Gene detection of staphylococcal enterotoxins in production strain of staphylococcin injection and superantigenic activity of rSEK and rSEQ

In China, staphylococcin injection has been commonly used in the combined treatment of cancer to enhance the systemic immune response and reduce the toxicities associated with chemotherapy and radiation therapy. It is claimed that the main active component in the injection is staphylococcal enterotoxin C2 (SEC2). To determine whether other serological types of staphylococcal enterotoxins (SEs) could also be present in the injection products, in this study, the distribution of se genes (from sea to see, from seg to seu) in the one and only production strain of Staphylococcus aureus from one manufacturing company was analyzed by PCR method. In addition, sek and seq genes were cloned from the strain and the corresponding recombinant proteins, rSEK and rSEQ, were expressed in Escherichia coli and purified by affinity chromatography and anion-exchange chromatography. The superantigenic properties of the two recombinant proteins were then measured by MTT method. The PCR results showed that seven se genes are harbored by the production strain. However, sec2 gene was not detected. The results of MTT assay showed that rSEK and rSEQ could elicit strong stimulatory effects on proliferation and cytotoxicity of murine splenocytes in vitro. Overall, the results in this study indicated that one or a plurality of the seven SEs may be present in the related products, and that the two recombinant SEs are promising candidates as immunomodulatory agents for cancer therapy.     

Simultaneous detection of dual proteins using quantum dots coated silica nanoparticles as labels

Simultaneous detection of multianalytes associated with a particular cancer is beneficial for disease diagnosis. Here, a facile immunosensing strategy was designed to allow simultaneous electrochemical detection of dual proteins, in a single run. CdSe and PbS water-soluble quantum dots (QDs) were prepared and coated on monodisperse silica nanoparticles as labels for proteins detection. Rabbit immunoglobulin G antigen (IgG) and carcinoembryonic antigen (CEA) were chosen as model proteins for analysis. After a typical sandwich immunoassay, CdSe and PbS QDs labels were introduced onto the Au substrates' surface, which were then dissolved and could be simultaneously monitored by square-wave-voltammetric (SWV) stripping measurements. Under selected conditions, IgG and CEA could be assayed in the ranges of 0.05-40 ng mL(-1) and 0.05-25 ng mL(-1), respectively. The proposed method possessed high sensitivity, good precision, and satisfactory reproducibility and regeneration.     

Fabrication of an oxytetracycline molecular-imprinted sensor based on the competition reaction via a GOD-enzymatic amplifier

A highly sensitive molecular-imprinted polymer sensor (MIP sensor) for ultratrace oxytetracycline (OTC) determination was prepared based on the competition reaction between template molecule OTC and glucose oxidase (GOD)-labeled OTC (GOD-OTC). Sensitivity improved dramatically due to the detection of a huge amount of enzyme catalytic production, which was inversely proportional to template molecule concentration. The MIP sensor was characterized by alternating current impedance spectroscopy and cyclic voltammetry, and its voltammetric behavior was also verified. Experimental conditions including isolation, incubation, and competition were optimized. OTC can be determined at concentrations between 0 and 4.0×10(-7) mol/L with a detection limit of 3.30×10(-10) mol/L by the differential pulse voltammetry technique. The MIP sensor showed high sensitivity, selectivity, reproducibility, and good recovery in sample determination.     

An enhanced ELISA based on modified colloidal gold nanoparticles for the detection of Pb(II)

A novel probe based on colloidal gold nanoparticles (AuNPs) modified with goat anti-mouse IgG and horseradish peroxidase (HRP) was synthesized and an enhanced enzyme-linked immunosorbent assay (ELISA) based on the probe was developed. In the assay, the synthesized probe is bound with a monoclonal antibody (McAb) which is competitively bound by coated BSA-ITCBE-Pb(II) on plate and Pb(II) in samples. The HRP, used here for signal amplification catalytically oxidize the substrate and generate optical signals that is related to the concentration of Pb(II) and can be measured spectrophotometrically. For the monodisperse AuNPs having high surface areas, it can be conjugated with more amount of HRP than that of IgG. Therefore, compared with traditional ELISA, the signal amplification of catalytically oxidized substrate was enhanced. The detection limit for this novel modified AuNPs probe-based assay was 9 pg mL(-1). The recoveries obtained by standard Pb(II) addition to real samples, including a commercial mineral water, tap water, and lake water were all from 94.9% to 102.9%. And the coefficient of variation (CV) value of all samples was less than 10%. The results indicated that the enhanced assay gave higher sensitivity and reliable reproducibility. It could provide a general detection format for low-molecular weight contaminants.     

