WorldWideScience

Sample records for putative manganese-oxidizing enzyme

  1. Dietary supplementation of green synthesized manganese-oxide nanoparticles and its effect on growth performance, muscle composition and digestive enzyme activities of the giant freshwater prawn Macrobrachium rosenbergii.

    Science.gov (United States)

    Asaikkutti, Annamalai; Bhavan, Periyakali Saravana; Vimala, Karuppaiya; Karthik, Madhayan; Cheruparambath, Praseeja

    2016-05-01

    The green synthesized Mn3O4 nanoparticles (manganese-oxide nanoparticles) using Ananas comosus (L.) peel extract was characterized by various techniques. HR-SEM photograph showed that manganese-oxide nanoparticles (Mn-oxide NPs) were spherical in shape, with an average size of 40-50 nm. The Zeta potential revealed the surface charge of Mn-oxide NPs to be negative. Further, the Mn-oxide NPs were dietary supplemented for freshwater prawn Macrobrachium rosenbergii. The experimental basal diets were supplemented with Mn-oxide NPs at the rates of 0 (control), 3.0, 6.0, 9.0, 12, 15 and 18 mg/kg dry feed weight. The as-supplemented Mn-oxide NPs were fed in M. rosenbergii for a period of 90 days. The experimental study demonstrated that prawns fed with diet supplemented with 3-18 mg Mn-oxide NPs/kg shows enhanced (Pgrowth performance, including final weight and weight gain (WG). Significant differences (Pgrowth performance, digestive enzyme activities and muscle biochemical compositions, while, the prawns fed with 16 mg/kg of Mn-oxide NPs showed enhanced performance. Prawns fed on diet supplemented with 16 mg/kg Mn-oxide NPs showed significantly (Pmuscle and hepatopancreas showed no significant (P>0.05) alterations in prawns fed with 3.0-18 mg/kg of Mn-oxide NPs supplemented diets. Consequently, the present work proposed that 16 mg/kg of Mn-oxide NPs could be supplemented for flexible enhanced survival, growth and production of M. rosenbergii. Therefore, the data of the present study recommend the addition of 16 mg/kg of Mn-oxide NPs diet to developed prawn growth and antioxidant defense system. Copyright © 2016 Elsevier GmbH. All rights reserved.

  2. Preparation of Manganese Oxide Nanobelts

    Institute of Scientific and Technical Information of China (English)

    Jisen WANG; Jinquan SUN; Ying BAO; Xiufang BIAN

    2003-01-01

    Oriented nanobelts of manganese oxide have been firstly and successfully prepared by a microemulsion techniqueunder controlled circumstances. The samples were characterized by X-ray diffraction (XRD), transmission electronmicroscope (TEM). Influences of sodium chloride and annealed temperature on the synthesis of Mn3O4 nanobeltswere investigated. It was found that NaCl is the key factor to synthesize oriented Mn3O4 nanobelts and 827 K isoptimum temperature to produce fine nanobelts. Oriented growth mechanism of Mn3O4 nanobelts was discussed.

  3. Manganese oxide nanoparticles, methods and applications

    Science.gov (United States)

    Abruna, Hector D.; Gao, Jie; Lowe, Michael A.

    2017-08-29

    Manganese oxide nanoparticles having a chemical composition that includes Mn.sub.3O.sub.4, a sponge like morphology and a particle size from about 65 to about 95 nanometers may be formed by calcining a manganese hydroxide material at a temperature from about 200 to about 400 degrees centigrade for a time period from about 1 to about 20 hours in an oxygen containing environment. The particular manganese oxide nanoparticles with the foregoing physical features may be used within a battery component, and in particular an anode within a lithium battery to provide enhanced performance.

  4. Amperometric biosensors based on carbon paste electrodes modified with nanostructured mixed-valence manganese oxides and glucose oxidase.

    Science.gov (United States)

    Cui, Xiaoli; Liu, Guodong; Lin, Yuehe

    2005-06-01

    Nanostructured, multivalent, manganese-oxide octahedral molecular sieves (OMS), including cryptomelane-type manganese oxides and todorokite-type manganese oxides, were synthesized and evaluated for chemical sensing and biosensing at low operating potential. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides are nanofibrous crystals with subnanometer open tunnels that provide a unique property for sensing applications. The electrochemical and electrocatalytic performance of OMS for the oxidation of H2O2 have been compared. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides can be used to fabricate sensitive H2O2 sensors. With glucose oxidase (GOx) as an enzyme model, amperometric glucose biosensors are constructed by bulk modification of carbon paste electrodes with GOx as a biocomponent and nanostructured OMS as a mediator. A Nafion thin film was applied as an immobilization/encapsulation and protective layer. The biosensors were evaluated as an amperometric glucose detector at phosphate buffer solution with a pH 7.4 at an operating potential of 0.3 V (vs Ag/AgCl). The biosensor is characterized by a well-reproducible amperometric response, linear signal-to-glucose concentration range up to 3.5 mmol/L and 1.75 mmol/L, and detection limits (S/N = 3) of 0.1 mmol/L and 0.05 mmol/L for todorokite-type manganese oxide and cryptomelane-type manganese oxide-modified electrodes, respectively. The biosensors based on OMS exhibit considerable good reproducibility and stability, and the construction and renewal are simple and inexpensive.

  5. Mixed iron-manganese oxide nanoparticles

    NARCIS (Netherlands)

    Lai, Jriuan; Shafi, Kurikka V.P.M.; Ulman, Abraham; Loos, Katja; Yang, Nan-Loh; Cui, Min-Hui; Vogt, Thomas; Estournès, Claude; Locke, Dave C.

    2004-01-01

    Designing nanoparticles for practical applications requires knowledge and control of how their desired properties relate to their composition and structure. Here, we present a detailed systematic study of mixed iron-manganese oxide nanoparticles, showing that ultrasonication provides the high-energy

  6. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    Science.gov (United States)

    Manigandan, R.; Suresh, R.; Giribabu, K.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  7. Neurotoxicity of manganese oxide nanomaterials

    Science.gov (United States)

    Stefanescu, Diana M.; Khoshnan, Ali; Patterson, Paul H.; Hering, Janet G.

    2009-11-01

    Manganese (Mn) toxicity in humans has been observed as manganism, a disease that resembles Parkinson's disease. The mechanism of Mn toxicity and the chemical forms that may be responsible for its neurotoxicity are not well understood. We examined the toxicity of Mn oxide nanomaterials in a neuronal precursor cell model, using the MTS assay to evaluate mitochondrial function in living cells and the LDH assay to quantify the release of the enzyme lactate dehydrogenase as a result of damage to the cell membrane. Both assays show that the toxicity of Mn is dependent on the type of Mn oxide nanomaterial and its concentration as well as on the state of cell differentiation. Following exposure to Mn oxide nanomaterials, reactive oxygen species (ROS) are generated, and flow cytometry experiments suggest that cell death occurred through apoptosis. During exposure to Mn oxide nanomaterials, increased levels of the transcription factor NF-κB (which mediates the cellular inflammatory response) were observed.

  8. Role of Amorphous Manganese Oxide in Nitrogen Loss

    Institute of Scientific and Technical Information of China (English)

    LILIANG-MO; WUQI-TU

    1991-01-01

    Studies have been made,by 15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4+-N medium under anaerobic conditions.The fact that the total nitrogen recovery was decreased and that 15NO2,15N2O,15N14NO,15NO,15N2 and 15N14N were emitted has proved that,like amorphous iron oxide,amorphous manganese oxide can also act as an electron acceptor in the oxidation of NH4+-N under anaerobic conditions and give rise to nitrogen loss.This once again illustrates another mechanism by which the loss of ammonium nitrogen in paddy soils is brought about by amorphous iron and manganese oxides.The quantity of nitrogen loss by amorphous manganese oxide increased with an increase in the amount of amorphous manganese oxide added and lessened with time of its aging.The nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss by cooperation of amorphous manganese oxide and microorganisms (soil suspension) was larger than that by amorphous manganese oxide alone.In the system,nitrogen loss was associated with the specific surface ares and oxidation-reduction of amorphous manganese oxide.However,their quantitative relationship and the exact reaction processes of nitrogen loss induced by amorphous manganese oxide remain to be further studied.

  9. Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles

    Science.gov (United States)

    2012-12-01

    electrolytes : 0.5 M K2SO4, 1 M sodium chloride (NaCl), and 1 M calcium chloride (CaCl2). The qualitative CV behavior of the three electrolytes can be seen...Carbon Nanotube/ Graphene Supercapacitors Containing Manganese Oxide Nanoparticles by Matthew Ervin, Vinay Raju, Mary Hendrickson, and...Laboratory Adelphi, MD 20783-1197 ARL-TR-6289 December 2012 Carbon Nanotube/ Graphene Supercapacitors Containing Manganese Oxide

  10. Manganese oxide nanowires, films, and membranes and methods of making

    Science.gov (United States)

    Suib, Steven Lawrence [Storrs, CT; Yuan, Jikang [Storrs, CT

    2011-02-15

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves and methods of making the same are disclosed. A method for forming nanowires includes hydrothermally treating a chemical precursor composition in a hydrothermal treating solvent to form the nanowires, wherein the chemical precursor composition comprises a source of manganese cations and a source of counter cations, and wherein the nanowires comprise ordered porous manganese oxide-based octahedral molecular sieves.

  11. A multicopper oxidase is essential for manganese oxidation and laccase-like activity in Pedomicrobium sp. ACM 3067.

    Science.gov (United States)

    Ridge, Justin P; Lin, Marianne; Larsen, Eloise I; Fegan, Mark; McEwan, Alastair G; Sly, Lindsay I

    2007-04-01

    Pedomicrobium sp. ACM 3067 is a budding-hyphal bacterium belonging to the alpha-Proteobacteria which is able to oxidize soluble Mn2+ to insoluble manganese oxide. A cosmid, from a whole-genome library, containing the putative genes responsible for manganese oxidation was identified and a primer-walking approach yielded 4350 bp of novel sequence. Analysis of this sequence showed the presence of a predicted three-gene operon, moxCBA. The moxA gene product showed homology to multicopper oxidases (MCOs) and contained the characteristic four copper-binding motifs (A, B, C and D) common to MCOs. An insertion mutation of moxA showed that this gene was essential for both manganese oxidation and laccase-like activity. The moxB gene product showed homology to a family of outer membrane proteins which are essential for Type I secretion in Gram-negative bacteria. moxBA has not been observed in other manganese-oxidizing bacteria but homologues were identified in the genomes of several bacteria including Sinorhizobium meliloti 1021 and Agrobacterium tumefaciens C58. These results suggest that moxBA and its homologues constitute a family of genes encoding an MCO and a predicted component of the Type I secretion system.

  12. Nanoflake Manganese Oxide and Nickel-Manganese Oxide Synthesized by Electrodeposition for Electrochemical Capacitor

    Directory of Open Access Journals (Sweden)

    Man Van Tran

    2015-01-01

    Full Text Available Nanoflake structures of electrochemical manganese oxide (EMD and nickel mixed manganese oxide (NiMD were directly deposited on a stainless steel by using Chronoamperometry and Cyclic Voltammetry (CV techniques. The structure, morphology, and capacitive behavior of EMD or NIMD nanoflake were affected by the electrodeposition modes and deposition time. The highest specific capacitance (Csp was obtained for only two-minute deposition by both methods. EMD nanoflakes electrodeposited by CV technique show higher specific capacitance values than those prepared by Chronoamperometry owing to its homogenous and highly porous surface. All EMD samples exhibited excellent cycle behavior, less than 5% capacitance loss after 1000 cycles. Ni mixed MnO2 was prepared at different Mn2+/Ni2+ ratios for 2 minutes of electrodeposition. The presence of Ni2+ ion enhanced the Csp value at high charge-discharge rate due to the decrease of the charge transfer resistance. The supercapacitor prototype of 2 cm × 2 cm was assembled using EMD and NiMD as electrode material and tested at 1 A·g−1.

  13. Supported lipid bilayers as templates to design manganese oxide nanoparticles

    Indian Academy of Sciences (India)

    J Maheshkumar; B Sreedhar; B U Nair; A Dhathathreyan

    2012-09-01

    This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) have been used as templates to synthesize these nanoparticles in a waterbased medium at room temperature. The Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) show manganese oxide nanostructures that are composed of crystals or small clusters in the size range of 20-50 nm in diameter. Small angle XRD showed that template removal through calcining process results in nanostructures of the manganese oxide in sizes from 30 to 50 nm. Using these organized assemblies it is possible to control the nano and mesoscopic morphologies of particles and both rod-like and spherical particles can be synthesized.

  14. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for...

  15. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN...

  16. Structural Characterization of Biogenic Manganese Oxides Produced in Sea Water

    Science.gov (United States)

    Webb, S. M.; Bargar, J. R.; Tebo, B. M.

