Electrophoretic applications of phycobiliproteins

A Review on a Hidden Gem: Phycoerythrin from Blue-Green Algae

Phycoerythrin (PE) is a pink/red-colored pigment found in rhodophytes, cryptophytes, and blue-green algae (cyanobacteria). The interest in PE is emerging from its role in delivering health benefits. Unfortunately, the current cyanobacterial-PE (C-PE) knowledge is still in the infant stage. It is essential to acquire a more comprehensive understanding of C-PE. This study aimed to review the C-PE structure, up and downstream processes of C-PE, application of C-PE, and strategies to enhance its stability and market value. In addition, this study also presented a strengths, weaknesses, opportunities, and threats (SWOT) analysis on C-PE. Cyanobacteria appeared to be the more promising PE producers compared to rhodophytes, cryptophytes, and macroalgae. Green/blue light is preferred to accumulate higher PE content in cyanobacteria. Currently, the prominent C-PE extraction method is repeated freezing-thawing. A combination of precipitation and chromatography approaches is proposed to obtain greater purity of C-PE. C-PE has been widely exploited in various fields, such as nutraceuticals, pharmaceuticals, therapeutics, cosmetics, biotechnology, food, and feed, owing to its bioactivities and fluorescent properties. This review provides insight into the state-of-art nature of C-PE and advances a step further in commercializing this prospective pigment.

Confocal Microscopy in Ecophysiological Studies of Algae: A Door to Understanding Autofluorescence in Red Algae

Alga in the genus Chroothece have been reported mostly from aquatic or subaerial continental environments, where they grow in extreme conditions. The strain Chroothece mobilis MAESE 20.29 was exposed to different light intensities, red and green monochromatic light, ultraviolet (UV) radiation, high nitrogen concentrations, and high salinity to assess the effect of those environmental parameters on its growth. Confocal laser scanning microscopy (CLSM) was used as an “in vivo” noninvasive single-cell method for the study. The strain seemed to prefer fairly high light intensities and showed a significant increase in allophycocyanin (APC) and chlorophyll a [photosystem I (PSI) and photosystem II (PSII)] fluorescence with 330 and 789 μM/cm2/s intensities. Green monochromatic light promoted a significant increase in the fluorescence of APC and chlorophyll a (PSI and PSII). UV-A significantly decreased phycocyanin and increased APC, while UV-A + B showed a greater decreasing effect on c-Phycocyanin but did not significantly change concentrations of APC. The increase in nitrogen concentration in the culture medium significantly and negatively affected all pigments, and no effect was observed with an increase in salinity. Our data show that CLSM represents a very powerful tool for ecological research of microalgae in small volumes and may contribute to the knowledge of phycobiliproteins in vivo behavior and the parameters for the large-scale production of these pigments.

Phycobiliproteins Production Enhancement and Lipidomic Alteration by Titanium Dioxide Nanoparticles in Synechocystis sp. PCC 6803 Culture

This study aimed to improve the production of phycobiliproteins using TiO₂ nanoparticles (NPs) in Synechocystis sp. PCC 6803. The growth characteristics of Synechocystis cells were not affected by TiO₂ NPs treatment, but this treatment increased the chlorophyll content significantly by 62.2% (14.6 mg/L) compared to that of control (9.0 mg/L) on day 16. Phycocyanin production was increased by 33.8% (29.3 g/L) compared to that of control (21.9 g/L) on day 8. Allophycocyanin production was increased by 55.0% (6.2 g/L) compared to that of control (4.0 g/L) on day 8, and by 22.4% (16.4 g/L) compared to that of control (13.4 g/L) on day 16. Direct infusion mass spectrometry revealed that TiO₂ NPs treatment significantly increased the levels of major thylakoid membranes of monogalactosyldiacylglycerols (18:2/18:3, 18:2/18:2, 18:1/18:2), phosphatidylglycerol (16:0/16:1), and sulfoquinovosyldiacylglycerols (16:0/16:1, 16:0:18:4) on day 8. These findings indicate that TiO₂ NPs have potential for commercial applications in Synechocystis species or other microalgal strains.

A microfluidic chip with a staircase pH gradient generator, a packed column and a fraction collector for chromatofocusing of proteins

A microfluidic device for pH gradient chromatofocusing is presented, which performs creation of a micro-column, pH gradient generation, and fraction collection in a single device. Using a sieve micro-valve, anion exchange particles were packed into a microchannel in order to realize a solid-phase absorption column. To fractionate proteins according to their isoelectric points, elution buffer solutions with a stepwise pH gradient were prepared in 16 parallel mixing reactors and flowed through the micro-column, wherein a protein mixture was previously loaded. The volume of the column is only 20 nL, hence it allows extremely low sample consumption and fast analysis compared with a conventional system. We demonstrated separation of two proteins, albumin-fluorescein isothiocyanate conjugate (FITC-BSA) and R-Phycoerythrin (R-PE), by using a microcolumn of commercial charged polymeric particles (Source 15Q). The microfluidic device can be used as a rapid diagnostic tool to analyse crude mixtures of proteins or nucleic acids and determine adsorption/desorption characteristics of various biochemical products, which can be helpful for scientific fundamental understanding as well as instrumental in various industrial applications, especially in early stage screening and process development.

