A traffic control system for molecules

Researchers from Delft University of Technology in the Netherlands have built a traffic control system able to force individual molecules active in our cells to choose between 'roads' by applying strong electrical fields locally at Y-junctions. This traffic control system could lead to new nano-fabrication techniques.

Our cells contain small protein factories which have to deliver materials inside the cell via a network of microtubules. And the transportation is carried out by biomolecular motors. Now, researchers from Delft University of Technology in the Netherlands have built a traffic control system able to force individual molecules to choose between 'roads' by applying strong electrical fields locally at Y-junctions. This traffic control system can potentially lead to new nano-fabrication techniques. Read more...

Researchers from the Kavli Institute of Nanoscience, led by Professor Cees Dekker, director of the Molecular Biophysics group, have discovered how to "control and address individual microtubules."

An important step in this was to allow microtubule-transport to occur in small closed liquid channels. This made it possible to apply a strong electrical field locally at the Y-junction in the channels. Because of this, the electrical force could be exerted on the individual microtubules. The researchers discovered that by using this electrical force they could push the front of the microtubule into the determined direction.

Below is an "artist impression of the sorting of green and red microtubules in nanochannels. Kinesin motors on the walls push the microtubule forward while an external experimentalist can steer the direction by exerting an electrical force on the tube" (Credit for image: TU Delft/Tremani; credit for caption: this page at PhysOrg.com)

Sorting microtubules

To demonstrate this, the researchers allowed a mixture of green and red fluorescent microtubules to arrive at a Y-junction. By changing the direction of the electrical force, depending on the color of the microtubule, the Delft researchers were able to collect the green and red microtubules in different reservoirs.

Below is an illustration showing how a molecules is forced to choose a direction when arriving at a Y junction. "By changing the direction of the electrical force, depending on the color of the microtubule, the Delft researchers were able to collect the green and red microtubules in different reservoirs." (Credit: TU Delft)

Sorting microtubules

This research work has been published by Science under the name "Molecular Sorting by Electrical Steering of Microtubules in Kinesin-Coated Channels" (Vol. 312, No. 5775, Pages 910-914, May 12, 2006). The magazine also wrote a specific introduction to this paper, "Manipulating Microtubule Motion" (Vol. 312, No. 5775, Page 809, May 12, 2006).

[The researchers] studied the behavior of microtubules in constant electric fields. With detailed experiments and theory, they show that individual microtubules driven by the motor protein kinesin across the surface of micrometer-sized fluidic channels can be driven in a desired direction and that the sorting occurs with high efficiency.

And here is a link to the abstract of this paper.

We have managed to integrate kinesin motor proteins in closed submicron channels and to realize active electrical control of the direction of individual kinesin-propelled microtubule filaments at Y junctions. Using this technique, we demonstrate molecular sorting of differently labeled microtubules. We attribute the steering of microtubules to electric field–induced bending of the leading tip.

For more pictures about this project, here is a link to additional figures and explanations provided by Science.

Sources: Delft University of Technology news release, via EurekAlert!, May 11, 2006; and various web sites

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