Living cells contain tiny transport systems made from a pair of proteins -- microtubules and kinesin -- that act much like railroad tracks and railroad cars.

The researchers coated tiny synthetic tracks with the motor molecule kinesin and coaxed microtubules to glide across the kinesin surface. This is different from the way the proteins work in cells, where kinesin glides across microtubule tracks.

The researchers worked out how the microtubules move across junctions, and found ways to use different types of junctions to sort and concentrate materials. The modified cell-transport proteins could eventually be used to transport materials around labs-on-a-chip. Using motor proteins like kinesin rather than diffusion to move materials promises to speed transport by several orders of magnitude, according to the researchers.

The researchers' next step is to find ways to target biological and synthetic molecules, binding them to the molecular shuttles and deliver the cargo to specific destinations.

Microtubule networks could be used in practical applications and five to ten years, according to the researchers. The work appeared in the February 27, 2004 issue of Lab on a Chip.