A laser flash photolysis and fluorescence study of aminomethyltrimethylpsoralen in the presence and absence of DNA

An investigation of the singlet excited state lifetime for 4'-aminomethyl-4,5',8-tri- methylpsoralen was undertaken. The fluorescence lifetime, t , for free aminomethylpsoralen was found to be 2.0 ± 0.2 ns, whilst for bound (to DNA) aminomethylpsoralen the fluorescence lifetime was found to be 0.3 ± 0.04 ns. Since no evidence for triplet-state formation for DNA-complexed aminomethylpsoralen was obtained, these results are interpreted in terms of a singlet excited state mechanism for photoinduced monoadduct formation between aminomethylpsoralen and DNA.