Annexin V fluorescent conjugates can be used to detect apoptotic cells. The human anticoagulant Annexin V is a 35-36 kDa calcium-dependent phospholipid-binding protein with high affinity for phosphatidylserine (PS). In normal viable cells, PS is located on the inner leaflet of the cytoplasmic membrane. In apoptotic cells, however, PS is translocated from the inner to the outer leaflet of the plasma membrane, where it can be detected by fluorescently labeled Annexin V. CF® Dye Annexin V Conjugates are provided at 50 ug/mL in buffer with azide as a preservative. CF® dyes are Biotium's line of next-generation fluorescent dyes with advantages in brightness, photostability, and conjugate specificity compared to other fluorescent dyes. Orange-red fluorescent CF®555 dye has excitation/emission at 555/565 nm.