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
Engineering Village 2
? 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


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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