(112f) Characterization of Actin-Based Motility on Patterned Substrata

The on-going goal of this project is to exploit in vitro actin-based motility to propel beads and other particles against diffusion gradients and opposing forces for potential use in microdevices. Nano- and micro-particles can be propelled by actin polymerization by filament end-tracking motors. These particle-bound protein complexes (consisting of ActA-VASP in our system) facilitate processive addition of monomers onto actin filament ends, thereby harnessing the energy of filament-bound ATP hydrolysis to propel particles. Our strategy for guiding the propulsion direction is to align the elongating actin filaments on surfaces by confining them to sub-regions of a substratum. To this end, microcontact printing was used to pattern glass substrata with stripes of filament-binding inactivated myosin, and the resulting effect on orientation of individual actin filaments was evaluated under different polymerization and surface conditions using total internal reflection fluorescence microscopy (TIRFM). We found that patterned substrata can guide the directional polymerization of individual actin filaments in a manner that depends on the surface density of myosin and the width and spacing of the patterned filament-binding stripes. Our interpretation of this finding is that filament thermal undulations allow the unbound elongating filament segments to sample the actin-binding substrata and thereby guide filament elongation along the edge of the actin-binding regions. This interpretation is supported by computational simulations of polymerizing filaments on patterned actin-binding substrata.