Rheology of Microtubule Solutions
Motivation
In eukaryotic cells, microtubules
form a network that guides active intracellular transport and supports the
overall cell structure. Microtubules also play an important role in the
organization of cell locomotion, morphogenesis, and reproduction. By studying
the mechanical properties of microtubules and trying to understand the length
scale dependence of the mechanical properties of the networks, we hope to
understand more about the mechanism of these fundamental cellular processes.
We study the microtubule networks in
vitro by using the multiple particle tracking technique and the conventional
rheometry.
Current projects
1. Previously, we have used the
multiparticle video tracking to observe the thermal motion of micron-sized
colloidal particles embedded in F-actin networks. We are using the same method
to examine the dynamics of probe particles in microtubule networks.
Confocal microscopy of
microtubule networks. Colloidal
particles embedded in microtubule networks.
2. We are also exploring the rheology
of microtubule networks by using the conventional rheometry. For F-action networks, we found good agreement between the two particle
microrheology and bulk rheology, while one particle microrheology is affected
by the local properties of the material.
However, in microtubule networks,
which have a larger mesh size and distance between entanglements than actin
networks, we can not see this behavior. We are
trying to figure out what causes this discrepancy.
The microscopic structure of the microtubules
network can be revealed through measurements of nonlinear rheological
responses. We measure the yield strain of microtubule networks in different
concentrations and temperatures so that we can get the mesh size and filament
length dependence.
3. We are also studying the reptation for
microtubule filaments. The direct observation of reptation is obtained by video
microscopy of fluorescently labeled single filaments in a solution of
unlabelled microtubule filaments. We hope to observe the characteristic
thermally excited sliding of the filament out of the end of the tube. The
translational and rotational diffusion coefficients are then able to be
measured.
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Department of Physics
Mckay Laboratory,