Instant nano blocks: one-step process makes trillions of DNA pyramids.

As if carrying life's genetic code weren't enough, DNA molecules are in demand these days as raw material for microscopic constructions. For instance, nanotechnologists have fashioned cubic and octahedral cages from the molecules (SN: 2/14/04, pg. 99). Processes for crafting those frameworks, however, have been arduous and give only low yields of desired structures.

Now, a team of physicists in England and the Netherlands has unveiled a three-dimensional building component that can be created from DNA in a simple procedure. The technique produces trillions of the components in a few minutes.

The new DNA construct has the shape of a tetrahedron--a pyramid with three faces and a base. Composed solely of open triangles, the new object is rigid and only about 10 nanometers wide, making it an ideal building block for larger structures, says physicist Russell F. Goodman of the University of Oxford in England. "You can get a lot of mileage out of building things with tetrahedra," he says.

He and his colleagues at Oxford and Vrije University in Amsterdam describe their new component in the Dec. 9 Science.

Because the pyramidal units are stiff, they hold their shapes, says Goodman. That should make them suitable as bricks for nanostructures of high spatial precision, such as three-dimensional electronic circuits.

The new work is "brilliant," comments John H. Reif of Duke University in Durham, N.C. "It provides exactly the capabilities needed to form the components of large, 3-D, DNA lattices."

The team, led by Oxford's Andrew J. Turberfield, designed a set of four single-stranded DNA molecules, each one with components in an order that would result in certain DNA-DNA bonds. The scientists mixed trillions of those strands in salt water, heated the mixture almost to a boil, and then cooled it quickly.

As the researchers had predicted, each strand bent to outline a tetrahedral face. Simultaneously, each strand intertwined with an adjoining face's DNA as complementary regions formed bonds. The result was tetrahedral cages composed of DNA with a sturdy, double-helix rod along each edge.

The scientists also showed that single DNA strands called linkers could bind two adjacent tetrahedra. The next challenge, says Goodman, is to coax multiple tetrahedra into more-complex structures.