    2003-12-01

    Manganese oxides have been coined as the "scavengers of the sea" and play important roles in both marine and freshwater systems. Natural manganese oxide nanoparticles and grain coatings are ubiquitous in the environment and profoundly impact the quality of sediments via their ability to degrade and sequester contaminants. These oxides are believed to form dominantly via oxidation of Mn(II) by marine and freshwater bacteria and have extremely high sorptive capacities for heavy metals. We have used XANES, EXAFS, and synchrotron (SR)-XRD techniques to study biogenic manganese oxides produced by spores of the marine Bacillus sp., strain SG-1 in seawater as a function of reaction time under fully in-situ conditions. The primary biogenic solid-phase Mn oxide product is a hexagonal layered phyollomanganate with an oxidation state similar to that in delta-MnO2. XRD data show the biooxides to have a phyllomanganate 10 basal plane spacing, suggesting the interlayer is hydrated and contains calcium. As the experiment continues, the initial biooxide changes to show triclinic symmetry. Fits to these EXAFS spectra suggest the octahedral layers have low Mn octahedral site vacancies in the lattice and the latyers bend to accommodate Jahn-Teller distortions creating the change in symmetry. The oxides observed in this study as models of Mn(II) bio-oxidation may be representative of the most abundant manganese oxide phase suspended in the oxic and sub-oxic zones of the oceanic water column.

  17. Production of Manganese Oxide Nanoparticles by Shewanella Species

    Science.gov (United States)

    Farooqui, Saad M.; White, Alan R.

    2016-01-01

    ABSTRACT Several species of the bacterial genus Shewanella are well-known dissimilatory reducers of manganese under anaerobic conditions. In fact, Shewanella oneidensis is one of the most well studied of all metal-reducing bacteria. In the current study, a number of Shewanella strains were tested for manganese-oxidizing capacity under aerobic conditions. All were able to oxidize Mn(II) and to produce solid dark brown manganese oxides. Shewanella loihica strain PV-4 was the strongest oxidizer, producing oxides at a rate of 20.3 mg/liter/day and oxidizing Mn(II) concentrations of up to 9 mM. In contrast, S. oneidensis MR-1 was the weakest oxidizer tested, producing oxides at 4.4 mg/liter/day and oxidizing up to 4 mM Mn(II). Analysis of products from the strongest oxidizers, i.e., S. loihica PV-4 and Shewanella putrefaciens CN-32, revealed finely grained, nanosize, poorly crystalline oxide particles with identical Mn oxidation states of 3.86. The biogenic manganese oxide products could be subsequently reduced within 2 days by all of the Shewanella strains when culture conditions were made anoxic and an appropriate nutrient (lactate) was added. While Shewanella species were detected previously as part of manganese-oxidizing consortia in natural environments, the current study has clearly shown manganese-reducing Shewanella species bacteria that are able to oxidize manganese in aerobic cultures. IMPORTANCE Members of the genus Shewanella are well known as dissimilatory manganese-reducing bacteria. This study shows that a number of species from Shewanella are also capable of manganese oxidation under aerobic conditions. Characterization of the products of the two most efficient oxidizers, S. loihica and S. putrefaciens, revealed finely grained, nanosize oxide particles. With a change in culture conditions, the manganese oxide products could be subsequently reduced by the same bacteria. The ability of Shewanella species both to oxidize and to reduce manganese indicates

  18. Observation of ferromagnetic semiconductor behavior in manganese-oxide doped graphene

    Directory of Open Access Journals (Sweden)

    Chang-Soo Park

    2014-08-01

    Full Text Available We have doped manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement system. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the surface of graphene. In addition, the semiconducting behavior is caused by the formation of manganese-oxide on graphene.

  19. Electrochemical Property Bundles with of Manganese Oxide Nanobelt Layered Structure%Electrochemical Property Bundles with of Manganese Oxide Nanobelt Layered Structure

    Institute of Scientific and Technical Information of China (English)

    Kang, Liping; Jiang, Yishu; Tang, Xiuhua; Yang, Mingyang; Liu, Zonghuai

    2012-01-01

    One-dimensional manganese oxide nanobelt bundles with birnessite-type structure have been synthesized by a hydrothermal process in a NaOH solution employing K-type layered manganese oxide as a precursor. The obtained manganese oxide nanobelt bundles exhibit excellent discharge properties and cycle stability. The initial capacity is 376 mAh-g-1 and the reversible capacity of 243 mAhog-1 is maintained after the 50th cycle at a current density of 20 mA·g-t. Meanwhile, the manganese oxide nanobelt bundles show an excellent cycle performance even if at relative high current density.

  20. Structural and surface changes of copper modified manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Gac, Wojciech, E-mail: wojciech.gac@umcs.lublin.pl; Słowik, Grzegorz; Zawadzki, Witold

    2016-05-01

    Highlights: • Formation of MnO with regular rippled-like surface patterns. • Synthesis of copper nanorods supported on MnO nanoparticles. • Hydrogen production in steam methanol reforming over supported copper nanorods. - Abstract: The structural and surface properties of manganese and copper–manganese oxides were investigated. The oxides were prepared by the redox-precipitation method. X-ray diffraction and electron microscopy studies evidenced transformation of cryptomelane-type nanoparticles with 1-D channel structure into the large MnO crystallites with regular rippled-like surface patterns under reduction conditions. The development of Cu/CuO nanorods from strongly dispersed species was evidenced. Coper-modified manganese oxides showed good catalytic performance in methanol steam reforming reaction for hydrogen production. Low selectivity to CO was observed in the wide range of temperatures.

  1. Characterization of carbon nanomaterial formation and manganese oxide reactivity

    Science.gov (United States)

    Shumlas, Samantha Lyn

    Characterization of a material's surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. (Abstract shortened by ProQuest.).

  2. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    Science.gov (United States)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-01-30

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  3. Diode laser heat treatment of lithium manganese oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Proell, J., E-mail: johannes.proell@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Kohler, R.; Mangang, A.; Ulrich, S.; Bruns, M.; Seifert, H.J. [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Pfleging, W. [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Karlsruhe Nano Micro Facility, H.-von-Helmholtz-Platz 1, 76344 Egg.-Leopoldshafen (Germany)

    2012-04-01

    The crystallization of lithium manganese oxide thin films prepared by radio frequency magnetron sputtering on stainless steel substrates under 10 Pa argon pressure is demonstrated by a laser annealing technique. Laser annealing processes were developed as a function of annealing time and temperature with the objective to form an electrochemically active lithium manganese oxide cathode. It is demonstrated, that laser annealing with 940 nm diode laser radiation and an annealing time of 2000 s at 600 Degree-Sign C delivers appropriate parameters for formation of a crystalline spinel-like phase. Characteristic features of this phase could be detected via Raman spectroscopy, showing the characteristic main Raman band at 627 cm{sup -1}. Within cyclic voltammetric measurements, the two characteristic redox pairs for spinel lithium manganese oxide in the 4 V region could be detected, indicating that the film was well-crystallized and de-/intercalation processes were reversible. Raman post-analysis of a cycled cathode showed that the spinel-like structure was preserved within the cycling process but mechanical degradation effects such as film cracking were observed via scanning electron microscopy. Typical features for the formation of an additional surface reaction layer could be detected using X-ray photoelectron spectroscopy.

  4. Characterization of Synthetic and Natural Manganese Oxides as Martian Analogues

    Science.gov (United States)

    Fox, V. K.; Arvidson, R. E.; Jolliff, B. L.; Carpenter, P. K.; Catalano, J. G.; Hinkle, M. A. G.; Morris, R. V.

    2015-01-01

    Recent discoveries of highly concentrated manganese oxides in Gale Crater and on the rim of Endeavour Crater by the Mars Science Laboratory Curiosity and Mars Exploration Rover Opportunity, respectively, imply more highly oxidizing aqueous conditions than previously recognized. Manganese oxides are a significant environmental indicator about ancient aqueous conditions, provided the phases can be characterized reliably. Manganese oxides are typically fine-grained and poorly crystalline, making the mineral structures difficult to determine, and they generally have very low visible reflectance with few distinctive spectral features in the visible to near infrared, making them a challenge for interpretation from remote sensing data. Therefore, these recent discoveries motivate better characterization using methods available on Mars, particularly visible to near infrared (VNIR) spectroscopy, X-ray diffractometry (XRD), and compositional measurements. Both rovers have complementary instruments in this regard. Opportunity is equipped with its multispectral visible imager, Pancam, and an Alpha Particle X-ray Spectrometer (APXS), and Curiosity has the multispectral Mastcam, ChemCam (laser-induced breakdown spectroscopy and passive spectroscopy), and APXS for in situ characterization, and ChemMin (XRD) for collected samples.

  5. Microbial Manganese Oxidation in Saltmarsh Surface Sediments Using a Leuco Crystal Violet Manganese Oxide Detection Technique

    Science.gov (United States)

    Spratt, Henry G.; Siekmann, Ellen C.; Hodson, Robert E.

    1994-01-01

    Microbial manganese (Mn) oxide production in surface sediments of a Georgia saltmarsh was directly measured using an assay involving the oxidation of 4,4',4″-methylidynetris (N,N-dimethylaniline), leuco crystal violet (LCV), by Mn oxides to produce crystal violet. The assay exhibits high specificity for Mn oxides without interference by Mn(II) and is sufficiently sensitive to determine rates of Mn oxidation in surface sediment or saltmarsh creek water suspensions. Sample salinity affects crystal violet absorbance in the 0-25 salinity range and must be corrected for in Mn oxide determinations for estuarine samples of variable salinity. Other oxidants found to oxidize LCV slowly included Cl(I), Cr(III), I(V), Fe(III), and Mn(III), although the sensitivity of the assay for Mn(IV) oxides was found to be seven times greater than for Mn(III), and at least 100 times greater than for any of the other oxidants. Rates of abiotic Mn oxide production in sediment suspensions treated with either sodium azide or formalin, or autoclaved, were much slower than rates determined for untreated sediments. Sodium azide (7·7 mM) inhibited Mn oxide production in these sediment suspensions to rates between 5 and 10% of the rates of Mn oxidation determined for unamended suspensions. Manganese oxidation was highly temperature dependent, with maximal rates on a dry weight basis (8·9 nmol mg dwt -1 h -1), occurring at 60°C, and negligible activity at 100 and 0°C. Rates were also dependent on sample pH, with maximal rates at pH 6·7, decreasing to near 0 as the pH was lowered to approximately 3·0. For Mn(II) concentrations ranging from 9 to 91 μM, rates of Mn oxide production were independent of Mn(II) concentration, while Mn oxide production was inhibited at concentrations greater than 91 μM (e.g. by 25-40% at 450 μM). Rates of microbial Mn oxide production in surface sediment/saltmarsh creek water suspensions incubated under natural conditions of temperature, pH, and Mn

  6. The influence of environmental conditions on kinetics of arsenite oxidation by manganese-oxides

    OpenAIRE

    Fischel, Matthew H. H.; Fischel, Jason S.; Lafferty, Brandon J.; Sparks, Donald L.

    2015-01-01

    Background Manganese-oxides are one of the most important minerals in soil due to their widespread distribution and high reactivity. Despite their invaluable role in cycling many redox sensitive elements, numerous unknowns remain about the reactivity of different manganese-oxide minerals under varying conditions in natural systems. By altering temperature, pH, and concentration of arsenite we were able to determine how manganese-oxide reactivity changes with simulated environmental conditions...

  7. Self-assembled manganese oxide structures through direct oxidation

    KAUST Repository

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  8. Metal Inhibition of Growth and Manganese Oxidation in Pseudomonas putida GB-1

    Science.gov (United States)

    Pena, J.; Sposito, G.

    2009-12-01

    Biogenic manganese oxides (MnO2) are ubiquitous nanoparticulate minerals that contribute to the adsorption of nutrient and toxicant metals, the oxidative degradation of various organic compounds, and the respiration of metal-reducing bacteria in aquatic and terrestrial environments. The formation of these minerals is catalyzed by a diverse and widely-distributed group of bacteria and fungi, often through the enzymatic oxidation of aqueous Mn(II) to Mn(IV). In metal-impacted ecosystems, toxicant metals may alter the viability and metabolic activity of Mn-oxidizing organisms, thereby limiting the conditions under which biogenic MnO2 can form and diminishing their potential as adsorbent materials. Pseudomonas putida GB-1 (P. putida GB-1) is a model Mn-oxidizing laboratory culture representative of freshwater and soil biofilm-forming bacteria. Manganese oxidation in P. putida GB-1 occurs via two single-electron-transfer reactions, involving a multicopper oxidase enzyme found on the bacterial outer membrane surface. Near the onset of the stationary phase of growth, dark brown MnO2 particles are deposited in a matrix of bacterial cells and extracellular polymeric substances, thus forming heterogeneous biomineral assemblages. In this study, we assessed the influence of various transition metals on microbial growth and manganese oxidation capacity in a P. putida GB-1 culture propagated in a nutrient-rich growth medium. The concentration-response behavior of actively growing P. putida GB-1 cells was investigated for Fe, Co, Ni, Cu and Zn at pH ≈ 6 in the presence and absence of 1 mM Mn. Toxicity parameters such as EC0, EC50 and Hillslope, and EC100 were obtained from the sigmoidal concentration-response curves. The extent of MnO2 formation in the presence of the various metal cations was documented 24, 50, 74 and 104 h after the metal-amended medium was inoculated. Toxicity values were compared to twelve physicochemical properties of the metals tested. Significant

  9. Permanganate-based synthesis of manganese oxide nanoparticles in ferritin

    Science.gov (United States)

    Olsen, Cameron R.; Smith, Trevor J.; Embley, Jacob S.; Maxfield, Jake H.; Hansen, Kameron R.; Peterson, J. Ryan; Henrichsen, Andrew M.; Erickson, Stephen D.; Buck, David C.; Colton, John S.; Watt, Richard K.

