FIGURE 6.
DC displacement assay for interaction of Hb peptides with lipid A in solution. The occupancy of DC (50 μm) on lipid A (20 μg/ml) was measured in the presence of 0, 0.1, 1, 10, 50, and 100 μm of the various peptides at pH 7.4 in HBS. The fluorescence intensity was measured by excitation at 340 nm and emission at 560 nm. The occupancy was calculated using the formula: occupancy = (FP − FD)/(FL − FD), where FD is the fluorescence intensity of DC in the absence of lipid A, FL is the fluorescence intensity of DC in the presence of lipid A; and FP is the fluorescence intensity of the solution of DC and lipid A upon the addition of the different concentrations of the peptides. Occupancy is plotted against the log-peptide concentrations for peptides that bind LPS (A) and do not bind LPS (B). Results are the means ± S.D. of three independent experiments done in triplicate.