Annexin V predicts a molecular mass of 36.8 kDa. is commonly used to detect apoptotic cells by its ability to bind to phosphatidylserine, a marker of apoptosis when it is on the outer leaflet of the plasma membrane. Annexin V forms a shield around negatively charged phospholipid molecules. The formation of an annexin V shield blocks the entry of phospholipids into coagulation reactions.