    2017-05-01

    This paper investigates the comproportionation reaction of MnII with {{{{MnO}}}4}- as a route for manganese oxide nanoparticle synthesis in the protein ferritin. We report that {{{{MnO}}}4}- serves as the electron acceptor and reacts with MnII in the presence of apoferritin to form manganese oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of MnII and permanganate were varied at each pH. The manganese-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample. Manganese cores were deposited inside ferritin under both the acidic and basic conditions. All resulting manganese ferritin samples were found to be indirect band gap materials with band gap energies ranging from 1.01 to 1.34 eV. An increased UV/Vis absorption around 370 nm was observed for samples formed under acidic conditions, suggestive of MnO2 formation inside ferritin.

  10. Kinetics of oxytetracycline reaction with a hydrous manganese oxide.

    Science.gov (United States)

    Rubert, Kennedy F; Pedersen, Joel A

    2006-12-01

    Tetracycline antibiotics comprise a class of broad spectrum antimicrobial agents finding application in human therapy, animal husbandry, aquaculture, and fruit crop production. To better understand the processes affecting these antibiotics in soils and sediments, the kinetics of oxytetracycline transformation by a hydrous manganese oxide (MnO2) were investigated as a function of reactant concentration, pH, and temperature. Oxytetracycline was rapidly degraded by MnO2. Initial reaction rates exhibited pronounced pH-dependence, increasing as pH decreased. Reaction of oxytetracycline with MnO2 was accompanied by generation of Mn(II) ions, suggesting oxidative transformation of the antibiotic. At pH 5.6, apparent reaction orders for oxytetracycline and MnO2 were 0.7 and 0.8. Reaction order with respect to H+ was 0.6 between pH 4 and 9. Initial reaction rates increased by a factor of approximately 2.4 for 10 degrees C temperature increases; the apparent activation energy (60 kJ x mol(-1)) was consistent with a surface-controlled reaction. Reactivity of tetracycline antibiotics toward MnO2 increased in the following order: rolitetracyline oxytetracycline manganese oxides in soils and sediments are likely to promote appreciable degradation of tetracycline antibiotics, and that reaction rates are strongly dependent on reaction time scale and solution conditions.

  11. Catalytic properties of manganese oxide polyhedra with hollow and solid morphologies in toluene removal

    Science.gov (United States)

    Liao, Yinnian; Zhang, Xuan; Peng, Ruosi; Zhao, Mengqi; Ye, Daiqi

    2017-05-01

    In order to develop an efficient and active catalyst to degrade the toxic volatile organic compounds, manganese oxide polyhedra with hollow and solid morphologies were synthesized by a convenient hydrothermal route without any surfactants or templates. The catalytic performances of the two manganese oxides were assessed in the oxidation reaction of toluene. Compared with the solid polyhedral manganese oxide, an excellent catalytic activity of the hollow one has been found, resulting from its cavity nature, the high content of active oxygen and the high manganese oxidation state of hollow MnOx. Meanwhile, the probable reaction pathway for toluene oxidation over the hollow polyhedral manganese oxide was initially discussed by means of in situ FTIR.

  12. Factors Affection Cr(Ⅲ) Oxidation by Manganese Oxides

    Institute of Scientific and Technical Information of China (English)

    CHENYINGXU; CHENYIYI; 等

    1997-01-01

    The high oxidation ability of manganese oxides or soils was used to study effects of PH and coating on Cr(Ⅲ) oxidation,The results indicated that Cr(Ⅲ) oxidation peaked in PH 4.0-6.5,The amount and rate of Cr(Ⅲ) being oxidized by uncoated δ-MnO2 were larger than those by Fe oxide- of CaCo3-coated one.Inorganic Cr(Ⅲ) wa more easily oxidzed by MnO2 than organic complex Cr(Ⅲ) due to different surface affinities. Precipitated Cr(Ⅲ) and adsorbed Cr(Ⅲ) might be transferred onto MnO2 surface and then oxidized to Cr(Ⅵ)

  13. Manganese oxide microswitch for electronic memory based on neural networks

    Science.gov (United States)

    Ramesham, R.; Daud, T.; Moopenn, A.; Thakoor, A. P.; Khanna, S. K.

    1989-01-01

    A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.

  14. Modeling the viscosity of silicate melts containing manganese oxide

    Directory of Open Access Journals (Sweden)

    Kim Wan-Yi

    2013-01-01

    Full Text Available Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.

  15. Creation of a putative third metal binding site in type II dihydroorotases significantly enhances enzyme activity.

    Science.gov (United States)

    Huang, Yen-Hua; Huang, Cheng-Yang

    2015-01-01

    Dihydroorotase (DHOase) is the third enzyme in the de novo biosynthesis pathway of pyrimidine nucleotides. DHOase is divided into two types (I and II). Type II DHOase generally contains a binuclear metal center in its active site. Recently, the crystal structure of DHOase domain in human CAD protein (huDHOase) has revealed three metal ions in the protein's active site. However, whether type II DHOase can have the critical third metal ion, as observed in huDHOase, remains unknown. In the present study, the putative third metal binding site in type II enzymes, such as the prokaryotic Salmonella enterica serovar Typhimurium LT2 DHOase (StDHOase) and the eukaryotic Saccharomyces cerevisiae DHOase (ScDHOase), was created and identified. StDHOase T198E and ScDHOase T208E mutants had higher activities compared with their wild-type enzymes. The need for a higher DHOase stability and activity may drive creation of the third metal ion binding site in huDHOase, which can be achieved by mutating a highly conserved position T in type II dihydroorotases to E, similar to that in huDHOase.

  16. Cobalt promoted copper manganese oxide catalysts for ambient temperature carbon monoxide oxidation.

    Science.gov (United States)

    Jones, Christopher; Taylor, Stuart H; Burrows, Andrew; Crudace, Mandy J; Kiely, Christopher J; Hutchings, Graham J

    2008-04-14

    Low levels of cobalt doping (1 wt%) of copper manganese oxide enhances its activity for carbon monoxide oxidation under ambient conditions and the doped catalyst can display higher activity than current commercial catalysts.

  17. Water defluoridation by aluminium oxide-manganese oxide composite material.

    Science.gov (United States)

    Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

    2014-08-01

    In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3

  18. Fabrication of Bionic Superhydrophobic Manganese Oxide/Polystyrene Nanocomposite Coating

    Institute of Scientific and Technical Information of China (English)

    Xianghui Xu; Zhaozhu Zhang; Fang Guo; Jin Yang; Xiaotao Zhu; Xiaoyan Zhou; Qunji Xue

    2012-01-01

    A superhydrophobic manganese oxide/polystyrene (MnO2/PS) nanocomposite coating was fabricated by a facile spraying process.The mixture solution of MnO2/PS was poured into a spray gun,and then sprayed onto the copper substrate using 0.2 MPa nitrogen gas to construct superhydrophobic coating.The wettability of the composite coating was measured by sessile drop method.When the weight ratio of MnO2 to PS is 0.5:1,the maximum of contact angle (CA) (140°) is obtained at drying temperature of 180 ℃.As the content of MnO2 increases,the maximum of CA (155°) is achieved at 100 ℃.Surface morphologies and chemical composition were analyzed to understand the effect of the content of MnO2 nanorods and the drying temperature on CA.The results show that the wettability of the coating can be controlled by the content ofMnO2 nanorods and the drying temperature.Using the proposed method,the thickness of the coating can be controlled by the spraying times.If damaged,the coating can be repaired just by spraying the mixture solution again.

  19. Titanium-Manganese Oxides. Optical and Photocatalytic Properties

    Directory of Open Access Journals (Sweden)

    V. Chernyak

    2010-01-01

    Full Text Available Nanocrystalline titanium-manganese mixed oxides (ТМО with the Mn content of 13÷16 % at. were first synthesized by manganese hydroxide precipitation on anatase or rutile particles. The structure, morphology and chemical composition of the samples were characterized using XRD and XRF methods showing that the synthesized mixed oxides are the polydisperse materials of different phase composition containing TiO2, Mn2O3 and MnTiO3. The phase transformations and structure defects of the prepared compounds were characterized by FTIR, FT-FIR, FT-Raman spectroscopies. UV-VIS absorption spectra were investigated in 2,4÷6,0 eV region, and it was revealed that the presence of manganese oxides results in absorption increase and significant red shift of the ТМО absorption edge in comparison with pure TiO2. Photocatalytic activity of pure TiO2, Mn2+-doped TiO2 and ТМО during the photocatalytic decomposition of the safranine dye under UV irradiation was studied. A great improvement of photocatalytic activity is registered for Mn2+-doped TiO2 (anatase and rutile, and rutile-based ТМО sample.

  20. Directed vapor deposition of lithium manganese oxide films

    Science.gov (United States)

    Jin, Sang-Wan

    Electron beam evaporation and sputtering techniques are used to fabricate multilayered thin film structures. However, these techniques suffer several drawbacks resulting from (i) the complex chemistries of the lithiated oxide layers used for the cathode and electrolyte, (ii) the need for precise microstructure control in systems with many metastable phases, and (iii) the low deposition rate and poor material utilization efficiency, which slows the application of this energy storage approach. This dissertation has investigated the use of a novel electron-beam directed vapor deposition (EB-DVD) method for the synthesis of thin film batteries. The dissertation focuses upon the cathode layer of a representative Li-ion thin film battery system and investigates in detail the deposition of lithium manganese oxide films. Many phases with offering various electrochemical performance exist in the Li-Mn-O system and the thesis also investigates the use of processing conditions to control the structure and composition of these cathode layers. In the EB-DVD approach, a high voltage electron beam is used to evaporate a source material in the throat of a nozzle that forms a coaxial transonic gas jet around the vapor. The gas jet entrains and transports the vapor to a substrate where the deposition occurs. Directed simulation of Monte Carlo (DSMC) methods indicated that the vapor plume could be matched to a substrate diameter, and the deposition rate (and vapor utilization efficiency) therefore controlled by adjusting the pressure ratio up and downstream of the nozzle opening in the deposition chamber, and by varying the gas jet density and speed. The highest deposition rates were obtained with a high pressure ratio and the gas jet density. These observations are found to be consistent with the experimental results. Deposition rates up to 16 nm/s could be achieved using the most effective gas entrainment conditions identified by DSMC calculation. This was about a factor of ten

  1. Synthesis and characterization of cobalt-manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Valencia, J. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis 55455-0153 (United States); Arias, N.P. [Laboratorio de Materiales Nanoestructurados y Funcionales, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Departamento de Ingenieria Electrica, Electronica y Computacion, Facultad de Ingenieria y Arquitectura, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Giraldo, O. [Laboratorio de Materiales Nanoestructurados y Funcionales, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia)

    2012-08-15

    Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn{sup 4+} to Mn{sup 3+}. VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.

  2. Towards a mechanistic understanding of carbon stabilization in manganese oxides

    Science.gov (United States)

    Johnson, Karen; Purvis, Graham; Lopez-Capel, Elisa; Peacock, Caroline; Gray, Neil; Wagner, Thomas; März, Christian; Bowen, Leon; Ojeda, Jesus; Finlay, Nina; Robertson, Steve; Worrall, Fred; Greenwell, Chris

    2015-01-01

    Minerals stabilize organic carbon (OC) in sediments, thereby directly affecting global climate at multiple scales, but how they do it is far from understood. Here we show that manganese oxide (Mn oxide) in a water treatment works filter bed traps dissolved OC as coatings build up in layers around clean sand grains at 3%w/wC. Using spectroscopic and thermogravimetric methods, we identify two main OC fractions. One is thermally refractory (>550 °C) and the other is thermally more labile (<550 °C). We postulate that the thermal stability of the trapped OC is due to carboxylate groups within it bonding to Mn oxide surfaces coupled with physical entrapment within the layers. We identify a significant difference in the nature of the surface-bound OC and bulk OC . We speculate that polymerization reactions may be occurring at depth within the layers. We also propose that these processes must be considered in future studies of OC in natural systems. PMID:26194625

  3. The effect of manganese oxide on the sinterability of hydroxyapatite

    Directory of Open Access Journals (Sweden)

    S. Ramesh et al

    2007-01-01

    Full Text Available The sinterability of manganese oxide (MnO2 doped hydroxyapatite (HA ranging from 0.05 to 1 wt% was investigated. Green samples were prepared and sintered in air at temperatures ranging from 1000 to 1400 °C. Sintered bodies were characterized to determine the phase stability, grain size, bulk density, hardness, fracture toughness and Young's modulus. XRD analysis revealed that the HA phase stability was not disrupted throughout the sintering regime employed. In general, samples containing less than 0.5 wt% MnO2 and when sintered at lower temperatures exhibited higher mechanical properties than the undoped HA. The study revealed that all the MnO2-doped HA achieved >99% relative density when sintered at 1100–1250 °C as compared to the undoped HA which could only attained highest value of 98.9% at 1150 °C. The addition of 0.05 wt% MnO2 was found to be most beneficial as the samples exhibited the highest hardness of 7.58 GPa and fracture toughness of 1.65 MPam1/2 as compared to 5.72 GPa and 1.22 MPam1/2 for the undoped HA when sintered at 1000 °C. Additionally, it was found that the MnO2-doped samples attained E values above 110 GPa when sintered at temperature as low as 1000 °C if compared to 1050 °C for the undoped HA.

