Salt sensitivity of antimicrobial peptides. Various concentrations of NaCl (0 to 300 mM) were added to 10 mM NaPi (pH 6.8), and each peptide (50 μg/ml) was reacted with S. aureus cells by using the method described in Materials and Methods. The data are means ± standard deviations from three independent experiments. Symbols: ▪, hBD1; •, hBD2; ▴, hBD3; ⧫, CAP18.