dimethylated residue alpha-amino methylated residue alpha-amino dimethylated residue 28.031299591064453125 28.049999237060546875 A protein modification that effectively replaces two alpha amino hydrogen atoms with two methyl group. C 2 H 4 Dimethyl For alpha-amino acids, both N-alpha-monomethylation and complete N-alpha protonation and trimethylation have been observed, but incomplete dimethylation has not been reported as a natural process. For N-terminal proline residues, dimethylation can only be effectively accomplished with a protonated imino group, whereas this process accounts only for dimethylation and not protonation. See MOD:00889. MOD:01686 N-term N2Me2Res PSI-MOD Unimod:36 X di-Methylation ntermpepdimethyl