Annexin V is a calcium-dependent phospholipid binding protein that can be used to bind Phosphatidylserine(PS) during an early apoptosis event where the PS becomes exposed at the cell surface.
The Annexin V-FITC Kit is supplied with an optimized Binding Buffer and propidium iodide. Propidium iodide may be used on unfixed samples to determine the population of cells that have lost membrane integrity, allowing discrimination between apoptotic and necrotic (or late apoptotic) cells.