One of the earliest indications of apoptosis is the translocation of phosphatidylserine from the inner to the outer leaflet of the plasma membrane. Once exposed to the extracellular environment, phosphatidylserine becomes available for annexin V, a 35–36 kDa Ca2+ dependent phospholipid-binding protein with a high affinity for it. The early apoptotic cells have still intact plasma membrane, so their DNA is not accessible for propidium iodide dye, and these cells are annexin V positive and propidium iodide negative, unlike viable cells (annexin V negative, propidium iodide negative) and necrotic cells or late apoptotic cells (annexin V positive, propidium iodide positive).
EXBIO offers a complex solution for apoptosis detection via flow cytometry method: ApoFlowEx kit, annexin V in multiple formats, annexin V binding buffer and antibodies to apoptosis related antigens.
