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N ‐Hydroxy‐4‐(4‐chlorophenyl)thiazole‐2(3 H )‐thione as a Photochemical Hydroxyl‐radical Source: Photochemistry and Oxidative Damage of DNA (Strand Breaks) and 2′‐Deoxyguanosine (8‐oxodG Formation) ¶
Author(s) -
Adam Waldemar,
Hartung Jens,
Okamoto Hideki,
SahaMöller Chantu R.,
Špehar Kristina
Publication year - 2000
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 - 10.1562/0031-8655(2000)0720619nhctht2.0.co2
Subject(s) - photochemistry , chemistry , deoxyguanosine , thiazole , dna damage , 8 hydroxy 2' deoxyguanosine , hydroxyl radical , radical , dna , dna oxidation , stereochemistry , organic chemistry , biochemistry
On irradiation of N ‐hydroxythiazole‐2(3 H )‐thione 3 at 300 nm, the photoproducts disulfide 4, bisthiazole 5 and thiazole 6 are formed. During this photolysis, hydroxyl radicals are released, which have been detected by spin trapping with 5,5‐dimethyl‐1‐pyrroline N ‐oxide (DMPO), coupled with electron paramagnetic resonance spectroscopy. In the presence of supercoiled pBR322 DNA, irradiation of thiazolethione 3 induces strand breaks through the photogenerated hydroxyl‐radicals, as confirmed by control experiment with the hydroxyl‐radical scavenger isopropanol. Singlet oxygen appears not to be involved, as attested by the lack of a D 2 O isotope effect. During the photoreaction of thiazolethione 3 in the presence of 2′‐deoxyguanosine (dG), the latter is photooxidized ( ca 10% conversion after 2 h of irradiation) to the 7,8‐dihydro‐8‐oxo‐2′‐deoxyguanosine as the main oxidation product. The dG conversion levels off after complete consumption of thiazolethione 3 and is suppressed by the addition of the hydroxyl‐radical scavenger 2,6‐di‐ tert ‐butylcresol or DMPO. Since the photoproducts 4–6 are ineffective as sensitizers for the photooxidation of dG and DNA, the hydroxyl radicals released in the photolysis of thiazolethione 3 are the oxidizing species of DNA and dG. These results suggest that the thiazolethione 3 may serve as a novel and effective photochemical hydroxyl‐radical source for photobiological studies.