial title: Biophys. J. (USA)
Volume: 89
Issue: 1
Publication date: July 2005
Pages: 543-53
Language: English
ISSN: 0006-3495
CODEN: BIOJAU
Document type: Journal article (JA)
Publisher: Biophys. Soc
Country of publication: USA
Material Identity Number: B154-2005-008
Abstract: F-actin gels of increasing concentrations (25-300 ?M) display in vitro a progressive onset of birefringence due to orientational ordering of actin filaments. At F-actin concentrations <100 ?M, this birefringence can be erased and restored at will by sonication and gentle flow, respectively. Hence, the orientational ordering does not result from a thermodynamic transition to a nematic phase but instead is due to mechanical stresses stored in the gels. In contrast, at F-actin concentrations ⩾100 ?M, gels display spontaneous birefringence recovery, at rest, which is the sign of true nematic ordering, in good agreement with statistical physics models of the isotropic/nematic transition. Well-aligned samples of F-actin gels could be produced and their small-angle X-ray scattering patterns are quite anisotropic. These patterns show no sign of filament positional short-range order and could be modeled by averaging the form factor with the Maier-Saupe nematic distribution function. The derived nematic order parameter S of the gels ranged from S = 0.7 at 300 ?M to S = 0.4 at 25 ?M. Both birefringence and small-angle X-ray scattering data indicate that, even in absence of cross-linking proteins, spontaneous cooperative alignment of actin filaments may arise in motile regions of living cells where F-actin concentrations can reach values of a few 100 ?M
Number of references: 54
Inspec controlled terms: biomechanics - birefringence - cell motility - gels - proteins - thermodynamic properties - viscoelasticity - X-ray scattering
Uncontrolled terms: viscoelastic properties - thermodynamic properties - birefringence - F-actin gels - sonication - gentle flow - orientational ordering - thermodynamic transition - mechanical stresses - isotropic/nematic transition - small-angle X-ray scattering - Maier-Saupe nematic distribution function - cross-linking proteins - living cells
Inspec classification codes: A8745 Biomechanics, biorheology, biological fluid dynamics - A8715B Biomolecular structure, configuration, conformation, and active sites - A8725D Biological transport; cellular and subcellular transmembrane physics - A8270G Gels and sols - A3345 Magneto-optical and electro-optical effects in molecules; birefringence, dichroism and optical activity - A0570F Phase transitions: general thermodynamic aspects
Treatment: Experimental (EXP)
Discipline: Physics (A)
DOI: 10.1529/biophysj.104.050245
Database: Inspec
Copyright 2005, IEE
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