Annexin V binding. HUVECs treated with staurosporine (left panels) or kept in suspension with serum deprivation (right panels) for 4, 8, and 16 hours were stained with FITC-conjugated recombinant annexin V in a buffer containing 2.5 mmol/L CaCl₂ and subsequently analyzed using flow cytometry. Almost 100% of normal cells (upper panel, right peak) show an increased fluorescence compared with cells stained in EDTA. The marker M1 represents the percentage of cells exhibiting a higher fluorescence than the control (lower 6 panels, left peak). The results of one representative experiment of three performed are shown.