  4. Oxidative removal of aqueous steroid estrogens by manganese oxides.

    Science.gov (United States)

    Xu, Lei; Xu, Chao; Zhao, Meirong; Qiu, Yuping; Sheng, G Daniel

    2008-12-01

    This study investigated the oxidative removal of steroid estrogens from water by synthetic manganese oxide (MnO2) and the factors influencing the reactions. Using 1 x 10(-5)M MnO2 at pH 4, estrone (E1), 17beta-estradiol (E2), estriol (E3) and 17alpha-ethinylestradiol (EE2), all at 4 x 10(-6)M, were rapidly removed within 220 min, indicating the effectiveness of MnO2 as an oxidizing agent towards estrogens. E2 removal increased with decreasing pH over the tested range of 4-8, due most likely to increased oxidizing power of MnO2 and a cleaner reactive surface in acidic solutions. Coexisting metal ions of 0.01 M (Cu(II), Zn(II), Fe(III) and Mn(II)) and Mn(II) released from MnO2 reduction competed with E2 for reactive sites leading to reduced E2 removal. Observed differential suppression on E2 removal may be related to different speciations of metals, as suggested by the MINTEQ calculations, and hence their different adsorptivities on MnO2. By suppressing the metal effect, humic acid substantially enhanced E2 removal. This was attributed to complexation of humic acid with metal ions. With 0.01 M ZnCl2 in solutions containing 1 mg l(-1) humic acid, the binding of humic acid for Zn(II) was determined at 251 mmol g(-1). An in vitro assay using human breast carcinoma MCF-7 cells indicated a near elimination of estrogenic activities without secondary risk of estrogen solutions treated with MnO2. Synthetic MnO2 is therefore a promising chemical agent under optimized conditions for estrogen removal from water. Metal chelators recalcitrant to MnO2 oxidation may be properly used to further enhance the MnO2 performance.

  5. Catalytic ozonation of sulfosalicylic acid over manganese oxide supported on mesoporous ceria.

    Science.gov (United States)

    Xing, Shengtao; Lu, Xiaoyang; Liu, Jia; Zhu, Lin; Ma, Zichuan; Wu, Yinsu

    2016-02-01

    Manganese oxide supported on mesoporous ceria was prepared and used as catalyst for catalytic ozonation of sulfosalicylic acid (SA). Characterization results indicated that the manganese oxide was mostly incorporated into the pores of ceria. The synthesized catalyst exhibited high activity and stability for the mineralization of SA in aqueous solution by ozone, and more than 95% of total organic carbon was removed in 30 min under various conditions. Mechanism studies indicated that SA was mainly degraded by ozone molecules, and hydroxyl radical reaction played an important role for the degradation of its ozonation products (small molecular organic acids). The manganese oxide in the pores of CeO2 improved the adsorption of small molecular organic acids and the generation of hydroxyl radicals from ozone decomposition, resulting in high TOC removal efficiency.

  6. Durable rechargeable zinc-air batteries with neutral electrolyte and manganese oxide catalyst

    Science.gov (United States)

    Sumboja, Afriyanti; Ge, Xiaoming; Zheng, Guangyuan; Goh, F. W. Thomas; Hor, T. S. Andy; Zong, Yun; Liu, Zhaolin

    2016-11-01

    Neutral chloride-based electrolyte and directly grown manganese oxide on carbon paper are used as the electrolyte and air cathode respectively for rechargeable Zn-air batteries. Oxygen reduction and oxygen evolution reactions on manganese oxide show dependence of activities on the pH of the electrolyte. Zn-air batteries with chloride-based electrolyte and manganese oxide catalyst exhibit satisfactory voltage profile (discharge and charge voltage of 1 and 2 V at 1 mA cm-2) and excellent cycling stability (≈90 days of continuous cycle test), which is attributed to the reduced carbon corrosion on the air cathode and decreased carbonation in neutral electrolyte. This work describes a robust electrolyte system that improves the cycle life of rechargeable Zn-air batteries.

  7. Insights into the solar light driven thermocatalytic oxidation of VOCs over tunnel structured manganese oxides.

    Science.gov (United States)

    Zheng, Yali; Wang, Wenzhong; Jiang, Dong; Zhang, Ling; Li, Xiaoman; Wang, Zhong

    2016-07-21

    Different tunnel structured manganese oxides (1*1, 2*2, and 3*3) have been synthesized via a facile hydrothermal strategy. The three catalysts exhibit high photothermal performance, resulting in a considerable increase of temperature above the light-off temperature for VOC oxidation. On this point, aerobic oxidation reactions of propane and propylene under simulated sunlight and infrared light irradiation were selected as probe reactions to explore their light driven thermocatalytic activity. Furthermore, the light-off curves of the manganese oxides for propane and propylene were carefully investigated, which clearly explained the possibility of combining both the efficient photothermal effect and excellent thermocatalytic activity of the manganese oxides. Results show that the catalytic effects follow the order of 1*1 structure and the presence of more Mn(4+). This work suggests new applications for traditional catalysts with intense photoabsorption and provides insights into the overall utilization of solar energy.

  8. Preparation of Manganese Oxide Hollow Spheres Using pH-responsive Microgels as Templates

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Zhi-cheng Zhang

    2009-01-01

    Manganese oxide hollow spheres were prepared by a novel and facile approach using pH-responsive microgels as templates. The final products were thoroughly characterized with X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared, and transmission electron microscopy. The results reveal that the shell thickness of manganese oxide hollow spheres increased with the dosage of KMnO4, which implies that a controllable and feasible strategy for manganese oxide hollow spheres prepa-ration has been established. Further studies on the microgels template showed some of them had an irreversible swelling/deswelling transition due to the uneven cross-link extent. Based on the results, a probable formation mechanism for the hollow spheres was proposed.

  9. Electro-catalytic effect of manganese oxide on oxygen reduction at teflonbonded carbon electrode

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Oxygen reduction(OR)on Teflon-bonded carbon electrodes with manganese oxide as catalyst in 6 mol/L KOH solution was investigated using AC impedance spectroscopy combined with other techniques. For OR at this electrode, the Tafel slope is-0.084V/dec and the apparent exchange current density is (1.02-3.0)×10-7 A/cm2. In the presence of manganese oxide on carbon electrode,the couple Mn3+/Mn4+ reacts with the O2 adsorbed on carbon sites forming O2- radicals and acceletes the dismutation of O2-, which contributes to the catalytic effect of manganese oxide for OR reaction.

  10. Iron and manganese oxide mineralization in the Pacific

    Science.gov (United States)

    Hein, J.R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Kang, J.-K.; Lubick, N.

    1997-01-01

    Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ΣREEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ΣREE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect

  11. Arsenite oxidation by three types of manganese oxides

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Oxidation of As(Ⅲ) by three types of manganese oxides and the effects of pH, ion strength and tartaric acid on the oxidation were investigated by means of chemical analysis, equilibrium redox, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Three synthesized Mn oxide minerals, birnessite, cryptomelane, and hausmarnite, which widely occur in soil and sediments, could actively oxidize As(Ⅲ) to As(Ⅴ). However, their ability in As(Ⅲ)-oxidation varied greatly depending on their structure, composition and surface properties. Tunnel structured cryptomelane exhibited the highest ability of As (Ⅲ) oxidation, followed by the layer structured birnessite and the lower oxide hausmannite. The maximum amount of As (Ⅴ) produced by the oxidation was in the order (mmol/kg) ofcryptomelane (824.2) > birnessite (480.4) > hausmannite (117.9). As pH increased from the very low value(pH 2.5), the amount of As(Ⅲ) oxidized by the tested Mn oxides was firstly decreased, then negatively peaked in pH 3.0-6.5,and eventually increased remarkably. Oxidation of As(Ⅲ) by the Mn oxides had a buffering effects on the pH variation in the solution.It is proposed that the oxidative reaction processes between As( Ⅲ ) and birnessite(or cryptomelane) are as follows: (1) at lower pH condition: (MnO2)x + H3AsO3 + 0.5H+=0.5H2AsO4- + 0.5HAsO42- +Mn2++ (MnO2)x-1 + H2O; (2) at higher pH condition: (MnO2)x +cryptomelane decreased and was negatively correlated with ion strength. However, ion strength had little influence on As (Ⅲ) oxidation by the hausmannite. The presence of tartaric acid promoted oxidation of As(Ⅲ) by birnessite. As for cryptomelane and hausmannite, the same effect was observed when the concentration of tartaric acid was below 4 mmol/L, otherwise the oxidized As(Ⅲ)decreased. These findings are of great significance in improving our understanding of As geochemical cycling and controlling As contamination.

  12. Preparation and capacitive properties of lithium manganese oxide intercalation compound

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Fang; Xie, Yibing, E-mail: ybxie@seu.edu.cn [Southeast University, School of Chemistry and Chemical Engineering (China)

    2015-12-15

    Lithium manganese oxide intercalation compound (Li{sub 0.7}MnO{sub 2}) supported on titanium nitride nanotube array (TiN NTA) was applied as cathode electrode material for lithium-ion supercapacitor application. Li{sub 0.7}MnO{sub 2}/TiN NTA was fabricated through electrochemical deposition and simultaneous intercalation process using TiN NTA as a substrate, Mn(CH{sub 3}COO){sub 2} as manganese source, and Li{sub 2}SO{sub 4} as lithium source. The morphology and microstructure of the Li{sub 0.7}MnO{sub 2}/TiN NTA were characterized by scanning electron microscopy and X-ray diffraction analysis. The electrochemical performance of the Li{sub 0.7}MnO{sub 2}/TiN NTA was investigated by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge measurements. Li{sub 0.7}MnO{sub 2}/TiN NTA exhibited higher capacitive performance in Li{sub 2}SO{sub 4} electrolyte solution rather than that in Na{sub 2}SO{sub 4} electrolyte solution, which was due to the different intercalation effects of lithium-ion and sodium-ion. The specific capacitance was improved from 503.3 F g{sup −1} for MnO{sub 2}/TiN NTA to 595.0 F g{sup −1} for Li{sub 0.7}MnO{sub 2}/TiN NTA at a current density of 2 A g{sup −1} in 1.0 M Li{sub 2}SO{sub 4} electrolyte solution, which was due to the intercalation of lithium-ion for Li{sub 0.7}MnO{sub 2}. Li{sub 0.7}MnO{sub 2}/TiN NTA also kept 90.4 % capacity retention after 1000 cycles, presenting a good cycling stability. An all-solid-state lithium-ion supercapacitor was fabricated and showed an energy density of 82.5 Wh kg{sup −1} and a power density of 10.0 kW kg{sup −1}.

  13. Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab

    Science.gov (United States)

    Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

    2006-01-01

    A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

  14. Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab

    Science.gov (United States)

    Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

    2006-01-01

    A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

  15. Hyperthermia HeLa cell treatment with silica coated manganese oxide nanoparticles

    CERN Document Server

    Villanueva, A; Alonso, JM; Rueda, T; Martínez, A; Crespo, P; Morales, MP; Fernandez, MA Gonzalez; Valdes, J; Rivero, G

    2009-01-01

    HeLa tumour cells incubated with ferromagnetic nanoparticles of manganese oxide perovskite La0.56(SrCa)0.22MnO3 were treated with a high frequency alternating magnetic field. The particles were previously coated with silica to improve their biocompatibility. The control assays made with HeLa tumour cells showed that cell survival and growth rate were not affected by the particle internalization in cells, or by the electromagnetic field on cells without nanoparticles. The application of an alternating electromagnetic field to cells incubated with this silica coated manganese oxide induced a significant cellular damage that finally lead to cell death by an apoptotic mechanism.

  16. Nickel mobilization in a groundwater well field: Release by pyrite oxidation and desorption from manganese oxides

    DEFF Research Database (Denmark)

    Postma, Dieke; Larsen, Flemming

    1997-01-01

    is furthermore characterized by enhanced Mn2+ concentrations. Apparently nickel accumulates on manganese oxides during pyrite oxidation. When the water table rises again, partially oxidized pyritic layers are resubmerged, and due to an insufficient supply of oxygen, the oxidation of Fe2+ released during pyrite...... oxidation becomes incomplete. The mobilized Fe2+ may reduce manganese oxides and thereby release large amounts of Ni2+ to the groundwater. Calculations using a surface complexation model indicate retardation of nickel to be strongly affected by bulk water composition. At the background groundwater...

  17. Synthesis and structural characterization of defect spinels in the Lithium-Manganese-Oxide system

    CSIR Research Space (South Africa)

    Thackeray, MM

    1993-10-01

    Full Text Available Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structures of two defect-spinel compounds synthesised by the reaction of MnCO3 and Li2CO3 at 400...

