Annexin V and propidium iodide are used to measure apoptosis and necrosis. Annexin V is a member of the annexin family of intracellular proteins that binds to phosphatidylserine (PS) in a calciumdependent manner. PS is normally only found on the intracellular leaflet of the plasma membrane in healthy cells, but during early apoptosis, PS translocates to the external leaflet. Fluorochrome-labeled Annexin V can then be used to specifically target and identify the PS on the surface of apoptotic cells. Annexin V binding alone cannot differentiate between apoptotic and necrotic cells. Propidium Iodide (PI) solution is a membrane-exclusion dye that permeates cells with compromised cell membranes and binds to DNA. Early apoptotic and healthy cells with intact membranes will exclude PI, while late stage
apoptotic and necrotic cells with compromised membranes are stained. Use of both Annexin V-FITC and PI allows researchers to characterize a cell population based on % normal, % apoptotic, and % necrotic /very late-stage apoptotic cells.
Learn more about Apoptosis Reagents