Annexin V is a Ca2 -dependent phospholipid-binding protein that specifically binds to phosphatidylserine (PS) PS is normally located on the inner leaflet of the cell membrane phospholipid bilayer However during the early stages of apoptosis PS moves from the inner surface to the outer surface of the cell membrane becoming exposed to the extracellular environment Labeled with a fluorescence dye such as PE Annexcin V is commonly used as a fluorescent probe to detect apoptosis through flow cytometry or fluorescence microscopy within 15-30 minutes To use this reagent additional purchase of 10X Binding Buffer (Cat No K2284) is required or you can directly purchase the Annexin V-PE Apoptosis Kit which includes the buffer (Cat No K2281) To further identify different stages of apoptosis we provide ready-to-use double-staining kits Annexin V-PE/7-AAD Apoptosis Kit (K2283) or Annexin V-PE/DAPI Apoptosis Kit (K2282)