ESI-Q-TOF MS and MS/MS analysis of of Y. enterocolitica O:9 glycobioconjugates. A) MS of high molecular weight glycosylated AcrA purified from Ye O:9 WT revealed the peak 1954.7 M/Z. MS/MS of this peak showed a disaccharide of HexNAc-Hex linking a characteristic 173 M/Z pattern corresponding to the N-formylperosamine subunit to the known glycopeptide DFNR. B) MS of high molecular weight glycosylated AcrA purified from Ye O:9 O antigen mutant revealed the peak 1284.63+ M/Z. MS/MS of this peak shows the second known glycosylated site of AcrA (AVFDNNNS TLLPGAFATITSEGFIQK) modified with the hexasaccharide HexNAc-HexNAc-Hex-Hex-HexNAc-Hex.