Lasers drive nano locomotive

A researcher from Texas A&M University and Fudan University in China has designed a laser-powered molecular locomotive that runs along a molecular track and can generate a pulling force ten times greater than that of kinesin, a biological molecular motor.

This is enough force to break multiple hydrogen bonds, break apart molecules held together by electric charge, and loosen molecules held together by hydrophobic, or water-repelled, sticking.

The molecular locomotive could someday be used to automatically deliver molecular building blocks with nanometer accuracy, according to the researcher. The mechanism could also eventually be used for drug delivery, he said. A nanometer is one millionth of a millimeter, or the span of ten hydrogen atoms.

The locomotive design calls for a polymer molecule that expands and contracts when exposed to a laser with heads at both ends that chemically bind to anchors on the track. Laser light would trigger binding and unbinding.

A series of six laser pulses of different frequencies powers the locomotive. The molecule begins contracted, with both ends attached to the track. The first pulse detaches the front end, the second pulse expands the molecule, the third attaches the front end to a new binding sites further down the track, the fourth detaches the rear end, the fifth contracts the molecule, and the sixth attaches the rear end to a new binding site.

The molecular locomotive would measure about four nanometers in diameter, with each unit of the molecule two nanometers long in its contracted state. It would be capable of moving a few microns per second, which is comparable to its biological counterparts.

A working prototype of the motor could be made within five years, and practical applications are possible within ten years, according to the researcher. The work appeared in the September 15, 2004 issue of Physical Review E.