Radiation stability of methionine-35S and selenomethionine-75Se

The radiation stability of methionine-35S and selenomethionine 75Se was investigated using the methods of thin-layer chromatography, gas chromatography and ESR. Radiation decomposition of methionine- 35S mainly consists in an oxidation process and in the release of volatile products. The ESR-spectra of irradiated DL-methionine indicated a strong localization of the unpaired electrons on sulfur atoms. Radiation damage to selenomethionine-75Se as a function of radiation dose proved an increased stability of this compound and its radiation decomposition consists in the formation of oxidized products and by direct rupture of the selenium bounds accompanied by the formation of volatile compounds like CH3SEH and SeH2. The self-radiolysis of the aqueous solution of selenomethionine-75Se during its storage in air leads, however, to a lower decomposition rate which consists in the release of inorganic selenium and in an oxidation process. (author)