Effect of intracellular RESA F5 fragment on red cell membrane stability. RESA F5 at concentrations of 0, 5, 20, 40, 60, and 80 μM was added to ghosts before resealing. Membrane mechanical stability of resealed ghosts was measured by ektacytometry. The deformability index (DI) measures the deformation of the membranes under constant shear stress. The decay of DI with time is due to progressive breakdown of the cells to vesicles, and thus reflects the extent of shear resistance. The fragmentation profiles for 0, 40, and 80 μM are labeled. It should be noted there is a progression in membrane stability with increasing concentrations of RESA peptide.