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Find video protocols related to scientific articles indexed in Pubmed.
High responsivity photoconductors based on iron pyrite nanowires using sulfurization of anodized iron oxide nanotubes.
Nano Lett.
PUBLISHED: 09-22-2014
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Iron pyrite (FeS2) nanostructures are of considerable interest for photovoltaic applications due to improved material quality compared to their bulk counterpart. As an abundant and nontoxic semiconductor, FeS2 nanomaterials offer great opportunities for low-cost and green photovoltaic technology. This paper describes the fabrication of FeS2 nanowire arrays via sulfurization of iron oxide nanotubes at relatively low temperatures. A facile synthesis of ordered iron oxide nanotubes was achieved through anodization of iron foils. Characterization of the iron sulfide nanowires indicates that pyrite structures were formed. A prototype FeS2 nanowire photoconductor demonstrates very high responsivity (>3.0 A/W). The presented method can be further explored to fabricate various FeS2 nanostructures, such as nanoparticles, nanoflowers, and nanoplates.
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Synergistic effect of Aspergillus niger and Trichoderma reesei enzyme sets on the saccharification of wheat straw and sugarcane bagasse.
Biotechnol J
PUBLISHED: 09-10-2014
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Plant-degrading enzymes can be produced by fungi on abundantly available low-cost plant biomass. However, enzymes sets after growth on complex substrates need to be better understood, especially with emphasis on differences between fungal species and the influence of inhibitory compounds in plant substrates, such as monosaccharides. In this study, Aspergillus niger and Trichoderma reesei were evaluated for the production of enzyme sets after growth on two "second generation" substrates: wheat straw (WS) and sugarcane bagasse (SCB). A. niger and T. reesei produced different sets of (hemi-)cellulolytic enzymes after growth on WS and SCB. This was reflected in an overall strong synergistic effect in releasing sugars during saccharification using A. niger and T. reesei enzyme sets. T. reesei produced less hydrolytic enzymes after growth on non-washed SCB. The sensitivity to non-washed plant substrates was not reduced by using CreA/Cre1 mutants of T. reesei and A. niger with a defective carbon catabolite repression. The importance of removing monosaccharides for producing enzymes was further underlined by the decrease in hydrolytic activities with increased glucose concentrations in WS media. This study showed the importance of removing monosaccharides from the enzyme production media and combining T. reesei and A. niger enzyme sets to improve plant biomass saccharification.
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Co-immobilization of Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12 with polyvinyl alcohol-alginate for removal of nitrogen and phosphorus from synthetic wastewater.
Environ Technol
PUBLISHED: 06-04-2014
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Nitrogen (N) and phosphorus (P) are the two main factors causing water eutrophication. Immobilized micro-organisms have been widely studied in N and P removal. However, the effects of various immobilizing conditions on the removal efficiency of N and P using immobilized micro-organism beads (IMOBs) remain unclear. Polyvinyl alcohol (PVA) and alginate, as the two frequently immobilizing-used matrixes, were used for co-immobilizing Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12. PVA, alginate and CaCl 2 contents, immobilization time and different wet biomass ratios of P. stutzeri to Alcaligenes sp. were conducted to elucidate their roles in and influences on the removal efficiency of N and P from synthetic wastewater. The application potential of IMOBs was estimated as well. Results showed that IMOBs prepared by cross-link of 4% PVA and 2-3% alginate with 5% CaCl 2 and saturated boric acid solution for 10-15 min are the best ones in removal of N and P. Though IMOBs containing P. stutzeri and/or Alcaligenes sp. were capable of removal of the two nutrients, the highest removal efficiency was observed when the wet biomass ratio of P. stutzeri to Alcaligenes sp. was adjusted to 2:2. In addition, the IMOBs were of good ability to remove chemical oxygen demand (COD), NO 3(-), NO 2(-), NH 4(+)- N, total nitrogen (TN) and total phosphorus (TP) from artificial wastewater. Of which, micro-organisms immobilized in matrixes were mainly responsible for NO 3(-) and TP removal. Therefore, P. stutzeri YHA-13 and Alcaligenes sp. ZGED-12 are reliable bioresources to remove N and P from wastewater.
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A 10-second fluid challenge guided by transthoracic echocardiography can predict fluid responsiveness.
Crit Care
PUBLISHED: 05-12-2014
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The accurate assessment of intravascular volume status for the therapy of severe hypovolemia and shock is difficult and critical to critically ill patients. Non-invasive evaluation of fluid responsiveness by the rapid infusion of a very limited amount of volume is an important clinical goal. This study aimed to test whether echocardiographic parameters could predict fluid responsiveness in critically ill patients following a low-volume (50-ml crystalloid solution) infusion over 10 seconds.
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PD-1 mRNA expression is associated with clinical and viral profile and PD1 3'-untranslated region polymorphism in patients with chronic HBV infection.
Immunol. Lett.
PUBLISHED: 05-02-2014
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Programmed cell death-1 (PD-1) is involved in hepatitis B virus (HBV) infection and single-nucleotide polymorphism (SNP) rs10204525 in the 3'-untranslated region (3' UTR) of PD1 gene was shown to be associated with the disease course of HBV infection. This study examined the associations of PD-1 mRNA expression with the clinical and viral profiles and the genotypes of rs10204525 in HBV infection. PD-1 mRNA levels in peripheral blood nuclear cells were determined by real-time quantitative reverse transcription polymerase chain reaction (PCR). PD1 rs10204525 was genotyped by bidirectional PCR amplification of specific alleles. The results showed that patients with chronic HBV infection had significantly elevated PD-1 mRNA levels than healthy controls. Patients with chronic hepatitis and hepatocellular carcinoma had significantly higher PD-1 mRNA levels than healthy controls. HBeAg (+) patients had significantly higher PD-1 mRNA levels than HBeAg (-) patients (P<0.001). PD-1 mRNA levels were sequentially increased with the elevation of HBV DNA levels. In HBV patients, but not in healthy controls, PD-1 mRNA levels were sequentially decreased from rs10204525 genotypes AA, AG to GG and the levels in genotype AA were significantly higher than in genotype GG (P=0.039). These findings suggest that increased PD-1 expression may affect the disease course of chronic HBV infection by facilitating HBV viral replication, and this may at least partially relate to PD1 3' UTR polymorphism.
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Draft Genome Sequence of Clostridium ultunense Strain BS (DSMZ 10521), Recovered from a Mixed Culture.
Genome Announc
PUBLISHED: 02-08-2014
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Clostridium ultunense BS is the first isolated strain (type strain) of C. ultunense that was identified as a mesophilic syntrophic acetate-oxidizing bacterium (SAOB). Here, we report the draft genome sequence of this strain, which will help us to elucidate the mechanism of syntrophic acetate oxidization.
