Application of the spin-trap HPLC-ESR method to radiation chemistry of amino acids in aqueous solutions

Our recent studies of the application of the newly developed spin-trap HPLC-ESR method to γ-radiolysis of aqueous solutions containing amino acids are reviewed. 2-Methyl-2-nitrosopropane (MNP) was used as a spin trap to convert generated unstable free radicals into relatively stable aminoxyl radicals, which were separated individually by HPLC with cation-exchange columns. Compounds derived from MNP during the preparation of aqueous MNP solutions were found to be t-butylnitrosohydroxylamine, t-butyl alcohol and isobutene. The preparation procedure of the solution in which these undesirable products are minimized is proposed. γ-Radiolysis of aqueous MNP solutions resulted in the formation of five aminoxyl radicals. The chromatographic retention times of the radicals were found to be different from those of the spin adducts from the amino acids studied here. Amino acids investigated in the present work were glycine, L-alanine, L-valine, L-isoleucine, L-leucine and DL-methionine. Twenty-five spin adducts from the amino acids were detected and identified by the method. The reactions by which short-lived radicals are produced in γ-irradiated aqueous solutions of the amino acids have been found to be H-abstraction by hydroxyl radicals and deamination by hydrated electrons. (author)