  18. Synthesis of lithium-manganese-oxide spinels: A study by thermal analysis

    CSIR Research Space (South Africa)

    Thackeray, MM

    1994-12-01

    Full Text Available demonstrated that lithium-manganese-oxide spinel compounds that fall within the solid solution range XLi1-xMn2-2xO4 (0 < = X < = 0.11) can be synthesized by reaction of MnCO3 and Li2CO3 in air at moderate temperatures. It is difficult, however, to control...

  19. Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Schmit, F. [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon (UMR 5256 CNRS/Université Lyon 1), Lyon (France); Bois, L., E-mail: laurence.bois@univ-lyon1.fr [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); Chiriac, R.; Toche, F.; Chassagneux, F. [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); Besson, M.; Descorme, C. [IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon (UMR 5256 CNRS/Université Lyon 1), Lyon (France); Khrouz, L. [ENS LYON Laboratoire de Chimie (LR6, site Monod), 46, allée d’Italie, 69364 Lyon Cedex 07 (France)

    2015-01-15

    Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol–gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  20. High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

    CSIR Research Space (South Africa)

    Bello, A

    2013-01-01

    Full Text Available -ray diffractionmeasurements showed the presence of nanocrystallineMnO(sub2) on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite...

  1. Synthesis, characterization and catalytic activity of birnessite type potassium manganese oxide nanotubes and nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Khalid Abdelazez Mohamed, E-mail: khalidgnad@hotmail.com [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Chemistry, School of Chemistry and Chemical Technology, Faculty of Science and Technology, Al-Neelain University, P.O. Box 12702, Khartoum (Sudan); Huang Kaixun, E-mail: hxxzrf@mail.hust.edu.cn [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Birnessite type manganese oxides nanotubes and nanorods were prepared by calcination route. Black-Right-Pointing-Pointer The transition from tube to rod structure is described by an oriented attachment-thermodynamical (OA-TD) process. Black-Right-Pointing-Pointer The catalytic degradation efficiency of safranin O by as-prepared products was compared. - Abstract: Birnessite-type manganese oxide nanotubes and nanorods were synthesized via a calcination process using manganese acetate and potassium hydroxide as precursors in presence of polyethylene glycol-melamine-formaldehyde. As-prepared products were characterized by XRD, FT-IR, FE-SEM, TEM, SA-ED, HR-TEM, Brunauer-Emmett-Teller (BET) and TGA analyses. The influences of reaction temperature and time on the morphology of manganese oxide nanocrystals were investigated. The oriented attachment-thermodynamical (OA-TD) process is suggested to describe the transition from tube to rod structure. Their capability of catalytic degradation of safranin O was compared. The results indicate that birnessite-type manganese oxide nanotube has higher catalytic activity for than nanorod crystal in aqueous solution, because it has a larger surface area. The decomposition of safranin O follows pseudo-first order kinetics and is markedly affected by pH.

  2. Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system

    CSIR Research Space (South Africa)

    Thackeray, MM

    1993-10-01

    Full Text Available Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structures of two defect-spinel compounds synthesized by the reaction of MnCO3 and Li2CO3 at 400°C...

  3. Synthesis of nanostructured manganese oxides based materials and application for supercapacitor

    Science.gov (United States)

    Dung Dang, Trung; Le, Thi Thu Hang; Bich Thuy Hoang, Thi; Mai, Thanh Tung

    2015-01-01

    Manganese oxides are important materials with a variety of applications in different fields such as chemical sensing devices, magnetic devices, field-emission devices, catalysis, ion-sieves, rechargeable batteries, hydrogen storage media and microelectronics. To open up new applications of manganese oxides, novel morphologies or nanostructures are required to be developed. Via sol—gel and anodic electrodeposition methods, M (Co, Fe) doped manganese oxides were prepared. On the other hand, nanostructured (nanoparticles, nanorods and hollow nanotubes) manganese oxides were synthesized via a process including a chemical reaction with carbon nanotubes (CNTs) templates followed by heat treatment. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV) and impedance spectroscopy (EIS) were used for characterization of the prepared materials. The influence of chemical reaction conditions, heat treatment and template present on the morphology, structure, chemical and electrochemical properties of the prepared materials were investigated. Chronopotentiometry (CP) and CV results show high specific capacitance of 186.2 to 298.4 F g-1 and the charge/discharge stability of the prepared materials and the ideal pseudocapacitive behaviors were observed. These results give an opening and promising application of these materials in advanced energy storage applications.

  4. A Highly Active and Selective Manganese Oxide Promoted Cobalt-on-Silica Fischer-Tropsch Catalyst

    NARCIS (Netherlands)

    den Breejen, Johan P.; Frey, Anne M.; Yang, Jia; Holmen, Anders; van Schooneveld, Matti M.; de Groot, Frank M. F.; Stephan, Odile; Bitter, Johannes H.; de Jong, Krijn P.

    2011-01-01

    A highly active and selective manganese oxide-promoted silica-supported cobalt catalyst for the Fischer-Tropsch reaction is reported. Co/MnO/SiO2 catalysts were prepared via impregnation of a cobalt nitrate and manganese nitrate precursor, followed by drying and calcination in an NO/He flow. The cat

  5. Amperometric Biosensors Based on Carbon Paste Electrodes Modified with Nanostructured Mixed-valence Manganese Oxides and Glucose Oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Xiaoli; Liu, Guodong; Lin, Yuehe

    2005-06-01

    Nanostructured multivalent manganese oxides octahedral molecular sieve (OMS), including cryptomelane-type manganese oxides and todorokite-type manganese oxides, were synthesized and evaluated for chemical sensing and biosensing at low operating potential. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. The electrochemical and electrocatalytic performance of OMS for the oxidation of H2O2 have been compared. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides can be used to fabricate sensitive H2O2 sensors. Amperometric glucose biosensors are constructed by bulk modification of carbon paste electrodes (CPEs) with glucose oxidase as a biocomponent and nanostructured OMS as a mediator. A Nafion thin film was applied as an immobilization/encapsulation and protective layer. The biosensors were evaluated as an amperometric glucose detector at phosphate buffer solution with a pH 7.4 at an operating potential of 0.3 V (vs. Ag/AgCl). The biosensor is characterized by a well-reproducible amperometric response, linear signal-to-glucose concentration range up to 3.5 mM and 1.75 mM, and detection limits (S/N = 3) of 0.1 mM and 0.05 mM for todorokite-type manganese oxide and cryptomelane-type manganese oxide modified electrodes, respectively. The biosensors based on OMS exhibit considerable good reproducibility and stability, and the construction and renewal are simple and inexpensive.

  6. Growth and Dissolution of Iron and Manganese Oxide Films

    Energy Technology Data Exchange (ETDEWEB)

    Scot T. Martin

    2008-12-22

    Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx were approximately 40 pN and 600 pN, respectively

  7. A Review on the Synthesis of Manganese Oxide Nanomaterials and Their Applications on Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Xiaodi Liu

    2013-01-01

    Full Text Available Most recently, manganese oxides nanomaterials, including MnO and MnO2, have attracted great interest as anode materials in lithium-ion batteries (LIBs for their high theoretical capacity, environmental benignity, low cost, and special properties. Up to now, manganese oxides nanostructures with excellent properties and various morphologies have been successfully synthesized. Herein, we provide an in-depth discussion of recent development of the synthesis of manganese oxides nanomaterials and their application in the field of LIBs.

  8. Comparison of cardiolipins from Drosophila strains with mutations in putative remodeling enzymes.

    Science.gov (United States)

    Schlame, Michael; Blais, Steven; Edelman-Novemsky, Irit; Xu, Yang; Montecillo, Fleurise; Phoon, Colin K L; Ren, Mindong; Neubert, Thomas A

    2012-07-01

    Cardiolipin is a dimeric phospholipid with a characteristic acyl composition that is generated by fatty acid remodeling after de novo synthesis. Several enzymes have been proposed to participate in acyl remodeling of cardiolipin. In order to compare the effect of these enzymes, we determined the pattern of cardiolipin molecular species in Drosophila strains with specific enzyme deletions, using MALDI-TOF mass spectrometry with internal standards. We established the linear range of the method for cardiolipin quantification, determined the relative signal intensities of several cardiolipin standards, and demonstrated satisfying signal-to-noise ratios in cardiolipin spectra from a single fly. Our data demonstrate changes in the cardiolipin composition during the Drosophila life cycle. Comparison of cardiolipin spectra, using vector algebra, showed that inactivation of tafazzin had a large effect on the molecular composition of cardiolipin, inactivation of calcium-independent phospholipase A(2) had a small effect, whereas inactivation of acyl-CoA:lysocardiolipin-acyltransferase and of the trifunctional enzyme did not affect the cardiolipin composition.

  9. Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

    Science.gov (United States)

    Wang, Liang; Wang, Guoxiong; Zhang, Jian; Bian, Chaoqun; Meng, Xiangju; Xiao, Feng-Shou

    2017-05-01

    The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds.

  10. Types and Genesis of Manganese Oxide Ores in Guangxi,Southwest China

    Institute of Scientific and Technical Information of China (English)

    刘腾飞

    1999-01-01

    Systematic studies are diven to the genesis and spatial distribution of manganese oxide deposits in Guangxi,Southwest China.The deposits are classified as 3 types and 7 subtypes among which the karst depression type is regionally characteristic an of reat potential.A genetic model is presented for the mineralization on the basis of proto-rock,tectonic background,topographic features and climatic and hydrogeological conditions.

  11. Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

    Science.gov (United States)

    Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

    2014-08-01

    We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    Science.gov (United States)

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication.

  13. Effect of copper doping on the crystal structure and morphology of 1D nanostructured manganese oxides.

    Science.gov (United States)

    Lee, Sun Hee; Park, Dae Hoon; Hwang, Seong-Ju; Choy, Jin-Ho

    2007-11-01

    We have tried to control the aspect ratio and physicochemical properties of 1D nanostructured manganese oxides through copper doping. Copper-doped manganese oxide nanostructures have been synthesized by one-pot hydrothermal treatment for the mixed solution of permanganate anions and copper cations. According to powder X-ray diffraction and electron microscopic analyses, all the present materials commonly crystallize with alpha-MnO2-type structure but their aspect ratio decreases significantly with increasing the content of copper. Such a variation of crystallite dimension is attributable to the limitation of crystal growth by the incorporation of copper ions. X-ray absorption spectroscopic studies at Mn K- and Cu K-edges clearly demonstrate that the average oxidation state of manganese ions is increased by the substitution of divalent copper ions. Electrochemical measurements reveal the improvement of the electrode performance of nanostructured manganate upon copper doping, which can be interpreted as a result of the decrease of aspect ratio and the increase of Mn valence state. From the present experimental findings, it becomes certain that the present Cu doping method can provide an effective way of controlling the crystal dimension and electrochemical property of 1D nanostructured manganese oxide.

  14. Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering

    Science.gov (United States)

    Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

    2006-01-01

    Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

  15. Facile synthesis of birnessite-type manganese oxide nanoparticles as supercapacitor electrode materials.

    Science.gov (United States)

    Liu, Lihu; Luo, Yao; Tan, Wenfeng; Zhang, Yashan; Liu, Fan; Qiu, Guohong

    2016-11-15

    Manganese oxides are environmentally benign supercapacitor electrode materials and, in particular, birnessite-type structure shows very promising electrochemical performance. In this work, nanostructured birnessite was facilely prepared by adding dropwise NH2OH·HCl to KMnO4 solution under ambient temperature and pressure. In order to fully exploit the potential of birnessite-type manganese oxide electrode materials, the effects of specific surface area, pore size, content of K(+), and manganese average oxidation state (Mn AOS) on their electrochemical performance were studied. The results showed that with the increase of NH2OH·HCl, the Mn AOS decreased and the corresponding pore sizes and specific surface area of birnessite increased. The synthesized nanostructured birnessite showed the highest specific capacitance of 245Fg(-1) at a current density of 0.1Ag(-1) within a potential range of 0-0.9V, and excellent cycle stability with a capacitance retention rate of 92% after 3000 cycles at a current density of 1.0Ag(-1). The present work implies that specific capacitance is mainly affected by specific surface area and pore volume, and provides a new method for the facile preparation of birnessite-type manganese oxide with excellent capacitive performance.

  16. Effects of a manganese oxide-modified biochar composite on adsorption of arsenic in red soil.

    Science.gov (United States)

    Yu, Zhihong; Zhou, Li; Huang, Yifan; Song, Zhengguo; Qiu, Weiwen

    2015-11-01

    The arsenic adsorption capacity of a manganese oxide-modified biochar composite (MBC), prepared by pyrolysis of a mixture of potassium permanganate and biochar, was investigated in red soil. Adsorption experiments using batch procedures were used to estimate the arsenic adsorption capacities of the absorbent materials. Adsorption and desorption isotherms, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterise the prepared adsorbent materials, and a plausible mechanism for arsenic removal by MBC was proposed. Arsenic in red soil-MBC mixtures exhibited lower mobility than that in soils amended with pristine biochar. The improved removal performance of soil-MBC mixtures was attributed to a lower H/C ratio, higher O/C ratio, higher surface hydrophilicity, and higher surface sorption capacity, even though the impregnation of manganese oxide decreased the specific surface area of the biochar. Arsenic retention increased as the biochar content increased, mainly owing to an increase in soil pH. Several oxygenated functional groups, especially O-H, CO, Mn-O, and Si-O, participated in the adsorption process, and manganese oxides played a significant role in the oxidation of arsenic. This study highlights the potential of MBC as an absorbent to immobilise arsenic for use in contaminated land remediation in the red soils region.

