Phycocyanin is a pigment -protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll.
Allophycocyanin absorbs and emits at longer wavelengths than phycocyanin C or phycocyanin R. Phycocyanins are found in cyanobacteria (also called blue-green algae ). Phycobiliproteins have fluorescent properties that are used in immunoassay kits.
Phycocyanobilin Phycocyanin is a pigment -protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble, so they cannot exist within the membrane like carotenoids can.
Phycocyanin has both anti-oxidant and anti-inflammation properties. Peroxyl, hydroxyl, and alkoxyl radicals are all oxidants scavenged by C-PC. C-PC, however, has a greater effect on peroxyl radicals.
Phycocyanin is light harvesting, pigment binding protein isolated from algae. In Japan and China phycocyanin used as a usual coloring agent in dairy and nutritional like jellies, gums, candies, beverages and cosmetics products. Phycocyanin is light and heat sensibilized, but it is a more epitome blue colorant than indigo and gardenia. Phycocyanin isolated from algal is also valuable in management of diverse types of cancers. Like S. platensis extracted phycocyanin exhibited antitumor activity beside squamous cell carcinoma. A major biliproteins, C-phycocyanins (C-PC) isolated from S. platensis having many therapeutic potentials like free radical scavenging activity and antioxidant, anti inflammatory and anticancer properties. The enhanced phycocyanin isolated from S. platensis trigger apoptosis by CD59 proteins expression in HeLa cells line via activation of apoptosis enzymes, different caspases 2, 3, 4, 6, 8, 9, and 10. ( Li et al., 2005 ). It has been reported that apoptosis is caused by discharge of cytochrome c from mitochondria into the cytosol in HeLa cell treated with C-phycocyanine. PC is a potent tumor chemopreventive ( Li et al., 2005 ). Selenium-containing phycocyanin (Se-PC) isolated from S. platensis (selenium-enriched) is powerful anticarcinogenic agent on MCF-7 and A375 cells, human breast adenocarcinoma and human melanoma cells respectively. The apoptosis is trigger by Se-PC through accumulation of cells in sub-G1phase, condensation of nuclear and fragmentation of DNA in both MCF-7 and A375 cell line ( Chen et al., 2008 ). The pure c-phycocyanin and polysaccharides isolated from S. platensis induce proliferation and differentiation of committed hematopoietic progenitor cell and can be reduce the probability of anemia in mice and also amplify immunity by activation of macrophage functions, production of IL-I, phagocytic process.
Phycobilisomes in cyanobacteria and red algae are large antennae complexes that absorb light energy and transfer the energy for use in photosynthesis. These phycobiliprotein complexes absorb much of the visible spectrum and thus benefit the organisms by greatly extending their absorbance capacity. They are intimately attached to the photosynthetic membrane and project into the stromal region. When viewed by electron microcopy their dense packing on the photosynthetic membrane is seen in cross sections and also when the membrane surface is viewed from the stromal side ( Figure 6 (a) and 6 (b), respectively). Phycobilisomes vary in size and shape and the largest are found in red algae where they are oblong in shape and the total diameter may be equivalent to the diameter of two ribosomes. Cyanobacterial phycobilisomes tend to be smaller and disc-shaped. The simplest ones in Gloeobacter Violaceus occur as single rods extending from a membrane that serves as both plasma and photosynthetic membranes. When cells are broken in an aqueous medium the phycobilisomes dissolve into their individual protein components: phycobiliproteins and linker polypeptides. For isolation of intact phycobilisomes, high-molarity phosphate buffer (0.5–0.75 M, pH 6.8) plus detergent solubilization of the photosynthetic membrane are required. Normally denatured phycobiliproteins resolve into α- and β-subunits (15–21 kDa) on SDS-PAGE, except for the core-membrane linker (L CM ).
Phycobilisomes in cyanobacteria and red algae are large antennae complexes that absorb light energy and transfer the energy for use in photosynthesis. These phycobiliprotein complexes absorb much of the visible spectrum and thus benefit the organisms by greatly extending their absorbance capacity. They are intimately attached to the photosynthetic membrane and project into the stromal region. When viewed by electron microcopy their dense packing on the photosynthetic membrane is seen in cross sections and also when the membrane surface is viewed from the stromal side ( Figure 6 (a) and 6 (b), respectively). Phycobilisomes vary in size and shape and the largest are found in red algae where they are oblong in shape and the total diameter may be equivalent to the diameter of two ribosomes. Cyanobacterial phycobilisomes tend to be smaller and disc-shaped. The simplest ones in Gloeobacter Violaceus occur as single rods extending from a membrane that serves as both plasma and photosynthetic membranes. When cells are broken in an aqueous medium the phycobilisomes dissolve into their individual protein components: phycobiliproteins and linker polypeptides. For isolation of intact phycobilisomes, high-molarity phosphate buffer (0.5–0.75 M, pH 6.8) plus detergent solubilization of the photosynthetic membrane are required. Normally denatured phycobiliproteins resolve into α- and β-subunits (15–21 kDa) on SDS-PAGE, except for the core-membrane linker (L CM ).
Green sulfur bacteria get their color from bacteriochlorophyll c, d, or e in the chlorosome complex, red algae from phycoerythrin, and cyanobacteria from phycocyanin in their phycobilisomes. Green algae and higher plants have chlorophyll (chl) a and b in their LHC I and LHC II. The antenna proteins from these phylogenetic groups complexes share no sequence homology and light-harvesting systems are therefore likely to have evolved several times in contrast to photosynthetic reaction centers that seem to have only evolved once. The LHC systems of all higher plants (angiosperms, gymnosperms) as well as ferns, mosses, and green algae are, however, homologous structures and have a lot in common and these antenna systems will be described using examples from angiosperms, whose antennas are best studied.