Physical and technical parameters determining the functioning of a kinesin-based cell-free motor system

Kinesin is a microtubule-associated protein, converting chemical into mechanical energy. Based on its ability to also work outside cells, it has recently been shown that this biological machinery might be usable for nanotechnological developments. Possible applications of the kinesin-based motor system require the solution of numerous methodological and technical problems, including the orientation of force generation into a desired direction and the determination of the tolerable roughness of the surfaces used, the minimal free vertical space still enabling force-generating activity, and the temporal stability of the system. This paper reports on the example of microtubules gliding across kinesin-coated surfaces and shows that the force-generating system needs a minimal foe working space of about 100 nm height and works up to 3 h with nearly constant velocity. Individual microtubules were observed to cover distances of at least 1 mm without being detached from the surface and to overcome steps of up to 286 nm height. In addition, mechanically induced how fields were shown to force gliding microtubules to move in one and the same direction. This result is regarded as being an essential step towards future developments of kinesin-based microdevices as this approach avoids neutralization of single forces acting in opposite directions.