derives from 4-sulfophenyl isothiocyanate derivatized residue 6x(13)C labeled 4-sulfophenyl isothiocyanate derivatized residue (12)C 1 (13)C 6 H 5 N 1 O 3 S 2 220.9900054931640625 220.9912109375 4-sulfophenyl isothiocyanate (Heavy C13) A protein modification produced by formation of an adduct with 6x(13)C labeled 4-sulfophenyl isothiocyanate. MOD:00880 PSI-MOD SPITC:13C(6) Unimod:464 X artifact (13)C isotope tagged reagent