Biliverdin

Biliverdin (from the Latin for green bile) is a green tetrapyrrolic bile pigment, and is a product of heme catabolism.

It is the pigment responsible for a greenish color sometimes seen in bruises.

Biliverdin can be observed during the healing process of bruises, being responsible for the green color of a healing bruise. Its further breakdown into bilirubin leads to the bruise changing to a yellowish color.

Bile pigments such as biliverdin possess significant anti-mutagenic and antioxidant properties and therefore, may fulfill a useful physiological function. as well as having beneficial effects in asthma

Research has shown that the biliverdin of egg shells is produced from the shell gland, rather than from the breakdown of erythrocytes in the blood stream, although there is no evidence that the sources of the material are neither tetrapyrroles nor free heme from the blood plasma.

Along with its presence in avian egg shells, other studies have also shown that biliverdin is present in the blue-green blood of many marine fish, the blood of the tobacco hornworm, the wings of moth and butterfly, the serum and eggs of frogs, and the placenta of dogs. With dogs, this can lead, in extremely rare cases, to the birth of puppies with green fur; however, the green color fades out soon after birth. In the garfish (Belone belone) and related species, the bones are bright green because of biliverdin. The green coloration of many grasshoppers and lepidopteran larvae is also due to biliverdin.

Biliverdin is also present in the green blood, muscles, bones, and mucosal lining of skinks of the genus Prasinohaema, found in New Guinea. It is uncertain whether this presence of biliverdin is an ecological or physiological adaptation of any kind. It has been suggested that accumulation of biliverdin might deter harmful infection by Plasmodium malaria parasites, although no statistically significant correlation has been established. The Cambodian frog, Chiromantis samkosensis, also exhibits this characteristic along with turquoise bones.

In fluorescence imaging

thumb|320x320px|Fluorescent proteins visualize the cell cycle progression. IFP2.0-hGem(1/110) fluorescence is shown in green and highlights the S/G₂/M phases. [[smURFP-hCdtI(30/120) fluorescence is shown in red and highlights the G₀/G₁ phases.]]

In a complex with reengineered bacterial phytochrome, biliverdin has been employed as an IR-emitting chromophore for in vivo imaging. In contrast to fluorescent proteins which form their chromophore through posttranslational modifications of the polypeptide chain, phytochromes bind an external ligand (in this case, biliverdin), and successful imaging of the first bacteriophytochrome-based probe required addition of the exogenous biliverdin. Jellyfish- and coral-derived fluorescent proteins require oxygen and produce a stoichiometric amount of hydrogen peroxide upon chromophore formation. smURFP does not require oxygen or produce hydrogen peroxide and uses the chromophore biliverdin. smURFP has a large extinction coefficient (180,000 M⁻¹ cm⁻¹) and has a modest quantum yield (0.20), which makes it comparable biophysical brightness to eGFP and about 2-fold brighter than most red or far-red fluorescent proteins derived from coral. smURFP spectral properties are similar to the organic dye Cy5.