In addition, fluorescence detection of phycocyanin pigments in water samples is a useful method to monitor cyanobacteria biomass.

[3] The phycobiliproteins are made of two subunits (alpha and beta) having a protein backbone to which 1–2 linear tetrapyrrole chromophores are covalently bound.

C-phycocyanin is often found in cyanobacteria which thrive around hot springs, as it can be stable up to around 70 °C, with identical spectroscopic (light absorbing) behaviours at 20 and 70 °C.

Photo-spectral analysis of the protein after 1 min exposure to 65 °C conditions in a purified state demonstrated a 50% loss of tertiary structure.

[4] The structure begins with the assembly of phycobiliprotein monomers, which are heterodimers composed of α and β subunits, and their respective chromophores linked via thioether bond.

Monomers spontaneously aggregate to form ring-shaped trimers (αβ)3, which have rotational symmetry and a central channel.

Despite the overall similarity in structure and assembly of phycobiliproteins, there is a large diversity in hexamer and rod conformations, even when only considering phycocyanins.

This additional PCB faces the exterior of the trimeric ring and is therefore implicated in inter-rod energy transfer in the phycobilisome complex.

In addition to cofactors, there are many predictable non-covalent interactions with the surrounding solvent (water) that are hypothesized to contribute to structural stability.

[7] C-phycocyanin has a single absorption peak at ~621 nm,[8][9] varying slightly depending on the organism and conditions such as temperature, pH, and protein concentration in vitro.

[12] Even if cyanobacteria have large concentrations of phycocyanin, productivity in the ocean is still limited due to light conditions.

[13] For instance a study in the Baltic Sea used phycocyanin as a marker for filamentous cyanobacteria during toxic summer blooms.

[15] Photoautotrophic production of phycocyanin is where cultures of cyanobacteria are grown in open ponds in either subtropical or tropical regions.

[15] G. sulphuraria is an example of the heterotrophic production of C-PC because its habitat is hot, acidic springs and uses a number of carbon sources for growth.

As shown in the highly specific association between Lichina species and Rivularia strains, phycocyanin has enough phylogenetic resolution to resolve the evolutionary history of the group across the northwestern Atlantic Ocean coastal margin.

[17] The two genes cpcA and cpcB, located in the cpc operon and translated from the same mRNA transcript, encode for the C-PC α- and β-chains respectively.

[18] Additional elements such as linker proteins, and enzymes involved in phycobilin synthesis and the phycobiliproteins are often encoded by genes in adjacent gene clusters, and the cpc operon of Arthrospira platensis also encodes a linker protein assisting in the assembly of C-PC complexes.

In A. platensis, six putative promoter sequences have been identified in the region, with four of them showing expression of green fluorescent protein when transformed into E.

[25] Temperature has also been shown to affect synthesis, with specific pigment concentrations showing a clear maximum at 36 °C in Arthronema africanum, a cyanobacterium with particular high C-PC and APC contents.

Organic carbon sources stimulate C-PC synthesis in Anabaena spp., but seem to have almost no effector negative effect in A. platensis.

[27][28] In the rhodophytes Cyanidium caldarium and Galdieria sulphuraria, C-PC production is repressed by glucose but stimulated by heme.

C-phycocyanin scavenges hydrogen peroxide, a type of ROS species, from the inside of astrocyte, reducing oxidative stress.

[31][39] Vadiraja et al. (1998) found an increase in the serum glutamic pyruvic transaminase (SGPT) when C-PC is treated against heptatoxins such as Carbon tetrachloride (CCl4) or R-(+)-pulegone.