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Crosslinked actin networks show liquid crystal elastomer behaviour, including soft-mode elasticity

Nature Physics volume 3, pages 354–360 (2007)Cite this article

Abstract

Actin filament networks with protein crosslinks of distinct length and flexibility resemble liquid crystal elastomers. We simulate actin filament systems with flexible crosslinkers of varying length and connectivity to understand general phase behaviour and elasticity. Simulated networks with very short filaments and long crosslinkers resemble the cytoskeleton of the red blood cell and remain isotropic in compression and shear, seeming well-suited to blood flow. In contrast, networks with longer filaments as found in many cell types show three regimes of nematic phase behaviour dependent on crosslinker length: (1) ‘loose’ networks are isotropic at zero stress but align under compression or shear; (2) ‘semi-loose’ networks are nematic at low stress but become isotropic under dilation and (3) ‘tight’ networks possess a locked-in nematic order as represented by the cytoskeleton of the outer hair cell in the ear, for which anisotropic compliance directs sound propagation. Furthermore, for a subset of loose networks with ‘periodic’ connections among filaments, extremely soft stress–strain behaviour is found, as predicted for liquid crystal elastomers.

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Figure 1: Prototypical membrane cytoskeletons with crosslinked actin filaments.
Figure 2: Density-dependent phase behaviour for loose networks and uncrosslinked fluids as a function of Lactin/Dactin with Lactin/LX<χloose.
Figure 3: Phase diagram with shear for loose networks (Lactin/LX<χloose).
Figure 4: Effects of LX on networks with Lactin/Dactin>η.
Figure 5: The nature of network crosslinking plays a key role in response to shear.

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Acknowledgements

Support from Penn’s NSF-MRSEC and from NIH and NSF grants is gratefully acknowledged.

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Authors and Affiliations

  1. Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA

    Paul Dalhaimer

  2. Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6391, USA

    Paul Dalhaimer & Dennis E. Discher

  3. Physics and Astronomy Graduate Group, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396, USA

    Dennis E. Discher & Tom C. Lubensky

  4. Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6202, USA

    Dennis E. Discher & Tom C. Lubensky

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  1. Paul Dalhaimer
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  2. Dennis E. Discher
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Contributions

P.D., D.E.D. and T.C.L. designed the research problem and wrote the manuscript; P.D. wrote and conducted the simulations.

Corresponding authors

Correspondence to Dennis E. Discher or Tom C. Lubensky.

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The authors declare no competing financial interests.

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Dalhaimer, P., Discher, D. & Lubensky, T. Crosslinked actin networks show liquid crystal elastomer behaviour, including soft-mode elasticity. Nature Phys 3, 354–360 (2007). https://doi.org/10.1038/nphys567

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