DNA folds into paired pyramids

Researchers from the Scripps Research Institute have formed strings of DNA that spontaneously fold into a wireframe octahedron, a shape that has eight triangular faces.

The shape is a step forward in the quest to use DNA to make nanoscale templates that can be used to make materials molecule-by-molecule and structures that form microscopic machines.

The octahedron has two advantages over other artificially-formed three-dimensional DNA shapes, according to the researchers. First, because the structures are triangular, they're relatively strong. Second, like a three-dimensional paper airplane made from a flat piece of paper, the octahedron is made from straight DNA strands. The three-dimensional shape forms when one long DNA strand and five shorter strands are mixed and heated.

The straight strands can be coaxed to self-replicate, making it possible to quickly produce large numbers of the octahedrons, according to the researchers. Other three-dimensional DNA shapes must be synthesized chemically rather than biologically. DNA is made up of strings of four bases attached to a sugar-phosphate backbone. DNA strands that contain complementary sequences of bases can attach to each other.

The DNA octahedron measures 22 nanometers across, or about one fiftieth the width of an E. coli bacterium.

The DNA octahedron could be used in practical applications in five to ten years, according to the researchers. The work appeared in the February 12, 2004 issue of Nature.