Influence of Ionic Strength, pH, and SDS Concentration on Subunit Analysis of Phycoerythrins by SDS-PAGE

Biosynthesis of selenoproteins by Saccharomyces cerevisiae and characterization of its antioxidant activities

The study investigated biosynthesis of selenoproteins by Saccharomyces. cerevisiae using inorganic selenium. Selenium supplement via two stages was carried out during fermentation and the physicochemical characteristics of selenoproteins and its antioxidant activities were examined through in vitro assessment procedures. After fermentation, dry cells weight (7.47 g/L) and selenium content (3079.60 μg/kg) in the yeast were achieved when fermentation time points at the 6th hour and the 9th hour were chosen to supplement 30% and 70% of 30 μg/mL Na₂SeO₃ respectively. A maximal yield of selenium content in selenoproteins reached 1013.07 μg/g under optimized culture conditions and was 133-fold higher than the control. One new band with molecular weight of 26.76 KDa appeared in conjugated selenoproteins of sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Surface structure of selenoproteins and the control was different by Scanning electron microscopy images. Infrared spectrometry analysis demonstrated that groups of HSe, SeO and C-Se-O involved in selenoproteins were important pieces of evidence showing presence of Se embedded in the protein molecule. Selenoproteins showed strong antioxidant activities on DPPH·, OH and ·O^2-, which was much higher than the control proteins. Therefore, the study provided an efficient selenium-enriched culture method of inorganic selenite to organic selenium and basis for selenoproteins applications.

Effect of pH on physicochemical properties of oil bodies from different oil crops

The objective of this study was to determine the effects of pH on the physicochemical properties of soybean oil bodies (SBOBs), peanut oil bodies (PNOBs) and sunflower oil bodies (SFOBs). The mean particle diameter_[4,3] (D_[4,3]) of oil bodies (OBs) changed to a stationary trend with increased pH. The surface hydrophobicity (H₀) of SBOBs, PNOBs and SFOBs significantly decreased with increasing pH 2-12. The emulsifying activity index of SBOBs, PNOBs and SFOBs decreased with increased pH from 2 to 10. The viscosity modulus (G″) value of SBOBs at pH 4 was significantly higher than at pH 7 and pH 9. The initial elastic modulus (G') and G″ values of PNOBs at pH 9 were significantly higher than at pH 4 and pH 7. The G″ values of SFOBs at pH 4 and pH 9 were significantly lower than at pH 7. The steroleosin protein bands of SBOBs significantly decreased at pH 12. The protein bands of PNOBs were reduced at pH 2-4 and pH 10-12, and protein bands decreased most obviously at pH 2. The enthalpy of denaturation (ΔH) values of the oil body (OB) protein at pH 9 were significantly higher than at pH 4 and pH 7. The results showed that the ζ-potential, D_[4,3], emulsifying property and H₀ of SBOBs, PNOBs and SFOBs were similar to the change of pH value. The three types of OBs have better stability away from the isoelectric point.

Concentration and detection of hepatitis A virus and its indicator from artificial seawater using zeolite

Hepatitis A virus (HAV) infection is the leading worldwide cause of acute viral hepatitis, and outbreaks caused by this virus often occur in fecal polluted waters. Rapid concentration and detection of viral contamination in water environments can prevent economic loss and can identify the source of contamination within a short time. However, conventional methods for virus concentration are often laborious, time consuming, and subject to clogging. Furthermore, most methods require a secondary concentration step to reduce the final volume of samples. We developed a method to concentrate HAV from seawater using zeolite in aid of rapid detection. In this method,artificial seawater was inoculated with HAV (7-8 log TCID50) and filtered with zeolite. The viruses were then eluted from zeolite with sodium dodecyl sulfate and detected via real-time PCR (qPCR). Zeolite was able to concentrate HAV from artificial seawater with ∼99% efficiency in less than 5min and was more efficient in seawater than in fresh water. The entire concentration and detection can be done in approximately 2h. Compared to existing methods, this method eliminated the need for a secondary concentration step as well as the necessity to modify the pH or salinity of the seawater during concentration, and was simple and inexpensive.

The 42.1 and 53.7 kDa bands in SDS-PAGE of R-phycoerythrin from Polysiphonia urceolata

In SDS-PAGE gels of three purified R-phycoerythrins (R-PEs) isolated from three species of red algae, two bands whose molecular weights were about 40 kDa and 50 kDa can stably be found when the sample loading amount was enough. It is important for structure study of R-PE to clarify what these bands represent and how they are formed. According to results of the second SDS-PAGE, as well as molecular weights, fluorescences under UV and abundance, the 42.1 kDa and 53.7 kDa bands in SDS-PAGE gels of R-PE from Polysiphonia urceolata were believed to be complexes of αβ and βγ1, respectively. Formation of these bands may be related to light and phycourobilins (PUB) in subunits; and appearance of these two bands provided some proofs on position of chromophores and directions of energy transfer in R-PE. R-PE containing γ1 subunit was obviously more stable than R-PE containing γ2 subunit when they were exposed to protein denaturants, so γ subunits of R-PE may play important roles in structural stability of R-PE aggregates and the main forces that maintain the stability of R-PE may be interactions between γ subunit and β subunits.