Molecular side step
How can you make a molecule walk in one direction? To fuel this basic translational motion, which would be a necessary component of any microscopic machine made up of molecular parts, requires converting chemical energy into kinetic energy.
In a paper appearing in Physical Review Letters, Simon Green, Jonathan Bath, and Andrew Turberfield of the University of Oxford in the UK propose a scheme for a two-footed molecular motor, made from DNA, that walks along a reusable track. The essential idea is that the motor binds in two places (its two feet) to a complementary DNA strand (the track). When a further strand of DNA is introduced—the fuel strand—the left foot unbinds, consumes the fuel (via a catalytic reaction), and moves to the other side of the right foot on the track. As this process repeats, the molecule moves in one direction along the track.
While they have not yet demonstrated that the motor can move a significant distance, the group has demonstrated two necessary conditions. With fluorescent tagging, they show that the left foot is more likely to be lifted and move to a new position than the right foot and that it is unlikely that both feet will move at the same time. – Jessica Thomas