Phycoerythrin is a red protein from the light-harvesting phycobiliprotein family, isolated from red, blue-green, and cryptomonad algae.

A strong absorption peak exists at about 566nm, and a strong emission peak exists at 575nm +/-10 nm. (I.e.: phycoerythrin absorbs green light and emits red light.)

Like all phycobiliproteins, phycoerythrin contains as chromophore (light-capturing part) a molecule that consists of an open chain of four pyrrole rings. This chromophore is known as phycoerythrobilin.

In algae, phycoerythrin is an accessory pigment to the main light-absorbing chlorophyll pigments responsible for photosynthesis. The light energy is captured by phycoerythrin and is then passed on to chlorophyll.

R-Phycoerythrin is useful in the laboratory as a fluorescence-based indicator for the presence of cyanobacteria and for labeling antibodies in a technique called immunofluorescence, among other applications.

Proteins | Photosynthetic pigments | Fluorescent dyes