(2)H deuterium labeled residue (13)C labeled residue modified L-methionine residue 1x(13)C,3x(2)H C(6)-labeled L-methionine (12)C -1 (13)C 1 (1)H -3 (2)H 3 (12)C 4 (13)C 1 (1)H 6 (2)H 3 N 1 O 1 S 1 135.05999755859375 135.0626678466796875 4.0199999809265136719 4.0221848487854003906 A protein modification that effectively converts an L-methionine residue containing common isotopes to 1x(13)C,3x(2)H C(6)-labeled L-methionine. M MOD:01795 Methyl:2H(3)13C(1) PSI-MOD artifact