| Cells have evolved molecular machinery for active transport and assembly processes that enable the building of protein and biochemical complexes. These complexes regulate cellular functions that cannot be carried out by single proteins or molecules: sensing and signaling, secretion of biochemicals, structural reorganization, coordinated movement for cell motility. A promising area of nanotechnology seeks to emulate nature by integrating these highly-controlled, active transport cellular processes into synthetic environments to enhance the performance and sophistication of man-made devices and materials. The constituents of the cellular transport system (i.e. motor proteins and filaments) can be reconstructed on synthetic surfaces to serve as molecular shuttles that actively transport nanoscale cargo. Our approach uses microfabricated tracks on which the motor protein kinesin adsorbs and transports microtubule filaments using chemical energy released by hydrolysis of adenosine 5 ′-triphosphate (ATP). This thesis uncovers the principles of microtubule guiding by surface properties for tracks (surface chemistry and topography, track width) that are based on our experimental findings and theoretical derivations of microtubule and surface physical properties (microtubule length, bending stiffness, persistence length; wall steepness, wall height). Our findings indicate that microtubules are best guided in channels were kinesin coats only the channel bottom where channel walls aid in bending. Finally, we arrange straight and curved intersecting tracks to give life to a functional device that sorts microtubules into one direction along a “figure 8” shaped track. Future work may use these “molecular shuttles” for miniaturizing simple assembly tasks, for ultra-sensitive biosensors, and pave the road toward new self-healing materials that are able to rebuild themselves using motor-protein transport. |
