-
Yang Zhang,
Gang Zhang,
Ying Wan,
Chengji Zhao,
Ke Shao, Hongtao Li,
Miaomiao Han,
Jing Zhu,
Shuai Xu,
Zhongguo Liu,
Hui Na
Journal of Polymer Science Part A Polymer Chemistry 10/2010; 48(24):5824 - 5832. · 3.92 Impact Factor
-
Journal of Materials Chemistry - J MATER CHEM. 01/2010; 20(16).
-
[show abstract]
[hide abstract]
ABSTRACT: To prepare a cross-linked hybrid proton exchange membrane with high mechanical and oxidative stability, a silane monomer, namely 3-glycidoxypropyltrimethoxysilane (KH-560), is first grafted to sulfonated poly(arylene ether ether ketone)s bearing carboxyl groups (SPAEK-C) and hydrolysis–condensation is then performed on the grafted membranes to make them cross-link. 1H NMR measurements and Fourier transform infrared spectroscopy are used to characterize and confirm the structures of SPAEK-Cs and hybrid polymer electrolyte membranes, respectively. The Si–O–Si cross-linking structure enhances the stability of the PEM greatly. The proton conductivities of the hybrid membranes with 5% KH-560 in weight reach 0.155Scm−1 at 80°C which is comparable to that of Nafion® membranes. The ion-exchange capacity, water uptake and swelling, methanol permeability, mechanical properties are investigated to confirm their applicability in fuel cells.
Journal of Power Sources 01/2010; 195(3):762-768. · 4.95 Impact Factor
-
Ke Shao,
Jing Zhu,
Chengji Zhao,
Xianfeng Li,
Zhiming Cui,
Yang Zhang, Hongtao Li,
Dan Xu,
Gang Zhang,
Tiezhu Fu,
Jing Wu,
Hui Na,
Wei Xing
Journal of Polymer Science Part A Polymer Chemistry 09/2009; 47(21):5772 - 5783. · 3.92 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Bacterial pathogens have evolved effector proteins with ubiquitin E3 ligase activities through structural mimicking. Here we report the crystal structure of the Shigella flexneri type III effector IpaH3, a member of the leucine-rich repeat (LRR)-containing bacterial E3 family. The LRR domain is structurally similar to Yersinia pestis YopM and potentially binds to substrates. The structure of the C-terminal E3 domain differs from the typical RING- and HECT-type E3s. IpaH3 synthesizes a Lys48-linked ubiquitin chain, and the reaction requires noncovalent binding between ubiquitin and a specific E2, UbcH5. Free ubiquitin serves as an acceptor for IpaH3-catalyzed ubiquitin transfer. Cys363 within a conserved CXD motif acts as a nucleophile to catalyze ubiquitin transfer through a transthiolation reaction. The D365N mutant is devoid of E3 activities but turns into a potent ubiquitin-E2 thioesterase. Our analysis establishes a structurally and mechanistically distinct class of ubiquitin ligases found exclusively in pathogenic or symbiotic bacteria.
Nature Structural & Molecular Biology 12/2008; 15(12):1302-8. · 12.71 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The OspF family of phosphothreonine lyase, including SpvC from Salmonella, irreversibly inactivates the dual-phosphorylated host MAPKs (pT-X-pY) through beta elimination. We determined crystal structures of SpvC and its complex with a phosphopeptide substrate. SpvC adopts a unique fold of alpha/beta type. The disordered N terminus harbors a canonical D motif for MAPK substrate docking. The enzyme-substrate complex structure indicates that recognition of the phosphotyrosine followed by insertion of the threonine phosphate into an arginine pocket places the phosphothreonine into the enzyme active site. This requires the conformational flexibility of pT-X-pY, which suggests that p38 (pT-G-pY) is likely the preferred physiological substrate. Structure-based biochemical and enzymatic analysis allows us to propose a general acid/base mechanism for beta elimination reaction catalyzed by the phosphothreonine lyase. The mechanism described here provides a structural understanding of MAPK inactivation by a family of pathogenic effectors conserved in plant and animal systems and may also open a new route for biological catalysis.
Molecular Cell 01/2008; 28(5):899-913. · 14.18 Impact Factor
-
Jie Zhang,
Feng Shao,
Yan Li,
Haitao Cui,
Linjie Chen, Hongtao Li,
Yan Zou,
Chengzu Long,
Lefu Lan,
Jijie Chai,
She Chen,
Xiaoyan Tang,
Jian-Min Zhou
[show abstract]
[hide abstract]
ABSTRACT: Pathogen-associated molecular patterns (PAMPs) elicit basal defense responses in plants, and, in turn, pathogens have evolved mechanisms to overcome these PAMP-induced defenses. To suppress immunity, the phytopathogenic bacterium Pseudomonas syringae secretes effector proteins, the biochemical function and virulence targets of which remain largely unknown. We show that HopAI1, an effector widely conserved in both plant and animal bacterial pathogens, inhibits the Arabidopsis mitogen-activated protein kinases (MAPKs) activated by exposure to PAMPs. HopAI1 inactivates MAPKs by removing the phosphate group from phosphothreonine through a unique phosphothreonine lyase activity, which is required for HopAI1 function. The inhibition of MAPKs by HopA1 suppresses two independent downstream events, namely the reinforcement of cell wall defense and transcriptional activation of PAMP response genes. The MAPKs MPK3 and MPK6 physically interact with HopAI1 indicating that they are direct targets of HopAI1. These findings uncover a mechanism by which Pseudomonas syringae overcomes host innate immunity to promote pathogenesis.
Cell host & microbe 06/2007; 1(3):175-85. · 13.02 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pathogenic bacteria use the type III secretion system to deliver effector proteins into host cells to modulate the host signaling pathways. In this study, the Shigella type III effector OspF was shown to inactivate mitogen-activated protein kinases (MAPKs) [extracellular signal-regulated kinases 1 and 2 (Erk1/2), c-Jun N-terminal kinase, and p38]. OspF irreversibly removed phosphate groups from the phosphothreonine but not from the phosphotyrosine residue in the activation loop of MAPKs. Mass spectrometry revealed a mass loss of 98 daltons in p-Erk2, due to the abstraction of the alpha proton concomitant with cleavage of the C-OP bond in the phosphothreonine residue. This unexpected enzymatic activity, termed phosphothreonine lyase, appeared specific for MAPKs and was shared by other OspF family members.
Science 03/2007; 315(5814):1000-3. · 31.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Sandstone-hosted roll-type U deposits has recently been found in the Middle Jurassic Zhiluo Formation in the Dongsheng area, north of the Ordos Basin. In order to assess the origin of the uranium mineralization, the host sandstone has been investigated, with emphasis on δ 34 S values of ore-stage pyrite, δ 13 C of calcite, fluid inclusion oil biomarkers, X-ray diffraction, ICP-MS, as well as studies by electron microprobe and scanning electron microscope. The mineralization consists mainly of coffinite. Some of the coffinite is intimately intergrown with ore-stage pyrite, indicating co-precipitation. Ore-stage pyrite has δ 34 S values from −34 to +17‰, suggesting the pyrite sulfur originated from bacterial sulfate reduction. In the host sandstone, calcite cement exhibits δ 13 C values from −27.6 to −2.1‰ and fluid inclusion oils show evidence of biodegradation. These lines of evidence indicate petroleum was likely oxidized by sulfate-reducing bacteria (SRB) and thus supplied a source of some of the carbon in the calcite. Microbial degradation of petroleum is partially supported by the low-temperature diagenetic environment (< 70 °C). Thus, SRB were likely to reduce sulfates to sulfides simultaneously with petroleum oxidization, and caused direct or indirect reduction of hexavalent uranium [U(VI)] to tetravalent uranium [U(IV)]. U(VI) pre-concentration by adsorption and subsequent inorganic reduction is likely to be less significant than direct reduction of U(VI) by SRB in the Dongsheng deposit. This is because ore-stage solution is non-acidic (pH = 8 to 10), as indicated by abundance of ore-stage pyrite and calcite cement and lack of marcasite in the host sandstone.
