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Posted: Oct 20, 2006
Nanoscale structuring of surfaces with biomolecular motors
(Nanowerk Spotlight) Sophisticated biomolecular motors have evolved in nature, where motor proteins actively control the delivery and assembly of materials within cells. In contrast, the development of synthetic nanomotors is in its infancy. Such nanomotors are currently explored for an increasing number of applications in hybrid bionanodevices. Along these lines, gliding motility assays, where reconstituted microtubule filaments are propelled over a substrate by surface-attached motor proteins, have been used to transport micro- and nanosized objects, such as small beads, quantum dots or DNA molecules. However, one prerequisite for controllable nanotransport is the reliable guiding of filament movement along predefined paths, a challenging task that has recently been achieved only via costly and labor-intensive topographical surface modifications. Researchers have now demonstrated a novel approach for the nanostructuring of surfaces with functional motor proteins. In contrast to all other current methods, their approach allows the three-dimensionally oriented deposition of proteins on surfaces, being the result of first binding them to the highly oriented and regulated structures of microtubules and then transferring them to the surface.
Dr. Stefan Diez, Group Leader Bionanotechnology and Optical Technology Development at the Max-Planck-Institute of Molecular Cell Biology and Genetics in Dresden/Germany, and his colleagues developed a very simple setup of microtubule guiding and transport systems. This highly-oriented deposition of proteins on surfaces will also allow novel sensing and detection applications.
Diez explained the novel approach to Nanowerk: "Other approaches to stamp proteins onto surfaces have the disadvantage that a lot of proteins denature during the process. In our method, the stamp is a natural substrate of the proteins to be stamped."
With regard to the reliable guiding of motile microtubule transporters along predefined paths, all recent approaches are costly and labor-intensive because they involve modifications of the surface topography.
"Our method demonstrates the possibility to get along with just patterned motors on planar surfaces - without the need for topographical changes" Diez says.
Biotemplated stamping of proteins onto planar surfaces. Motor molecules are bound in an oriented manner to the surface of a
microtubule in the absence of ATP. In a "stamping" process the molecules can be transferred to the surface and the microtubule can be walked off by ATP. (Source: Dr. Diez)
Inspired by biological transport systems found within cells, Diez and collaborators from the Nencki Institute of Experimental Biology in Warsaw/Poland and the University of Florida investigated two different methods of biotemplated nanopatterning of planar surfaces with motor proteins: “biotemplated stamping” and “biotemplated binding”.
In the stamping approach, kinesin-1 molecules were bound in solution with their motor domains to “template” microtubules in the absence of ATP. The generated complexes were then adsorbed onto the surface and ATP was added in order to propel the template microtubules off the surface-bound motor proteins. This way, tracks of oriented motor molecules, with their motor domains pointing away from the surface, were generated.
In the binding approach, the template microtubules were first immobilized on the surface. Kinesin-1 or Ncd motor proteins were then specifically bound to the template microtubules via specific linker molecules or the second microtubule binding site in their tail domain, respectively.
For both approaches, based on either biotemplated stamping or binding, the addition of “transport” microtubules in a motility solution containing ATP led to guided movement along the motor tracks.
These created motor tracks showed that nanoscale-patterning is possible and can lead to reliable guiding of microtubules without topographical barriers.
Biotemplated nanopatterning is not only a promising tool for in vitro studies on the individual and cooperative action of motor proteins but also for the reconstitution of complex subcellular machineries in synthetic environments.
Diez and his colleagues are planning to do further extensive studies on cellular machinery: "We will explore other means to structure planar surfaces with nanometer-wide protein patterns, not only for microtubule guiding but also any other kind of applications. Those range all the way from cell-adhesion studies to molecular sorting systems."