DNA machine

A DNA machine is a machine that uses DNA as a material for molecular-scale construction of objects and devices. It was pioneered in the late 1980s by Nadrian Seeman and co-workers from New York University. DNA is used because of the numerous biological tools already found in nature that can affect DNA, and the immense knowledge of how DNA works previously researched by biochemists.

In 2000, Andrew Turberfield and co-workers at Lucent Technologies in New Jersey, USA made such a tweezer out of DNA.

The DNA molecule is double-stranded, because the bases on one strand stick to partners on another. There are strict rules to this base pairing: A sticks only to T, and C to G. The 'selective stickiness' is a key feature of the machine.

Turberfield et al.'s molecular machine contains three strands: A, B and C. Strand A latches onto half of strand B and half of strand C, and so it joins them all together. Strand A acts as a hinge so that the two 'arms' &mdash; AB and AC &mdash; can move.

The structure floats with its arms open wide. They can be pulled shut by adding a fourth strand of DNA (D) 'programmed' to stick to both of the dangling, unpaired sections of strands B and C.  The closing of the tweezers was proven by tagging strand A at either end with light-emitting molecules that do not emit light when they are close together.

To re-open the tweezers add a further strand (E) with the right sequence to pair up with strand D. Once paired up, they have no connection to the machine BAC, so float away.

The DNA machine can be opened and closed repeatedly by cycling between strands D and E.