✦ LIBER ✦

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

✍ Scribed by Ho Kwon Kang; Eun Ju Shin; Sang Chul Shim

Publisher: Elsevier Science
Year: 1992
Tongue: English
Weight: 653 KB
Volume: 13
Category: Article
ISSN: 1011-1344
DOI: 10.1016/1011-1344(92)80036-u

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✦ Synopsis

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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