Abstract
Motor proteins associate with filaments of the cellular cytoskeleton to
generate directed forces. These interactions have been studied
extensively in vitro. Here we present measurements on beads engulfed
into living cells, where near the cell center the bead performs a
direction-less wandering motion due to collective activity of
microtubule-associated motors. This driven diffusion shows anomalous
scaling in the mean square displacement, where ~ t^3/2 on
short time scales accessible by video-based measurement techniques, and
~ t^1/2 on longer time scales. These exponents can be
explained in terms of a time-dependent friction, or a generalized
Einstein relation, that links them as well to the t^3/4 monomer
diffusion scaling observed in semi-flexible polymer networks. As the
passive movement is sub-diffusive, the driven movement is sub-ballistic
in the non-Newtonian environment. In order to access shorter time
scales, we developed and apply an optical force correlation spectroscopy
based on two-photon fluorescence excitation of the probe bead.
| Original language | English |
|---|---|
| Title of host publication | American Physical Society, Annual March Meeting, March 12 - 16, 2001 Washington State Convention Center Seattle, Washington |
| State | Published - 1 Mar 2001 |
| Externally published | Yes |