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Trapping and Wiggling: Elastohydrodynamics of Driven Microfilaments
We present a general theoretical analysis of semiflexible filaments subject
to viscous drag or point forcing. These are the relevant forces in dynamic
experiments designed to measure biopolymer bending moduli. By analogy with the
``Stokes problems" in hydrodynamics (fluid motion induced by that of a wall
bounding a viscous fluid), we consider the motion of a polymer one end of which
is moved in an impulsive or oscillatory way. Analytical solutions for the
time-dependent shapes of such moving polymers are obtained within an analysis
applicable to small-amplitude deformations. In the case of oscillatory driving,
particular attention is paid to a characteristic length determined by the
frequency of oscillation, the polymer persistence length, and the viscous drag
coefficient. Experiments on actin filaments manipulated with optical traps
confirm the scaling law predicted by the analysis and provide a new technique
for measuring the elastic bending modulus. A re-analysis of several published
experiments on microtubules is also presented.Comment: RevTex, 24 pages, 15 eps figs, uses cite.sty, Biophysical
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