Featured Research

from universities, journals, and other organizations

Scientists use X-rays to look at how DNA protects itself from UV light

Date:
June 23, 2014
Source:
DOE/SLAC National Accelerator Laboratory
Summary:
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.
Credit: Illustration by Greg Stewart/SLAC

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.

Related Articles


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.

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.


Story Source:

The above story is based on materials provided by DOE/SLAC National Accelerator Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. B. K. McFarland, J. P. Farrell, S. Miyabe, F. Tarantelli, A. Aguilar, N. Berrah, C. Bostedt, J. D. Bozek, P. H. Bucksbaum, J. C. Castagna, R. N. Coffee, J. P. Cryan, L. Fang, R. Feifel, K. J. Gaffney, J. M. Glownia, T. J. Martinez, M. Mucke, B. Murphy, A. Natan, T. Osipov, V. S. Petrović, S. Schorb, Th. Schultz, L. S. Spector, M. Swiggers, I. Tenney, S. Wang, J. L. White, W. White, M. Gühr. Ultrafast X-ray Auger probing of photoexcited molecular dynamics. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5235

Cite This Page:

DOE/SLAC National Accelerator Laboratory. "Scientists use X-rays to look at how DNA protects itself from UV light." ScienceDaily. ScienceDaily, 23 June 2014. <www.sciencedaily.com/releases/2014/06/140623142017.htm>.
DOE/SLAC National Accelerator Laboratory. (2014, June 23). Scientists use X-rays to look at how DNA protects itself from UV light. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2014/06/140623142017.htm
DOE/SLAC National Accelerator Laboratory. "Scientists use X-rays to look at how DNA protects itself from UV light." ScienceDaily. www.sciencedaily.com/releases/2014/06/140623142017.htm (accessed October 24, 2014).

Share This



More Matter & Energy News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Police Testing New Gunfire Tracking Technology

Police Testing New Gunfire Tracking Technology

AP (Oct. 24, 2014) — A California-based startup has designed new law enforcement technology that aims to automatically alert dispatch when an officer's gun is unholstered and fired. Two law enforcement agencies are currently testing the technology. (Oct. 24) Video provided by AP
Powered by NewsLook.com
3D Printed Instruments Make Sweet Music in Sweden

3D Printed Instruments Make Sweet Music in Sweden

Reuters - Innovations Video Online (Oct. 23, 2014) — Students from Lund University's Malmo Academy of Music are believed to be the world's first band to all use 3D printed instruments. The guitar, bass guitar, keyboard and drums were built by Olaf Diegel, professor of product development, who says 3D printing allows musicians to design an instrument to their exact specifications. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
NYPD Gives High Tech Anti-Terror Weapon to 41,000 Officers

NYPD Gives High Tech Anti-Terror Weapon to 41,000 Officers

Buzz60 (Oct. 23, 2014) — New York City officials announce a new technology initiative for the NYPD. Tim Minton reports smartphones and tablets will be given to more than 40,000 NYPD officers and detectives in an effort to change the way they perform their duties. Video provided by Buzz60
Powered by NewsLook.com
Chameleon Camouflage to Give Tanks Cloaking Capabilities

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Reuters - Innovations Video Online (Oct. 22, 2014) — Inspired by the way a chameleon changes its colour to disguise itself; scientists in Poland want to replace traditional camouflage paint with thousands of electrochromic plates that will continuously change colour to blend with its surroundings. The first PL-01 concept tank prototype will be tested within a few years, with scientists predicting that a similar technology could even be woven into the fabric of a soldiers' clothing making them virtually invisible to the naked eye. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins