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Query: EC:6.2.1.1 (ACS)
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Generation of oxygen free radicals at the time of reperfusion has been implicated as a major causative factor for myocardial reperfusion injury. In order to examine if oxygen free radical scavenger superoxide dismutase (SOD) in human plasma prevent reperfusion injury with successful thrombolysis and limit infarct size, we studied the relationship between infarct size and plasma SOD activity in 25 patients received thrombolytic therapy in antero-septal acute myocardial infarction. Plasma SOD activities were measured by the nitrate method. There was no variance in plasma SOD activity in patients with acute myocardial infarction before and after thrombolysis. Infarct size was evaluated by using % abnormally contracting segments (% ACS) correlation with % ACS (r = -0.58, p less than 0.05) in 17 patients with successful thrombolysis. This significant correlation was still shown in 14 patients without collaterals before recanalization (r = -0.56, p less than 0.05). On the other hand, there was no significant relationship between plasma SOD activities and % ACS in 8 patients with a complete occlusion after thrombolysis (r = -0.081). These results showed that human plasma SOD prevent the reperfusion injury and limit the infarct size in patients with successful thrombolysis and imply that the generation of free radical at the time of reperfusion results in myocardial reperfusion injury.
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PMID:Human plasma superoxide dismutase (SOD) activity on reperfusion injury with successful thrombolysis in acute myocardial infarction. 273 45

Expression from the Escherichia coli nrfA promoter (pnrfA) is activated by both the FNR protein (an anaerobically triggered transcription activator) and the NarL or NarP proteins (transcription activators triggered by nitrite and nitrate). Under anaerobic conditions, FNR binds to a site centred at position -41.5 at pnrfA and activates transcription. Further activation, induced by the presence of nitrite, results from the binding of NarL and NarP to a site centred at position -74.5. A second promoter (pacsP1), which directs transcription into the adjacent gene encoding acetyl coenzyme A synthetase (acs), is overlapping and divergent to pnrfA. Despite extensive overlap of regulatory elements, pnrfA and pacsP1 are regulated independently. We demonstrate that at least two nucleoid-associated factors bind to the nrfA-acs intergenic region. The Fis protein binds to a site centred at position -15 (in relation to pnrfA transcription), whereas the IHF protein binds to a site centred at position -54. Both Fis and IHF repress in vivo expression from pacsP1, but have smaller repressive effects on expression from pnrfA. Gel retardation assays were used to investigate the pairwise binding of FNR, NarL, Fis and IHF proteins to the nrfA-acs intergenic region. The binding of NarL and IHF is mutually exclusive, whereas all other combinations can bind simultaneously. Experiments in which deletions and point mutations were introduced into the upstream region of pnrfA demonstrated that an additional factor must bind upstream to inhibit FNR-dependent transcription. We conclude that the nrfA-acs intergenic region is folded into an ordered nucleoprotein structure that permits the two divergent promoters to be regulated independently in response to different physiological signals.
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PMID:Independent regulation of the divergent Escherichia coli nrfA and acsP1 promoters by a nucleoprotein assembly at a shared regulatory region. 1192 25

Fungal ammonia fermentation is a novel dissimilatory metabolic mechanism that supplies energy under anoxic conditions. The fungus Fusarium oxysporum reduces nitrate to ammonium and simultaneously oxidizes ethanol to acetate to generate ATP (Zhou, Z., Takaya, N., Nakamura, A., Yamaguchi, M., Takeo, K., and Shoun, H. (2002) J. Biol. Chem. 277, 1892-1896). We identified the Aspergillus nidulans genes involved in ammonia fermentation by analyzing fungal mutants. The results showed that assimilatory nitrate and nitrite reductases (the gene products of niaD and niiA) were essential for reducing nitrate and for anaerobic cell growth during ammonia fermentation. We also found that ethanol oxidation is coupled with nitrate reduction and catalyzed by alcohol dehydrogenase, coenzyme A (CoA)-acylating aldehyde dehydrogenase, and acetyl-CoA synthetase (Acs). This is similar to the mechanism suggested in F. oxysporum except A. nidulans uses Acs to produce ATP instead of the ADP-dependent acetate kinase of F. oxysporum. The production of Acs requires a functional facA gene that encodes Acs and that is involved in ethanol assimilation and other metabolic processes. We purified the gene product of facA (FacA) from the fungus to show that the fungus acetylates FacA on its lysine residue(s) specifically under conditions of ammonia fermentation to regulate its substrate affinity. Acetylated FacA had higher affinity for acetyl-CoA than for acetate, whereas non-acetylated FacA had more affinity for acetate. Thus, the acetylated variant of the FacA protein is responsible for ATP synthesis during fungal ammonia fermentation. These results showed that the fungus ferments ammonium via coupled dissimilatory and assimilatory mechanisms.
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PMID:Fungal ammonia fermentation, a novel metabolic mechanism that couples the dissimilatory and assimilatory pathways of both nitrate and ethanol. Role of acetyl CoA synthetase in anaerobic ATP synthesis. 1472 82

The strict anaerobic, thermophilic bacterium Moorella thermoacetica metabolizes C1 compounds for example CO(2)/H(2), CO, formate, and methanol into acetate via the Wood/Ljungdahl pathway. Some of the key steps in this pathway include the metabolism of the C1 compounds into the methyl group of methylenetetrahydrofolate (MTHF) and the transfer of the methyl group from MTHF to the methyl group of acetyl-CoA catalyzed by methyltransferase, corrinoid protein and CO dehydrogenase/acetyl CoA synthase. Recently, we reported the crystallization of a 25 kDa methanol-induced corrinoid protein from M. thermoacetica (Zhou et al., Acta Crystallogr F 2005; 61:537-540). In this study we analyzed the crystal structure of the 25 kDa protein and provide genetic and biochemical evidences supporting its role in the methanol metabolism of M. thermoacetia. The 25 kDa protein was encoded by orf1948 of contig 303 in the M. thermoacetica genome. It resembles similarity to MtaC the corrinoid protein of the methanol:CoM methyltransferase system of methane producing archaea. The latter enzyme system also contains two additional enzymes MtaA and MtaB. Homologs of MtaA and MtaB were found to be encoded by orf2632 of contig 303 and orf1949 of contig 309, respectively, in the M. thermoacetica genome. The orf1948 and orf1949 were co-transcribed from a single polycistronic operon. Metal analysis and spectroscopic data confirmed the presence of cobalt and the corrinoid in the purified 25 kDa protein. High resolution X-ray crystal structure of the purified 25 kDa protein revealed corrinoid as methylcobalamin with the imidazole of histidine as the alpha-axial ligand replacing benziimidazole, suggesting base-off configuration for the corrinoid. Methanol significantly activated the expression of the 25 kDa protein. Cyanide and nitrate inhibited methanol metabolism and suppressed the level of the 25 kDa protein. The results suggest a role of the 25 kDa protein in the methanol metabolism of M. thermoacetica.
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PMID:Characterization of a corrinoid protein involved in the C1 metabolism of strict anaerobic bacterium Moorella thermoacetica. 1721 93

The ion exchange membrane bioreactor (IEMB) proved to be an effective technology for the removal of nitrate and perchlorate from polluted drinking water when using a mono-anion permselective membrane such as Neosepta ACS. Aiming at reducing the cost of the system, this study evaluates the use of a lower-cost anion exchange membrane, which exhibits no preferential mono-anion permselective properties. With this purpose an Excellion I-200 membrane was tested, for the removal of anionic micropollutants, such as nitrate and perchlorate from drinking water supplies. The impact of the lower anion permselectivity of this membrane on the quality of the treated water was determined. It was demonstrated that differences between the membrane properties are responsible for the different permselectivities observed towards multi-valent and mono-valent anions. The use of Excellion I-200 resulted in a less selective removal of perchlorate and nitrate, allowing anions such as sulphate and phosphate species to be transported. When treating 3.1l/m(2)h of water contaminated with 100microg/l of perchlorate and 60mg/l of nitrate, lower removal degrees were obtained (85% of perchlorate and 88% of nitrate), compared with 96% of perchlorate and 99% of nitrate achieved with the Neosepta ACS membrane, operating under the same conditions. However, the Excellion I-200 membrane shows no target anion flux decline during a relatively long period of operation (1 month) and no secondary contamination of the treated water by the carbon source used. These characteristics are essential for a membrane to be successfully used in the IEMB system. Additionally, the selection of the membrane depends on the latter characteristics and on the water quality requirements.
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PMID:Removal of mono-valent oxyanions from water in an ion exchange membrane bioreactor: influence of membrane permselectivity. 1805 85

The synthesis and characterization of colloidal mesoporous silica (CMS) functionalized with vinyl-, benzyl-, phenyl-, cyano-, mercapto-, aminopropyl- or dihydroimidazole moieties is reported. Uniform mesoporous particles ranging in size from 40 to 150 nm are generated in a co-condensation process of tetraethylorthosilicate (TEOS) and organotriethoxysilanes (RTES) in alkaline aqueous media containing triethanolamine (TEA) in combination with cetyltrimethylammonium chloride (CTACl) serving as a structure-directing agent. The materials are obtained as colloidal suspensions featuring long-term stability after template removal by ion exchange with an ethanolic solution of ammonium nitrate or HCl. The spherical particles exhibit a wormlike pore system with defined pore sizes and high surface areas. Samples are analyzed by a number of techniques including TEM, SEM, DLS, TGA, Raman, and cross-polarized (29)Si-MAS NMR spectroscopy, as well as nitrogen sorption measurements. We demonstrate that co-condensation and grafting methods result in similar changes in the nitrogen adsorption behavior, indicating a successful internal lining of the pores with functional groups through both procedures.
ACS Nano 2008 Apr
PMID:Colloidal suspensions of functionalized mesoporous silica nanoparticles. 1920 12

