FIG. 1.

Bactericidal kinetics and hemolytic activities of K₄-S4(1-13), MSI-78, and PG-1. A peptide concentration of 20 μM [corresponding to 30, 50, and 43 μg/ml, respectively, for K₄-S4(1-13) (asterisks), MSI-78 (squares), and PG-1 (circles)] was used to treat cultures of E. coli (A) and S. aureus (B). After 0, 5, 30, and 60 min of exposure time at 37°C, aliquots were diluted (serial 10-fold dilutions) and plated for CFU counts after overnight incubation at 37°C. The peptide hemolytic activity (C) was assessed against human erythrocytes (1% hematocrit). Hemolysis was determined by measuring absorbance (405 nm) of the supernatants after 4 h of incubation at 37°C in the presence of water (100% hemolysis), PBS (baseline), or serial twofold dilutions of peptides in PBS starting from 200 μM [corresponding to 300, 500, and 430 μg/ml, respectively, for K₄-S4(1-13), MSI-78, and PG-1]. Plotted values correspond to the means ± standard deviations.