## Abstract

We report a systematic study of the linear rheology of solutions of model semiflexible polymers, actin filaments (F-actin), using mechanical rheometry, diffusing wave spectroscopy (DWS), and video-based single-particle tracking microrheology. For pure actin at c = 24 μM and after full polymerization, the elastic and loss moduli still increase with time as G′(t) ∞ t^{0.25±0.02} and G″(t) ∞ t^{0.15±0.03}, when measured at 1 rad/s, during network formation and reach a plateau after 12 h. At equilibrium, the linear small-frequency elastic modulus has a small magnitude, G′_{p} = 14 ± 3 dynes/cm^{2}. The magnitude of G′_{p} depends weakly on concentration as G′_{p}(c) ∞ c^{1.2±0.2}, with an exponent much smaller than for flexible polymers. At large concentrations, F-actin network becomes a liquid crystal and G′_{p} is independent of concentration. Using the large bandwidth of DWS, we show that the high-frequency viscoelastic modulus of F-actin solutions varies with the shear frequency as |G*(ω)| ∞ ω^{0.78±0.10} for both the isotropic phase and liquid crystalline phase. These results are in good agreement with a recent model of semiflexible polymer solutions (the "curvature-stress" model) and reflect the finite rigidity of F-actin.

Original language | English (US) |
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Pages (from-to) | 6486-6492 |

Number of pages | 7 |

Journal | Macromolecules |

Volume | 31 |

Issue number | 19 |

DOIs | |

State | Published - Sep 22 1998 |

## ASJC Scopus subject areas

- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry