Annexin V-APC/SYTOX Green Apoptosis Kit is possible to differentiate cells at various stages of apoptosis and distinguish dead cells Annexin V is a calcium-dependent phospholipid-binding protein which specifically binds to phosphatidylserine (PS) Under normal conditions PS is located on the inner surface of the cell membrane lipid bilayer but during early apoptosis PS translocates from the inner leaflet to the outer leaflet of the plasma membrane becoming exposed to the extracellular environment By using Annexin V-APC labeling apoptotic cells can be detected easily through flow cytometry or fluorescence microscopy within 15-30 minutes Moreover this kit contains SYTOX Green a nuclear probe that binds specifically to double-stranded DNA emitting green fluorescence SYTOX Green normally cannot permeate intact cell membranes It can penetrate the membranes of late-stage apoptotic cells or dead cells thus staining their nuclei