phycoérythrine

Phycoerythrin is a red phycobiliprotein pigment–protein complex that serves as part of the light-harvesting antennae in cyanobacteria and red algae. It is one of several phycobiliproteins that capture light energy and transfer it to the photosynthetic apparatus.

Phycoerythrin is water-soluble and consists of alpha and beta subunits that bind chromophores called phycoerythrobilins. Depending on the organism, different isoforms (such as C-phycoerythrin and R-phycoerythrin) are produced, with small variations in chromophore content and spectral properties.

Spectral properties: PE absorbs strongly in the green to yellow-green region (roughly 495–570 nm) and emits fluorescence in the yellow-red region, typically around 575–585 nm when excited by visible light. The exact maxima vary with the isoform and environment. Some PE molecules also carry different chromophores (phycoerythrobilin and related pigments) that influence absorption and emission.

Function: In phycobilisomes, PE forms part of the light-harvesting rods and transfers absorbed energy to allophycocyanin and the reaction centers of photosystem II or I, extending usable light into parts of the spectrum where chlorophyll absorbs poorly.

Applications: Phycoerythrin is widely used as a fluorescent label in biotechnology. It is intensely bright and can be excited by common lasers (e.g., blue 488 nm or green 561 nm) with emission around 575 nm, making it a standard dye for antibody labeling, flow cytometry, and fluorescence microscopy. It is available as purified PE and as PE-conjugates.