08/2006;
-
[show abstract]
[hide abstract]
ABSTRACT: Sandstone-hosted roll-type uranium deposits were found to occur in the Middle Jurassic Zhiluo Formation sandstone in Dongsheng
area, north of the Ordos basin. The uranium occurs mainly as coffinite. Some of the coffinite is intergrown intimately with
secondary pyrite, indicating simultaneous precipitation. The pyrite has δ34S values from −34‰ to +18‰, suggesting an origin of bacterial sulfate reduction. Calcite cement of the host sandstones has
δ13C values from +0.3‰ to −27.6‰. The most negative δ13C value is more negative than those of terrestrial higher plants-derived organic matter in the Jurassic in the basin, thus
the carbon of the calcite cement is likely derived from oil and natural gas, most likely from mixing of preexisting inorganically
derived CO2 and methane-derived CO2. The hypothesis is supported by the great, number of oil/gas inclusions found in the calcite cement and healed fractures
through quartz grains. Interestingly, in the sandstone with high content of uranium, secondary pyrite has δ34S as light as −34‰, calcite cement has δ13C lower than −10‰. Thus, it can be concluded that sulfate reducing bacteria likely oxidized hydrocarbons, and directly or
indirectly reduced uranium (VI) to uranium (IV).
KeywordsBacterial sulfate reduction (BSR)–petroleum–δ34S–δ13C–uranium–sandstone
12/2004: pages 229-232;
-
[show abstract]
[hide abstract]
ABSTRACT: Multilayered polyelectrolyte complexes (PECs) modified proton exchange membranes are successfully prepared from alternating deposition of oppositely charged polyelectrolyte chitosan (CS) and sulfonated poly (aryl ether ketone) bearing carboxyl groups (SPAEK-C) on the surface of Nafion®117 via the layer-by-layer (LBL) method. The cross-linked PEC-coated Nafion® membranes (c-PEC-coated Nafion® membranes) are prepared from heat-induced cross-linking between CS and SPAEK-C via formation of amide bonds. Fourier transform infrared spectroscopy (FT-IR) verifies that cross-linking between ammonium groups of CS and carboxyl groups of SPAEK-C occurs by the formation of amide bonds. The morphology of the membranes is studied in detail by SEM. The c-PEC-coated Nafion® membranes exhibit low water uptake (23.5%, 80 °C), water swelling (14.0%, 80 °C) and methanol permeability (2.7 × 10−7 cm2 s−1). Proton conductivity of the c-PEC-coated Nafion® membranes increase at elevated temperature, reaching the value of 0.131 S cm−1 at 80 °C. These results show that cross-linking of layered CS/SPAEK-C films can effectively reduce water uptake, water swelling and methanol permeability while improve the dimensional stability and maintain high proton conductivity.
Journal of Membrane Science.
-
[show abstract]
[hide abstract]
ABSTRACT: Poly(ether ether ketone) (PEEK) and sulfonated poly(ether ether ketone) (SPEEK, IEC = 2.07 mequiv.g−1) have been synthesized via nucleophilic aromatic substitution reaction. Bromomethylated poly(ether ether ketone) (PEEK-Br) is then prepared and reacted with 2-benzimidazolethiol to obtain the benzimidazole grafted poly(ether ether ketone) (PEEK-BI). The structures of PEEK-Br and PEEK-BI are characterized by 1H NMR spectra. Composite membranes based on SPEEK and PEEK-BI are prepared and their properties used for fuel cells are studied in detail. The results show that the composite membranes exhibit greatly improved mechanical properties as well as reduced water uptake and methanol permeability compared with the pristine SPEEK membrane. The increased oxidative stability and selectivity indicate that the composite membranes are promising to be used as proton exchange membranes.
International Journal of Hydrogen Energy.
-
[show abstract]
[hide abstract]
ABSTRACT: A series of cross-linkable sulfonated poly(arylene ether ketone)s bearing carboxylic acid groups (C-SPAEKs) have been prepared for direct methanol fuel cells (DMFCs). The chemical structure of the cross-linkable copolymers was analyzed by 1H NMR and 13C NMR spectra. Cross-linked membranes were obtained by thermal curing cross-linkable copolymers. The cross-linked network structure caused significant enhancement in the mechanical properties and large reduction in water uptake (WU), swelling ratio and methanol permeability of the membranes. The water uptake and methanol permeability of C-SPAEK-50 membrane was 506.9% (80 °C) and 14.83 × 10−7 cm2/s, but after cross-linking they reduced to 75.2% and 1.74 × 10−7 cm2/s, while maintaining proton conductivity of 0.197 S/cm, which was higher than 0.146 S/cm of Nafion 117.
