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The molecular building blocks that make up DNA absorb ultraviolet light so immensely that sunlight should deactivate them - but they don't. Researchers are explaining this phenomenon in a new study while describing a  "relaxation response" that protects these molecules. 

The experiment focuses on thymine - one of the four DNA building blocks. Researchers hit thymine with a short pulse of ultraviolet light while using a powerful X-ray laster to watch the molecule's response: A single chemical bond stretched and snapped back into place within 200 quadrillionths of a second, setting off a wave of vibrations that harmlessly dissipated the destructive UV energy, the press release added. 

While protecting the genetic information encoded in DNA is vitally important, the significance of this result goes far beyond DNA chemistry, said Philip Bucksbaum, director of the Stanford PULSE Institute and a co-author of the report, in the press release.

"The new tool the team developed for this study provides a new window on the motion of electrons that control all of chemistry," he said. "We think this will enhance the value and impact of X-ray free-electron lasers for important problems in biology, chemistry and physics."

"This is the first time we've been able to distinguish between two fundamental responses in the molecule - movements of the atomic nuclei and changes in the distribution of electrons - and time them within a few quadrillionths of a second," said the paper's first author, Brian McFarland, a postdoctoral researcher who has since moved from SLAC to Los Alamos National Laboratory, in the press release.

The findings of the study have been published in the journal Nature Communications.