the SLAC research revealed rapid changes of DNA that act as molecular sunscreen

the SLAC research revealed rapid changes of DNA that act as molecular sunscreen -

The molecular building blocks that make up DNA absorb ultraviolet light so strongly that sunlight must disable - yet it is not. Now scientists have made detailed a "relaxation response" comments that protects these molecules, and the genetic information they encode, damage caused by UV. The experience in the Department of SLAC National Accelerator Laboratory of energy focused on thymine, one of the four building blocks of DNA researchers thymine struck with a short pulse of ultraviolet light and used a powerful X-ray laser to see the response of the molecule. a chemical bond simply stretched and broken up within 0 quadrillionths of a second, triggering a wave of vibration that dissipated harmlessly destructive UV energy.

international research team reported in the June 23 results Nature Communications .
Although the protection of the genetic information encoded in DNA is of vital importance, the significance of this result goes far beyond chemistry DNA said Philip Bucksbaum, director of the Institute of PULSE Stanford and co-author of the report.
"the new tool the team developed for this study provides a new window on the movement of electrons that control the whole of chemistry," he said. "We believe this will enhance the value and impact of free electron lasers at x-rays to important problems in biology, chemistry and physics."

The light becomes Heat
researchers noticed that there are years thymine seemed resistant to damage from UV rays in sunlight, that cause sunburn and skin cancer. Thymine theorists proposed that gets rid of the UV energy by rapidly moving form. But they differed on the details and previous experiences could not solve what was happening.
The SLAC experiment took place at Coherent Light Source Linac (from LCLS), a user installation DOE Office of Science, whose brilliant, ultra-short X-ray laser pulses can see the changes that take place at the level of individual atoms in quadrillionths of a second
thymine scientists turned into a gas and hit with two pulses of light in quick succession :. first UV, to trigger the protection relaxation response, then X-rays, to detect and measure the response.
"as soon as thymine swallows light, energy is channeled as quickly as possible into heat, rather than making or breaking of chemical bonds," said Markus Guehr, a beneficiary of the program Career early DOE and senior staff scientist at PULSE who led the study. "It is like a system of balls connected by springs, when lying that a bond between two atoms and let it loose, the whole molecule begins trembling. "
ejected electrons Changes Signal
X-rays measured the relaxation response indirectly by removing part of the innermost electrons from the atoms in the thymine molecule. This triggers a process called Auger decay that ultimately ejects more electrons. the ejected electrons fly through a detector, carrying information about the nature and state of their original atoms.
By comparing the speed of the ejected electrons before and after thymine was hit with UV, the researchers were able to quickly identify changes in a single carbon-oxygen: It stretched when hit by UV light and shortened 0 quadrillionths of a second later, triggering vibrations continued to billionths of a second
"This is the first time we. were able to distinguish between two fundamental answers in the molecule - movements of atomic nuclei and changes in the distribution of electrons - and time them in a few quadrillionths of a second, "said the paper's first author, Brian McFarland, a postdoctoral researcher who has since moved to SLAC National Laboratory in Los Alamos.
Guehr said the team is planning other experiments to further explore the protective response of relaxation and expand the new method, called Auger spectroscopy Time-resolved, in other scientific fields.