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Transient absorption spectra and quenching of coumarin excited states by nucleic acid bases

Authors
Journal
Journal of Photochemistry and Photobiology B Biology
1011-1344
Publisher
Elsevier
Publication Date
Volume
13
Issue
1
Identifiers
DOI: 10.1016/1011-1344(92)80036-u
Keywords
  • Coumarins
  • Excited Singlet
  • Excited Triplet
  • Quenching
  • Termolecular Interaction
  • Dna Bases.

Abstract

Abstract Triplet—triplet absorption spectra of coumarin show different profiles and maxima in ethanol from those in water, which are very similar to those reported in benzene. Long-lived transient species other than triplet states were generated as initial photoproducts between coumarins and nucleic acid bases. The excited singlet and triplet states of coumarins were quenched by nucleic acid bases. Adenine base quenched the excited singlet state of coumarins more efficiently than thymine base. However, photocycloadducts of furocoumarins are formed predominantly with thymine, and not with adenine. Moreover, it is reported that the poly[dA-dT]· poly[dA-dT] sequence region is the most favourable site for the photocycloaddition reaction of furocoumarins. The results imply that adenine contributes to singlet-state photocycloaddition reaction of furocoumarins with thymine, probably through an adenine—furocoumarin—thymine termolecular interaction.

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