Making factories and computers with DNA

By Michael Schirber

updated 6:53 p.m. ET June 21, 2006

As if the blueprint for life wasn't busy enough, nanotech researchers are putting DNA to work in tiny mechanical devices and as templates for electronic circuits.

Recent DNA constructions include microscopic patterns, tiny gears and a molecular assembly line. Although still mostly at the demonstration level, DNA nanotech is a rapidly growing field.

The first person to see DNA's potential beyond biology was Naiman Seeman, a chemist at New York University. More than twenty years ago, he began imagining how the genetic information in DNA might be engineered to perform useful tasks.

"DNA structures are programmable by sequence, and so are their intermolecular interactions," Seeman says. "That makes them unique."

Whereas nature alone dictates how most molecules interact, DNA comes with a built-in code that researchers can re-formulate to control which DNA molecules bond with each other. The goal of this DNA tinkering is microscopic factories that can produce made-to-order molecules, as well as electronic components 10 times smaller than current limits.

"Nanofabrication is where we are going," Seeman told LiveScience. "It will happen soon."

Smart glue
A single strand of DNA is essentially a long sequence made up of the chemical bases adenine (A), thymine (T), cytosine (C) and guanine (G). Every living thing carries a unique genetic code in its cells written out in these "letters."

Two strands of DNA can fuse together and form the famous double helix, discovered by Crick and Watson in 1953. But this twisted ladder arrangement can only happen if all the bases on the two strands match up, so that A's bond with T's and C's bond with G's.

Scientists use this selective adhesive to build and control DNA machines.

"The bonds are like smart glue that know which pieces go together," explains Thomas LaBean of Duke University.

LaBean and others typically begin with a design for a structure that has several DNA pieces. A computer program writes out the code for the different strands, which are then synthesized using standard biological methods. Mixed together in a water-based solution, the pieces with matching codes will link up to form several copies of the desired structure.

It's like an airplane model kit, except all you have to do is shake the box and all the little parts automatically find each other and glue together.

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