Quenching and Electrical Current Poling Effect on Improved Ferroelectric and Piezoelectric Properties in BiFeO3-Based High-Temperature Piezoceramics.

The effects of quenching on the structural, electrical, dielectric, ferroelectric (FE), and piezoelectric properties are investigated systematically in the 0.85BiFe1-xCrxO3-0.15BaTi1-xMnxO3 (0 ≤ x ≤ 0.03) ceramics. Optimal piezoelectricity and FE Curie temperature are obtained through optimized quenching rate and temperature. Quenching effect on piezoelectricity is especially significant for the samples near morphotropic phase boundaries (MPB), which can be ascribed to quenching-induced changes in phase ratio (rhombohedral and tetragonal phase) and domain structure/defect dipole orientation. Moreover, a new poling method, that is, cooling the sample at a constant dc current across FE TC, is established to improve the piezoelectricity. This work not only reveals the possible mechanism of quenching effect on the improved piezoelectricity in the BFO-based piezoceramics (especially near the MPB) but also suggests an electric current poling strategy for improving piezoelectricity by suppressing the defect dipole effects in BFO-based and even other piezoelectrics.

Identification of a metagenome-derived prephenate dehydrogenase gene from an alkaline-polluted soil microorganism.

A novel prephenate dehydrogenase gene designated pdhE-1 was cloned by sequence-based screening of a plasmid metagenomic library from uncultured alkaline-polluted microorganisms. The deduced amino acid sequence comparison and phylogenetic analysis indicated that PdhE-1 and other putative prephenate dehydrogenases were closely related. The putative prephenate dehydrogenase gene was subcloned into pETBlue-2 vector and overexpressed in Escherichia coli BL21(DE3) pLacI. The recombinant protein was purified to homogeneity. The maximum activity of the PdhE-1 protein occurred at pH 8.0 and 45 °C using prephenic acid as the substrate. The prephenate dehydrogenase had an apparent K m value of 0.87 mM, a V max value of 41.5 U/mg, a k cat value of 604.8/min and a k cat/K m value of 1.16 × 10(4)/mol/s. L-Tyrosine did not obviously inhibit the recombinant PdhE-1 protein. The identification of a metagnome-derived prephenate dehydrogenase provides novel material for studies and application of proteins involved in tyrosine biosynthesis.

[Evaluation of norovirus rapid detection kit].

OBJECTIVE: Evaluating the accuracy and safety as well as the equivalence compared with the control kit of RIDA QUICK Norovirus detection kit(R-Biopharm, Germany). METHODS: Based on the results of commercially available IDEA Norovirus detection kit (ELISA), the sensitivity and specificity and accuracy of RIDA QUICK Norovirus detection kit (immunochromatographic assay) were evaluated. RESULTS: The sensitivity and specificity of RIDA QUICK Norovirus detection kit were 98.4% and 92.4%, and the accuracy was 97.6% compared with the control kit. CONCLUSION: RIDA QUICK Norovirus detection kit has good sensitivity and specificity for the detection of norovirus antigens.

Biochemical characterization of two novel ß-glucosidase genes by metagenome expression cloning.

Two novel ß-glucosidase genes designated as bgl1D and bgl1E, which encode 172- and 151-aa peptides, respectively, were cloned by function-based screening of a metagenomic library from uncultured soil microorganisms. Sequence analyses indicated that Bgl1D and Bgl1E exhibited lower similarities with some putative ß-glucosidases. Functional characterization through high-performance liquid chromatography demonstrated that purified recombinant Bgl1D and Bgl1E proteins hydrolyzed D-glucosyl-ß-(1-4)-D-glucose to glucose. Using p-nitrophenyl-ß-D-glucoside as substrate, K(m) was 0.54 and 2.11 mM, and k(cat)/K(m) was 1489 and 787 mM(-1) min(-1) for Bgl1D and Bgl1E, respectively. The optimum pH and temperature for Bgl1D was pH 10.0 and 30°C, while the optimum values for Bgl1E were pH 10.0 and 25°C. Bgl1D exhibited habitat-specific characteristics, including higher activity in lower temperature and at high concentrations of AlCl(3) and LiCl. Bgl1D also displayed remarkable activity across a broad pH range (5.5-10.5), making it a potential candidate for industrial applications.

Identification and characterization of a novel fumarase gene by metagenome expression cloning from marine microorganisms.

