FIG. 4.

ESI-MS spectra of LPS fractions. The LPS samples were resolved by anion-exchange chromatography and subjected to mild acid hydrolysis prior to the ESI-MS studies. (A) wapR knockout mutant. (B) rmlC knockout mutant. (C) migA rmd knockout mutant, containing four phosphate groups. Peaks labeled with protein designations correspond to the structures shown in Fig. 3. Unlabeled arrows indicate a difference in phosphate groups. Arrows labeled Ac indicate a difference in acetate groups (42 atomic mass units [amu]). Every structure is represented by two variants, one with full Kdo and one with anhydro-Kdo (18-atomic mass unit difference).