Scientists uncover DNA’s hidden defence against UV radiation

Working with researchers from Aix Marseille University, the French National Centre for Scientific Research (CNRS) and Université Claude Bernard Lyon 1, the team used advanced computer simulations to watch what happens to DNA in real time at the atomic scale. 

DNA constantly absorbs UV light from the Sun, which can potentially trigger harmful chemical reactions. However, DNA is remarkably photostable – meaning it can rapidly deactivate excited energy states before lasting damage occurs. 

In the study, published in The Journal of Physical Chemistry Letters, researchers focused on guanine and cytosine base pairs – two of the fundamental building blocks of genetic material. Using high-level quantum chemistry simulations, the researchers found that, after absorbing UV light, the excited energy is funnelled through a series of molecular processes that safely return it to its stable state. The simulations showed that DNA does not rely on a single protective mechanism but instead accesses a complex network of competing ultrafast relaxation pathways. 

These pathways are far more diverse and dynamic than previously thought. Rather than following a single route, DNA appears to use multiple ultrafast reactions involving moving electrons and protons that dissipate the energy within femtoseconds – a femtosecond being one quadrillionth of a second. 

The findings could improve understanding of how radiation damages DNA and how cells naturally protect themselves, with potential long-term implications for fields including cancer biology, ageing research, biotechnology and astrobiology. 

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Notes to editors 

• Dr Marco Sacchi and Juliana de Abrantes are available for interview; please contact mediarelations@surrey.ac.uk to arrange. 
• The full paper can be found here: https://pubs.acs.org/doi/10.1021/acs.jpclett.6c00376