Grażyna Strzelczak1, Krzysztof Bobrowski1, Halina Kozubek2, Jacek Michalik1
1 Institute of Nuclear Chemistry and Technology, 16 Dorodna Str., 03-195 Warsaw, Poland,
2 Faculty of Chemistry, A. Mickiewicz University, 6 Grunwaldzka Str., 60-780 Poznan, Poland
The radicals formed on g-radiolysis of oligopeptides containing methionine and glycine residues in the polycrystalline state at 77 K and on subsequent warming over the temperature range of 77-293 K were identified using the electron spin resonance (ESR) technique. In all oligopeptides studied, anion peptide radicals and monomeric sulfur radical cations over the temperature range of 77-95 K and decarboxylation and deamination radicals over the temperature range of 180-250 K were detected. In addition, in oligopeptides containing adjacent methionyl residues, three-electron-bonded dimeric sulfur radical cations (S\S)+ were detected at 110 K. In oligopeptides containing N-terminal methionine residue, H-abstraction radicals in the side chain of methionine residue were observed over the temperature range of 180-250 K. H-abstraction radicals at the a-carbon of the C-terminal amino acid residue were detected at 293 K in most of oligopeptides studied, in contrast to Met-Gly-Met and Met-Gly-Met-Met peptides were H-abstraction radicals at the a-carbon of the internal glycine residue were obserwed.