Magazine article Science News

Long Strand Folds into Octahedron

Magazine article Science News

Long Strand Folds into Octahedron

Article excerpt

DNA may embody the blueprint of life, but it could also be the stuff of future nanotechnologies. In a feat of molecular engineering, scientists recently designed a strand of DNA that can spontaneously fold into an octahedron.

Although scientists have made three-dimensional geometric shapes out of DNA before, those structures have readily deformed, says molecular biologist Gerald Joyce of the Scripps Research Institute in La Jolla, Calif. In contrast, his lab's new octahedron is extremely rigid and could serve as a reliable nanoscale component. The structure has eight triangular faces and resembles two pyramids attached at their bases.

The rigidity of the octahedron comes not only from its overall geometry but also from the brawn of its 12 DNA struts. Each strut consists of two DNA stretches joined "like two ribbons wrapping around each other," says Joyce.

To ensure that the DNA would spontaneously fold into the desired structure, Scripps team member William Shih first used computer software to come up with stretches of unique sequences of nucleotides, or DNA building blocks, that would bind together to form each strut. The final DNA strand contains close to 1,700 nucleotides.

When the researchers heated and cooled their DNA strands in a Lest tube, each one folded in on itself and snapped into a virus-size structure, 22 nanometers in diameter. Using a powerful electron microscope, the researchers confirmed that the structures were octahedral. "We zoomed in and saw them," says Joyce. …

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