R-phycoerythrin (R-PE) Annexin V conjugate is Annexin V labeled with R-phycoerythrin. Annexin V is a 35-36 kDa protein that has a high affinity for phosphatidylserine (PS). In normal viable cells, PS is located on the cytoplasmic surface of the cell membrane. In apoptotic cells, however, PS is translocated from the inner to the outer leaflet of the plasma membrane, making itself available for Annexin V binding.
R-PE belongs to the family of phycobiliproteins, which are derived from cyanobacteria and eukaryotic algae. R-PE has absorption maxima at 496, 546, and 565 nm respectively and emission at 578 nm. Because of the high extinction coefficient (1,960,000) and high fluorescence quantum yield (0.82), R-PE is by far the brightest dye for the 565 nm wavelength region.