ScienceDaily (Nov. 14, 2006) — James Watson and Francis Crick deciphered the structure of regular DNA 53 years ago. Now, scientists from Stanford University have determined the structure of xDNA. That's "expanded DNA," a strange double helix molecule that is 20 percent wider and more heat-resistant than natural DNA. Inherently fluorescent, expanded DNA glows in ways that may make xDNA useful as a medical and scientific probe.

Eric T. Kool and colleagues developed xDNA in 2003 by adding a benzene ring to the chemical bases that form natural DNA. Natural DNA, which is 20 angstroms wide, and benzene, with a girth of 2.4 angstroms, produced the wholly new wider double helix.

The researchers now have combined all four expanded DNA bases with the four natural DNA bases to produce a complete eight-base molecule. They then used nuclear magnetic resonance to reveal the structure of xDNA and study the molecule.

In an article scheduled for publication Nov. 22 in the weekly Journal of the American Chemical Society, they describe the features needed for DNA that encodes and transfers genetic information.

They report: "The present work shows that the eight-base xDNA system may have most if not all of these features, which suggests the future possibility of a functioning, replicable genetic system using xDNA as the genetic material."

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