Fluctuations of the semi-flexible polymers dissolved in a nematic phase
We study the fluctuations of semi-flexible polymers dissolved in a nematic liquid crystal. A
coil to rod transition of polymers with persistence length larger then 0.2 µm is observed by changing the background
phase from isotropic to nematic. Using image analysis it is possible to measure the orientational distribution function.
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Fluorescently labeled actin filaments fluctuating in a invisible nematic background. By analyzing these
fluctuations we can show that at long wavelengths, the fluctuations of the polymers are driven by tight coupling to the nematic
filed that is itself fluctuating. This has been predicted theoretically by Randy Kamien and David Nelson. In addition we directly observe the
existence of hairpin defects where the direction of the polymer rapidly changes by 180 degrees. Our recent results on this subject are
summarized in the following paper.
Images of fluoresecently labeled biopolymers in the isotropic and
nematic phase of fd virus
in the left and right column respectively. The persistence length (Lp) of these polymers varies from
0.05 µm to 16 µm. Figures a to d are images of DNA (Lp=0.05 µm), neurofilaments
(Lp=0.2 µm), wormlike micelles (Lp=0.5 µm) and actin (Lp=
16 µm) respectively. Part e shows a sequence of images illustrating an escape of an actin filament from a
hairpin defect. Scale bar is 5 µm.
Z. Dogic, J. Zhang, A. W. C. Lau, P. Dalhaimer, H. Aranda-Espinoza, D. Disher, P. Janmey, T. C
Lubensky and A. G. Yodh, , submitted to Phys. Rev. Lett.