Ultraviolet Radiation Damage in DNA

Introduction The evolution of most forms of life has occurred in an environment exposed to the ultraviolet (UV) and visible radiation emanating from the sun. When molecules in living cells absorb photons in this region of the electromagnetic spectrum they are promoted to excited electronic states and this process can have profound biological consequences. In general, visible wavelengths (400-780 nm) are associated with effects which are beneficial to living organisms, such as photosynthesis and vision. However, ultraviolet photons, with wavelengths below 400nm, have a capacity for damaging cells which becomes increasingly pronounced at shorter wavelengths and higher energies. Conventionally, the UV spectrum is sub-divided into three discrete sections: UVA (320-400 nm), UVR (280-320 nm) and UVC (wavelengths < 280 nm). Radiation at UVB and UVC wavelengths has genotoxic properties and is invariably harmful to living cells. By damaging the genetic material, DNA, it can induce such deleterious processes as mutagenesis, carcinogenesis and cell death [ 1,2]. This paper reviews the nature of the radiation damage produced in DNA by the direct absorption of UV photons. Special reference is made to the environmental impact of increased levels of UVB radiation in the biosphere resulting from depletion of the Ozone layer. The main focus is on the structural identity and detection of the intramolecular photoproducts derived from the purine and pyrimidine nucleobases in DNA. The role of repair