Abstract

Ultraviolet radiation induces a number of different photo damages in DNA. Among them the CPD (cyclobutane-pyrimidine-dimer) photolesion of neighbouring thymines is most frequent while the Dewar valence isomer is very serious. With time-resolved infrared spectroscopy we address the dynamics of the formation of the two photolesions. We show that these reactions occur on the timescale of picoseconds via excited singlet states. The understanding of reaction dynamics gives new insight into the molecular parameters controlling lesion formation and shows how nature preserves the integrity of DNA on the molecular level.