Determination of apoptosis and membrane integrity by FACS. Cells were treated with etoposide, mellitin and Pep27 anal2. Apoptosis and membrane integrity were determined using annexin V and propidium iodide (PI), respectively, as described in Materials and Methods. A, control; B, 100 μM etoposide; C, 12.5 μM mellitin; D, 12.5 μM Pep27anal2; E, 62.5 μM Pep27anal2. Left, dual staining for annexin V-FITC (FL1-H) and PI (FL2-H); Middle, distribution of annexin V-FITC staining in cell populations; Right, distribution of PI staining. Similar results were obtained in independent duplicated experiments.