Figure 3

Binding of PG-1 to LPS and lipid A. Binding/radial diffusion assays were conducted by mixing various amounts of LPS or lipid A with 50 ng of PG-1 in a final volume of 5 μl. In Panel A, the LPS and lipid A preparations were isolated from P. aeruginosa strain 9027 and B. cepacia strain 25416. In Panel B, the LPS and lipid A were isolated from P. aeruginosa FRD-2 and B. cepacia C4813. The mixtures of PG-1 with LPS or lipid A were introduced into the wells of radial diffusion assay plates seeded with P. aeruginosa FRD-1, a highly susceptible test organism. All data points are means (n = 3), and EC₅₀ values were extrapolated from these graphs. When these binding isotherms were subjected to linear regression analysis, the 95% confidence limits of the LPS and lipid A binding isotherms for P. aeruginosa and B. cepacia were non-overlapping, and the isotherms for the LPS preparations in Panel A overlapped only at the lowest ligand concentrations (data not shown).