E.S.R. of Spin-trapped Radicals in Aqueous Solutions of Amino Acids

Summary

The reactions of hydrated electrons (e_aq⁻) with amino acids were investigated by the spin-trapping method and by electron spin resonance. Tertiary nitrosobutane was used as a spin-trap to stabilize the short-lived radicals. Hydrated electrons were produced by γ-radiolysis of de-aerated aqueous solutions of amino acids in the presence of sodium formate or tertiary butanol to scavenge OH. Radicals produced by reductive deamination of 19 amino acids were identified. Radicals formed by scission of the CH₃-S- and -S-CH₂- bonds of methionine as well as by deamination were observed. In the case of phenylalanine the radical formed by electron addition followed by proton transfer was identified. The reaction of proline and of hydroxyproline with e_aq⁻ resulted in the opening of the cyclic structure.