RADIATION-INDUCED DECOMPOSITION OF TRYPTOPHAN IN THE PRESENCE OF OXYGEN

Tryptophan decomposition in oxygenated aqueous solutions in neutral me dia was investigated by gamma and pulsed electron irradiation. By usin g pulse radiolysis it was found that 27% of tryptophan OH-adducts elim inate water. Tryptophan neutral radical, Trp, thus formed reacts rapid ly with O2-., k(Trp. + O2-.) = (4.5 +/- 0.7) x 10(9) M-1 s-1. The rema ining tryptophan OH-adducts react with oxygen to give peroxy radicals which may eliminate O2-., produce N-formylkynurenine and disproportion ate yielding organic peroxides. Peroxy radicals derived from tryptopha n H-adducts regenerate tryptophan by the elimination of HO2., and reco mbine with TrpH(OH)OO. radicals producing organic peroxides.