Deamination of Lysine and Asparagine in ammonia gas. Deamination (−17 Da) peaks are labeled as (a) for Lys (K), (b) for Asn (N) and (c) for Lys (K). No deamination is observed for the two Gln (Q) residues. The MALDI mass spectrum was not calibrated. The peptide was synthesized on Tenta Gel (TG) beads without a cleavable linker and treated in ammonia for 1 hour at 100 PSI.