Effect of synthetic peptides derived from PfI2 and PfI3 on blood P. falciparum parasite growth. A and B. Inhibition of growth of 3D7 P. falciparum strain parasites by PfI2 derived peptides. Parasites were incubated with different concentrations of synthetic peptides for 72 hr in a 96-well microtiter plate. Parasitemia was quantified as described in Methods. P1 and P4 correspond to KTISW and HYNE motifs respectively. P6 (penetrating peptide alone) and P10 (mutated version of P1) were used as control peptides. C. Schematic representation of PfI3 sequence (Pf Inhibitor 3): P5 peptide corresponds to 41KVVRW45 (RVxF motif) and P11 is the mutated version of P5 used as control peptide. D. Inhibition of growth of P. falciparum 3D7 by synthetic peptides derived from PfI3. Results presented as% of parasite growth inhibition are means ± SEM of seven independent experiments performed in duplicate. E. IC50 values of P1 and P5 against 3D7 and HB3 P. falciparum strains and against stimulated primary mouse spleen cells. F. Selective penetration of FITC-labeled P1 (F) and P5 (G) peptides in P. falciparum 3D7. The left panel represents the DAPI staining, the middle panel represents the fluorescence signal and the right panel represents the bright field image.