has functional parent N-acetyl-L-serine O-acetyl-L-serine N,O-diacetylated L-serine 172.0609893798828125 172.160003662109375 84.02112579345703125 84.06999969482421875 In one paper, the samples were prepared using glacial acetic acid, and were probably artifactual [JSG]. A protein modification that effectively converts an L-serine residue to N,O-diacetyl-L-serine. N-term PSI-MOD MOD:00648 N,O-diacetylserine (S)-2-acetamido-3-acetyloxypropanoic acid artifact C 4 H 4 O 2 C 7 H 10 N 1 O 4 NOAc2Ser S N,O-diacetyl-L-serine diacetylated L-serine