摘要：

This chapter describes the photochemistry and photobiology of furocoumarins and the applications of furocoumarins in biology and medicine. Furocoumarins and their congeners are found in many plants. The photoreactivity of psoralens regarding the cycloaddition to DNA is determined by three main factors: kinetic, steric, and electronic. RNA can also be photochemically modified with psoralens and near-UV radiation. When psoralens are intercalated in DNA, the singlet reaction can be a predominant path, because the singlet excited psoralen intercalated need not diffuse too far to encounter its substrate. The probability of the photocycloaddition of psoralen to thymine in solution is enhanced if the excited singlet state of the psoralen encounters thymine and forms an exciplex. In mammalian cells, PUVA-induced mutagenesis is linear with dose, following one-hit kinetics. PUVA treatment is a well-established clastogen. Caffeine enhances the yield of chromosome aberrations when added after PUVA treatment. PUVA treatment inactivates transforming DNA in Bacillus subtilis. DNA cross-links contribute to this effect by preventing entry of DNA into the bacterial cells.

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