  17. Electrochemical Supercapacity of Manganese Oxide and Carbon/Manganese Oxide Composite%氧化锰及炭/氧化锰复合材料的电化学电容性能

    Institute of Scientific and Technical Information of China (English)

    王晶日; 田颖

    2011-01-01

    Manganese oxide and carbon/manganese oxide composite were prepared by liquid oxidation method with Mn(Ac) 2 as manganese source and K2S208 as oxidizer. The electrochemical capacitance performance of the supercapacitor was tested by cyclic voltammetry, galvanostatic charge-discharge and impetance spectroscopy. The results indicate that carbon-loading manganese composite shows excellent capacitive behavior compared with pure manganese oxide. The calculated results demonstrates that the specific capacitance of the carbon/manganese oxide composite is 7 ~ 12 times higher than that of manganese oxide. However, the internal resistance of the manganese oxide is 4.4 ~ 6.4 times higher than that of carbon/manganese oxide composite.%以Mn(Ac)2为锰源,以K2S2O8为氧化剂,采用液相氧化法制备了氧化锰材料和炭/氧化锰复合材料.采用循环伏安、交流阻抗和恒流充放电方法对两种电极材料的电化学电容性能进了表征.结果表明:由于炭的担载,复合材料的电化学电容性能优于纯氧化锰.氧化锰对称型电容器的比电容要远远低于炭/氧化锰的比电容,后者是前者的7~12倍.而氧化锰对称型电容器的内阻要远远高于炭/氧化锰的内阻,前者是后者的4.4~4.5倍.

  18. Solid-Phase Synthesis of Modified Peptides as Putative Inhibitors of Histone Modifying Enzymes

    DEFF Research Database (Denmark)

    Cohrt, Anders Emil O'Hanlon

    and purities. Libraries of histone H2B tail pieces were synthesised using both parallel and split-pool synthesis protocols. Changes in the acetylation pattern of the individual library members upon treatment with HDAC3 enzyme were measured using LCMS-MS techniques. An MSMS deconvolution strategy was employed......,2,3-triazoles were cleanly deprotected by treatment with TFA (CH2Cl2). Four different libraries of histone demethylase inhibitor candidates have been synthesised based on metal chelation, cofactor mimicking and radial stabilising inhibition strategies. The libraries have all been synthesised on solid......-phase using various handle strategies for the clean release of products. Two cofactor mimicking inhibitor candidates, which were synthesised using a safety-catch benzyl hydrazide handle, were found to inhibit the histone demethylase JMJD2C with IC50-values of 23.5µM and 24µM. Two mild and selective methods...

  19. Identification of genes coding for putative wax ester synthase/diacylglycerol acyltransferase enzymes in terrestrial and marine environments.

    Science.gov (United States)

    Lanfranconi, Mariana P; Alvarez, Adrián F; Alvarez, Héctor M

    2015-12-01

    Synthesis of neutral lipids such as triacylglycerols (TAG) and wax esters (WE) is catalyzed in bacteria by wax ester synthase/diacylglycerol acyltransferase enzymes (WS/DGAT). We investigated the diversity of genes encoding this enzyme in contrasting natural environments from Patagonia (Argentina). The content of petroleum hydrocarbons in samples collected from oil-producing areas was measured. PCR-based analysis covered WS/DGAT occurrence in marine sediments and soil. No product was obtained in seawater samples. All clones retrieved from marine sediments affiliated with gammaproteobacterial sequences and within them, most phylotypes formed a unique cluster related to putative WS/DGAT belonging to marine OM60 clade. In contrast, soils samples contained phylotypes only related to actinomycetes. Among them, phylotypes affiliated with representatives largely or recently reported as oleaginous bacteria, as well as with others considered as possible lipid-accumulating bacteria based on the analysis of their annotated genomes. Our study shows for the first time that the environment could contain a higher variety of ws/dgat than that reported from bacterial isolates. The results of this study highlight the relevance of the environment in a natural process such as the synthesis and accumulation of neutral lipids. Particularly, both marine sediments and soil may serve as a useful source for novel WS/DGAT with biotechnological interest.

  20. Microbial manganese oxide formation and interaction with toxic metal ions.

    Science.gov (United States)

    Miyata, Naoyuki; Tani, Yukinori; Sakata, Masahiro; Iwahori, Keisuke

    2007-07-01

    Diverse bacteria and fungi oxidize Mn(II) enzymatically and produce insoluble Mn(III, IV) oxides, and these organisms are considered to be the primal agents for the occurrence of natural Mn oxide phases in most environments. Biogenic Mn oxides have a high sorption capacity for metal cations and an ability to oxidize numerous inorganic and organic compounds, owing to their structural and redox features. Thus, the microbial process is of significance in both biogeochemical and biotechnological contexts. In this article we summarize the enzymatic Mn(II) oxidation and interactions of biogenic Mn oxides with toxic metal and metalloid ions. Although Mn oxide formation by fungi has not been fully characterized yet, recent researches with ascomycetes emphasize the similarity between the bacterial and fungal Mn(II) oxidation with respect to the involved catalyst (i.e., multicopper oxidase-type enzymes) and the reaction product [i.e., layer-type Mn(IV) oxides]. Laboratory cultures of bacterial and fungal Mn oxidizers are expected to provide fundamental knowledge in their potential use for remediation of environments and effluents contaminated with toxic metal(loid) ions.

  1. Electroless preparation and ASAXS microstructural analysis of pseudocapacitive carbon manganese oxide supercapacitor electrodes.

    Science.gov (United States)

    Weber, Christian; Reichenauer, Gudrun; Pflaum, Jens

    2015-01-20

    Anomalous small angle X-ray scattering (ASAXS) has been utilized as a noninvasive, integral tool to access the structural properties of carbon xerogel-manganese oxide electrodes with nanometer resolution. As these electrodes constitute the elementary functional units in supercapacitors and as their microstructure governs the macroscopic electrical performance, it is essential to gain a detailed morphological understanding of the underlying carbon particle scaffold coated with manganese oxide. We demonstrate that, in this regard, ASAXS provides a powerful technique and in combination with a theoretical core-shell model enables a quantitative estimation of the relevant structural parameters. As a result, we determined the thicknesses of the solution deposited MnO2 shells to range between 3 and 26 nm depending on the carbon particle size and thus on their effective surface area. By our core-shell modeling we conclude the revealed manganese oxide coatings on the carbon support to be rather thick, but nevertheless to show a high uniformity in thickness. At 1.8 ± 0.2 to 2.2 ± 0.1 g/cm(3) the related effective MnO2 densities of the shells are about 30% lower than the corresponding bulk density of 3.0 g/cm(3). This mainly originates from a substructure within the shell, whose growth is controlled by a pronounced reduction of the manganese precursor during layer formation. Finally, the presented ASAXS data are complemented by SEM and N2 sorption measurements, proving not only qualitatively the proposed flake-like MnO2 surface morphology but also confirming quantitatively the manganese shell thickness, complementary, on a local scale.

  2. Effects of carrier and Mn loading on supported manganese oxide catalysts for catalytic combustion of methane

    Institute of Scientific and Technical Information of China (English)

    Jinyan Hu; Wei Chu; Limin Shi

    2008-01-01

    Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane cat-alytic combustion, and effects of the support (Al2O3, SiO2 and TiO2) and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn cata-lyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance.

  3. Effect of Co on the magnetism and phase stability of lithiated manganese oxides

    Indian Academy of Sciences (India)

    R Prasad; R Benedek; M M Thackeray

    2003-01-01

    We present first-principles calculations of the relative energies of various phases of lithiated manganese oxides with and without Co. We use the ultrasoft pseudopotential method as implemented in the Vienna ab initio simulation package (VASP). The calculations employ the local spin density approximation (LSDA) as well as the generalized gradient approximation (GGA). We consider monoclinic and rhombohedral structures in paramagnetic, ferromagnetic and antiferromagnetic (AF3) spin configurations. Spinpolarization significantly lowers the total energy in all cases. The effect of Co on the stability of these phases is discussed.

  4. Bright blue photoluminescence from a mixed tin and manganese oxide xerogel prepared via sol-hydrothermal-gel process

    Institute of Scientific and Technical Information of China (English)

    Xiang Xia; Cheng Xiao-Feng; He Shao-Bo; Yuan Xiao-Dong; Zheng Wan-Guo; Li Zhi-Jie; Liu Chun-Ming; Zhou Wei-Lie; Zu Xiao-Tao

    2011-01-01

    A new blue photoluminescent material,a mixed tin and manganese oxide xerogel,is prepared via sol-hydrothermalgel process assisted by citric acid.The composition xerogel exhibits strong blue emission at room temperature,with an emission maximum at 434 nm under short (234 nm) or long-wavelength (343 nm) ultraviolet excitation.The photoluminescent excitation spectrum of the mixed tin and manganese oxide xerogel,monitored at an intensity maximum wavelength of 434 nm of the emission,consists of two excitation peaks at 234 nm and 343 nm.With heat treatment temperature increasing from 110 ℃ to 200 ℃,the blue emission intensity increases remarkably,whereas it is almost completely quenched after being treated at 300 ℃.The carbon impurities in the mixed tin and manganese oxide xerogel,confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy,should be responsible for the bright blue photoluminescence.

  5. Use of manganese oxide and activated carbon fibers for removing a particle, volatile organic compound or ozone from a gas

    Science.gov (United States)

    Sidheswaran, Meera A.; Destaillats, Hugo; Fisk, William J.

    2016-08-30

    The present invention provides for a device for reducing a volatile organic compound (VOC) content of a gas comprising a manganese oxide (MnO.sub.x) catalyst. The manganese oxide (MnO.sub.x) catalyst is capable of catalyzing formaldehyde at room temperature, with complete conversion, to CO.sub.2 and water vapor. The manganese oxide (MnO.sub.x) catalyst itself is not consumed by the reaction of formaldehyde into CO.sub.2 and water vapor. The present invention also provides for a device for reducing or removing a particle, a VOC and/or ozone from a gas comprising an activated carbon filter (ACF) on a media that is capable of being periodically regenerated.

  6. Roles of manganese oxides in degradation of phenol under UV-Vis irradiation: adsorption, oxidation, and photocatalysis.

    Science.gov (United States)

    Zhang, Qin; Cheng, Xiaodi; Zheng, Chen; Feng, Xionghan; Qiu, Guohong; Tan, Wenfeng; Liu, Fan

    2011-01-01

    Manganese oxides are known as one type of semiconductors, but their photocatalysis characteristics have not been deeply explored. In this study, photocatalytic degradation of phenol using several synthesized manganese oxides, i.e, acidic birnessite (BIR-H), alkaline birnessite (BIR-OH), cryptomelane (CRY) and todorokite (TOD), were comparatively investigated. To elucidate phenol degradation mechanisms, X-ray diffraction (XRD), ICP-AES (inductively coupled plasma-atomic emission spectroscopy), TEM (transmission electronic microscope), N2 physisorption at 77 K and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed to characterize the structural, compositional, morphological, specific surface area and optical absorption properties of the manganese oxides. After 12 hr of UV-Vis irradiation, the total organic carbon (TOC) removal rate reached 62.1%, 43.1%, 25.4%, and 22.5% for cryptomelane, acidic birnessite, todorokite and alkaline birnessite, respectively. Compared to the reactions in the dark condition, UV-Vis exposure improved the TOC removal rates by 55.8%, 31.9%, 23.4% and 17.9%. This suggests a weak ability of manganese oxides to degrade phenol in the dark condition, while UV-Vis light irradiation could significantly enhance phenol degradation. The manganese minerals exhibited photocatalytic activities in the order of: CRY > BIR-H > TOD > BIR-OH. There may be three possible mechanisms for photochemical degradation: (1) direct photolysis of phenol; (2) direct oxidation of phenol by manganese oxides; (3) photocatalytic oxidation of phenol by manganese oxides. Photocatalytic oxidation of phenol appeared to be the dominant mechanism.

  7. Roles of manganese oxides in degradation of phenol under UV-Vis irradiation: Adsorption, oxidation, and photocatalysis

    Institute of Scientific and Technical Information of China (English)

    Qin Zhang; Xiaodi Cheng; Chen Zheng; Xionghan Feng; Guohong Qiu; Wenfeng Tan; Fan Liu

    2011-01-01

    Manganese oxides are known as one type of semiconductors,but their photocatalysis characteristics have not teen deeply explored.In this study,photocatalytic degradation of phenol using several synthesized manganese oxides,i.e,acidic birnessite (BIR-H),alkaline birnessite (BIR-OH),cryptomelane (CRY) and todorokite (TOD),were comparatively investigated.To elucidate phenol degradation mechanisms,X-ray diffraction (XRD),ICP-AES (inductively coupled plasma-atomic emission spectroscopy),TEM (transmission electronic microscope),N2 physisorption at 77 K and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed to characterize the structural,compositional,morphological,specific surface area and optical absorption properties of the manganese oxides.After 12 hr of UV-Vis irradiation,the total organic carbon (TOC) removal rate reached 62.1%,43.1%,25.4%,and 22.5% for cryptomelane,acidic birnessite,todorokite and alkaline birnessite,respectively.Compared to the reactions in the dark condition,UVVis exposure improved the TOC removal rates by 55.8%,31.9%,23.4% and 17.9%.This suggests a weak ability of manganese oxides to degrade phenol in the dark condition,while UV-Vis light irradiation could significantly enhance phenol degradation.The manganese minerals exhibited photocatalytic activities in the order of:CRY > BIR-H > TOD > BIR-OH.There may be three possible mechanisms for photochemical degradation:(1) direct photolysis of phenol; (2) direct oxidation of phenol by manganese oxides; (3) photocatalytic oxidation of phenol by manganese oxides.Photocatalytic oxidation of phenol appeared to be the dominant mechanism.

