Mobile proton triggered radical fragmentation of nitroarginine containing peptides

Abstract

Protonated nitroarginine, [RNO2 + H]+, which contains the nitroguanidine 'explosophore,' undergoes homolytic N - N nitro-imine bond cleavage to expel NO2 • and form a radical cation of arginine in high yield (100 % relative abundance) upon low-energy collision-induced dissociation (CID). Other ionization states of nitroarginine, including [RNO2 - H]-, and a fixed-charge derivative of nitroarginine do not expel NO2 • (<1 %), but instead dissociate via heterolytic bond cleavage with abundant losses of small molecules (N2O and H2N2O2) from the nitroguanidine group. The effects of proton mobility on the CID reactions of nitroarginine containing peptides was investigated for peptide derivatives o..