FIG. 4.
FTICR mass spectra of LPSs from strains C6706 (A), C6706 ΔmsbB (B), O395 (C), and O395 ΔmsbB (D). Peak assignments were confirmed by accurate masses and by tandem mass spectrometry as shown in Fig. 5. Unassigned peaks differ from the assigned lipid A peaks mainly by the mass of water, phosphate, or ethylene. Lipid A containing six acyl chains (m/z 1,766.165) is labeled LAhexa, lipid A containing five acyl chains (m/z 1,539.971) is labeled LApenta, lipid A containing four acyl chains (m/z 1,341.809) is labeled lipid Atetra, and lipid A containing three acyl chains (m/z 1,045.671) is labeled LAtri.