Tritiated free radical scavengers

Tritiated Free Radical Scavengers in the Study of the Irradiated Protein Molecule... 

Most tritiated sugars are best stored in aqueous solution, sometimes containing a small proportion of ethanol. Under these conditions, radiolysis usually does not exceed 5 to 10% per year. In the frozen state, between 0° and —196°, the rate of decomposition can be high, presumably due to concentration of the sugar in pockets on freezing.87 Nucleotides are stored at —20° in 50% ethanol, which acts as a free-radical scavenger,68 and decompose at the rate of 12% per year polymers should be stored as freeze-dried solids. 

The use of gaseous tritiated radical scavengers to determine the secondary free radical distribution in y-irradiated lyo-philized macromolecules has been explored. For proteins the similarity of the tritium distributions obtained with tritiated H2S and HI as well as studies with H235S, support the assumption that these distributions are an approximate measure of the secondary radical distribution. Radical distributions of several native proteins were characteristically different, those of denatured proteins approximately the same, thus demonstrating a pronounced effect of conformation. In contrast to proteins, the reaction of irradiated dry DNA with tritiated H2S or HI gave approximately 100 times more tritium label on the DNA than expected from the initial concentration of free radicals in the DNA. 

Reactions Involved in Radical Interception. Some of the reactions which have been considered in the radical interceptor technique are shown in Reactions 1-8. Reactions 1 and 2 are schematic and do not describe the mechanism of formation of secondary free radicals in proteins by ionizing radiation. The reactions of the carbon radicals with tritiated scavengers (Reactions 3 and 3a) lead to the formation of carbon-tritium bonds. 

Fromme etal. (1966) localised tritiated poly-2-vinylpyridine-N-oxide of about 55kDa injected subcutaneously into rats (FW 49) on the surface of tridymite dust given into the peritoneal cavity 0, 3, or 5 d before. The free radical scavenging properties of PVPNO may be a mechanism for its action in pneumoconiosis (Gulumian and van Wyk 1987). 

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