Peptide peroxyl radicals: base-induced superoxide radical ion elimination versus bimolecular decay. A pulse radiolysis and product study

Abstract

Radiolytically generated OH radicals react with the cyclic dipeptides glycine anhydride (1) and alanine anhydride (2), forming a single type of peptide radical in each case by abstracting a carbon-bound H atom at the ring. In the case of sarcosine anhydride (3), besides the C(3) or C(6) H atoms (78%), the H atoms at the N-methyl groups are also targets of the OH radical attack (22%). In N 2 O/O 2 (4:1 v/v) saturated solutions these peptide radicals add oxygen (k≃2×10 9 dm 3 mol -1 s -1 ) to form the corresponding peroxyl radicals 6 (from 1), 7 (from 2), and 12 and 13 (from 3)