Computational Analysis of Viscoelastic Properties of Crosslinked Actin Networks
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Author(s)
Lee, Hyungsuk
Hwang, Wonmuk
Kamm, Roger Dale
Kim, Taeyoon
Alternative Title
Computational Analysis of a Cross-linked Actin-like Network
Date Issued
February 2009
Journal
Experimental Mechanics
Publisher
Springer Boston
Citation
T. Kim, W. Hwang, and R. Kamm, “Computational Analysis of a Cross-linked Actin-like Network,” Experimental Mechanics, vol. 49, Feb. 2009, pp. 91-104.
Version
Author's final manuscript
Abstract
Mechanical force plays an important role in the physiology of eukaryotic cells
whose dominant structural constituent is the actin cytoskeleton composed mainly of actin and actin crosslinking proteins (ACPs). Thus, knowledge of rheological properties of actin networks is crucial for understanding the mechanics and processes of cells. We used Brownian dynamics simulations to study the viscoelasticity of crosslinked actin networks.
Two methods were employed, bulk rheology and segment-tracking rheology where the
former measures the stress in response to an applied shear strain, and the latter analyzes thermal fluctuations of individual actin segments of the network. Bulk rheology demonstrates that the storage shear modulus (G’) increases more by the addition of ACPs that form orthogonal crosslinks than for those that form parallel bundles. In networks with
orthogonal crosslinks, as crosslink density increases, the power law exponent of G’ as a function of the oscillation frequency decreases from 0.75, which reflects the transverse thermal motion of actin filaments, to near zero at low frequency. Under increasing prestrain, the network becomes more elastic, and three regimes of behavior are observed, each dominated by different mechanisms: bending of actin filaments, bending of ACPs, and
at the highest prestrain tested (55%), stretching of actin filaments and ACPs. In the last case, only a small portion of actin filaments connected via highly stressed ACPs support the strain. We thus introduce the concept of a ‘supportive framework,’ as a subset of the full network, which is responsible for high elasticity. Notably, entropic effects due to thermal fluctuations appear to be important only at relatively low prestrains and when the average crosslinking distance is comparable to or greater than the persistence length of the
filament. Taken together, our results suggest that viscoelasticity of the actin network is attributable to different mechanisms depending on the amount of prestrain.
MIT Department
Massachusetts Institute of Technology. Department of Biological Engineering
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1007/s11340-007-9091-3
