Certain peptides exposed to UV radiation transition to more reactive triplet quantum states instead of immediately breaking down
The most obvious effects of too much sun exposure are cosmetic, like wrinkled and rough skin. Some damage, however, goes deeper—ultraviolet light can damage DNA and cause proteins in the body to break down into smaller, sometimes harmful pieces that may also damage DNA, increasing the risk of skin cancer and cataracts. Understanding the specific pathways by which this degradation occurs is an important step in developing protective mechanisms against it.
Researchers from the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have shown that certain peptides (small proteins) degrade under UV light by first passing through a triplet quantum state, a reactive arrangement that can cause greater damage than fragmentation alone.
Their results, described in a paper appearing this week in The Journal of Chemical Physics, from AIP Publishing, explore this pathway of protein degradation and could facilitate the development of better UV protection mechanisms.
The researchers took gas-phase peptides containing tyrosine or phenylalanine, light-absorbing amino acids found throughout our bodies, and subjected them to ultraviolet laser radiation. Then, they used ultraviolet-infrared spectroscopy to examine the resulting structural changes over time. They found that instead of immediately degrading once excited, some of the molecules formed intermediate triplet states.
Normally, electron spins are paired—if two electrons are present, one spin points one direction and the other points the opposite direction. But under certain conditions, the spin of one of the electrons can flip so that they both point in the same direction. This arrangement is known as a triplet state.
Because electronic configurations can affect how a molecule will react, knowing that it passes through a triplet state can provide additional insight into the potential consequences of photodamage for these molecules.
"Triplet states are long-lived and can be involved in harmful chemical reactions," said chemical physicist Aleksandra Zabuga, an author of the new paper. "Long-lived" is relative—they still only last from microseconds to milliseconds—but it does give them a greater opportunity to do damage.
"During that time the triplet species may transfer their energy to nearby oxygen and produce highly reactive singlet oxygen or other free radicals. These radicals can in turn move around the cell and cause DNA damage that is much more dangerous than the fragmentation of peptides," she said.
A number of other research groups have studied UV fragmentation in solution and also report the presence of triplet states. Peptides are less likely to fragment in this environment, however, because they can interact with the surrounding molecules and deactivate through alternative mechanisms, mediating the damage. In addition, pigments like melanin in our skin and kynurenine in our eyes reduce the amount of UV radiation that reaches cells.
"It is interesting to consider the fact that all of these protection mechanisms are external to the peptide. In other words, peptides do not seem to have very efficient means of protecting themselves," said Zabuga.
In the future, the researchers hope to examine the impact of the local environment on light-induced fragmentation. For instance, it is possible that nearby water molecules or additional amino acids on the same peptide chain could interact with the triplet state and alter the fragmentation mechanism—an important consideration in real-world systems.
The article, "Fragmentation mechanism of UV-excited peptides in the gas phase," is authored by Aleksandra V. Zabuga, Michael Z. Kamrath, Oleg V. Boyarkin, and Thomas R. Rizzo. It will be published in The Journal of Chemical Physics on October 21, 2014 (DOI: 10.1063/1.4897158). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/jcp/141/14/10.1063/1.4897158
ABOUT THE JOURNAL
The Journal of Chemical Physics publishes concise and definitive reports of significant research in the methods and applications of chemical physics. See: http://jcp.aip.org
Jason Socrates Bardi | Eurek Alert!
New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center
Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research