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Phylogenetic and functional analysis of gut microbiota of a fungus-growing higher termite: bacteroidetes from higher termites are a rich source of ?-glucosidase genes.
Microb. Ecol.
PUBLISHED: 02-04-2014
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Fungus-growing termites, their symbiotic fungi, and microbiota inhibiting their intestinal tract comprise a highly efficient cellulose-hydrolyzing system; however, little is known about the role of gut microbiota in this system. Twelve fosmid clones with ?-glucosidase activity were previously obtained by functionally screening a metagenomic library of a fungus-growing termite, Macrotermes annandalei. Ten contigs containing putative ?-glucosidase genes (bgl1-10) were assembled by sequencing data of these fosmid clones. All these contigs were binned to Bacteroidetes, and all these ?-glucosidase genes were phylogenetically closed to those from Bacteroides or Dysgonomonas. Six out of 10 ?-glucosidase genes had predicted signal peptides, indicating a transmembrane capability of these enzymes to mediate cellulose hydrolysis within the gut of the termites. To confirm the activities of these ?-glucosidase genes, three genes (bgl5, bgl7, and bgl9) were successfully expressed and purified. The optimal temperature and pH of these enzymes largely resembled the environment of the host's gut. The gut microbiota composition of the fungus-growing termite was also determined by 454 pyrosequencing, showing that Bacteroidetes was the most dominant phylum. The diversity and the enzyme properties of ?-glucosidases revealed in this study suggested that Bacteroidetes as the major member in fungus-growing termites contributed to cello-oligomer degradation in cellulose-hydrolyzing process and represented a rich source for ?-glucosidase genes.
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The effect of pristine carbon-based nanomaterial on the growth of green gram sprouts and pH of water.
Nanoscale Res Lett
PUBLISHED: 01-01-2014
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We examined the toxicity of four carbon-based nanomaterials (unmodified) by using carbon quantum dots (CQDs), graphene quantum dots (GQDs), graphene oxide (GO), and single-walled carbon nanotubes (SWCNTs) to cultivate bean sprout. Results showed that the toxicity of these four carbon nanomaterials increases with the increasing of concentration and cultivating time. In addition, pH test was applied to study the effect of carbon-based nanomaterials on water. pH of culture solution displayed unconspicuous dose-dependent, but nanomaterials indeed have a considerable impact on the pH even at low concentration.
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Phase-pure iron pyrite nanocrystals for low-cost photodetectors.
Nanoscale Res Lett
PUBLISHED: 01-01-2014
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Earth-abundant iron pyrite (FeS2) shows great potential as a light absorber for solar cells and photodetectors due to their high absorption coefficient (>10(5) cm(-1)). In this paper, high-quality phase-pure and single crystalline pyrite nanocrystals were synthesized via facile, low-cost, and environment friendly hydrothermal method. The molar ratio of sulphur to iron and the reaction time play a crucial role in determining the quality and morphology of FeS2 nanocrystals. X-ray diffraction and high-resolution transmission electron microscopy confirm that phase-pure and single crystalline pyrite nanocrystals can be synthesized with high sulphur to iron molar ratio and sufficient reaction time. For the first time, a crystalline nanogap pyrite photodetector with promising photocurrent and UV-visible photoresponse has been fabricated. This work further demonstrates a facile route to synthesize high-quality FeS2 nanomaterials and their potential in optoelectronic applications.
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Microwave fabrication of Cu2ZnSnS4 nanoparticle and its visible light photocatalytic properties.
Nanoscale Res Lett
PUBLISHED: 01-01-2014
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Cu2ZnSnS4 nanoparticle with an average diameter of approximately 31 nm has been successfully synthesized by a time effective microwave fabrication method. The crystal structure, surface morphology, and microstructure of the Cu2ZnSnS4 nanoparticle were characterized. Moreover, the visible light photocatalytic ability of the Cu2ZnSnS4 nanoparticle toward degradation of methylene blue (MB) was also studied. About 30% of MB was degraded after 240 min irradiation when employing Cu2ZnSnS4 nanoparticle as a photocatalyst. However, almost all MB was decomposed after 90 min irradiation when introducing a small amount of H2O2 as a co-photocatalyst. The enhancement of the photocatalytic performance was attributed to the synergetic effect between the Cu2ZnSnS4 nanoparticle and H2O2. The detailed photocatalytic degradation mechanism of MB by the Cu2ZnSnS4 was further proposed.
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Ammonia gas sensors based on chemically reduced graphene oxide sheets self-assembled on Au electrodes.
Nanoscale Res Lett
PUBLISHED: 01-01-2014
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We present a useful ammonia gas sensor based on chemically reduced graphene oxide (rGO) sheets by self-assembly technique to create conductive networks between parallel Au electrodes. Negative graphene oxide (GO) sheets with large sizes (>10 ?m) can be easily electrostatically attracted onto positive Au electrodes modified with cysteamine hydrochloride in aqueous solution. The assembled GO sheets on Au electrodes can be directly reduced into rGO sheets by hydrazine or pyrrole vapor and consequently provide the sensing devices based on self-assembled rGO sheets. Preliminary results, which have been presented on the detection of ammonia (NH3) gas using this facile and scalable fabrication method for practical devices, suggest that pyrrole-vapor-reduced rGO exhibits much better (more than 2.7 times with the concentration of NH3 at 50 ppm) response to NH3 than that of rGO reduced from hydrazine vapor. Furthermore, this novel gas sensor based on rGO reduced from pyrrole shows excellent responsive repeatability to NH3. Overall, the facile electrostatic self-assembly technique in aqueous solution facilitates device fabrication, the resultant self-assembled rGO-based sensing devices, with miniature, low-cost portable characteristics and outstanding sensing performances, which can ensure potential application in gas sensing fields.
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N-glycosylation affects the proper folding, enzymatic characteristics and production of a fungal ß-glucosidase.
Biotechnol. Bioeng.
PUBLISHED: 12-06-2013
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Heterologous expression of ß-glucosidase is one of the approaches to enhance the efficiency of fungal cellulase preparations. It has been reported that N-glycosylation affects the structure framework, function and stability of proteins. In this study, a ß-glucosidase from Aspergillus terreus (GenBank: XP_001216552, BglS) was heterologously expressed in Pichia pastoris and Trichoderma reesei. The four asparagine residues were all linked with high-mannose-type oligosaccharides in P. pastoris, whereas only N224 carried high-mannosetype glycan in T. reesei (the other three sites carried one N-acetylglucosamine). The long N-glycan chains on PpBglS weakened its substrate affinity, activity and thermostability. The moderate post-translational and post-secretory glycan modification in T. reesei makes it a suitable expression system for BglS. The N224 glycan played a critical role in BglS folding. The elucidation of the correlation between the different N-glycosylation patterns of BglS and their corresponding enzymatic characteristics is an important step towards improving the activity, thermostability and even production of heterologous ß-glucosidase by glycan engineering.