Journal of Membrane Science.
-
[show abstract]
[hide abstract]
ABSTRACT: In this series of two articles, the concepts and approaches of environomic (thermodynamic, economic and environmental) performance ‘Typification’ of power generation technologies (Part I) and of combined heat and power (CHP) cogeneration technologies (Part II) in the context of CO2 abatement are introduced. A methodology is then proposed for a flexible and fast project based power or CHP cogeneration system design evaluation though post-optimization integration of the operating and capital costs. This allows to effectively deal with the uncertainty of the project specific design and operation conditions (fuel, electricity and heat selling prices, project financial conditions such as investment amortization periods, annual operating hours, etc). Furthermore, the uncertainties linked to the external cost such as the CO2 tax level under a tax scheme or the CO2 permit price in the emission trading market can be assessed.Application examples, including gas turbine and combined cycles are treated with the proposed methodology, by using the superstructure based generic environomic models and a multi-objective optimizer. Furthermore an extension of the methodology using statistical approach is also presented and illustrated with different generation technologies.
Energy.
-
[show abstract]
[hide abstract]
ABSTRACT: Bisphenol monomer 4-carboxylphenyl hydroquinone (4C-PH) containing carboxyl groups was synthesized by diazotization reaction of p-aminobenzoic acid and 1,4-benzoquinone and subsequent reductive reaction. Copolymerization of bisphenol A, 4C-PH, sodium 5,5′-carbonylbis(2-fluorobenzene-sulfonate) and 4,4′-difluorobenzophenone at various molar ratios through aromatic nucleophilic substitution reaction resulted in a new sulfonated poly(ether ether ketone) containing pendant carboxyl groups (C-SPEEK). The structures of the monomer 4C-PH and copolymers were confirmed by FT-IR and 1H NMR. Flexible and transparent membranes with sulfonic and carboxylic acid groups as the proton conducting sites were prepared. The dependence of ion-exchange capacity (IEC), water uptake, proton conductivity and methanol permeability on the degree of sulfonation has been studied. The highest proton conductivity of 0.16 S cm−1 was obtained from C-SPEEK-4 (IEC = 1.44 mequiv. g−1) at 80 °C, higher than that of Nafion117 (0.12 S cm−1). Incorporating carboxylic acid groups into copolymers led to higher dimensional stability and lower water uptake. The methanol permeability coefficients of C-SPEEK membranes were in the range of 3.54 × 10−7 cm2 s−1 to 5.9 × 10−9 cm2 s−1, which were significantly lower than that of Nafion117 (1.61 × 10−6 cm2 s−1). Accordingly, the C-SPEEK membranes exhibited much higher selectivity (conductivity/methanol permeability coefficient) compared with Nafion117 membrane.
Journal of Membrane Science.
-
[show abstract]
[hide abstract]
ABSTRACT: Composite membranes based on Sulfonated poly(ether ether ketone) (SPEEK) and sulfonated organically modified Si-SBA-15 (S-SBA-15) were investigated with the purpose of increasing the proton conductivity. The novelty of the composite membranes was attributed to two special structures and different ion exchange capacities (IEC) of S-SBA-15 fillers, which were embedded in membranes. The typical hexagonal channels array of S-SBA-15 was confirmed by XRD and TEM. The regular vermiculate and amorphous structures of the inorganic fillers were proved by SEM. Composite membranes were prepared through common solvent casting method. SEM images indicated that the inorganic filler with regular structure dispersed homogeneously in the composite membranes, but the amorphous filler caused an agglomeration phenomenon at the same loading content. The composite membranes exhibited good thermal stability, enhanced water uptake and proton conductivity. The proton conductivity of the composite membranes with low IEC filler was higher than the composite membranes with high IEC filler at the same loading content. The highest proton conductivity value of 0.156 S cm−1 was obtained for the composite membrane containing 5 wt.% S-SBA-15 with the IEC of 1.41 mequiv g−1 at 80 °C. This composite membrane also showed other promising properties such as good thermal and mechanical stability which exceeded the other composite membranes with different loading contents.
