### Abstract

We study the short-time relaxation dynamics of crosslinked and uncrosslinked networks of semi-flexible polymers using diffusing wave spectroscopy (DWS). The networks consist of concentrated solutions of actin filaments, crosslinked with increasing amounts of α-actinin. Actin filaments (F-actin) are long semi-flexible polymers with a contour length 1-100 μm and a persistence length of 5-15 μm; α-actinin is a small 200 kDa homodimer with two actin-binding sites. Using the large bandwidth of DWS, we measure the mean-square-displacement of 0.96 μm diameter microspheres imbedded in the polymer network, from which we extract the frequency-dependent viscoelastic moduli via a generalized Langevin equation. DWS measurements yield, in a single measurement, viscoelastic moduli at frequencies up to 10^{5} Hz, almost three decades higher in frequency than probed by conventional mechanical rheology. Our measurements show that the magnitude of the small-frequency plateau modulus of F-actin is greatly enhanced in the presence of α-actinin, and that the frequency dependence of the viscoelastic moduli is much stronger at intermediate frequencies. However, the frequency-dependence of loss and storage moduli become similar for both crosslinked and uncrosslinked networks at large frequencies, G′(ω) ∝ G″(ω) ∝ ω^{0.75±0.08}. This high-frequency behavior is due to the small-amplitude, large-frequency lateral fluctuations of actin filaments between entanglements.

Original language | English (US) |
---|---|

Pages (from-to) | 97-106 |

Number of pages | 10 |

Journal | Rheologica Acta |

Volume | 37 |

Issue number | 2 |

State | Published - Apr 1998 |

### Fingerprint

### Keywords

- α-actinin
- Actin
- Diffusing wave spectroscopy
- Semi flexible polymer

### ASJC Scopus subject areas

- Computational Mechanics
- Mechanics of Materials

### Cite this

*Rheologica Acta*,

*37*(2), 97-106.

**High-frequency viscoelasticity of crosslinked actin filament networks measured by diffusing wave spectroscopy.** / Palmer, Andre; Xu, Jingyuan; Wirtz, Denis.

Research output: Contribution to journal › Article

*Rheologica Acta*, vol. 37, no. 2, pp. 97-106.

}

TY - JOUR

T1 - High-frequency viscoelasticity of crosslinked actin filament networks measured by diffusing wave spectroscopy

AU - Palmer, Andre

AU - Xu, Jingyuan

AU - Wirtz, Denis

PY - 1998/4

Y1 - 1998/4

N2 - We study the short-time relaxation dynamics of crosslinked and uncrosslinked networks of semi-flexible polymers using diffusing wave spectroscopy (DWS). The networks consist of concentrated solutions of actin filaments, crosslinked with increasing amounts of α-actinin. Actin filaments (F-actin) are long semi-flexible polymers with a contour length 1-100 μm and a persistence length of 5-15 μm; α-actinin is a small 200 kDa homodimer with two actin-binding sites. Using the large bandwidth of DWS, we measure the mean-square-displacement of 0.96 μm diameter microspheres imbedded in the polymer network, from which we extract the frequency-dependent viscoelastic moduli via a generalized Langevin equation. DWS measurements yield, in a single measurement, viscoelastic moduli at frequencies up to 105 Hz, almost three decades higher in frequency than probed by conventional mechanical rheology. Our measurements show that the magnitude of the small-frequency plateau modulus of F-actin is greatly enhanced in the presence of α-actinin, and that the frequency dependence of the viscoelastic moduli is much stronger at intermediate frequencies. However, the frequency-dependence of loss and storage moduli become similar for both crosslinked and uncrosslinked networks at large frequencies, G′(ω) ∝ G″(ω) ∝ ω0.75±0.08. This high-frequency behavior is due to the small-amplitude, large-frequency lateral fluctuations of actin filaments between entanglements.

AB - We study the short-time relaxation dynamics of crosslinked and uncrosslinked networks of semi-flexible polymers using diffusing wave spectroscopy (DWS). The networks consist of concentrated solutions of actin filaments, crosslinked with increasing amounts of α-actinin. Actin filaments (F-actin) are long semi-flexible polymers with a contour length 1-100 μm and a persistence length of 5-15 μm; α-actinin is a small 200 kDa homodimer with two actin-binding sites. Using the large bandwidth of DWS, we measure the mean-square-displacement of 0.96 μm diameter microspheres imbedded in the polymer network, from which we extract the frequency-dependent viscoelastic moduli via a generalized Langevin equation. DWS measurements yield, in a single measurement, viscoelastic moduli at frequencies up to 105 Hz, almost three decades higher in frequency than probed by conventional mechanical rheology. Our measurements show that the magnitude of the small-frequency plateau modulus of F-actin is greatly enhanced in the presence of α-actinin, and that the frequency dependence of the viscoelastic moduli is much stronger at intermediate frequencies. However, the frequency-dependence of loss and storage moduli become similar for both crosslinked and uncrosslinked networks at large frequencies, G′(ω) ∝ G″(ω) ∝ ω0.75±0.08. This high-frequency behavior is due to the small-amplitude, large-frequency lateral fluctuations of actin filaments between entanglements.

KW - α-actinin

KW - Actin

KW - Diffusing wave spectroscopy

KW - Semi flexible polymer

UR - http://www.scopus.com/inward/record.url?scp=0002362584&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0002362584&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0002362584

VL - 37

SP - 97

EP - 106

JO - Rheologica Acta

JF - Rheologica Acta

SN - 0035-4511

IS - 2

ER -