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The distinctive regulatory roles of PrtT in the cell metabolism of Penicillium oxalicum.
Fungal Genet. Biol.
PUBLISHED: 10-10-2013
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PrtT is a fungal-specific transcription activator of extracellular proteases in Aspergilli. In this study, the roles of the PrtT homolog from Penicillum oxalicum was investigated by transcription profiling in combination with electrophoretic mobility shift assay (EMSA). The prtT deletion dramatically reduced extracellular protease activities and caused intracellular nutrient limitation cultured on casein as the sole carbon source. PrtT was found to directly regulate the expression of an intracellular peptidase encoding gene (tripeptidyl-peptidase) and the gene encoding the extracellular dipeptidyl-aminopeptidase V, in addition to the expected extracellular peptidase genes (carboxypeptidase and aspergillopepsin). Five amylase genes (?-amylase, glucoamylase, ?-glucosidase) and three major facilitator superfamily transporter genes related to maltose, monosaccharide and peptide transporting were also confirmed as putative targets of PrtT by EMSA. In contrast, the transcription levels of other genes encoding polysaccharide degrading enzymes (e.g. cellulases) and most iron or multidrug transporter encoding genes were up- or down-regulated in the ?prtT mutant due to nutrient limitation resulting from the reduced usage of the sole carbon source, casein. These results deepen the understanding of the interaction of regulation systems for nitrogen and carbon catabolism, which benefit strain improvement of P. oxalicum for industrial enzyme production.
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High-performance solid-state supercapacitors based on graphene-ZnO hybrid nanocomposites.
Nanoscale Res Lett
PUBLISHED: 09-17-2013
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In this paper, we report a facile low-cost synthesis of the graphene-ZnO hybrid nanocomposites for solid-state supercapacitors. Structural analysis revealed a homogeneous distribution of ZnO nanorods that are inserted in graphene nanosheets, forming a sandwiched architecture. The material exhibited a high specific capacitance of 156 F g-1 at a scan rate of 5 mV.s-1. The fabricated solid-state supercapacitor device using these graphene-ZnO hybrid nanocomposites exhibits good supercapacitive performance and long-term cycle stability. The improved supercapacitance property of these materials could be ascribed to the increased conductivity of ZnO and better utilization of graphene. These results demonstrate the potential of the graphene-ZnO hybrid nanocomposites as an electrode in high-performance supercapacitors.
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Chelating stability of an amphoteric chelating polymer flocculant with Cu(II), Pb(II), Cd(II), and Ni(II).
Spectrochim Acta A Mol Biomol Spectrosc
PUBLISHED: 09-08-2013
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The absorption spectra of Cu(2+), Pb(2+), Cd(2+), and Ni(2+) chelates of an amphoteric chelating polymer flocculant (ACPF) were measured by ultraviolet spectrophotometry, and their compositions and stability constants (?) were calculated. ACPF exhibited three apparent absorption peaks at 204, 251, and 285 nm. The CSS(-) group of ACPF reacted with Cu(2+), Ni(2+), Pb(2+), and Cd(2+) to form ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) chelates, respectively, according to a molar ratio of 2:1. The maximum absorption peaks of ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) appeared at 319, 326, 310, and 313.5 nm, respectively. The maximum absorption peaks of the chelates showed significant red shifting compared with the absorption peaks of ACPF. The ? values of the ACPF-Cu(2+), ACPF-Pb(2+), ACPF-Cd(2+), and ACPF-Ni(2+) chelates were (1.37±0.35)×10(12), (3.26±0.39)×10(11), (2.05±0.27)×10(11), and (3.04±0.45)×10(10), respectively. The leaching rate of heavy metal ions from the chelating precipitates decreased with increasing pH. ACPF-Cu(2+), ACPF-Ni(2+), ACPF-Pb(2+), and ACPF-Cd(2+) were very stable at pH?5.6. Cu(2+), Ni(2+), Pb(2+), and Cd(2+) concentrations in the leaching liquors were lower than the corresponding limits specified by the Integrated Wastewater Discharge Standard of China.
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[Clinical and genetic study of Wilsons disease in affected twins and siblings].
Zhonghua Yi Xue Yi Chuan Xue Za Zhi
PUBLISHED: 06-08-2013
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To study the clinical and genetic characteristics of twins and siblings affected with Wilsons disease (WD).
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The Inhibitory Effect of 3 ? -Hydroxy-12-oleanen-27-oic Acid on Growth and Motility of Human Hepatoma HepG2 Cells through JNK and Akt Signaling Pathway.
Evid Based Complement Alternat Med
PUBLISHED: 05-31-2013
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3 ? -Hydroxy-12-oleanen-27-oic acid (ATA) was a main antitumor active triterpene from the rhizomes of Astilbe chinensis. In this study, we investigated its effects on growth, apoptosis, cell cycle, motility/invasion, and metatasis in human hepatoma HepG2 cells in vitro and antimetastasis of B16-F10 melanoma in mice in vivo, as well as its molecular mechanisms of action using a high-throughput Cancer Pathway Finder PCR Array. ATA could not only induce tumor cells into apoptosis through the activation of both extrinsic and intrinsic pathways, arrest HepG2 cells in G2/M phase, but also suppress the invasion and metastasis abilities of HepG2 cells and the lung metastasis of B16-F10 melanoma in mice. PCR array assay revealed that ATA upregulated 9 genes including CDKN1A, MDM2, CFLAR (CASPER), TNFRSF10B (DR5), c-Jun, IL-8, THBS1, SERPINB5 (maspin), and TNF and downregulated 8 genes such as CCNE1, AKT, ANGPT1, TEK, TGFBR1, MMP9, U-PA, and S100A4. These results indicate that ATA could exert antitumor effects through activating JNK/MAPK and suppressing AKT signal transduction pathways and that ATA might be a potent anticancer agent.
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[Isolation and characterization of the salt-tolerant aerobic denitrifying bacterial strain A-13].
Wei Sheng Wu Xue Bao
PUBLISHED: 04-26-2013
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This study is aimed to isolate and identify an aerobic denitrifying bacterium with high ability for nitrogen removing, and optimize its growing and denitrifying conditions to obtain the theory basis for controlling the eutrophic artificial lake.
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Blocking the butyrate-formation pathway impairs hydrogen production in Clostridium perfringens.