Upgrading of high-boiling fraction of bio-oil in supercritical methanol

In this work, the upgrading reactions of high-boiling fraction (HBF) of bio-oil were carried out over a series of supported mono- and bi-metallic catalysts under the supercritical methanol condition. During these reactions, esterification and cracking (alcoholysis and hydrocracking) were the two dominant processes. PtNi/MgO exhibited good performance, and gave a high yield (72.4 wt.%) of refined oil. The acid-base properties of the supports have an important effect on the coke deposition on the catalyst surface. The acidic catalysts gave the somewhat lower product yields, but tended to inhibit coking reaction. This would improve the life of the catalysts in the practical applications. The refined oil is believed to be a potential substitute or partial substitute for the fossil transportation fuel.     

Stereoselective degradation of Diclofop-methyl during alcohol fermentation process

Stereoselective degradation of Diclofop-methyl (DM) has been found in alcohol fermentation of grape must and sucrose solution with dry yeast. A method was developed for separation and determination the two enantiomers of DM during the fermentation process by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase. The results showed that the enantiomers of DM degraded following the first-order kinetics in the sucrose solution and the degradation of DM enantiomers in grape must were biphasic (slow-fast-slow process). In the sucrose solution, half lives of (+)-(R)-DM and (-)-(S)-DM were calculated to be 8.5 h and 3.1 h, respectively. In the grape must, half life of (+)-(R)-DM was calculated to be 41.7 h while (-)-(S)-DM was 16.0 h. The result was that (-)-(S)-enantiomer degraded faster than the (+)-(R)-enantiomer in both alcohol fermentation. The results also showed that the differences of the enantioselective degradation of DM depended on the fermentation matrix. DM was configurationally stable in fermentation, showing no interconversion of (-)-(S)- to (+)-(R)- enantiomer, and vice-versa.     

Mix and match: heterodimers and opioid tolerance

The mechanism by which multiple brain structures interact to support working memory is not yet fully understood. In this issue of Neuron, Fujisawa and Buzsáki report that coordinated oscillatory activities between the hippocampus, prefrontal cortex, and ventral tegmental area (VTA) may be a key neural correlate of working memory.     

The effect of feed salinity on the biofouling dynamics of seawater desalination

A persistent cell labeling dye and a novel microbial counting method were used to explore the effects of salinity on a microbial population in a reverse osmosis (RO) desalination system, and these clearly distinguished microbial cell multiplication from cell adherence. The results indicated that microbial multiplication is more active at the front of a seawater RO pressure vessel, while adhesion dominates the back of the vessel. A severe reduction in RO permeate flux and total dissolved solid (TDS) rejection were detected at low salinity, attributed to marked cell multiplication and release of extracellular polymeric substances, whilst a relatively stable flux was observed at medium and high salinity. The results from PCR-DGGE revealed the variation in microbial species distribution on the membrane with salinity. The results imply the critical role of membrane modification in biofouling mitigation in the desalination process.     

Trifluoperazine regulation of calmodulin binding to Fas: a computational study

Death-inducing signaling complex (DISC) formation is a critical step in Fas-mediated signaling for apoptosis. Previous experiments have demonstrated that the calmodulin (CaM) antagonist, trifluoperazine (TFP) regulates CaM-Fas binding and affects Fas-mediated DISC formation. In this study, we investigated the anti-cooperative characteristics of TFP binding to CaM and the effect of TFP on the CaM-Fas interaction from both structural and thermodynamic perspectives using combined molecular dynamics simulations and binding free energy analyses. We studied the interactions of different numbers of TFP molecules with CaM and explored the effects of the resulting conformational changes in CaM on CaM-Fas binding. Results from these analyses showed that the number of TFP molecules bound to CaM directly influenced α-helix formation and hydrogen bond occupancy within the α-helices of CaM, contributing to the conformational and motion changes in CaM. These changes affected CaM binding to Fas, resulting in secondary structural changes in Fas and conformational and motion changes of Fas in CaM-Fas complexes, potentially perturbing the recruitment of Fas-associated death domain for DISC formation. The computational results from this study reveal the structural and molecular mechanisms that underlie the role of the CaM antagonist, TFP, in regulation of CaM-Fas binding and Fas-mediated DISC formation in a concentration-dependent manner.