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]
There are four types of phycobilins: [1]
They can be found in different combinations attached to phycobiliproteins to confer specific spectroscopic properties.
In chemical terms, phycobilins consist of an open chain of four pyrrole rings ( tetrapyrrole) [5] and are structurally similar to the bile pigment bilirubin, [6] which explains the name. (Bilirubin's conformation is also affected by light, a fact used for the phototherapy of jaundiced newborns.) [7] Phycobilins are also closely related to the chromophores of the light-detecting plant pigment phytochrome, [8] which also consist of an open chain of four pyrroles. Chlorophylls are composed of four pyrroles as well, but there the pyrroles are arranged in a ring and contain a metal atom in the center of it.
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]
There are four types of phycobilins: [1]
They can be found in different combinations attached to phycobiliproteins to confer specific spectroscopic properties.
In chemical terms, phycobilins consist of an open chain of four pyrrole rings ( tetrapyrrole) [5] and are structurally similar to the bile pigment bilirubin, [6] which explains the name. (Bilirubin's conformation is also affected by light, a fact used for the phototherapy of jaundiced newborns.) [7] Phycobilins are also closely related to the chromophores of the light-detecting plant pigment phytochrome, [8] which also consist of an open chain of four pyrroles. Chlorophylls are composed of four pyrroles as well, but there the pyrroles are arranged in a ring and contain a metal atom in the center of it.