FIG. 3.

Linear negative-ion MALDI-TOF spectra of O-LOS from M. catarrhalis strains. (A) Wild-type 7169; (B) lgt1 mutant-7169::lgt1KB; (C) lgt2 mutant-7169::lgt1KM; (D) lgt3 mutant-7169::lgt3KH. All ions are represented as average (M-H)⁻ masses. Intact O-LOS molecules show numerous molecular ions due to heterogeneity in hexose and phosphoethanolamine content. Molecular ions undergo in-source fragmentation to give lipid A and oligosaccharide prompt fragments as shown. *, ions occurring due to β-elimination of phosphoric acid (H₃PO₄) from the O-LOS; OS, oligosaccharide; lipid A, O-deacylated lipid A; Hex, Hexose; Kdo, 2-keto-3-deoxyoctonate.