Recent advances in production, purification and applications of phycobiliproteins

An obligatory sunlight requirement for photosynthesis has exposed cyanobacteria to different quantity and quality of light. Cyanobacteria can exhibit efficient photosynthesis over broad region (450 to 650 nm) of solar spectrum with the help of brilliantly coloured pigment proteins called phycobiliproteins (PBPs). Besides light-harvesting, PBPs are found to involve in several life sustaining phenomena including photoprotection in cyanobacteria. The unique spectral features (like strong absorbance and fluorescence), proteineous nature and, some imperative properties like hepato-protective, anti-oxidants, anti-inflammatory and anti-aging activity of PBPs enable their use in food, cosmetics, pharmaceutical and biomedical industries. PBPs have been also noted to show beneficial effect in therapeutics of some disease like Alzheimer and cancer. Such large range of applications increases the demand of PBPs in commodity market. Therefore, the large-scale and coast effective production of PBPs is the real need of time. To fulfil this need, many researchers have been working to find the potential producer of PBPs for the production and purification of PBPs. Results of these efforts have caused the inventions of some novel techniques like mixotrophic and heterotrophic strategies for production and aqueous two phase separation for purification purpose. Overall, the present review summarises the recent findings and identifies gaps in the field of production, purification and applications of this biological and economically important proteins.

One-step purification of R-phycoerythrin from the red edible seaweed Grateloupia turuturu

A one-step chromatographic method for the purification of R-phycoerythrin (R-PE) of Grateloupia turuturu Yamada is described. Native R-PE was obtained with a purity index of 2.89 and a recovery yield of 27% using DEAE-Sepharose Fast Flow chromatography with a three-step increase in ionic strength. The analysis by SDS electrophoresis showed a broad band between 18 and 21kDa in size corresponding to subunits α and β and a low intensity band of 29kDa corresponding to the γ subunit. Two forms of R-PE were identified by gel filtration chromatography: a native form with a molecular weight of 260±5kDa and a dissociated form with a molecular weight of 60±2kDa. The native form presented the characteristic absorption spectrum of R-PE with three absorbance maxima at 498, 540 and 565nm, whereas the dissociated form presented only the 498 and 540nm peaks. Moreover, the two forms displayed two different fluorescence maxima.

PHYCOBILIPROTEIN COMPONENTS AND CHARACTERISTICS OF THE PHYCOBILISOME FROM A THERMOPHILIC CYANOBACTERIUM MYXOSARCINA CONCINNA(1)

A phycocyanin (PC) and three allophycocyanin (AP) components (designated PC, AP1, AP2, and AP3) were prepared from Myxosarcina concinna Printz phycobilisomes by the native gradient PAGE performed in a neutral buffer system combined with the ion exchange column chromatography on DEAE-DE52 cellulose. PC contained one β subunit () and two α ones ( and ), and it carried two rod linkers ( and ) and one rod-core linker (). AP1 and AP3 were characterized as peripheral core APs, whereas AP2 was an inner-core one. AP2 and AP3 were demonstrated to function as the terminal emitters. Each of the three APs contained two β subunits ( and ), two α subunits ( and ) and an inner-core linker (). AP2 and AP3 had another subunit of the allophycocyanin B (AP-B) type () belonging to the β subunit group, and AP1 and AP3 carried their individual specific core linkers ( and ), respectively. No AP component was shown to associate with the core-membrane linker LCM . The functions of the linker polypeptides in the phycobilisome (PBS) construction are discussed.

Microchannel protein separation by electric field gradient focusing

A microchannel device is presented which separates and focuses charged proteins based on electric field gradient focusing. Separation is achieved by setting a constant electroosmotic flow velocity against step changes in electrophoretic velocity. Where these two velocities are balanced for a given analyte, the analyte focuses at that point because it is driven to it from all points within the channel. We demonstrate the separation and focusing of a binary mixture of bovine serum albumin and phycoerythrin. The device is constructed of intersecting microchannels in poly(dimethylsiloxane)(PDMS) inlaid with hollow dialysis fibers. The device uses no exotic chemicals such as antibodies or synthetic ampholytes, but operates instead by purely physical means involving the independent manipulation of electrophoretic and electroosmotic velocities. One important difference between this apparatus and most other devices designed for field-gradient focusing is the injection of current at discrete intersections in the channel rather than continuously along the length of a membrane-bound separation channel.

Extracting and purifying R-phycoerythrin from Mediterranean red algae Corallina elongata Ellis & Solander

R-Phycoerythrin (R-PE) is a protein acting as a photosynthetic accessory pigment in red algae (Rodophyta). This protein has gained importance in many biotechnological applications in food science, immunodiagnostic, therapy, cosmetics, protein and cell labelling, and analytical processes. In this paper we report on a new, one step procedure for the extraction and purification of R-PE from a new source: the Mediterranean red algae Corallina elongata Ellis & Solander. This red algae contains mainly R-PE and is suitable for the production in culture. No other contaminating phycobiliproteins could be detected in the extracts. The method we propose for the purification is based on the use of hydroxyapatite, a chromatographic resin that can be produced in the laboratory at very low cost and can be used batch-wise with large amounts of extracts, alternative to chromatography, and therefore can be scaled up. Both the yield and the purity of R-PE are very good.

