, Volume 19, Issue 12, pp 1799-1807

Dissociation of the N-Cα bond and competitive formation of the [z n −H]•+ and [c n +2H]+ product ions in radical peptide ions containing tyrosine and tryptophan: The influence of proton affinities on product formation


Dissociations at the N-Cα bond of tryptophan and tyrosine residues are the prevalent pathways in the fragmentations of radical cations of tripeptides that contain such as residues. This process involves a proton transfer from the β-carbon of the tryptophan or tyrosine residue to the carbonyl oxygen of the amide group, followed by cleavage of the N-Cα bond, generating low-lying proton-bound dimers that dissociate to give each an ionic and a neutral product. Formation of the [z n −H]∢+ or [c n +2H]+ ion is a competition between the two incipient fragments for the proton in a dissociating proton-bound dimer.

Published online October 1, 2008