Charge separation and charge delocalization identified in long-living states of photoexcited DNA

• DOI: 10.1073/pnas.1323700111
• Publication Date: 2014-03-11T01:34:20Z
• Authors: Dominik B. Bucher; Bert M. Pilles; Thomas Carell; Wolfgang Zinth
• Keywords: Photochemistry; Ultraviolet Rays; DNA; Oxidation-Reduction; 01 natural sciences; 0104 chemical sciences; 3. Good health

Significance The high photostability of single nucleobases is related to the rapid disposal of the UV excitation energy from high-lying electronic states into heat, preventing damaging reactions. However, in the biological important DNA strands, further long-living excited states are found. With femtosecond vibrational spectroscopy, these excited states in DNA are now identified as charge-separated states, which are delocalized along the strand. The charge separation is directed by the redox potential of the involved bases and is thus encoded in the DNA sequence. The presence of delocalized charged species in DNA strands for a considerably long time after UV light absorption may lead to reactions—oxidative or reductive damage—currently not considered in DNA photochemistry.