derives from monomethylated L-arginine 1x(13)C,3x(2)H labeled monomethylated L-arginine (12)C 6 (13)C 1 (1)H 11 (2)H 3 N 4 O 1 (13)C 1 (1)H -1 (2)H 3 174.138946533203125 174.1399993896484375 18.03783416748046875 18.04000091552734375 A protein modification that effectively replaces one hydrogen atom of an L-arginine residue with a (13)C,3x(2)H labeled methyl group to form a 1x(13)C,3x(2)H labeled monomethylated L-arginine. MOD:00637 Methyl:2H(3)13C(1) PSI-MOD R Unimod:329 artifact monomethylated arginine (2)H deuterium labeled residue (13)C labeled residue modified L-arginine residue