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KINETICS OF THE ULTRAVIOLET‐INDUCED DIMERIZATION OF THYMINE IN FROZEN SOLUTIONS *
Author(s) -
Füchtbauer Walter,
Mazur Peter
Publication year - 1966
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.1751-1097.1966.tb05801.x
Subject(s) - thymine , quantum yield , aqueous solution , yield (engineering) , photochemistry , chemistry , irradiation , eutectic system , pyrimidine dimer , ultraviolet , dimer , materials science , thermodynamics , physics , optics , crystallography , dna , organic chemistry , quantum mechanics , fluorescence , optoelectronics , biochemistry , dna damage , microstructure
— It is known that thymine forms dimers when aqueous solutions are irradiated with ultraviolet light while in the frozen state, but does not form dimers when solutions are irradiated in the liquid state. The eutectic point of aqueous thymine solutions was found to be. —0.02°C. Since the irradiation of frozen solutions is always carried out at lower temperatures, the dimerization must be occurring in the solid state. Activation energies and quantum yields for dimer formation were determined by irradiating 1–mm layers of thymine solution at —5°C to — 707deg;C for various lengths of time. As expected, the activation energy was zero. After measuring the amount of radiation scattered by samples of ice, the extreme values for the quantum yield were found to be 0.73 and 4.08. The lower limit assumed that all the scattered light was absorbed by thymine; the upper limit assumed that none was absorbed. Since the theoretical maximum quantum yield is 2, the best estimate of the quantum yield is considered to be between 1 and 2.