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| Poster, Friday, 19:00 |
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| Dynamics of Intermediate Filaments
Confined in Microchannels
Bernd Nöding, Sarah Köster
Institute for X-Ray Physics / Courant
Research Centre "Nano-Spectroscopy and X-Ray Imaging", Georg August University
of Göttingen, Germany |
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| Contact:
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The cytoskeleton of eukaryotes consists of three different polymer systems,
microtubules, actin filaments and intermediate filaments. While both microtubules
and actin filaments are highly conserved, intermediate filaments occur
in many different variations. The mechanical rigidity of any of these polymers
can be characterized by their persistence length LP.
In the case of the intermediate filament protein vimentin, LP
was found to be on the order of one micrometer using static measurement
methods. Here, we perform dynamic measurements on fluorescently labeled
intermediate filaments confined in microchannels, thereby realizing the
Odijk confinement regime. Since intermediate filaments can be classified
as semiflexible polymers (L ~ LP) we assume the
worm-like chain model for the fluctuation analysis. The channel walls are
included as a parabolic potential in our calculations. The interaction
of the filament and the confining microchannel gives rise to an additional
length scale, the deflection length lambda. We compare intermediate filament
data with literature data for actin, another semiflexible polymer. Thereby
we can vary both the channel width d and LP, which
together with lambda constitute the scaling law lambda = a d2/3
LP1/3. Here, a is a constant which
can be used to compare different experimental setups. Through this comparison
we find the scaling law fully confirmed. Additionally, our dynamic measurements
on vimentin filaments yield an improved value of two micrometers for LP.
The worm like-chain model in general assumes that movements in two perpendicular
planes decouple. Consequently the projection observed through the epi-fluorescence
microscope is expected to be independent of channel height. Filaments confined
in channels of the same width but different heights show identical behavior.
We therefore conclude that the motions in perpendicular planes indeed decouple
as predicted by the worm-like chain model.
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