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UPPER EXCITED STATE PHOTOCHEMISTRY OF DNA
Author(s) -
Gut Ivo G.,
Farmer Raymond,
Huang Russel C.,
Kochevar Irene E.
Publication year - 1993
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.1751-1097.1993.tb09567.x
Subject(s) - excited state , quantum yield , chemistry , alkali metal , singlet state , raman spectroscopy , excitation , photochemistry , radiation , atomic physics , fluorescence , optics , physics , organic chemistry , quantum mechanics
Abstract— The quantum yields for cyclobutylpyrimidine dimers, alkali‐labile sites, and frank strand breaks in double‐stranded DNA have been measured using low‐intensity radiation at 199.8, 217.8, and 239.5 nm from a Raman‐shifted frequency quadrupled Nd:YAG laser. The quantum yield for cyclobutylpyrimidine dimers was also measured using 254 nm radiation from a low‐pressure mercury lamp. The quantum yield for cyclobutylpyrimidine dimers is constant within a factor of two between 254 and 199.8 nm except for 239.5 nm, indicating that upper excited singlet states of bases convert efficiently to the lowest singlet state. The quantum yields for alkali‐labile sites and frank strand breaks both increase as the wavelength decreases but follow different patterns. These results indicate that alkali‐labile sites form from a higher excited state of the base, whereas frank strand breaks form by excitation of the sugar‐phosphate backbone.