Photosensitized splitting of pyrimidine dimers in DNA by indole derivatives and tryptophan-containing peptides.

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Abstract—Indole derivatives, such as serotonin or the oligopeptide Lys‐Trp‐Lys, are able to photosensitize the splitting of thymine dimers in DNA. These indole derivatives have to be bound to DNA in order to efficiently photosensitize the splitting reaction. Serotonin may also induce the photosensitized formation of thymine‐containing dimers in native DNA. In this case, an equilibrium is reached when 5 per cent of the total thymines are dimerized. In both cases (splitting and dimer formation), the formation of electron donor‐acceptor complexes between either dimers or two adjacent thymine monomers, and excited indole rings, could be an intermediate step in the reactions. Thymine‐dimer splitting would then result from an electron transfer reaction involving the indole ring as the electron donor. These results are discussed with respect to the mechanism of action of the photoreactivating enzyme.