Phycobiliprotein

Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae (rhodophytes, cryptomonads, glaucocystophytes) that capture light energy, which is then passed on to chlorophylls during photosynthesis. Phycobiliproteins are formed of a complex between proteins and covalently bound phycobilins that act as chromophores (the light-capturing part). They are most important constituents of the phycobilisomes.

Major phycobiliproteins:

Many applications and instruments were developed specifically for R-phycoerythrin. It is commonly used in immunoassays such as FACS, flow cytometry, multimer/tetramer applications.

Structural Characteristics

R-phycoerythrin is also produced by certain red algae. The protein is made up of at least three different subunits and varies according to the species of algae that produces it. The subunit structure of the most common R-PE is (αβ)₆γ. The α subunit has two phycoerythrobilins (PEB), the β subunit has 2 or 3 PEBs and one phycourobilin (PUB), while the different gamma subunits are reported to have 3 PEB and 2 PUB (γ₁) or 1 or 2 PEB and 1 PUB (γ₂).

(Phycobiliprotein overview information)

(563 nm) 2.33 10⁶

Because of its high quantum yield, B-PE is considered the world’s brightest fluorophore. It is compatible with commonly available lasers and gives exceptional results in flow cytometry, Luminex® and immunofluorescent staining. B-PE is also less “sticky” than common synthetic fluorophores and therefore gives less background interference.

Structural Characteristics

B-phycoerythrin (B-PE) is produced by certain red algae such as Rhodella sp. The specific spectral characteristics are a result of the composition of its subunits. B-PE is composed of at least three subunits and sometimes more. The chromophore distribution is as follows: α subunit with 2 phycoerythrobilins (PEB), β subunit with 3 PEB, and the γ subunit with 2 PEB and 2 phycourobilins (PUB). The quaternary structure is reported as (αβ)₆γ.

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