Acta Biochim. Biophys. Sin. (Shanghai)
PUBLISHED: 03-26-2013
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Inactivating competitive pathways will improve fermentative hydrogen production by obligate anaerobes, such as those of genus Clostridium. In our previous study, the hydrogen yield of Clostridium perfringens W13 in which l-lactate dehydrogenase was inactivated increased by 44% when compared with its original strain W12. In this study, we explored whether blocking butyrate formation pathway would increase hydrogen yield. The acetyl-CoA acetyltransferase gene (atoB) encodes the first enzyme in this pathway, which ultimately forms butyrate. Clostridium perfringens W14 and W15 were constructed by inactivating atoB in W13 and W12, respectively. The hydrogen yield of W14 and W15 was 44% and 33% of those of W13 and W12, respectively. Inactivation of atoB decreased the pyruvate synthesis and its conversion to acetyl-CoA in both mutants, and increased ethanol formation in W14 and W15. Proteomic analysis revealed that the expressions of five proteins involved in butyrate formation pathway were up-regulated in W14. Our results suggest that butyrate formation deficiency improved ethanol production but not hydrogen production, indicating the importance of butyrate formation pathway for hydrogen production in C. perfringens.
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Biochemical characterization and crystal structure of a GH10 xylanase from termite gut bacteria reveal a novel structural feature and significance of its bacterial Ig-like domain.
Biotechnol. Bioeng.
PUBLISHED: 03-22-2013
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Bacterial Ig-like (Big) domains are commonly distributed in glycoside hydrolases (GH), but their structure and function remains undefined. Xylanase is a GH, and catalyzes the hydrolysis of the internal ?-xylosidic linkages of xylan. In this study, we report the molecular cloning, biochemical and biophysical characterization, and crystal structure of a termite gut bacterial xylanase, Xyl-ORF19, which was derived from gut bacteria of a wood-feeding termite (Globitermes brachycerastes). The protein architecture of Xyl-ORF19 reveals that it has two domains, a C-terminal GH10 catalytic domain and an N-terminal Big_2 non-catalytic domain. The catalytic domain folds in an (?/?)8 barrel as most GH10 xylanases do, but it has two extra ?-strands. The non-catalytic domain is structurally similar to an immunoglobulin-like domain of intimins. The recombinant enzyme without the non-catalytic domain has fairly low catalytic activity, and is different from the full-length enzyme in kinetic parameters, pH and temperature profiles, which suggests the non-catalytic domain could affect the enzyme biochemical and biophysical properties as well as the role for enzyme localization. This study provides a molecular basis for future efforts in xylanase bioengineering.
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Development of dextran nanoparticles for stabilizing delicate proteins.
Nanoscale Res Lett
PUBLISHED: 03-16-2013
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One of the most challenging problems in the development of protein pharmaceuticals is to deal with stabilities of proteins due to its complicated structures. This study aims to develop a novel approach to stabilize and encapsulate proteins into dextran nanoparticles without contacting the interface between the aqueous phase and the organic phase. The bovine serum albumin, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), ?-galactosidase, and myoglobin were selected as model proteins. The proteins were added into an aqueous solution containing the dextran and polyethylene glycol, and then encapsulated into dextran nanoparticles by aqueous-aqueous freezing-induced phase separation. The encapsulation efficiency and recovery of dextran nanoparticles were determined. The dextran nanoparticles loaded with proteins were characterized by scanning electron microscopy and particle size analysis. The protein aggregation was determined by size-exclusion chromatography-high-performance chromatography, and the bioactivity of proteins recovered during formulation steps was determined. The bioactivity of GM-CSF, G-CSF, and ?-galactosidase were examined by the proliferation of TF-1 cell, NSF-60 cell, and ortho-nitrophenyl-?-galactoside assay, respectively. The results of bioactivity recovered show that this novel dextran nanoparticle can preserve the proteins bioactivity during the preparation process. LysoSensor™ Yellow/Blue dextran, a pH-sensitive indicator with fluorescence excited at two channels, was encapsulated into dextran nanoparticles to investigate the ability of dextran nanoparticles to resist the acidic microenvironment (pH < 2.5). The result shows that the dextran nanoparticles attenuate the acidic microenvironment in the poly (lactic-co-glycolic acid) microsphere by means of the dilution effect. These novel dextran nanoparticles provided an appealing approach to stabilize the delicate proteins for administration.
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Long-term strain improvements accumulate mutations in regulatory elements responsible for hyper-production of cellulolytic enzymes.
Sci Rep
PUBLISHED: 02-05-2013
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Long-term strain improvements through repeated mutagenesis and screening have generated a hyper-producer of cellulases and hemicellulases from Penicillium decumbens 114 which was isolated 30 years ago. Here, the genome of the hyper-producer P. decumbens JU-A10-T was sequenced and compared with that of the wild-type strain 114-2. Further, the transcriptomes and secretomes were compared between the strains. Selective hyper-production of cellulases and hemicellulases but not all the secreted proteins was observed in the mutant, making it a more specific producer of lignocellulolytic enzymes. Functional analysis identified that changes in several transcriptional regulatory elements played crucial roles in the cellulase hyper-producing characteristics of the mutant. Additionally, the mutant showed enhanced supply of amino acids and decreased synthesis of secondary metabolites compared with the wild-type. The results clearly point out that we can target gene regulators and promoters with minimal alterations of the genetic content but maximal effects in genetic engineering.
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Discovery of (hemi-) cellulase genes in a metagenomic library from a biogas digester using 454 pyrosequencing.
Appl. Microbiol. Biotechnol.
PUBLISHED: 02-04-2013
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In this study, 341, 246, and 386 positive clones with endo-?-1,4-glucanase, ?-glucosidase, and endo-?-1,4-xylanase activities, respectively, were identified by screening from a metagenomic fosmid library constructed from a biogas digester. Subsequently, pools of 4, 10, and 16 positive clones were subjected to 454 pyrosequencing in different subruns. In total, 21 unique glycosyl hydrolase (GH) genes were predicted by bioinformatic analysis, which showed similarities to their nearest neighbors from 39 % to 72 %. In addition to bioinformatics prediction, nine GH genes were expressed and purified to identify their activity with four kinds of substrates. The activities of the most expressed proteins were consistent with their annotation based on bioinformatics prediction; however, three GH genes belonging to the GH5 family showed different activities from their annotation. An efficient acidic cellulase En1 had an optimal condition at 55 °C, pH 5.5, with a specific activity toward carboxymethylcellulose at 118 U/mg and K m at 12.8 g/L. This study demonstrated that there are diverse GHs in the biogas digester system with potential industrial application in lignocellulose hydrolysis, and their activities should be investigated with different substrates before their application. Additionally, pool sequencing of positive fosmid clones might be a cost-effective approach to obtain functional genes from metagenomic libraries.
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Genomic and secretomic analyses reveal unique features of the lignocellulolytic enzyme system of Penicillium decumbens.