BACKGROUND: Fumarase catalyzes the reversible hydration of fumarate to L-malate and is a key enzyme in the tricarboxylic acid (TCA) cycle and in amino acid metabolism. Fumarase is also used for the industrial production of L-malate from the substrate fumarate. Thermostable and high-activity fumarases from organisms that inhabit extreme environments may have great potential in industry, biotechnology, and basic research. The marine environment is highly complex and considered one of the main reservoirs of microbial diversity on the planet. However, most of the microorganisms are inaccessible in nature and are not easily cultivated in the laboratory. Metagenomic approaches provide a powerful tool to isolate and identify enzymes with novel biocatalytic activities for various biotechnological applications. RESULTS: A plasmid metagenomic library was constructed from uncultivated marine microorganisms within marine water samples. Through sequence-based screening of the DNA library, a gene encoding a novel fumarase (named FumF) was isolated. Amino acid sequence analysis revealed that the FumF protein shared the greatest homology with Class II fumarate hydratases from Bacteroides sp. 2_1_33B and Parabacteroides distasonis ATCC 8503 (26% identical and 43% similar). The putative fumarase gene was subcloned into pETBlue-2 vector and expressed in E. coli BL21(DE3)pLysS. The recombinant protein was purified to homogeneity. Functional characterization by high performance liquid chromatography confirmed that the recombinant FumF protein catalyzed the hydration of fumarate to form L-malate. The maximum activity for FumF protein occurred at pH 8.5 and 55°C in 5 mM Mg(2+). The enzyme showed higher affinity and catalytic efficiency under optimal reaction conditions: K(m) = 0.48 mM, V(max) = 827 µM/min/mg, and k(cat)/K(m) = 1900 mM/s. CONCLUSIONS: We isolated a novel fumarase gene, fumF, from a sequence-based screen of a plasmid metagenomic library from uncultivated marine microorganisms. The properties of FumF protein may be ideal for the industrial production of L-malate under higher temperature conditions. The identification of FumF underscores the potential of marine metagenome screening for novel biomolecules.

[The analysis of the test results in HIV screening laboratory of Beijing Friendship Hospital in 2008].

OBJECTIVE: According to test results of the Hospital of AIDS screening laboratory in 2008, after counting analysis to assess the prevalence of AIDS, we can early detect positive cases in the future and effectively control the spread of AIDS. METHODS: All serum samples were screened by ELISA method and we reexaminated the samples by PA. As long as one result is positive by the two methods, then we sent the positive samples to Beijing Center for Disease Control and Prevention by Western Blot method to confirm the result. RESULTS: A total of 21 467 samples were detected and 29 (13.5% 0) were positive screening results. We confirm there were 7 (24.1%) positive samples and 12 (41.4%) suspected samples. We researched the epidemiology of the specimens by its source and age and sex. CONCLUSION: Application of ELISA method for HIV screening test has a practical significance, it is accurate and fit to record the results of the screening test for AIDS.

[In vitro inhibitory mechanism of respiratory syncytial virus with solution prescription of zhidanhuayu].

OBJECTIVE: To study the effective part of solution prescription of Zhidanhuayu (ZDHY) against respiratory syncytial virus (RSV) in vitro. METHODS: Observe the pathology of RSV to Hep-2 under the condition of different concentrations and each effective part of ZDHY. RESULTS: The concentration limit causing celluar toxicity of ZDHY is 5.5 mg/ml. The ZDHY failed to block the absorption of RSV to Hep-2 within this concentration, and consequently the cell fell into the full pathological changes. During the concentration of 2.75-5.50 mg/ml, the ZDHY directly destroyed virus array,meanwhile, the infected cells that treated by the medicine kept healthy also. CONCLUSION: ZDHY could not defend the infection of RSV, but is able to destroy the RSV directly and inhibit the RSV inhabiting in the cell.

[In vitro inhibition of respiratory syncytial virus with combined ribavirin and an oral preparation of traditional Chinese medicine Hu Fei].

OBJECTIVE: To study the in vitro antiviral effect of ribavirin combined with an oral preparation of traditional Chinese medicine "Hu Fei" (protecting the lung) on respiratory syncytial virus (RSV). METHODS: Cytopathic effects (CEP) of RSV on Hep2 cells were observed after adding different concentrations of ribavirin, Hu Fei and combination of both into the culture medium. RESULTS: The minimum concentration of ribavirin and Hu Fei for complete inhibition of CPE caused by RSV was 7.80 microg/ml and 5.00 mg/ml, respectively. When the combination of ribavirin and Hu Fei was applied, their minimum concentrations needed for complete inhibition were decreased to 0.98 ?g/ml and 0.63 mg/ml. CONCLUSIONS: Both ribavirin and Hu Fei showed in vitro anti-RSV effect, but the inhibitory effect of combined ribavirin and Hu Fei was more potent than either of the preparation alone.