FIG. 6.

MALDI-TOF mass spectral analysis of lipid A compositions with 1 μg of PCP extract material from M. catarrhalis mutant O35EkdtA (A) or phenol-water extract from wild-type strain O35E (B). This analysis was done in the negative mode, and all ions are represented as deprotonated [M-H]⁻ ions. The proposed lipid A composition for each ion is given in Table 2, and major ions with m/z values of 1,574.6 and 1,556.6 are due to the LOS oligosaccharide and its anhydro form, respectively. The upper portion of the figure shows the structure of the major species at 1,782.27.