ANNEXIN-V-FLUOS

In the early stages of apoptosis, changes occur at the cell surface. One of these plasma membrane alterations is the translocation of phosphatidylserine (PS) from the inner part of the plasma membrane to the outer layer, by which PS becomes exposed at the external surface of the cell.
Annexin-V-FLUOS detects apoptotic cells in suspension cells using flow cytometry (FACS) or fluorescence microscopy, by binding to phosphatidylserine on the outer leaflet of apoptotic cell membranes. A simultaneous labeling with, e.g., propidium iodide (PI) is needed for differentiation of apoptotic from necrotic cells.
Other secondary labeling is possible, e.g., membrane surface staining with a phycoerythrin or TRITC-labeled monoclonal antibody for further cellular characterization.

Annexin-V-FLUOS is a phospholipid-binding protein with a high affinity for phosphatidylserine (PS). Detection of cell-surface PS with annexin-V thus serves as a marker for apoptotic cells. Analysis may be by flow cytometry or by fluorescence microscopy.