12 October 2011
by David Shiga
IT’S DNA replication – but not as we know it. Elaborate webs of DNA have been made that can copy themselves outside cells. Unlike DNA in nature, which replicates inside cells, these webs exist freely and suggest how self-replication might one day be an alternative to conventional fabrication for very tiny structures.
A self-copying DNA double-helix would not be news. Living cells have been doing this for billions of years, and researchers have done it in test tubes for decades. But in a new twist, a team led by Paul Chaikin of New York University has created elaborate webs of DNA never seen in nature and persuaded these structures to make exact copies of themselves.
Each piece of the DNA web is a “tile” made by joining 10 double helices together. The team made two slightly different versions of these tiles, A and B, and joined them together to make a batch of identical strings of seven tiles. These “parent” strings then produced daughter strings made of tiles called A’ and B’, whose base pairs were exactly complementary to those on the A and B tiles. The researchers used the daughters as a further template to produce an exact copy of their parents (Nature, DOI: 10.1038/nature10500).
Although these particular strings were designed as a proof of principle, without any practical application in mind, the technique could allow more useful structures to be rapidly and easily grown, says Chaikin’s colleague Ned Seeman. Other molecules, with useful or novel properties, could be attached to the DNA tiles. The DNA itself would act as a scaffold, arranging the other molecules into the desired structure, and then later creating more and more copies.
“They demonstrated, for the first time, that one can replicate an [artificial] nano-pattern from seed patterns,” says Hao Yan of Arizona State University in Tempe.
Materials designed at the molecular level can have unusual properties such as extreme strength or the ability to efficiently convert light into electricity.