Researchers in the UK and Germany have developed nanoscopic DNA pyramids that change shape when subjected to different chemical signals, which they hope will be able to a act as the motors of nanoscale robots.

The researchers built tetrahedrons – structures with four triangular sides – using four short DNA “struts” that join at each end. The process exploits the way DNA is held together by complementary bases that form the rungs of a ladder-like structure.

Andrew Tuberfield and colleagues at Oxford University, England, first created DNA molecules with some bases on one side of the “ladder” left exposed. These bases were carefully chosen to match those of other DNA molecules so that, when mixed together, the right combination of DNA strands assembled into a tetrahedron.

The same trick can change the tetrahedron shape, by causing the struts to extend or shorten. This is possible if a strut has a loop of excess DNA in its middle. Adding a “fuel” strand of DNA straightens out the loop by binding onto it, and makes the strut extend.

A different sequence of “anti-fuel” DNA returns the strut to its normal length.

Turberfield explained: “The fuel is designed to have a dangling free end. The anti-fuel eventually displaces the fuel, allowing the loop to reform.”

The process can change the length of a strut from 3.4 nanometres in length 10.2 nm and back again.

In experiments, the researchers made cages with two extendible struts that could be independently controlled using different DNA sequences. In theory, it should be possible to create cages in which every strut can be controlled independently, Tuberfield says.

The researchers are now exploring ways to build larger structures using tetrahedral DNA structures as building blocks.

Read the whole story at New Scientist