Phycobiliproteins are photosynthetic antenna pigments found in cyanobacteria (blue-green algae), red algae, and the cryptomonads. Phycoerythrin and Allophycocyanin offer the most powerful illuminating signal available. Their fluorescent power comes from their large number of chromophores and the most efficient light transduction of any natural or synthesized fluorophore. Phycobiliproteins have a Stokes shift 5-20 times greater than synthetic fluorophores which thereby eliminates background noise caused by overlap between the excitation light source and the fluorescence detectors.
The strong fluorescent properties of phycobiliproteins make them ideal for use in medical diagnostics and life science research. In addition, they are water-soluble, chemically and optically stable. They have multi-year shelf lives, are available in many wavelength ranges, and can be conjugated to a wide variety of partners, including antibodies, streptavidin, biotin, and lectins.
Over the years a large number of life science reagents have been developed using phycobiliproteins as a label. For example, R-Phycoerythrin (PE) is a preferred label for cytometry, Luminex® systems, tetramers and Affymetrix GeneChip®. Allophycocyanin (APC) is a commonly used label in Time-Resolved Fluorescence Resonant Energy Transfer (TR-FRET) assays for High Throughput Screening and Flow Cytometry.