Microrheology of Microtubule Solutions and Actin-Microtubule Composite Networks
Microrheology of Microtubule Solutions and Actin-Microtubule Composite Networks, Vincent Pelletier, Naama Gal, Paul Fournier and Maria Kilfoil, PRL vol.102 188303 (2009) 
Original Abstract from Paper
"We perform local or microrheological measurements on microtubule solutions, as well as composite networks. The viscoelastic properties of microtubules as reported from two-point microrheology agree with the macroscopic measurement at high frequencies, but appear to show a discrepancy at low frequencies, at time scales on the order of a second. A composite of ﬁlamentous actin (F-actin) and microtubules has viscoelastic behavior between that of F-actin and pure microtubules. We further show that the Poisson ratio of the composite, measured by the length-scale dependent two-point microrheology, is robustly smaller than that of the F-actin network at time scale <math>\tau</math> > 1 s, suggesting that a local compressibility is conferred by the addition of microtubules to the F-actin network."