Kurt Gothelf and colleagues, Aarhus University, Denmark, report a DNA-based device that undergoes a sliding type motion between eleven discrete states. Previous DNA-based nanostructures have been able to expand and contract into two or three states.

The design is based on a Holliday junction, a mobile four-way junction: It consists of two aligned DNA strands with identical nucleotide regions at each end and a 21-nucleotide section in the middle that differs for each strand. A third strand acts as a roller, letting the two identical strands slid and lock into position based on interactions of the different nucleotide regions.

The ability to switch from state to state holds promise for applications such as a nanoscale robot arm and other dynamic DNA machines.

• A DNA Tile Actuator with Eleven Discrete States
  Z. Zhang, E. M. Olsen, M. Kryger, N. V. Voigt, T. Tørring, et al.,
  Angew. Chem. Int. Ed. 2011.
  DOI: 10.1002/anie.201007642