Lipid A structures of Tohama I, B0442, B1120, and B1121 B. pertussis strains. (A to D) Structural analyses of the lipid A moieties of the B. pertussis isolates Tohama I (A), B0442 (B), B1120 (C), and B1121 (D) was performed by using mass spectometry. Peaks at m/z 1,719.1 represent penta-acyl lipid A with a GlcN modification at either phosphate group. Peaks at m/z 1,558.1 represent penta-acyl lipid A without GlcN modification and with a C14-OH acyl chain, and the peaks at m/z 1,502.1 and 1,530.1 represent penta-acyl lipid A without GlcN modification and with a C10-OH and C12-OH acyl chain, respectively.