A facile ambient temperature route to the fabrication of surface silver-metallized polyimide films is described. Silver(I) trifluoromethanesulfonate or silver(I) nitrate and a polyimide, derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and an equimolar amount of 4,4'-oxydianiline and 3,5-diaminobenzoic acid, were dissolved together in dimethylacetamide. Silver(I)-doped films were prepared at thicknesses of 25-40 microm and depleted of solvent by evaporation at ambient temperature and low humidity. The silver(I)-ion-containing films were then treated with aqueous solutions of the reducing agents hydrazine hydrate and hydroxylamine, which brought forth surface-silvered films exhibiting conductivity on the order of bulk polycrystalline silver accompanied by modest-to-high specular reflectivity.
ACS Appl Mater Interfaces 2009 Jan
PMID:Latent synthesis of electrically conductive surface-silvered polyimide films. 2035 73

The polyaniline (PANI) base was ball-milled with silver nitrate in the solid state. Samples were prepared at various mole ratios of silver nitrate to PANI constitutional units ranging from 0 to 1.5 for three processing times, 0, 5, and 10 min. The emeraldine form of PANI was oxidized to pernigraniline, and the silver nitrate was reduced to metallic silver. Nitric acid is a byproduct, which may protonate the residual emeraldine and pernigraniline. The changes occurring in the structure of PANI are discussed on the basis of Fourier transform IR and Raman spectroscopies. Raman spectra revealed the formation of pernigraniline salt. The reaction between the two nonconducting components, emeraldine base and silver nitrate, produced a mixture of two conducting components, emeraldine or pernigraniline nitrate and metallic silver. The accompanying conductivity changes were determined. The increase in the conductivity of the original base, 10(-9) S cm(-1), up to 10(-2) S cm(-1) was found to depend on the mole ratio of silver nitrate to PANI base and on the processing time of the components in the ball mill.
ACS Appl Mater Interfaces 2009 Sep
PMID:Solid-state reduction of silver nitrate with polyaniline base leading to conducting materials. 2035 13

Core/shell nanostructures of polystyrene (PS)/CeO2 have been prepared on conductive glass substrates by using a novel electrochemical route consisting of (i) the electrophoretic deposition of a PS sphere monolayer on the substrate and (ii) the following potentiostatic electrodeposition of CeO2 on the PS sphere template in Ce(NO3)3 aqueous solutions. The structural morphologies of the deposit changed drastically depending on the Ce(NO3)3 concentration; i.e., spherical and needlelike shells were deposited. The deposit was formed only on the PS sphere surface because of an interaction between cationic cerium species and a sulfate group that was immobilized on the PS sphere surface. The spherical shell layer was assigned as CeO2, and the needlelike shells were composed of Ce(OH)3 needles formed on the CeO2 layer surface, indicating that the deposit species changes from CeO2 to Ce(OH)3 during electrodeposition only in a 1 mM Ce3+ solution. Deposition of Ce(OH)3 would begin when electrogenerated hydrogen peroxide was consumed by decomposition under reductive conditions and could no longer oxidize Ce3+ ions. The corresponding CeO2 hollow shells were obtained by thermal elimination of the PS sphere core and transformation of Ce(OH)3 into CeO2 while keeping their original shapes.
ACS Appl Mater Interfaces 2009 May
PMID:Preparation of core/shell and hollow nanostructures of cerium oxide by electrodeposition on a polystyrene sphere template. 2035 93

Benzoate (Bz), 2,4-dichlorobenzoate (BzDC), and p- and o-hydroxybenzoate (p- and o-BzOH) anions with antimicrobial activity have been intercalated into [Zn(0.65)Al(0.35)(OH)(2)](NO(3))(0.35).0.6H(2)O, layered double hydroxide (LDH), via anion-exchange reactions. The composition of the obtained intercalation compounds, determined by chemical, thermogravimetric, and ion chromatographic analyses, indicates that benzoate and benzoate derivative anions replace the nitrate counteranions, almost completely. Information on the interactions of the intercalated anions with the inorganic layer have been obtained from Fourier transform IR absorption spectroscopy and powder X-ray diffraction of the samples. It has been found that both the nature and the position of the aromatic ring substituents affect the value of the basal distance and the host-guest hydrogen bond network. Knowledge of the chemical composition, basal distance, and van der Waals dimensions of the guests has finally allowed the proposal of structural models of the intercalation compounds that have been used as fillers of poly(caprolactone), a biodegradable polymer. Films of polymeric composites were obtained by hot-pressing the powders of polymer and filler previously milled by a high-energy ball milling procedure. X-ray diffraction analysis and optical and scanning electron microscopy of the composites indicate that the LDH samples containing BzDC anions are delaminated into the polymeric matrix, whereas those containing p-BzOH anions maintain for the most part the crystal packing and give rise to microcomposites. Intermediate behavior was found for LDH modified with Bz and o-BzOH anions because exfoliated and partly intercalated composites were obtained. Preliminary antimicrobial tests indicate that the composites are able to inhibit the Saccharomyces cerevisiae growth of 40% in comparison with the growth in a pure culture medium. The composites can be studied as the model for "active packaging" systems because of the antimicrobial properties of the anions anchored to the LDH layer.
ACS Appl Mater Interfaces 2009 Mar
PMID:New polymeric composites based on poly(-caprolactone) and layered double hydroxides containing antimicrobial species. 2035 89


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