O-methylated residue L-aspartic acid 4-methyl ester (2S)-2-amino-4-methoxy-4-oxobutanoic acid 129.0425872802734375 129.1199951171875 14.015649795532226562 14.029999732971191406 2-aminobutanedioic acid 4-methyl ester 4-methyl L-2-aminosuccinic acid 4-methyl L-aspartate 4-methyl L-hydrogen aspartate A protein modification that effectively converts an L-aspartic acid residue to L-aspartate 4-methyl ester. C 1 H 2 N 0 O 0 C 5 H 7 N 1 O 3 CAUTION - observations of this modifation are attributable to artifacts produced in preparation. It is extremely unlikely that eukaryotes produce this modification, because an enzyme acting to form the methyl ester of L-aspartyl peptides would interfere with the D-aspartyl peptide repair mechanism [JSG]. D L-aspartic acid 4-methyl ester MOD:01181 Methyl O4MeAsp PSI-MOD Unimod:34 artifact aspartic acid 4-methyl ester aspartic acid beta-methyl ester meesterd monomethylated L-aspartic acid