A simple approach to making rigid DNA nanorings with tailor-made functionality has been developed by Michael Famulok and his team at the University of Bonn, Germany. The development could open up new pathways for the construction of DNA objects with a high level of organization for preparing nanocomposite materials.

Famulok's nanorings reveal themselves under the atomic force microscope to be composed of double-stranded DNA with a tiny gap in the form of a short single-stranded fragment. "From the structural point of view, miniature rings represent the simplest form for a rigid object made of DNA," says Famulok. The single-strand gap represents an entry point for functionalizing the nanorings.

Nucleic acids are fascinating building blocks for composite materials because they are easy to make with various molecular recognition characteristics. The difficulty in using these materials lies in creating defined two- or three-dimensional geometries, which usually requires rigid building blocks, whereas DNA molecules are generally flexible structures.

"From the structural point of view, miniature rings represent the simplest form for a rigid object made of DNA," explains Famulok. His team has now risen to the challenge of producing DNA molecules with a smooth circular structure, free of ring deformations, twists, or knots. They succeeded not only through grim determination but through the careful selection of sequence and number of nucleotides as well as the exploitation of a neat synthetic route that led to the desired rigid rings. "Our new, uncomplicated method for the production of rigid DNA nanorings with variable, tailor-made functionality opens new pathways for the construction of DNA objects with higher levels of organization," Famulok says.

Angew Chem Int Edn, 2007, in press;
http://dx.doi.org/10.1002/anie.200704004

http://www.chembiol.uni-bonn.de/index-e.html