The radicals produced in several polycrystalline amino acids, N-acetyl amino acids and dipeptides by gamma-radiolysis at room temperature were investigated by spin-trapping. After irradiation in the solid state, the samples were dissolved in aqueous solutions f t-nitrosobutane and the trapped radicals identified by e.s.r. For alpha-amino acids, deamination radicals were found, and in some cases H-abstraction radicals were also observed. No decarboxylation radicals could be detected. For N-acetyl amino acids, except for N-acetylglycine, the major radical was the decarboxylation radical. For N-acetyglycine the H-abstraction radical from the glycine residue was observed. For dipeptides of the x-glycine, the radical formed by removal of H from the alpha-carbon of the carboxyl-terminal residue was always spin-trapped. Some primary deamination radicals and minor amounts of decarboxylation radicals could also be observed. For dipeptides of the type x-alanine, glycine-x and alanine-x, the decarboxylation radical was always the major spin-trapped radical. Some primary and secondary deamination radicals were also detected.
Solid glycine has been radiolyzed by 60Co γ-rays in vacuo at room temperature, and all the products except H2 have been measured after dissolving the irradiated samples in water. The hydrogen has been collected and measured directly from the irradiated solid samples. All products except H2 increase linearly with the dose, while H2 shows a plateau from a relatively low dose. The yields of products are as follows: G(H2)∼0.2, G(NH3)=4.8, G(CH3NH2)=0.2, G(CHOCO2H)=2.5, G(CH3CO2H)=2.3, G(CO2)∼0.2, and G(HCHO)∼0.03. The mechanisms of the primary process and the reactions to give final products have been proposed with reference to the results of the ESR studies.
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