Allophycocyanin (APC) is a phycobiliprotein isolated from Spirulina sp., a blue-green alga. Like other phycobiliproteins, APC is fluorescent, with an extremely high absorptivity and a high quantum efficiency. It is a protein which can be easily linked to

R-Phycoerythrin (RPE+) is a phycobiliprotein isolated from a species of red algae chosen specifically because it yields one of the most highly fluorescent of the RPEs. Like other phycobiliproteins, RPE+ is fluorescent, with an extremely high absorptivity,