Twist and curl

DNA double helices can be assembled into curved three-dimensional nanostructures, with twists and bends that are finely tuned by the insertion and deletion of base pairs at specific locations.

Credit: © 2009 AAAS

The ability of DNA to self-assemble in a pre-programmed manner — relying on the hybridization of complementary strands — has been extremely useful for the construction of increasingly complex nanostructures. Now, William Shih and co-workers at the Dana-Farber Cancer Institute and Harvard Medical School in Boston have introduced precisely engineered curvatures to three-dimensional DNA assemblies¹.

The group recently extended the 'DNA origami' approach — in which a 'scaffold' strand is folded into the desired shape and held in place by hybridization with 'staple' strands — to three-dimensional structures². Parallel DNA double helices, each consisting of repeating seven-base-pair sequences, were attached together to form three-dimensional honeycomb arrays. Now, by altering the length of these seven-base-pair units, Shih and colleagues have been able to form twisted and bent DNA assemblies.

The insertion or deletion of one base pair of a double helix constrained within the honeycomb framework causes a local under- or over-twist, respectively, which in turn leads to a curvature of the overall array. Judiciously choosing the locations of these sequence adjustments enables the formation of twists (of either handedness) and curves with a finely tuned angle. These tailored arrays have been assembled into a variety of complex nanostructures, including a spherical capsule and a spiral.