Mass spectral characterization of lipooligosaccharides from Haemophilus influenzae 2019

Lipooligosaccharide (LOS) glycoforms from Haemophilus influenzae 2019 were profiled using the high-resolution and accurate mass capabilities of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Sequence and linkage for two previously unknown LOS glycoforms were subsequently obtained through MSn analyses on FT-ICR and quadrupole ion trap (qIT) instruments. MSn analysis of negative ion precursors confirmed structural details within the lipid moiety, while CID spectra of sodiated precursor ions provided monosaccharide sequence and linkage for the oligosaccharide portion of the molecule. Results obtained in this study indicate that extensive heterogeneity exists within the oligosaccharide moieties in LOS from H. influenzae 2019. More importantly, the data suggest that additional hexose moieties, which are added onto the LOS, are not simple extensions of one particular core structure but rather that structural isomers with different connectivities are present within the heterogeneous mixture.