Phycobilin
From Wikipedia, the free encyclopedia
Phycobilins (from Greek: φύκος (phykos) meaning "alga", and from Latin: bilis meaning "bile") are light-capturing bilins found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads (though not in green algae and plants).[1] Most of their molecules consist of a chromophore which makes them coloured.[1] They are unique among the photosynthetic pigments in that they are bonded to certain water-soluble proteins, known as phycobiliproteins. Phycobiliproteins then pass the light energy to chlorophylls for photosynthesis.[1]
The phycobilins are especially efficient at absorbing red, orange, yellow, and green light, wavelengths that are not well absorbed by chlorophyll a.[2] Organisms growing in shallow waters tend to contain phycobilins that can capture yellow/red light,[3] while those at greater depth often contain more of the phycobilins that can capture green light, which is relatively more abundant there.
The phycobilins fluoresce at a particular wavelength, and are, therefore, often used in research as chemical tags, e.g., by binding phycobiliproteins to antibodies in a technique known as immunofluorescence.[4]