Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists Use X-rays to Look at How DNA Protects Itself from UV Light

24.06.2014

SLAC Research Reveals Rapid DNA Changes that Act as Molecular Sunscreen

The molecular building blocks that make up DNA absorb ultraviolet light so strongly that sunlight should deactivate them – yet it does not. Now scientists have made detailed observations of a “relaxation response” that protects these molecules, and the genetic information they encode, from UV damage.


Thymine – the molecule in the foreground – is one of the four basic building blocks that make up the double helix of DNA. It’s such a strong absorber of ultraviolet light that the UV in sunlight should deactivate it, yet this does not happen. In a study reported in Nature Communications, researchers used an X-ray laser at SLAC National Accelerator Laboratory to make detailed observations of a “relaxation response” that protects these molecules, and the genetic information they encode, from UV damage. (Illustration by Greg Stewart/SLAC)

The experiment at the Department of Energy’s SLAC National Accelerator Laboratory focused on thymine, one of four DNA building blocks. Researchers hit thymine with a short pulse of ultraviolet light and used a powerful X-ray laser 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 international research team reported the results June 23 in Nature Communications.

... more about:
»Accelerator »DNA »LCLS »Laboratory »SLAC »X-ray »X-rays »energy »thymine

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.

“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.”

Light Becomes Heat

Researchers had noticed years ago that thymine seemed resistant to damage from UV rays in sunlight, which cause sunburn and skin cancer. Theorists proposed that thymine got rid of the UV energy by quickly shifting shape. But they differed on the details, and previous experiments could not resolve what was happening.

The SLAC experiment took place at the Linac Coherent Light Source (LCLS), a DOE Office of Science user facility, whose bright, ultrashort X-ray laser pulses can see changes taking place at the level of individual atoms in quadrillionths of a second.

Scientists turned thymine into a gas and hit it with two pulses of light in rapid succession: first UV, to trigger the protective relaxation response, and then X-rays, to detect and measure the response. 

“As soon as the thymine swallows the light, the energy is funneled as quickly as possible into heat, rather than into making or breaking chemical bonds,” said Markus Guehr, a DOE Early Career Program recipient and senior staff scientist at PULSE who led the study. “It’s like a system of balls connected by springs; when you elongate that one bond between two atoms and let it loose, the whole molecule starts to tremble.”

Ejected Electrons Signal Changes

The X-rays measured the relaxation response indirectly by stripping away some of the innermost electrons from atoms in the thymine molecule. This sets off a process known as Auger decay that ultimately ejects other electrons. The ejected electrons fly into a detector, carrying information about the nature and state of their home atoms.

By comparing the speeds of the ejected electrons before and after thymine was hit with UV, the researchers were able to pinpoint rapid changes in a single carbon-oxygen bond: It stretched when hit with UV light and shortened 200 quadrillionths of a second later, setting off vibrations that continued for billionths of a second.

“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.

Guehr said the team plans more experiments to further explore the protective relaxation response and extend the new method, called time-resolved Auger spectroscopy, into other scientific realms.

In addition to the Stanford PULSE Institute, which is a joint institute of SLAC and Stanford University, the study included researchers from LCLS, Stanford, the University of Perugia in Italy, Lawrence Berkeley National Laboratory, the University of Connecticut, Western Michigan University, the University of Gothenburg in Sweden, and UNIST in South Korea. Parts of the research were carried out at Berkeley Lab’s Advanced Light Source, a DOE Office of Science user facility. The work was funded by the DOE Office of Science, the Swedish Research Council, the Göran Gustafsson Foundation and the Knut and Alice Wallenberg Foundation.

Citation: B. K. McFarland, J. P. Farrell et al., Nature Communications, 23 June 2014 (10.1038/ncomms5235)

Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, Calif., SLAC is operated by Stanford University for the U.S. Department of Energy's Office of Science.

The Stanford PULSE Institute is a joint institute of SLAC National Accelerator Laboratory and Stanford University. PULSE seeks to advance the frontiers of ultrafast science, with particular emphasis on research using SLAC's Linac Coherent Light Source (LCLS). For more information, please visit www.stanford.edu/group/pulse_institute.

SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Andrew Gordon | Eurek Alert!
Further information:
https://www6.slac.stanford.edu/news/2014-06-23-scientists-use-x-rays-look-how-dna-protects-itself-uv-light.aspx

Further reports about: Accelerator DNA LCLS Laboratory SLAC X-ray X-rays energy thymine

More articles from Life Sciences:

nachricht From Receptor Structure to New Osteoporosis Drugs
20.11.2018 | Universität Zürich

nachricht Mutation that causes autism and intellectual disability makes brain less flexible
20.11.2018 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Mutation that causes autism and intellectual disability makes brain less flexible

20.11.2018 | Life Sciences

The sweet side of reproductive biology

20.11.2018 | Life Sciences

Fading stripes in Southeast Asia: First insight into the ecology of an elusive and threatened rabbit

20.11.2018 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>