Narrow Results

Thermal fluctuations of individual actin filaments confined in rectangular microchannels with dimensions similar to the mesh size of the cytoskeleton in eukaryotic cells are studied experimentally using fluorescence microscopy and theoretically by a combination of analytical methods and Monte Carlo simulations. Compared to freely fluctuating filaments, long filaments confined in narrow channels exhibit enhanced tangent correlations and a characteristic shape of their correlation function. The tangent correlation function is calculated analytically by approximating the confining geometry by a parabolic potential. This approximation is validated by Monte Carlo simulations. For the quantitative analysis of experimental data additional corrections for image analysis effects have to be included, for which we provide a modified analytical approximation formula which is corroborated by simulations. This allows us to obtain both the persistence length L_P describing the bending rigidity of the polymer and the deflection length λ characterizing confinement effects from fits to the experimental data. Our results confirm the scaling relation λ ∝ d^2/3 between the deflection length and the channel width d.