PLoS ONE
PUBLISHED: 02-01-2013
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Many Penicillium species could produce extracellular enzyme systems with good lignocellulose hydrolysis performance. However, these species and their enzyme systems are still poorly understood and explored due to the lacking of genetic information. Here, we present the genomic and secretomic analyses of Penicillium decumbens that has been used in industrial production of lignocellulolytic enzymes in China for more than fifteen years. Comparative genomics analysis with the phylogenetically most similar species Penicillium chrysogenum revealed that P. decumbens has evolved with more genes involved in plant cell wall degradation, but fewer genes in cellular metabolism and regulation. Compared with the widely used cellulase producer Trichoderma reesei, P. decumbens has a lignocellulolytic enzyme system with more diverse components, particularly for cellulose binding domain-containing proteins and hemicellulases. Further, proteomic analysis of secretomes revealed that P. decumbens produced significantly more lignocellulolytic enzymes in the medium with cellulose-wheat bran as the carbon source than with glucose. The results expand our knowledge on the genetic information of lignocellulolytic enzyme systems in Penicillium species, and will facilitate rational strain improvement for the production of highly efficient enzyme systems used in lignocellulose utilization from Penicillium species.
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Metagenomic insights into metabolic capacities of the gut microbiota in a fungus-cultivating termite (Odontotermes yunnanensis).
PLoS ONE
PUBLISHED: 01-01-2013
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Macrotermitinae (fungus-cultivating termites) are major decomposers in tropical and subtropical areas of Asia and Africa. They have specifically evolved mutualistic associations with both a Termitomyces fungi on the nest and a gut microbiota, providing a model system for probing host-microbe interactions. Yet the symbiotic roles of gut microbes residing in its major feeding caste remain largely undefined. Here, by pyrosequencing the whole gut metagenome of adult workers of a fungus-cultivating termite (Odontotermes yunnanensis), we showed that it did harbor a broad set of genes or gene modules encoding carbohydrate-active enzymes (CAZymes) relevant to plant fiber degradation, particularly debranching enzymes and oligosaccharide-processing enzymes. Besides, it also contained a considerable number of genes encoding chitinases and glycoprotein oligosaccharide-processing enzymes for fungal cell wall degradation. To investigate the metabolic divergence of higher termites of different feeding guilds, a SEED subsystem-based gene-centric comparative analysis of the data with that of a previously sequenced wood-feeding Nasutitermes hindgut microbiome was also attempted, revealing that SEED classifications of nitrogen metabolism, and motility and chemotaxis were significantly overrepresented in the wood-feeder hindgut metagenome, while Bacteroidales conjugative transposons and subsystems related to central aromatic compounds metabolism were apparently overrepresented here. This work fills up our gaps in understanding the functional capacities of fungus-cultivating termite gut microbiota, especially their roles in the symbiotic digestion of lignocelluloses and utilization of fungal biomass, both of which greatly add to existing understandings of this peculiar symbiosis.
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[Engineering of Escherichia coli for convenient expression of [FeFe]-hydrogenase].
Wei Sheng Wu Xue Bao
PUBLISHED: 11-10-2011
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A new method used to heterologously express [FeFe]-hydrogenase in Escherichia coli was investigated in our present study.
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Network identification and flux quantification of glucose metabolism in Rhodobacter sphaeroides under photoheterotrophic H(2)-producing conditions.
J. Bacteriol.
PUBLISHED: 11-04-2011
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The nonsulfur purple bacteria that exhibit unusual metabolic versatility can produce hydrogen gas (H(2)) using the electrons derived from metabolism of organic compounds during photoheterotrophic growth. Here, based on (13)C tracer experiments, we identified the network of glucose metabolism and quantified intracellular carbon fluxes in Rhodobacter sphaeroides KD131 grown under H(2)-producing conditions. Moreover, we investigated how the intracellular fluxes in R. sphaeroides responded to knockout mutations in hydrogenase and poly-?-hydroxybutyrate synthase genes, which led to increased H(2) yield. The relative contribution of the Entner-Doudoroff pathway and Calvin-Benson-Bassham cycle to glucose metabolism differed significantly in hydrogenase-deficient mutants, and this flux change contributed to the increased formation of the redox equivalent NADH. Disruption of hydrogenase and poly-?-hydroxybutyrate synthase resulted in a significantly increased flux through the phosphoenolpyruvate carboxykinase and a reduced flux through the malic enzyme. A remarkable increase in the flux through the tricarboxylic acid cycle, a major NADH producer, was observed for the mutant strains. The in vivo regulation of the tricarboxylic acid cycle flux in photoheterotrophic R. sphaeroides was discussed based on the measurements of in vitro enzyme activities and intracellular concentrations of NADH and NAD(+). Overall, our results provide quantitative insights into how photoheterotrophic cells manipulate the metabolic network and redistribute intracellular fluxes to generate more electrons for increased H(2) production.
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Rapid large-scale preparation of ZnO nanowires for photocatalytic application.
Nanoscale Res Lett
PUBLISHED: 08-31-2011
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ZnO nanowires are a promising nanomaterial for applications in the fields of photocatalysis, nano-optoelectronics, and reinforced composite materials. However, the challenge of producing large-scale ZnO nanowires has stunted the development and practical utilization of ZnO nanowires. In this study, a modified carbothermal reduction method for preparing large-scale ZnO nanowires in less than 5 min is reported. The preparation was performed in a quartz tube furnace at atmospheric pressure without using any catalysts. A mixed gas of air and N2 with a volume ratio of 45:1 was used as the reactive and carrier gas. About 0.8 g ZnO nanowires was obtained using 1 g ZnO and 1 g graphite powder as source materials. The obtained nanowires exhibited a hexagonal wurtzite crystal structure with an average diameter of about 33 nm. Good photocatalytic activity of the nanowires toward the photodegradation of methylene blue dye under UV irradiation was also demonstrated.
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Luminescent properties of Tb3+ and Gd3+ ions doped aluminosilicate oxyfluoride glasses.
Spectrochim Acta A Mol Biomol Spectrosc
PUBLISHED: 07-20-2011
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Tb(3+) and Gd(3+) ions doped lithium-barium-aluminosilicate oxyfluoride glasses have been prepared. The transmission, emission and excitation spectra were measured. It has been found that those Tb(3+)-doped lithium-barium-aluminosilicate oxyfluoride glasses exhibit good UV-excited luminescence. The luminescence intensity of Tb(3+) ion increases for those (Tb(3+), Gd(3+))-codoped glasses. Energy transfer process from Gd(3+) ion to Tb(3+) ion is indicated.
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[Preliminary study on polyvinyl alcohol/wild antheraea pernyi silk fibroin as nanofiber scaffolds for tissue engineered tendon].
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
PUBLISHED: 03-25-2011
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To investigate the cellular compatibility of polyvinyl alcohol (PVA)/wild antheraea pernyi silk fibroin (WSF), and to explore the feasibility for tendon tissue engineering scaffold in vitro.
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Improvement of cellulase activity in Trichoderma reesei by heterologous expression of a beta-glucosidase gene from Penicillium decumbens.
