GENOMICS: Watch the DNA Dance - scientists observe DNA strands - Brief Article

Applied Genetics News,  Feb, 2000  

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A probe designed by chemists at Ohio State University has revealed a new secret in the life of DNA: The strands of compounds making up the molecule vibrate, stretch, and swing to and fro in tiny movements that last only a fraction of a second. Their research, in collaboration with a team from the University of South Carolina, appears in the February issue of the Journal of the American Chemical Society.

"This research may allow us to answer fundamental questions about how DNA works," says Robert Coleman, associate professor of chemistry at Ohio State. Coleman and Mihaela Madaras, a former postdoctoral researcher in chemistry, constructed the fluorescent probe and a strand of synthetic DNA. The probe is an analogue of DNA base pairs incorporated into the DNA strand.

Previously, scientists could only measure the less delicate movements of the whole DNA helix. For instance, they could examine what happens when a strand of DNA coils and folds in upon itself. Ohio State's probe allowed the South Carolina scientists to measure much smaller movements--at the level of the base pairs. According to Coleman, as these base pairs move, they change the shape of the DNA molecule, and that may explain why certain proteins and drugs recognize certain sequences of DNA. The movements, captured using ultrafast bursts of light, last only trillionths of a second.

During the experiments, the intensity of light reflected from the probe rose and fell over the course of 300 picoseconds, or 300 trillionths of a second, indicating that the components of the DNA strand were moving energetically during that time. This technique mirrors that of Ahmed Zewail, 1999 Nobel Prizewinner in chemistry, who uses ultrafast pulses of light to view the movement of atoms inside molecules.

Coleman foresees many applications of the DNA probe; he is especially interested in DNA repair. "Maybe enzymes are able to recognize damaged areas because the shape of the DNA has changed. We could put our probe into a piece of DNA near a damaged site, and we could see how the function of the DNA changed as a result of being damaged," he explains.

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