derives from trimethylated residue alpha-amino methylated residue alpha-amino trimethylated residue 42.0469512939453125 42.0469512939453125 42.0800018310546875 42.0800018310546875 MOD:01687 tri-Methylation C 3 H 6 For amino acids residues, amine trimethylation can effectively only be accomplished with an aminium, protonated primary amino, group. This process accounts only for trimethylation and not protonation. The alternative N2Me3+Res process (MOD:01698) accounts for both protonation and trimethylation. C 3 H 6 N2Me3Res PSI-MOD natural 1+ A protein modification that effectively replaces an alpha-aminium group with a trimethylaminium group. N-term Trimethyl X ntermtrimethyl alpha-amino protonated residue