International Journal of Hydrogen Energy 34(16):6740-6748. · 4.05 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Novel side-chain-type sulfonated poly(arylene ether ketone) with pendant sulfoalkyl groups (SPAEK-xx) were synthesized by post-sulfonation method. Their structures were confirmed by FT-IR and NMR spectra. The all obtained membranes had excellent thermal stability and mechanical properties. The side-chain-type SPAEK films showed good dimensional stability, and their water uptake and swelling ratio were lower than those of the main-chain-type SPAEK with similar ion exchange capacity (IEC) value. It should be noted that the most highly sulfonated copolymer, SPAEK-100 (DS = 1.0) with IEC of 1.54 meq./g, showed proton conductivity of 0.083 S/cm and water swelling ratio of only 9.74% at 80 °C. Moreover, the methanol permeability of SPAEK-100 membrane was 3.95 × 10−7 cm2/s, which was much lower than 23.80 × 10−7 cm2/s of Nafion 117.Graphical abstract
Polymer. 50(19):4471-4478.
-
[show abstract]
[hide abstract]
ABSTRACT: Sulfonated poly(arylene ether ketone) bearing pendant carboxylic acid group (C-SPAEK) had been prepared for direct methanol fuel cell applications, and subsequently cross-linked by a thermal curing reaction using hexafluoro-bisphenol-A novolac epoxy resin (HFANER) as a cross-linker. The cross-linked network structure caused significant enhancement in the mechanical properties and oxidative stability. Meanwhile, water uptake, swelling ratio and methanol permeability substantially decreased with increasing the content of cross-linker. Notably, the water uptake of C-SPAEK was 506.9% at 80 °C, but after cross-linking, Cr-SPAEK-17 exhibited a water uptake of 32.3%. Meanwhile, a 12.1% of swelling ratio was obtained which was lower than that of Nafion 117 (17.2%). Although the proton conductivities of the cross-linked membranes were lower than that of the pristine membrane, the higher selectivity defined as the proton conductivity to methanol permeability was obtained for the cross-linked membranes.
International Journal of Hydrogen Energy.
-
[show abstract]
[hide abstract]
ABSTRACT: A series of sulfonated poly(ether ether ketone) containing pendant carboxyl (C-SPEEKs) have been synthesized using a nucleophilic polycondesation reaction. A condensation reaction between 1,2-diaminobenzene and carboxyl resulted in a new series of copolymers containing benzimidazole groups (SPEEK-BIms). The expected structures of the sulfonated copolymers are confirmed by 1H NMR. The dependence of ion exchange capacity, water uptake, proton conductivity and methanol diffusion coefficient of SPEEK-BIm membranes has been studied and compared with their carboxyl acid form. The results suggest that the introduction of benzimidazole groups may be responsible for many excellent properties of the membranes for fuel cell. It is noticeable that the markedly improved oxidative stability is benefit for the application of membrane.
International Journal of Hydrogen Energy.
-
[show abstract]
[hide abstract]
ABSTRACT: The surface of sulfonated poly(arylene ether ketone) bearing carboxyl groups (SPAEK-C) was modified by alternating deposition of oppositely charged polypyrrole (PPY) and phosphotungstic acid (PWA) via the layer-by-layer (LBL) method in order to prevent the crossover of methanol in the direct methanol fuel cell (DMFC). FT-IR confirms that PPY and PWA are assembled in the multilayers successfully. The morphology of the membranes studied in detail by SEM shows the presence and stability of thin PPY/PWA layers coated on SPAEK-C membranes. Methanol permeability was determined and was shown to be effectively reduced. The selectivity of SPAEK-C-(PPY/PWA)n is 1 order more than Nafion® 117, which is attractive in DMFCs. Thermal stability, water uptake, water swelling and proton conductivity of the SPAEK-C and SPAEK-C-(PPY/PWA)n membranes were also investigated.
International Journal of Hydrogen Energy.
