The structure of a protein encodes fluorescence. Such fluorescent proteins include green fluorescent protein (GFP), yellow fluorescent protein (YFP), red fluorescent protein (RFP), and various derivatives thereof.

Protein structure encodes fluorescence. These fluorescent proteins include green fluorescent protein (GFP), yellow fluorescent protein (YFP), red fluorescent protein (RFP), and various derivatives.

Phycoerythrin is isolated and purified from red algae. It emits intense fluorescence, exhibits excellent light absorption properties and a high quantum yield, and has a broad excitation and emission range in the visible spectral region.

Allophycocyanin (APC) is a phycobiliprotein isolated from spirulina. Like other phycobiliproteins, allophycocyanin is a fluorescent substance with extremely high absorption and quantum efficiency.

Since naturally extracted allophycocyanin (APC) undergoes hydrolysis in dilute solutions (low concentrations) or when exposed to lyotropic salt environments, APC is usually subjected to cross-linking treatment to maintain its stability in biological reaction systems.

Streptavidin-labeled phycoerythrin (SA-PE) can be used in combination with various affinity-purified secondary antibodies labeled with biotin or chromatography-grade proteins labeled with biotin for a variety of immunoassays. Compared with avidin, streptavidin is more stable, more sensitive, and has lower background, due to its smaller molecular structure and easier penetration into tissues.