9x(13)C labeled residue modified L-phenylalanine residue 9x(13)C labeled L-phenylalanine 156.098602294921875 156.1100006103515625 9.0299997329711914062 9.0301942825317382812 A protein modification that effectively converts an L-phenylalanine residue to 9x(13)C labeled L-phenylalanine. F (12)C -9 (13)C 9 13C(9) Silac label MOD:01327 H 9 (13)C 9 N 1 O 1 PSI-MOD none artifact Label:13C(9)