title: Thymidine free radicals generated during metallo-phthalocyanine photosensitization: a comparison with gamma-radiation.
abstract: In order to obtain information concerning the mechanism(s) of metallo-phthalocyanine (MePcS4) photosensitized damage of DNA constituents, the EPR-spin trapping method in conjunction with liquid chromatography was used to study thymidine (dThd) free radicals formed during photosensitization or exposure to gamma-radiation in solution. Under specified conditions two dThd free radical species, 5-hydroxy-5,6-dihydrothymidine-6-yl and 6-hydroxy-5,6-dihydrothymidine-5-yl, were formed both during exposure to ionizing radiation and photosensitization. These results imply that identical reactive intermediates (*OH radicals) are involved in the radiolytic and photosensitized oxidation of dThd. A light-dependent, Fenton-type mechanism is proposed to explain the generation of hydroxyl radicals during MePcS4 photosensitization.
authors.affiliation: Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
authors.forename: T G
authors.initials: TG
authors.lastname: Gantchev
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005720:Gamma Rays; D007211:Indoles / Q000494:pharmacology*; D054833:Isoindoles; D009942:Organometallic Compounds / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013936:Thymidine / Q000528:radiation effects*; D017967:Zinc Compounds
chemical_list: D005609:Free Radicals; D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D017967:Zinc Compounds; C052159:Zn(II)-phthalocyanine; C060570:aluminum phthalocyanine; D013936:Thymidine