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ULTRAVIOLET PHOTOCHEMISTRY OF THYMINE IN AQUEOUS SOLUTION
Author(s) -
FISHER G. J.,
JOHNS H. E.
Publication year - 1970
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1970.tb06015.x
Subject(s) - thymine , chemistry , photochemistry , quantum yield , uracil , triplet state , pyrimidine dimer , aqueous solution , singlet oxygen , yield (engineering) , dimer , singlet state , oxygen , excited state , molecule , fluorescence , organic chemistry , materials science , dna , biochemistry , physics , quantum mechanics , nuclear physics , metallurgy , dna damage
— We have investigated the ultraviolet photochemistry of thymine in aqueous solution. Four isomeric dimers are produced, and the yield of each has been measured as a function of thymine concentration, oxygen concentration, and temperature. At low thymine concentration, dimerization proceeds via the triplet state, while at high concentration it arises mainly from aggregates, probably from a singlet precursor. We have determined the ratios of rate constants for the triplet state mechanism and the quantum yield for dimerization from aggregates. The quantum yield for dimerization from the triplet state in thymine is smaller by a factor of about 10 than that in uracil, which in turn is smaller by another factor of 10 than that in orotic acid. It increases with the energy of the exciting radiation in a manner similar to the behaviour of uracil and orotic acid. On the other hand, dimer formation from aggregates is independent of photon energy. Dimerization from aggregates decreases with increasing temperature, while the total production of dimers from the triplet state is independent of temperature.