iTRAQ8plex-121 reporter+balance reagent acylated residue iTRAQ8plex-121 reporter+balance reagent O3-acylated threonine (12)C 12 (13)C 6 H 31 (14)N 3 (15)N 2 (16)O 5 (12)C 8 (13)C 6 H 24 (14)N 2 (15)N 2 (16)O 3 (4-methylpiperazin-1-yl)acetyl 304.19903564453125 304.20001220703125 405.2467041015625 405.25 A protein modification that effectively replaces an O3-hydrogen atom of a threonine residue with the Applied Biosystems iTRAQ8plex-121 reporter+balance group. MOD:01583 PSI-MOD T The reagent consists of a reporter group, a balance group and a protein reactive N-oxysuccinimide group. The reporter group, an isotopically labeled 1,4-dimethylpiperazine, is connected to a balance group that is isotopically labeled to produce a nominally isobaric combined modification. artifact iTRAQ8plex reporter+balance reagent O-acylated residue O3-acylated L-threonine