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Issue 2, 2013
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Microrheology of highly crosslinked microtubule networks is dominated by force-induced crosslinker unbinding

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Abstract

We determine the time- and force-dependent viscoelastic responses of reconstituted networks of microtubules that have been strongly crosslinked by biotin–streptavidin bonds. To measure the microscale viscoelasticity of such networks, we use a magnetic tweezers device to apply localized forces. At short time scales, the networks respond nonlinearly to applied force, with stiffening at small forces, followed by a reduction in the stiffening response at high forces, which we attribute to the force-induced unbinding of crosslinks. At long time scales, force-induced bond unbinding leads to local network rearrangement and significant bead creep. Interestingly, the network retains its elastic modulus even under conditions of significant plastic flow, suggesting that crosslinker breakage is balanced by the formation of new bonds. To better understand this effect, we developed a finite element model of such a stiff filament network with labile crosslinkers obeying force-dependent Bell model unbinding dynamics. The coexistence of dissipation, due to bond breakage, and the elastic recovery of the network is possible because each filament has many crosslinkers. Recovery can occur as long as a sufficient number of the original crosslinkers are preserved under the loading period. When these remaining original crosslinkers are broken, plastic flow results.

Graphical abstract: Microrheology of highly crosslinked microtubule networks is dominated by force-induced crosslinker unbinding

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Publication details

The article was received on 21 Aug 2012, accepted on 09 Oct 2012 and first published on 22 Oct 2012


Article type: Paper
DOI: 10.1039/C2SM26934A
Citation: Soft Matter, 2013,9, 383-393
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    Microrheology of highly crosslinked microtubule networks is dominated by force-induced crosslinker unbinding

    Y. Yang, M. Bai, W. S. Klug, A. J. Levine and M. T. Valentine, Soft Matter, 2013, 9, 383
    DOI: 10.1039/C2SM26934A

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