Phycobilin

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Phycobilin

Phycobilins (from Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
: (phykos) meaning "alga", and from Latin

Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
: bilis meaning "bile") are chromophore

Chromophore

A chromophore is part of a molecule responsible for its color.When a molecule absorbs certain wavelengths of visible spectrum and transmits or reflects others, the molecule has a color....
s (light-capturing molecules) found in cyanobacteria

Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
and in the chloroplast

Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....
s of red algae

Red algae

The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000?6,000 species of mostly multicellular, ocean algae, including many notable seaweeds....
, glaucophyte

Glaucophyte

The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater microscopic algae. Together with the red algae and Viridiplantae they form the Archaeplastida....
s and some cryptomonad

Cryptomonad

The cryptomonads are a small group of flagellates, most of which have chloroplasts. They are common in freshwater, and also occur in marine and brackish habitats....
s (though not in green algae

Green algae

The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic ....
and higher plant

Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s). They are unique among the photosynthetic pigments in that they are bonded to certain water-soluble protein

Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s, known as phycobiliprotein

Phycobiliprotein

Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae that capture light energy which is then passed on to chlorophylls during photosynthesis....
s. Phycobiliproteins then pass the light energy to chlorophyll

Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
s for photosynthesis

Photosynthesis

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Encyclopedia

Phycobilins (from Greek

Greek language

Latin

Chromophore

Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
and in the chloroplast

Chloroplast

Red algae

Glaucophyte

Cryptomonad

The cryptomonads are a small group of flagellates, most of which have chloroplasts. They are common in freshwater, and also occur in marine and brackish habitats....
s (though not in green algae

Green algae

Plant

Protein

Phycobiliprotein

Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
s for photosynthesis

Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
.

The phycobilins are especially efficient at absorbing red, orange, yellow and green light, wavelengths which are not well absorbed by chlorophyll a. Organisms growing in shallow waters tend to contain phycobilins that can capture yellow/red light, 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

Fluorescence

Fluorescence is a luminescence that is mostly found as an optical phenomenon in cold bodies, in which the molecular absorption of a photon triggers the emission of a photon with a longer wavelength....
at a particular wavelength, and are therefore often used in research as chemical tags, e.g. by binding phycobiliproteins to antibodies

Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
in a technique known as immunofluorescence

Immunofluorescence

Immunofluorescence is the labeling of antibody or antigens with Fluorescence dyes. This technique is often used to visualize the subcellular distribution of biomolecules of interest....
.

Types

There are four types of phycobilins:

Phycoerythrobilin
Phycoerythrobilin

Phycoerythrobilin is a red phycobilin, i.e. an open tetrapyrrole chromophore found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads....
, which is red
Phycourobilin
Phycourobilin

Phycourobilin is a tetrapyrrole orange molecule involved in photosynthesis in cyanobacteria and red algae. This chromophore is bound to the phycobiliprotein phycoerythrin, the distal component of the light-harvesting system of cyanobacteria and red algae ....
, which is orange
Phycoviolobilin (also known as phycobiliviolin) found in phycoerythrocyanin
Phycoerythrocyanin

Phycoerythrocyanin is a tetrapyrrole blue molecule involved in photosynthesis, notably in Cyanobacteria and red algae. This chromophore is bound to the phycobiliprotein phycocyanin, an important component of the light-harvesting system of cyanobacteria and red algae ....
Phycocyanobilin
Phycocyanobilin

Phycocyanobilin is a blue phycobilin, i.e. a tetrapyrrole chromophore found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads....
(also known as phycobiliverdin), which is blue.

They can be found in different combinations attached to phycobiliproteins to confer specific spectroscopic properties.

Structural relation to other molecules

Chemically, phycobilins consist of an open chain of four pyrrole

Pyrrole

Pyrrole, or pyrrol, is a heterocyclic aromatic organic compound, a five-membered ring with the chemical formula carbon4hydrogen4nitrogenH....
rings (tetrapyrrole
Tetrapyrrole

Tetrapyrroles are compounds containing four pyrrole rings. With the exception of corrin, the four pyrrole rings are interconnected through one-carbon bridges, either in a linear or cyclic fashion....
) and are structurally similar to the bile

Bile

Bile or gall is a bitter yellow or green fluid secreted by hepatocytes from the liver of most vertebrates. In many species, bile is stored in the gallbladder between meals and upon eating is discharged into the duodenum where the bile aids the process of digestion of lipids....
pigment bilirubin

Bilirubin

Bilirubin is the yellow breakdown product of normal heme catabolism. Heme is formed from hemoglobin, a principal component of red blood cells. Bilirubin is excreted in bile, and its levels are elevated in certain diseases....
, which explains the name. (Bilirubin's conformation is also affected by light, a fact used for the phototherapy of jaundice

Jaundice

Jaundice, also known as icterus , is a yellowish discoloration of the skin, the conjunctival membranes over the sclera , and other mucous membranes caused by hyperbilirubinemia ....
d newborns.) Phycobilins are also closely related to the chromophores of the light-detecting plant pigment phytochrome

Phytochrome

Phytochrome is a photoreceptor protein, a pigment that plants use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum....
which also consist of an open chain of four pyrroles. Chlorophyll

Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
s are composed of four pyrroles as well, but there the pyrroles are arranged in a ring and contain a metal atom in the center.