Enzyme Microb. Technol.
PUBLISHED: 02-02-2011
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Trichoderma reesei is a well-known cellulase producer and widely applied in enzyme industry. To increase its ability to efficiently decompose cellulose, the beta-glucosidase activity of its enzyme cocktail needs to be enhanced. In this study, a beta-glucosidase I coding sequence from Penicillium decumbens was ligated with the cellobiohydrolase I (cbh1) promoter of T. reesei and introduced into the genome of T. reesei strain Rut-C30 by Agrobacterium-mediated transformation. In comparison to that from the parent strain, the beta-glucosidase activity of the enzyme complexes from two selected transformants increased 6- to 8-fold and their filter paper activity (FPAs) was enhanced by 30% on average. The transformants saccharifying ability towards pretreated cornstalk was also significantly enhanced. To further confirm the effect of heterologous beta-glucosidase on the cellulase activity of T. reesei, the heterologously expressed pBGL1 was purified and added to the enzyme complex produced by T. reesei Rut-C30. Supplementation of the Rut-C30 enzyme complex with pBGL1 brought about 80% increase of glucose yield during the saccharification of pretreated cornstalk. Our results indicated that the heterologous expression of a beta-glucosidase gene in T. reesei might produce balanced cellulase preparation.
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Performance and spatial community succession of an anaerobic baffled reactor treating acetone-butanol-ethanol fermentation wastewater.
Bioresour. Technol.
PUBLISHED: 01-26-2011
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An anaerobic baffled reactor with four compartments (C1-C4) was successfully used for treatment of acetone-butanol-ethanol fermentation wastewater and methane production. The chemical oxygen demand (COD) removal efficiency was 88.2% with a CH(4) yield of 0.25L/(g COD(removed)) when organic loading rate (OLR) was 5.4kg CODm(-3)d(-1). C1 played the most important role in solvents (acetone, butanol and ethanol) and COD removal. Community structure of C2 was similar to that in C1 at stage 3 with higher OLR, but was similar to those in C3 and C4 at stages 1-2 with lower OLR. This community variation in C2 was consistent with its increased role in COD and solvent removal at stage 3. During community succession from C1 to C4 at stage 3, abundance of Firmicutes (especially OTUs ABRB07 and ABRB10) and Methanoculleus decreased, while Bacteroidetes and Methanocorpusculum became dominant. Thus, ABRB07 coupled with Methanoculleus and/or acetogen (ABRB10) may be key species for solvents degradation.
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Microbiome of fungus-growing termites: a new reservoir for lignocellulase genes.
Appl. Environ. Microbiol.
PUBLISHED: 11-05-2010
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Fungus-growing termites play an important role in lignocellulose degradation and carbon mineralization in tropical and subtropical regions, but the degradation potentiality of their gut microbiota has long been neglected. The high quality and quantity of intestinal microbial DNA are indispensable for exploring new cellulose genes from termites by function-based screening. Here, using a refined intestinal microbial DNA extraction method followed by multiple-displacement amplification (MDA), a fosmid library was constructed from the total microbial DNA isolated from the gut of a termite growing in fungi. Functional screening for endoglucanase, cellobiohydrolase, ?-glucosidase, and xylanase resulted in 12 ?-glucosidase-positive clones and one xylanase-positive clone. The sequencing result of the xylanase-positive clone revealed an 1,818-bp open reading frame (ORF) encoding a 64.5-kDa multidomain endo-1,4-?-xylanase, designated Xyl6E7, which consisted of an N-terminal GH11 family catalytic domain, a CBM_4_9 domain, and a Listeria-Bacteroides repeat domain. Xyl6E7 was a highly active, substrate-specific, and endo-acting alkaline xylanase with considerably wide pH tolerance and stability but extremely low thermostability.
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Evaluation of the potential cytotoxicity of metals associated with implanted biomaterials (II).
J Med Eng Technol
PUBLISHED: 10-06-2010
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The effects of metal ions on the cell DNA and RNA synthetic functions and the destruction of cell defensive system caused by metal ions were studied on the investigation of the effects of metal ions on cell alkaline phosphatase (ALP) activity and cell metabolism ability. The poisonous behaviours of metal ions [Cr (VI), Ni, V, Cr (III), Ag, and Al] on living tissue were both quantitatively and qualitatively measured. It was shown that Cr (VI) has a notable action on both cellular DNA and RNA synthetic functions, and following that, were Ni, V. The limitation action of Cr (III) on the synthetic abilities of DNA and RNA increased with the increase of Cr (III) concentration. Different to other five metal ions, the limitation of Al ion on RNA was greater than that on DNA. The limitation of V, Ag ions on DNA was same to that on RNA. Trace Cr (VI), in culture medium resulted in the decreasing of GSH in living tissue. Similar to that, a little higher Ni ion concentration seriously reduced the GSH content in living tissue. It was suggested that Cr (VI), Ni, might destroy and/or disturb the orientation of the microtubulin in cell skeleton. For other four metal ions, together with increasing the concentration in culture medium, the osmotic pressure increased. Consequently, more metal ions entered cell membrane, more GSH were lost in cell.
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Derepressive effect of NH4+ on hydrogen production by deleting the glnA1 gene in Rhodobacter sphaeroides.
Biotechnol. Bioeng.
PUBLISHED: 03-27-2010
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Purple non-sulfur (PNS) bacteria produce hydrogen by photofermentation of organic acids in wastewater. However, NH(4)(+) in wastewater may inhibit hydrogen synthesis by repressing the expression and activity of nitrogenase, the enzyme catalyzing hydrogen production in PNS bacteria. In this study, the Rhodobacter sphaeroides 6016 glnA gene encoding glutamine synthetase (GS) was knocked out by homologous recombination, and the effects on hydrogen production and nitrogenase activity were examined. Using 3 mM glutamine as the nitrogen source, hydrogen production (1,245-1,588 mL hydrogen/L culture) and nitrogenase activity were detected in the mutant in the presence of relatively high NH(4)(+) concentrations (15-40 mM), whereas neither was detected in the wild-type strain under the same conditions. Further analysis indicated that high NH(4)(+) concentrations greatly inhibited the expression of nifA and nitrogenase gene in the wild-type strain but not in the glnA1(-) mutant. These observations suggest that GS is essential to NH(4)(+) repression of nitrogenase and that deletion of glnA1 results in the complete derepression of nitrogenase by preventing NH(4)(+) assimilation in vivo, thus relieving the inhibition of nifA and nitrogenase gene expression. Knocking out glnA1 therefore provides an efficient approach to removing the inhibitory effects of ammonium ions in R. sphaeroides and possibly in other hydrogen-producing PNS bacteria.
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Succession of the bacterial community and dynamics of hydrogen producers in a hydrogen-producing bioreactor.