  8. Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides

    Science.gov (United States)

    Sharma, Vinit; Krogel, Jaron T.; Kent, P. R. C.; Reboredo, Fernando A.

    One of the critical scientific challenges of contemporary research is to obtain an accurate theoretical description of the electronic properties of strongly correlated systems such as transition metal oxides and rare-earth compounds, since state-of-art ab-initio methods based on approximate density functionals are not always sufficiently accurate. Quantum Monte Carlo (QMC) methods, which use statistical sampling to evaluate many-body wave functions, have the potential to answer this challenge. Owing to the few fundamental approximations made and the direct treatment of electron correlation, QMC methods are among the most accurate electronic structure methods available to date. We assess the accuracy of the diffusion Monte Carlo method in the case of rocksalt manganese oxide (MnO). We study the electronic properties of this strongly-correlated oxide, which has been identified as a suitable candidate for many applications ranging from catalysts to electronic devices. ``This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.'' Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides.

  9. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    Directory of Open Access Journals (Sweden)

    Matthias Augustin

    2015-01-01

    Full Text Available Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx+ oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.

  10. Room-Temperature Oxidation of Formaldehyde by Layered Manganese Oxide: Effect of Water.

    Science.gov (United States)

    Wang, Jinlong; Zhang, Pengyi; Li, Jinge; Jiang, Chuanjia; Yunus, Rizwangul; Kim, Jeonghyun

    2015-10-20

    Layered manganese oxide, i.e., birnessite was prepared via the reaction of potassium permanganate with ammonium oxalate. The water content in the birnessite was adjusted by drying/calcining the samples at various temperatures (30 °C, 100 °C, 200 °C, 300 °C, and 500 °C). Thermogravimetry-mass spectroscopy showed three types of water released from birnessite, which can be ascribed to physically adsorbed H2O, interlayer H2O and hydroxyl, respectively. The activity of birnessite for formaldehyde oxidation was positively associated with its water content, i.e., the higher the water content, the better activity it has. In-situ DRIFTS and step scanning XRD analysis indicate that adsorbed formaldehyde, which is promoted by bonded water via hydrogen bonding, is transformed into formate and carbonate with the consumption of hydroxyl and bonded water. Both bonded water and water in air can compensate the consumed hydroxyl groups to sustain the mineralization of formaldehyde at room temperature. In addition, water in air stimulates the desorption of carbonate via water competitive adsorption, and accordingly the birnessite recovers its activity. This investigation elucidated the role of water in oxidizing formaldehyde by layered manganese oxides at room temperature, which may be helpful for the development of more efficient materials.

  11. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    Science.gov (United States)

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices.

  12. Pathogenic prion protein is degraded by a manganese oxide mineral found in soils

    Science.gov (United States)

    Russo, F.; Johnson, C.J.; McKenzie, D.; Aiken, Judd M.; Pedersen, J.A.

    2009-01-01

    Prions, the aetiological agents of transmissible spongiform encephalopathies, exhibit extreme resistance to degradation. Soil can retain prion infectivity in the environment for years. Reactive soil components may, however, contribute to the inactivation of prions in soil. Members of the birnessite family of manganese oxides (MnO2) rank among the strongest natural oxidants in soils. Here, we report the abiotic degradation of pathogenic prion protein (PrPTSE) by a synthetic analogue of naturally occurring birnessite minerals. Aqueous MnO2 suspensions degraded the PrPTSE as evidenced by decreased immunoreactivity and diminished ability to seed protein misfolding cyclic amplification reactions. Birnessite-mediated PrPTSE degradation increased as a solution's pH decreased, consistent with the pH-dependence of the redox potential of MnO2. Exposure to 5.6 mg MnO2 ml-1 (PrPTSE:MnO2=1 : 110) decreased PrPTSE levels by ???4 orders of magnitude. Manganese oxides may contribute to prion degradation in soil environments rich in these minerals. ?? 2009 SGM.

  13. Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite.

    Science.gov (United States)

    Al-Ghouti, Mohammad A; Al-Degs, Yehya S; Khraisheh, Majeda A M; Ahmad, Mohammad N; Allen, Stephen J

    2009-08-01

    The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as delta-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the d-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern.

  14. High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

    Directory of Open Access Journals (Sweden)

    Abdulhakeem Bello

    2013-08-01

    Full Text Available We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF with ∼80 wt% of manganese oxide (MnO2 deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg−1 at a current density of 0.1 Ag−1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg−1 was obtained, with power density of 20 kWkg−1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.

  15. The Structure of manganese oxide formed by the fungus Acremonium sp. strain KR21-2

    Science.gov (United States)

    Saratovsky, Ian; Gurr, Sarah J.; Hayward, Michael A.

    2009-06-01

    Manganese oxides are observed to form by the oxidation of aqueous solutions of Mn(II) catalyzed by the action of microorganisms. In contrast to the widely studied material produced by bacteria, manganese oxide phases produced by the action of fungi have received only limited attention. A detailed study of the MnO x material produced by the action of the fungus Acremonium KR21-2, utilizing X-ray diffraction, XANES, EXAFS and transmission electron microscopy is reported. The MnO x material is produced as small crystalline particles which adopt a todorokite-like tunnel structure, in striking contrast to previously reported microbial MnO x materials which adopt layered birnessite-type structures. ICPMS measurements reveal there are no templating metal ions present in the fungally mediated MnO x material, in contrast to analogous bacterially mediated material, suggesting these cations play a critical role in determining the structure of the material precipitated. A phylogenetic analysis places KR21-2 with other Acremonium species in the Hypocreales.

  16. Microstructural characterization of the cycling behavior of electrodeposited manganese oxide supercapacitors using 3D electron tomography

    Science.gov (United States)

    Dalili, N.; Clark, M. P.; Davari, E.; Ivey, D. G.

    2016-10-01

    Manganese oxide has been investigated extensively as an electrochemical capacitor or supercapacitor electrode material. Manganese oxide is inexpensive to fabricate and exhibits relatively high capacitance values, i.e., in excess of 200 F g-1 in many cases; the actual value depends very much on the fabrication method and test conditions. The cycling behavior of Mn oxide, fabricated using anodic electrodeposition, is investigated using slice and view techniques, via a dual scanning electron microscope (SEM) and focused ion beam (FIB) instrument to generate three-dimensional (3D) images, coupled with electrochemical characterization. The initial as-fabricated electrode has a rod-like appearance, with a fine-scale, sheet-like morphology within the rods. The rod-like structure remains after cycling, but there are significant morphological changes. These include partial dissolution of Mn oxide followed by redeposition of Mn oxide in regions close to the substrate. The redeposited material has a finer morphology than the original as-fabricated Mn oxide. The Mn oxide coverage is also better near the substrate. These effects result in an increase in the specific capacitance.

  17. Manganese oxide as catalyst for tar cleaning of biomass-derived gas

    Energy Technology Data Exchange (ETDEWEB)

    Lind, Fredrik; Israelsson, Mikael; Seemann, Martin; Thunman, Henrik [Chalmers University of Technology, Division of Energy Technology, Department of Energy and Environment, Gothenburg (Sweden)

    2012-06-15

    The possibilities to upgrade raw gas with the use of a manganese oxide have been investigated in an application for secondary tar cleaning of biomass-derived gas. Experiments were conducted in a reactor system where a novel technique that combines tar cleaning with catalyst regeneration is applied. Raw gas from the Chalmers non-catalytic steam biomass gasifier - containing roughly 32 g{sub tar}/Nm{sub gas} {sup 3} - was fed to the tar cleaning reactor. The tar reforming qualities of the manganese oxide were evaluated in the reactor system using a mixture of 23 wt.% catalysts in silica sand at the temperatures 700 and 800 C. Experiments showed that the catalyst was continuously regenerated from carbon deposits and that the total amount of tars was decreased by as much as 44.5 % at a gas residence time of 0.4 s in the bed. The catalyst showed activity in water-gas shift reaction and the H{sub 2}/CO ratio increased from 0.6 in the raw gas to a peak value of 1 in the reformed gas at 800 C. Only a slight decrease in methane and acetylene content was observed for both operating temperatures. (orig.)

  18. Reduction of ripening time of full-scale manganese removal filters with manganese oxide-coated media

    NARCIS (Netherlands)

    Bruins, J.H.; Petrusevski, B.; Slokar, Y.M.; Huysman, K.; Joris, K.; Kruithof, J.C.; Kennedy, M.D.

    2015-01-01

    Effective manganese removal by conventional aeration-filtration with virgin filter media requires a long ripening time. The aim of this study was to assess the potential of manganese oxide-coated media to shorten the ripening time of filters with virgin media, under practical conditions. A full

  19. Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

    NARCIS (Netherlands)

    Kijlstra, W.S.; Poels, E.K.; Bliek, A.; Weckhuysen, B.M.; Schoonheydt, R.A.

    1996-01-01

    Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation of the acetate precursor solution, the [Mn(H2O)6]^2+ complex interacts strongly with

  20. Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

    NARCIS (Netherlands)

    Kijlstra, W.S.; Poels, E.K.; Bliek, A.; Weckhuysen, B.M.; Schoonheydt, R.A.

    2001-01-01

    Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation of the acetate precursor solution, the [Mn(H2O)6]^2+ complex interacts strongly with sur

  1. L-DOPA-Coated Manganese Oxide Nanoparticles as Dual MRI Contrast Agents and Drug-Delivery Vehicles.

    Science.gov (United States)

    McDonagh, Birgitte Hjelmeland; Singh, Gurvinder; Hak, Sjoerd; Bandyopadhyay, Sulalit; Augestad, Ingrid Lovise; Peddis, Davide; Sandvig, Ioanna; Sandvig, Axel; Glomm, Wilhelm Robert

    2016-01-20

    Manganese oxide nanoparticles (MONPs) are capable of time-dependent magnetic resonance imaging contrast switching as well as releasing a surface-bound drug. MONPs give T2/T2* contrast, but dissolve and release T1-active Mn(2+) and L-3,4-dihydroxyphenylalanine. Complementary images are acquired with a single contrast agent, and applications toward Parkinson's disease are suggested.

  2. Study of interaction and adsorption of aromatic amines by manganese oxides and their role in chemical evolution

    Science.gov (United States)

    Bhushan, Brij; Nayak, Arunima; Kamaluddin

    2017-04-01

    The role of manganese oxides in concentrating organic moieties and offering catalytic activity for prebiotic reactions is investigated by studying their interaction with different aromatic amines such as aniline, p-chloroaniline, p-toluidine and p-anisidine. For all amines, metal oxides showed highest adsorption at neutral pH. The order of their adsorption capacity and affinity as revealed by the Langmuir constants was found to be manganosite (MnO) > bixbyite (Mn2O3) > hausmannite (Mn3O4) > and pyrolusite (MnO2). At alkaline pH, these manganese oxides offered their surfaces for oxidation of amines to form coloured oligomers. Analysis of the oxidation products by gas chromatography-mass spectrometry showed the formation of a dimer from p-anisidine and p-chloroaniline, while a trimer and tetramer is formed from p-toluidine and aniline, respectively. A reaction mechanism is proposed for the formation of the oligomers. While field-emission scanning electron microscopic studies confirm the binding phenomenon, the Fourier transform infrared spectroscopy analysis suggests that the mechanism of binding of amines on the manganese oxides was primarily electrostatic. The adsorption behaviour of the studied aromatic amines followed the order: p-anisidine > p-toluidine > aniline > p-chloroaniline, which is related to the basicities and structure of the amines. Our studies confirmed the significance of the role of manganese oxides in prebiotic chemistry.

  3. Reduction of ripening time of full-scale manganese removal filters with manganese oxide-coated media

    NARCIS (Netherlands)

    Bruins, J.H.; Petrusevski, B.; Slokar, Y.M.; Huysman, K.; Joris, K.; Kruithof, J.C.; Kennedy, M.D.

    2015-01-01

    Effective manganese removal by conventional aeration-filtration with virgin filter media requires a long ripening time. The aim of this study was to assess the potential of manganese oxide-coated media to shorten the ripening time of filters with virgin media, under practical conditions. A full scal

  4. Transport and magnetic properties of the micro-fabricated perovskite-type manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Masuno, Atsunobu; Terashima, Takahito; Takano, Mikio

    2003-05-01

    We studied the resistivity under pulsed high electric field for thin films and micro-meter sized wires of perovskite-type manganese oxide, Pr{sub 0.65}Ca{sub 0.35}MnO{sub 3} (PCMO). The thin films were prepared by the pulsed laser deposition method. Wires of the oxides were fabricated by the electron-beam lithography and Ar-ion etching methods. By applying a pulsed electric field upto 5x10{sup 5} V/cm with a duration of 10 ms, the resistivity of the wire with the size of 10 {mu}mx10 {mu}m reduced by 60% at 150 K.

