The natural DNA bases are highly resistant to UV excitation as they dissipate more than 90% of their energy through efficient nonradiative channels leading to the ground state. Nonetheless, it is now well established in the literature that small structural changes might drastically modify the photochemical properties of DNA by lengthening the excited states lifetime and/or increasing intersystem crossing efficiency.
During this last decade, our group has focused its attention on studying DNA lesion photobehavior. The photochemistry of DNA damages is indeed of utmost importance as some of them are able to absorb in the UVA-UVB region and behave as a potential intrinsic photosensitizer. Here, we will discuss the photophysical and photochemical properties of damages such as the (6-4) photoproducts,[1]-[2] 5-formylpyrimidine derivatives,[3]-[5] or etheno adducts[6],[7] to evaluate if they fulfil the basic requirements of a good DNA photosensitizer: (i) to absorb in the UVA-UVB region, (ii) to populate efficiently their triplet excited state and (iii) to be able to interact with DNA components through a Type I or II process and/or a triplet-triplet energy transfer.