Appl. Environ. Microbiol.
PUBLISHED: 03-19-2010
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Variation in the hydrogen production rate was consistent with the succession of dominant bacteria during the batch fermentation process. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes and quantitative analysis of the hydA genes at both the DNA and mRNA levels confirmed that Clostridium perfringens was the most dominant hydrogen producer in the bioreactor.
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Effect of key factors on hydrogen production from cellulose in a co-culture of Clostridium thermocellum and Clostridium thermopalmarium.
Bioresour. Technol.
PUBLISHED: 01-13-2010
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A cellulolytic, hydrogen-producing bacterium (Clostridiumthermocellum DSM 1237) and a non-cellulolytic, hydrogen-producing bacterium (Clostridiumthermopalmarium DSM 5974) were co-cultured at 55 degrees C, using cellulose as the sole substrate. At a low load of cellulose (filter paper, 4.5g/L), yeast extract had a significant effect on cellulose degradation and hydrogen production. The extent of cellulose utilization and hydrogen production displayed a linear relationship with the logarithm of the yeast extract concentration, and the optimal weight ratio of yeast extract to cellulose was 1:1. At a high load of filter paper (9g/L), an alkali chemical was required to maintain efficient cellulose degradation. As the KHCO3 concentration increased from 0 to 60mM, the utilized cellulose increased from 1.23g/L (13.5%) to 8.59g/L (94.3%), and maximum hydrogen production (1387ml/L of culture) occurred at 40mM KHCO(3). Increasing the inoculation ratio of C. thermopalmarium to C. thermocellum from 0.05:1 to 0.17:1 had little influence on hydrogen production, probably because of the limited availability of soluble sugar in the medium during the early stages of the co-culture.
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Gas sensors based on deposited single-walled carbon nanotube networks for DMMP detection.
Nanotechnology
PUBLISHED: 08-04-2009
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Sensors based on single-walled carbon nanotube (SWNT) networks were fabricated and their sensitive properties for the nerve agent stimulant dimethyl methylphosphonate (DMMP) vapor were investigated at room temperature. The SWNT networks were deposited on oxidized silicon surface functionalized with 3-aminopropyltrimethysilane (APS). Combining with a traditional silicon process, SWNT-based gas sensors were made at a wafer scale. The effects of the density of deposited SWNTs on the sensor response were studied. The excellent response is obtained under a density of 30-40 tubes microm(-2). The sensors exhibit high resistance response, fast response time, rapid recovery and good reproducibility for DMMP vapor. The deposited SWNT sensors will be potentially extended to large-scale fabrication.
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Evaluation of the potential cytotoxicity of metals associated with implanted biomaterials (I).
Prep. Biochem. Biotechnol.
PUBLISHED: 02-03-2009
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The present assessments of potential toxicity of metal ions (Al, Ni, Cr, V, and Ag) that construct the metallic biomaterials were carried out in vitro. By measurements of cell alkaline phosphatase (ALP) activity and reduction ability of cell methyl tetrazolium (MTT), the cytotoxicity of prevalence metallic biomaterials has been investigated. Furthermore, the poison and erosion of metal ions and atoms on human tissue are discussed. Research results indicated that trace Cr(VI) showed serious cytotoxicity and Ni as well as V are cytotoxic if the ion concentration in culture medium is over 100 micromol x L(-1) and 1 micromol x L(-1), respectively. A strange phenomenon is that Ag also is cytotoxic if the ion concentration is higher than 500 micromol x L(-1). Al ion is biphasic in cytotoxicity. At low ion concentration (< 10 micromol x L(-1)), Al ions can stimulate cell proliferation, whereas at concentrations over 1,000 micromol x L(-1), cytotoxicity increases.
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Highly enhanced gas sensing in single-walled carbon nanotube-based thin-film transistor sensors by ultraviolet light irradiation.
Nanoscale Res Lett
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Single-walled carbon nanotube (SWCNT) random networks are easily fabricated on a wafer scale, which provides an attractive path to large-scale SWCNT-based thin-film transistor (TFT) manufacturing. However, the mixture of semiconducting SWCNTs and metallic SWCNTs (m-SWCNTs) in the networks significantly limits the TFT performance due to the m-SWCNTs dominating the charge transport. In this paper, we have achieved a uniform and high-density SWCNT network throughout a complete 3-in. Si/SiO2 wafer using a solution-based assembly method. We further utilized UV radiation to etch m-SWCNTs from the networks, and a remarkable increase in the channel current on/off ratio (Ion/Ioff) from 11 to 5.6 × 103 was observed. Furthermore, we used the SWCNT-TFTs as gas sensors to detect methyl methylphosphonate, a stimulant of benchmark threats. It was found that the SWCNT-TFT sensors treated with UV radiation show a much higher sensitivity and faster response to the analytes than those without treatment with UV radiation.
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Characterization of a novel thermostable ?-glucosidase from a metagenomic library of termite gut.
Enzyme Microb. Technol.
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A novel ?-glucosidase-encoding gene, bgl-gs1, which was identified from a positive fosmid clone in a metagenomic library of the gut of Globitermes brachycerastes, [corrected] encodes a 455 amino acid polypeptide that contains a catalytic domain belonging to glycoside hydrolase family 1 (GH1). It was expressed in Escherichia coli BL21 (DE3) and the expression product showed a molecular mass of ?51.7 kDa by SDS-PAGE. The optimal temperature and pH for the activity of the purified recombinant enzyme Bgl-gs1 with p-nitrophenyl-?-D-glucoside (pNPG) were 90°C and 6.0, respectively. The specific activities of Bgl-gs1 on pNPG and salicin were 110 and 14U/mg of protein, respectively, and its K(m) values were 0.18 and 2.59 mM, respectively. The residual activity of Bgl-gs1 was maintained above 70% after the recombinant enzyme was incubated at 75°C and pH 6.0 for 2h, and its half-life at 90°C was approximately 1h in the presence of 4mM pNPG. Bgl-gs1 showed synergistic effect with either a crude enzyme mixture of the fungal strain Trichoderma reesei Rut-C30 or a fusion protein (TcE1) created from the cellobiohydrolase cbh1 gene of T. reesei and endoglucanase from Acidothermus cellulolyticus; 87 and 137% increases in hydrolytic efficiency were noted on microcrystalline cellulose, respectively. These results suggest that the thermostable ?-glucosidase Bgl-gs1 is a likely candidate for industrial applications.
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Upregulated MALAT-1 contributes to bladder cancer cell migration by inducing epithelial-to-mesenchymal transition.
