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RADIATION ACTIVATION OF CARCINOGENS AND THE ROLE OF OH AND O 2 ‐
Author(s) -
Greenstock Clive L.,
Ruddock George W.
Publication year - 1978
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.1751-1097.1978.tb07035.x
Subject(s) - carcinogen , chemistry , radiolysis , adduct , covalent bond , reaction rate constant , photochemistry , redox , radical , kinetics , biochemistry , organic chemistry , physics , quantum mechanics
— Radiation‐induced covalent binding of labelled carcinogens to DNA has been investigated under a variety of conditions using ultrafiltration or millipore filtration of TCA precipitable complexes. High yields of carcinogen binding at high DNA concentrations are also observed for a variety of small molecules and are not carcinogen‐specific. At high carcinogen concentrations, radiation‐induced unstable electrophilic carcinogenic species are produced, and undergo free‐radical reactions which simulate cellular redox reactions involved in metabolic carcinogen activation, leading to the formation of covalently bound carcinogen adducts to DNA as a potential target macromolecule. The yields of carcinogen‐DNA adducts increase linearly with dose and depend upon carcinogen concentration. The results of scavenger studies indicate that the oxidising species O 2 ‐ and OH are the principal activating species. Rate constants for the selective radiation‐induced oxidation reactions of various chemical carcinogens with superoxide have been measured by a competition kinetic method using pulse radiolysis. The relatively long‐lived superoxide radical reacts with carcinogens at a rate which is two orders of magnitude slower than the diffusion‐controlled rate for the hydroxyl radical, thus allowing a measure of O 2 ‐ specificity in the presence of competing reactants within the cell.