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.
Understanding the specific pathways by which this degradation occurs is an important step in developing protective mechanisms against it.
Exploring the pathway of protein degradation
The researchers took gas-phase peptides containing tyrosine or phenylalanine, light-absorbing amino acids found throughout the body, and subjected them to ultraviolet laser radiation. Then used ultraviolet-infrared spectroscopy to examine the resulting structural changes over time.
The scientists found that instead of immediately degrading once excited, some of the molecules formed intermediate triplet states.
The results, described in a paper appearing this week in The Journal of Chemical Physics, explore this pathway of protein degradation and could facilitate the development of better UV protection mechanisms.
Work to lead to developing better UV protection mechanisms
As 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.
To date, 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 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. Published in The Journal of Chemical Physics which can be accessed at: http://scitation.aip.org/content/aip/journal/jcp/141/14/10.1063/1.4897158