Effect of membrane-bound RESA F5 fragment on malarial invasion. The proportion of cells infected by P falciparum in culture was assayed by flow cytometry, using YOYO-1 to stain parasite DNA. (A) Uninfected ghosts. (B) Control ghosts (no RESA fragment) exposed to parasites in culture. (C) Ghosts containing 80 μM RESA F5. (D) Dependence of invasion efficiency on intracellular RESA F5 concentration. At the highest concentration of RESA F5 used (80 μM), at which invasion is suppressed by about 60%, the calculated occupancy of spectrin sites in the cell by the peptide is about 60%. Results represent the mean value of triplicate samples.