Annexins are a family of calcium-dependent phospholipid-binding proteins, which bind to phosphatidylserine (PS) to identify apoptotic cells. In healthy cells, PS is predominantly located along the cytosolic side of the plasma membrane. Upon initiation of apoptosis, PS loses its asymmetric distribution in the phospholipid bilayer and translocates to the extracellular membrane, which is detectable with fluorescently labeled Annexin V. In early stages of apoptosis, the plasma membrane excludes viability dyes such as propidium iodide (PI), therefore cells which display only Annexin V staining (PI negative) are in early stages of apoptosis. During late-stage apoptosis, loss of cell membrane integrity allows Annexin V binding to cytosolic PS, as well as cell uptake of PI. Annexin V staining, paired with PI is widely used to identify apoptotic stages by flow cytometry.
Principles of the Test
Annexin V exhibits anti-phospholipase activity and binds to phosphatidylserine. FITC labelling allows simple direct detection by FACS analysis. Counterstaining by propidium iodide allows the discrimination of apoptotic cells.
Annexin V-FITC store at -20°C.
1×Binding Buffer and Propidium iodide (PI) store at 2-8°C.
All reagent stored protecting from light.
For Research Use Only. Not For Use In Diagnostic Procedures.