Characterization of actin-based motility on modified surfaces for in vitro applications in nanodevices

The cytoskeletal protein actin generates forces for various processes by polymerizing into filaments. In vivo, actin works with the motor protein myosin to produce muscle contractions and with proteins acting as end-tracking motors responsible for cell and bacterial motility, such as the motility of Listeria monocytogenes. End-tracking proteins bind the polymerizing end of an actin filament to a motile surface, creating persistent attachment during filament elongation. Both types of motors use the energy from ATP hydrolysis and can be exploited in vitro in bionanodevices, which require forces to transport objects on a micro- or nano-scale, possibly against flow or diffusion gradients.; Our study has focused on the guidance of single-filament elongation and filament bundles (rocket tails) to orient elongation in vitro. Microcontact printing, a technique that stamps protein patterns onto glass surfaces through adsorption, was used to create filament-binding tracks of modified myosin (void of its motor activity), which successfully bound and guided single actin filament elongation in a manner dependent on track width and surface conditions. These results confirm the capability of this method to be used for the motility of objects attached to single actin filaments and for the creation of immobilized tracks of actin filaments for myosin-mediated transport. Simulations were used to characterize the system further and have the ability to help make predictions for other types of filaments and systems.; Modified myosin surfaces also confined actin rocket tails attached to particles and bacteria, reducing the Brownian motion of the motile objects. Channels formed through photolithographic techniques on glass surfaces were used to attempt to guide these particles. Single actin filaments attached to smaller particles were also characterized to determine the potential for single-filament propulsion in nanodevices. We conclude that actin filament-binding proteins can be applied to surfaces using adsorption and microcontact printing and that this technique is effective in binding and guiding filaments in various systems, including single and bundled filaments. We predict this technique can be applied to other systems undergoing actin-based motility, making it a versatile method for bionanotechnology.