Crustacyanin is a carotenoprotein

biological pigment Biological pigments, also known simply as pigments or biochromes, are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biol ...

found in the exoskeleton of

lobster Lobsters are a family (biology), family (Nephropidae, Synonym (taxonomy), synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs ...

s and responsible for their blue colour. β-Crustacyanin (β-CR), is composed of two stacked

astaxanthin Astaxanthin is a keto- carotenoid within a group of chemical compounds known as terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-soluble pigment with r ...

carotenoids that absorb at λ = 580–590 nm (2.10–2.14 eV). α-crustacyanin (α-CR) is an assembly of eight β-CR

protein dimer In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' ha ...

s. It is a 320 kDa (

atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&nbs ...

) complex containing 16 astaxanthin molecules. Although the β-CR dimer has a peak wavelength of 580 nm, α-CR exhibits a

bathochromic shift Bathochromic shift (from Greek βαθύς ''bathys'', "deep"; and χρῶμα ''chrōma'', "color"; hence less common alternate spelling "bathychromic") is a change of spectral band position in the absorption, reflectance, transmittance, or emissi ...

to 632 nm; the mechanism and function of the additional wavelength shift is not understood.

References

{{reflist Biological pigments