Mol Biosyst
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Recent studies reveal that long non-coding RNAs (lncRNAs) have been shown to have important regulatory roles in cancer biology, and lncRNA MALAT-1 expression is upregulated in some tumors. However, the contributions of MALAT-1 to bladder cancer metastasis remain largely unknown. In the present study we evaluated MALAT-1 expression in bladder cancer tissues by real-time PCR, and defined its biological functions. We verified that MALAT-1 levels were upregulated in bladder cancer tissues compared with adjacent normal tissues, and MALAT-1 expression was remarkably increased in primary tumors that subsequently metastasized, when compared to those primary tumors that did not metastasize. SiRNA-mediated MALAT-1 silencing impaired in vitro bladder cancer cell migration. Downregulation of MALAT-1 resulted in a decrease of the epithelial-mesenchymal transition (EMT)-associated ZEB1, ZEB2 and Slug levels, and an increase of E-cadherin levels. We further demonstrated that MALAT-1 promoted EMT by activating Wnt signaling in vitro. These data suggest an important role for MALAT-1 in regulating metastasis of bladder cancer and the potential application of MALAT-1 in bladder cancer therapy.
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Functionalized self-assembled monolayers on mesoporous silica nanoparticles with high surface coverage.
Nanoscale Res Lett
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Mesoporous silica nanoparticles (MSNs) containing vinyl-, propyl-, isobutyl- and phenyl functionalized monolayers were reported. These functionalized MSNs were prepared via molecular self-assembly of organosilanes on the mesoporous supports. The relative surface coverage of the organic monolayers can reach up to 100% (about 5.06 silanes/nm.
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Study on cerium-doped nano-TiO2 coatings for corrosion protection of 316?L stainless steel.
Nanoscale Res Lett
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Many methods have been reported on improving the photogenerated cathodic protection of nano-TiO2 coatings for metals. In this work, nano-TiO2 coatings doped with cerium nitrate have been developed by sol-gel method for corrosion protection of 316?L stainless steel. Surface morphology, structure, and properties of the prepared coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion protection performance of the prepared coatings was evaluated in 3?wt% NaCl solution by using electrochemical techniques in the presence and absence of simulated sunlight illumination. The results indicated that the 1.2% Ce-TiO2 coating with three layers exhibited an excellent photogenerated cathodic protection under illumination attributed to the higher separation efficiency of electron-hole pairs and higher photoelectric conversion efficiency. The results also showed that after doping with an appropriate concentration of cerium nitrate, the anti-corrosion performance of the TiO2 coating was improved even without irradiation due to the self-healing property of cerium ions.
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Preemptive deceased-donor renal transplant in adults: single-center experience and outcome.
Exp Clin Transplant
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Preemptive renal transplant has been associated with better survival of both the allograft and the recipient than has conventional renal transplant. It remains unclear, however, whether preemptive transplant is optimal for renal replacement therapy. We describe our experience with preemptive renal transplant.
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Field emission from in situ-grown vertically aligned SnO2 nanowire arrays.
Nanoscale Res Lett
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Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/?m were obtained at anode-cathode separations of 100 to 200 ?m. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/?m. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters.
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Profiling the metatranscriptome of the protistan community in Coptotermes formosanus with emphasis on the lignocellulolytic system.
Genomics
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The symbiotic protists in the hindgut of lower termites are critical for lignocellulose decomposition. Due to the unculturability of these protists, information on lignocellulases and their abundance within the gut is unavailable. The advent of high-throughput sequencing technologies enables an investigation of the gene expression profile in this community without culturing these organisms. Here, we carried out 454 pyrosequencing to profile the metatranscriptome of the protistan community in Coptotermes formosanus. In total, 223,477 reads were obtained by sequencing the enriched protistan mRNA. Phagocytosis and cytoskeletal homeostasis pathways were highly represented in the metatranscriptome. Among the metabolic pathways, starch and sucrose metabolism were dominant. A detailed analysis combining Pfam and KEGG annotation identified 118 glycosyl hydrolases belonging to 18 different glycosyl hydrolase families (GHFs). Subsequently, a novel GHF10 endo-1,4-beta-xylanase was functionally characterized to complement our understanding of the protistan hemicellulases.
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Construction of a cellulase hyper-expression system in Trichoderma reesei by promoter and enzyme engineering.
Microb. Cell Fact.
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Trichoderma reesei is the preferred organism for producing industrial cellulases. However, a more efficient heterologous expression system for enzymes from different organism is needed to further improve its cellulase mixture. The strong cbh1 promoter of T. reesei is frequently used in heterologous expression, however, the carbon catabolite repressor CREI may reduce its strength by binding to the cbh1 promoter at several binding sites. Another crucial point to enhance the production of heterologous enzymes is the stability of recombinant mRNA and the prevention of protein degradation within the endoplasmic reticulum, especially for the bacteria originated enzymes.In this study, the CREI binding sites within the cbh1 promoter were replaced with the binding sites of transcription activator ACEII and the HAP2/3/5 complex to improve the promoter efficiency. To further improve heterologous expression efficiency of bacterial genes within T. reesei, a flexible polyglycine linker and a rigid ?-helix linker were tested in the construction of fusion genes between cbh1 from T. reesei and e1, encoding an endoglucanase from Acidothermus cellulolyticus.
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Expression and characterization of a novel metagenome-derived cellulase Exo2b and its application to improve cellulase activity in Trichoderma reesei.
Appl. Microbiol. Biotechnol.
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A metagenomic fosmid library containing 1?×?10(5) clones was constructed from a biogas digester fed with pig ordure and rice straw. In total, 121 clones with activity of 4-methylumbelliferyl-cellobiosidase were screened from the metagenomic library. A novel GH5 cellulase gene exo2b was identified from a sequenced clone EXO02C10 and expressed in Escherichia coli BL21. The corresponding recombinant Exo2b protein showed high specific activity toward both carboxymethylcellulose (CMC; 260 U/mg protein) and ?-D-glucan from barley (849 U/mg), with an optimal pH and temperature of 7.5 and 58 °C, respectively. Exo2b showed stable activity at a wide pH range from 5.5 to 9.0 and was highly thermostable at 60 °C in the presence of 60 mM cysteine. Residual activity was maintained at nearly 100% when Exo2b was incubated at 60 °C for 15 h. A thin-layer chromatography analysis of the hydrolysis products confirmed that Exo2b was an endo-?-1,4-glucanase and it could also produce oligosaccharide smaller than cellotetraose. The fragment encoding the Exo2b catalytic domain was then fused with the cbh1 gene from Trichoderma reesei, and the fused gene was successfully expressed in T. reesei Rut-C30. Compared to that of the parent strain, the filter paper activity and CMCase activity of the secreted proteins of a selected transformant A1 increased by 24% and 18%, respectively. Besides, the glucose concentration from the hydrolysis of pretreated corn stover by the A1 secreted proteins increased by 19.8%. The present study demonstrated the potential application of metagenome originated cellulase genes to modify cellulase producing fungi.
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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.