Determination of phycobiliproteins by capillary electrophoresis with laser-induced fluorescence detection

Phycobiliproteins are derived from the photosynthetic apparatus of cyanobacteria and eukaryotic algae. They are composed of a protein backbone to which linear tetrapyrrole chromophores are covalently bound. Furthermore, they are water-soluble highly fluorescent, and relatively stable at room temperature and neutral pH. For this reason, capillary electrophoresis-laser induced fluorescence (CE-LIF) seems the idea method for determination of these important proteins. The effects of buffer additives such as sodium dodecyl sulfate (SDS)and putrescine on the separation of the three major phycobiliprotein types, namely allophycocyanin, phycocyanin, and phycoerythrin, with excitation and emission maxima at 652/660, 615/647, and 565(494)/575 nm, respectively, are considered. Detection limits for these proteins by CE-LIF are some 60-500 times better than by absorbance detection. The development of a fast and sensitive CE-LIF assay such as this is of potential significance to our understand ing of chemical and biological oceanographic processes.

A thousand points of light: the application of fluorescence detection technologies to two-dimensional gel electrophoresis and proteomics

As proteomics evolves into a high-throughput technology for the study of global protein regulation, new demands are continually being placed upon protein visualization and quantitation methods. Chief among these are increased detection sensitivity, broad linear dynamic range and compatibility with modern methods of microchemical analyses. The limitations of conventional protein staining techniques are increasingly being encountered as high sensitivity electrophoresis methods are interfaced with automated gel stainers, image analysis workstations, robotic spot excision instruments, protein digestion work stations, and mass spectrometers. Three approaches to fluorescence detection of proteins in two-dimensional (2-D) gels are currently practiced: covalent derivatization of proteins with fluorophores, intercalation of fluorophores into the sodium dodecyl sulfate (SDS) micelle, and direct electrostatic interaction with proteins by a Coomassie Brilliant Blue-type mechanism. This review discusses problems encountered in the analysis of proteins visualized with conventional stains and addresses advances in fluorescence protein detection, including immunoblotting, as well as the use of charge-coupled device (CCD) camera-based and laser-scanner-based image acquisition devices in proteomics.

One-step purification of R-phycoerythrin from the red macroalga Palmaria palmata using preparative polyacrylamide gel electrophoresis

Phycoerythrin is a major light-harvesting pigment of red algae and cyanobacteria widely used as a fluorescent probe. In this study, phycoerythrin of the red macroalga Palmaria palmata was extracted by grinding the algal sample in liquid nitrogen, homogenisation in phosphate buffer and centrifugation. Phycoerythrin was then purified from this crude extract using preparative polyacrylamide gel electrophoresis (PAGE) with a continuous elution system and detected by its pink colour and fluorescence. The pigment presented a typical spectrum of R-phycoerythrin, with three absorbance maxima at 499, 545 and 565 nm, and displayed a fluorescence maximum at 578 nm. The absorbance ratio A565/A280, a criterion for purity, was 3.2. A single protein of relative molecular mass 240,000 was detected on native-PAGE with silver staining. Sodium dodecyl sulphate-PAGE demonstrated the presence of two major subunits with Mr 20,000 and 21,000, respectively, and a very minor subunit of Mr 30,000. These observations are consistent with the (alphabeta)6gamma subunit composition characteristic of R-phycoerythrin. Phycoerythrin of Palmaria palmata was determined to be present in larger amounts in autumn and showed a good stability up to 60 degrees C and between pH 3.5 and 9.5. In conclusion, phycoerythrin of Palmaria palmata was purified in a single-step using preparative PAGE. Obtaining pure R-phycoerythrin of Palmaria palmata will allow one to evaluate its fluorescence properties for future applications in biochemical techniques.

Differential behaviour of two cyanobacterium species to UV radiation. Artificial UV radiation induces phycoerythrin synthesis

Altitude is an important factor contributing to the local UV-B climate. In the European Alps solar UV-B increases approximately 21% 1000 m-1. A Nostoc muscorum (UTEX 389) originating from Scotland and a Nostoc sp. isolated from a highland lake (Yanaqocha) located 3980 m above sea level (Cusco, Perú) have been used in a study where the tolerance to UV radiation (UVR) stress of both species was determined. Following irradiation doses of 15 kJ UV (UV-A plus UV-B, equivalent to approximately 6 h exposure to unfiltered solar light at noon for a standard midlatitude region with normal ozone concentration), the viability of Nostoc sp. is 30% compared to 3% for Nostoc muscorum. UV-B induces the reduction of the number of phycobilisomes per cell, phycobilisome disassembly and/or degradation as well as phycobilisome uncoupling. Following UV exposure, phycoerythrin (PE) fluorescence emission increases dramatically in both species, indicating accumulation of PE in the phycobilisome rods. The detected increase in PE due to UVR is confirmed using a monoclonal antibody anti-PE.