Electron spin resonance studies of electron irradiated peptides. A single crystal of N-acetylglycine at 77 K.
Free radicals formed in single crystals of N-acetylglycine, irradiated and observed at 77 K, have been studied using ESR spectroscopy. Two different radical species were found. One radical (called ...
E.s.r. of spin-trapped radicals in gamma-irradiated polycrystalline amino acids, N-acetyl amino acids and dipeptides.
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.
Electron Spin Resonance of Two Radicals Formed in X‐Irradiated Cyanoacetylurea, Another Sigma‐Electron Radical of the RCOṄH Type
Two radical species were formed when cyanoacetylurea CNCH2CONHCONH2 crystals were irradiated with x ray. One was a π‐electron radical, CNĊHCONHCONH2, and the other a σ‐electron radical, CNCH2CONHCOṄH. The latter was found to have similar hyperfine coupling tensors as H2NCOCH2CONH which was formed in x‐irradiated malonamide, and the former as CNĊHCOOH which was formed in γ‐irradiated cyanoacetic acid.