Brownian motion of actin filaments in confining microchannels

Abstract

Since the cytoskeletal protein actin is one of the principal building blocks of mammaliancells, it has recently been arousing much interest. Here, we address questionsconcerning the mechanical and dynamic behaviour of individual actin filaments inconfining geometries which mimic the dense cytoskeletal network in eukaryotic cells.Microfluidic devices fabricated by soft photolithography in combination withfluorescence microscopy are used to manipulate, observe and characterize thesebiopolymers. The polymer statistics is strongly dependent on the characteristics ofthe surroundings such as the degree of confinement and hydrodynamical flow.Besides this, the intrinsic mechanical properties of the filaments are dominated bythe persistence length and the contour length. We analyse the tangent–tangentcorrelation and the radial distribution function in terms of a confining potential andthe contour length of the filaments. In addition, we show that hydrodynamicflow can be successfully used to apply controlled local stress on actin filaments.Our results can be surprisingly well described by a straightforward model whichapproximates the confining energy of the microchannels using a parabolic potential.