2-pyrrolidone-5-carboxylic acid (Pro) 112.03985595703125 112.1100006103515625 13.979265213012695312 13.979999542236328125 A modification that effectively oxygenates C5 of an L-proline residue to form a 2-pyrrolidone-5-carboxylic acid, pyroglutamic acid. C 5 H 6 N 1 O 2 H -2 O 1 MOD:00571 P PSI-MOD Pro->pyro-Glu PyrGlu(Pro) Pyroglutamic The review article PubMed:9252331 does not provide an original citation for this modification [JSG]. Unimod:359 artifact pyroglutamicp carbon oxygenated residue modified L-proline residue 2-pyrrolidone-5-carboxylic acid