  5. Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

    Directory of Open Access Journals (Sweden)

    Shu Taira, Kenji Kitajima, Hikaru Katayanagi, Eiichiro Ichiishi and Yuko Ichiyanagi

    2009-01-01

    Full Text Available We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm and developed nanoparticle-assited laser desorption/ionization (nano-PALDI mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB, 4-hydroxy-α-cinnamic acid (CHCA and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

  6. Formation of nickel-manganese oxide thermistors studied by XRD, SEM and auger spectroscopy

    Science.gov (United States)

    Azimi-Nam, S.; Golestani-Fard, F.; Hashemi, T.

    1987-03-01

    This paper describes the formation of nickel-manganeses oxide thermistor bodies at 1000 1340° C, employing analytical techniques of XRD, SEM/EPMA and AES. The micro-structural studies revealed that the main phase of nickel manganite coexists with a solid solution of NiO in Mn3O4 in the final product. The optimum firing conditions to achieve the necessary electrical properties as well as the development of the desired microstructure could be selected around 1200° C, for 4 hrs in an ambient atmosphere. Above this temperature, the density begins to decrease while the resistivity increases. These anomalous electrical resistivity variations could be partly attributed to the trapped oxygen which was evolved from the decomposition of the unreacted α-Mn2O3. At-lower temperatures, unreacted nickel oxide residuals as well as a high porosity of the samples would yield specimens with high resistivity.

  7. Natural manganese oxides as catalysts for oxidative coupling of methane: a structural and degradation study

    Energy Technology Data Exchange (ETDEWEB)

    Ioffe, L.M.; Bosch, P.; Viveros, T.; Sanchez, H.; Borodko, Y.G. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico (Mexico). Dept. of Chem.

    1997-12-01

    Natural manganese oxides were evaluated as oxidative coupling catalysts to convert methane into C{sub 2}-hydrocarbons. Reactions were done in a cyclic redox mode in which the oxidized catalyst was reacted with methane at 850 C in the absence of oxygen. The bulk and surface analyses (XRD, XPS, FT-IR) indicate that the catalyst deactivation in the methane atmosphere is related to reduction of manganese ions, oxygen depletion of the catalyst surface and formation of manganese carbide species. It is proposed that the XPS line of O1s electrons, Eb=528.6 eV should be assigned to the surface oxygen bound to the reduced Mn{sup 2+} cation with close oxygen vacancies, and lines ofMn2p{sub 3/2} electrons, Eb=641 eV and C1s at 282.5 eV may be assigned to the surface manganese carbide. (orig.) 27 refs.

  8. Manganese oxides supported on gold nanoparticles: new findings and current controversies for the role of gold.

    Science.gov (United States)

    Najafpour, Mohammad Mahdi; Hosseini, Seyedeh Maedeh; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

    2015-12-01

    We synthesized manganese oxides supported on gold nanoparticles (diameter gold nanoparticles under hydrothermal conditions. In this green method Mn oxide is deposited on the gold nanoparticles. The compounds were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activities of these compounds in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant were studied. The results show that these compounds are good catalysts toward water oxidation with a turnover frequency of 1.0 ± 0.1 (mmol O2/(mol Mn·s)). A comparison with other previously reported Mn oxides and important factors influencing the water-oxidizing activities of Mn oxides is also discussed.

  9. Fast degradation of dyes in water using manganese-oxide-coated diatomite for environmental remediation

    Science.gov (United States)

    Dang, Trung-Dung; Banerjee, Arghya Narayan; Tran, Quang-Tung; Roy, Sudipta

    2016-11-01

    By a simple wet-chemical procedure using a permanganate in the acidic medium, diatomite coated with amorphous manganese oxide nanoparticles was synthesized. The structural, microstructural and morphological characterizations of the as-synthesized catalysts confirmed the nanostructure of MnO2 and its stabilization on the support - diatomite. The highly efficient and rapid degradation of methylene blue and methyl orange over synthesized MnO2 coated Diatomite has been carried out. The results revealed considerably faster degradation of the dyes against the previously reported data. The proposed mechanism of the dye-degradation is considered to be a combinatorial effect of chemical, physicochemical and physical processes. Therefore, the fabricated catalysts have potential application in waste water treatment, and pollution degradation for environmental remediation.

  10. Manganese oxide octahedral molecular sieves as insertion electrodes for rechargeable Mg batteries

    KAUST Repository

    Rasul, Shahid

    2013-11-01

    Magnesium has been inserted electrochemically into manganese oxide octahedral molecular sieves (OMS-5 MnO2) at room temperature. Discharge/charge profiles show that a large amount of Mg, i.e., 0.37 Mg/Mn can be inserted electrochemically using 1 M Mg(ClO4)2/AN electrolyte when OMS-5 is prepared in presence of acetylene black. X-ray diffraction analysis and discharge/charge profiles verify that a solid state solution reaction takes place upon Mg insertion into the host lattice with concurrent reduction of Mn4+ to Mn2+. However, upon each reduction of Mn by Mg insertion and resultant dissolution into electrolyte, decrease in the active compound occurs consequently. A low intrinsic electronic conductivity of OMS-5 was suggested to play a vital role in Mg insertion into the host. © 2013 Elsevier Ltd.

  11. Heterogeneous catalytic ozonation of ciprofloxacin in water with carbon nanotube supported manganese oxides as catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Sui, Minghao, E-mail: suiminghao.sui@gmail.com [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Xing, Sichu; Sheng, Li; Huang, Shuhang; Guo, Hongguang [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Ciprofloxacin in water was degraded by heterogeneous catalytic ozonation. Black-Right-Pointing-Pointer MnOx were supported on MWCNTs to serve as catalyst for ozonation. Black-Right-Pointing-Pointer MnOx/MWCNT exhibited highly catalytic activity on ozonation of ciprofloxacin in water. Black-Right-Pointing-Pointer MnOx/MWCNT resulted in effective antibacterial activity inhibition on ciprofloxacin. Black-Right-Pointing-Pointer MnOx/MWCNT promoted the generation of hydroxyl radicals. - Abstract: Carbon nanotube-supported manganese oxides (MnOx/MWCNT) were used as catalysts to assist ozone in degrading ciprofloxacin in water. Manganese oxides were successfully loaded on multi-walled carbon nanotube surfaces by simply impregnating the carbon nanotube with permanganate solution. The catalytic activities of MnOx/MWCNT in ciprofloxacin ozonation, including degradation, mineralization effectiveness, and antibacterial activity change, were investigated. The presence of MnOx/MWCNT significantly elevated the degradation and mineralization efficiency of ozone on ciprofloxacin. The microbiological assay with a reference Escherichia coli strain indicated that ozonation with MnOx/MWCNT results in more effective antibacterial activity inhibition of ciprofloxacin than that in ozonation alone. The effects of catalyst dose, initial ciprofloxacin concentration, and initial pH conditions on ciprofloxacin ozonation with MnOx/MWCNT were surveyed. Electron spin resonance trapping was applied to assess the role of MnOx/MWCNT in generating hydroxyl radicals (HO{center_dot}) during ozonation. Stronger 5,5-dimethyl-1-pyrroline-N-oxide-OH signals were observed in the ozonation with MnOx/MWCNT compared with those in ozonation alone, indicating that MnOx/MWCNT promoted the generation of hydroxyl radicals. The degradation of ciprofloxacin was studied in drinking water and wastewater process samples to gauge the potential effects of water background matrix on

  12. Tuning the Synthesis of Manganese Oxides Nanoparticles for Efficient Oxidation of Benzyl Alcohol.

    Science.gov (United States)

    Fei, Jingyuan; Sun, Lixian; Zhou, Cuifeng; Ling, Huajuan; Yan, Feng; Zhong, Xia; Lu, Yuxiang; Shi, Jeffrey; Huang, Jun; Liu, Zongwen

    2017-12-01

    The liquid phase oxidation of benzyl alcohol is an important reaction for generating benzaldehyde and benzoic acid that are largely required in the perfumery and pharmaceutical industries. The current production systems suffer from either low conversion or over oxidation. From the viewpoint of economy efficiency and environmental demand, we are aiming to develop new high-performance and cost-effective catalysts based on manganese oxides that can allow the green aerobic oxidation of benzyl alcohol under mild conditions. It was found that the composition of the precursors has significant influence on the structure formation and surface property of the manganese oxide nanoparticles. In addition, the crystallinity of the resulting manganese nanoparticles was gradually improved upon increasing the calcination temperature; however, the specific surface area decreased obviously due to pore structure damage at higher calcination temperature. The sample calcined at the optimal temperature of 600 °C from the precursors without porogen was a Mn3O4-rich material with a small amount of Mn2O3, which could generate a significant amount of [Formula: see text] species on the surface that contributed to the high catalytic activity in the oxidation. Adding porogen with precursors during the synthesis, the obtained catalysts were mainly Mn2O3 crystalline, which showed relatively low activity in the oxidation. All prepared samples showed high selectivity for benzaldehyde and benzoic acid. The obtained catalysts are comparable to the commercial OMS-2 catalyst. The synthesis-structure-catalysis interaction has been addressed, which will help for the design of new high-performance selective oxidation catalysts.

  13. Tuning the Synthesis of Manganese Oxides Nanoparticles for Efficient Oxidation of Benzyl Alcohol

    Science.gov (United States)

    Fei, Jingyuan; Sun, Lixian; Zhou, Cuifeng; Ling, Huajuan; Yan, Feng; Zhong, Xia; Lu, Yuxiang; Shi, Jeffrey; Huang, Jun; Liu, Zongwen

    2017-01-01

    The liquid phase oxidation of benzyl alcohol is an important reaction for generating benzaldehyde and benzoic acid that are largely required in the perfumery and pharmaceutical industries. The current production systems suffer from either low conversion or over oxidation. From the viewpoint of economy efficiency and environmental demand, we are aiming to develop new high-performance and cost-effective catalysts based on manganese oxides that can allow the green aerobic oxidation of benzyl alcohol under mild conditions. It was found that the composition of the precursors has significant influence on the structure formation and surface property of the manganese oxide nanoparticles. In addition, the crystallinity of the resulting manganese nanoparticles was gradually improved upon increasing the calcination temperature; however, the specific surface area decreased obviously due to pore structure damage at higher calcination temperature. The sample calcined at the optimal temperature of 600 °C from the precursors without porogen was a Mn3O4-rich material with a small amount of Mn2O3, which could generate a significant amount of {O}_2- species on the surface that contributed to the high catalytic activity in the oxidation. Adding porogen with precursors during the synthesis, the obtained catalysts were mainly Mn2O3 crystalline, which showed relatively low activity in the oxidation. All prepared samples showed high selectivity for benzaldehyde and benzoic acid. The obtained catalysts are comparable to the commercial OMS-2 catalyst. The synthesis-structure-catalysis interaction has been addressed, which will help for the design of new high-performance selective oxidation catalysts.

  14. Thin film passivation of laser generated 3D micro patterns in lithium manganese oxide cathodes

    Science.gov (United States)

    Pröll, J.; Kohler, R.; Bruns, M.; Oberst, V.; Weidler, P. G.; Heißler, S.; Kübel, C.; Scherer, T.; Prang, R.; Seifert, H. J.; Pfleging, W.

    2013-03-01

    The increasing need for long-life lithium-ion batteries requires the further development of electrode materials. Especially on the cathode side new materials or material composites are needed to increase the cycle lifetime. On the one hand, spinel-type lithium manganese oxide is a promising candidate to be used as cathode material due to its non-toxicity, low cost and good thermal stability. On the other hand, the spinel structure suffers from change in the oxidation state of manganese during cycling which is also accompanied by loss of active material into the liquid electrolyte. The general trend is to enhance the active surface area of the cathode in order to increase lithium-ion mobility through the electrode/electrolyte interface, while an enhanced surface area will also promote chemical degradation. In this work, laser microstructuring of lithium manganese oxide thin films was applied in a first step to increase the active surface area. This was done by using 248 nm excimer laser radiation and chromium/quartz mask imaging techniques. In a second step, high power diode laser-annealing operating at a wavelength of 940 nm was used for forming a cubic spinel-like battery phase. This was verified by means of Raman spectroscopy and cyclic voltammetric measurements. In a last step, the laser patterned thin films were coated with indium tin oxide (ITO) layers with a thickness of 10 nm to 50 nm. The influence of the 3D surface topography as well as the ITO thickness on the electrochemical performance was studied by cyclic voltammetry. Post-mortem studies were carried out by using scanning electron microscopy and focused ion beam analysis.

  15. Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases.

    Science.gov (United States)

    Long, Jeffrey W; Wallace, Jean M; Peterson, Gregory W; Huynh, Kim

    2016-01-20

    We demonstrate that sol-gel-derived manganese oxide (MnOx) nanoarchitectures exhibit broad-spectrum filtration activity for three chemically diverse toxic gases: NH3, SO2, and H2S. Manganese oxides are synthesized via the reaction of NaMnO4 and fumaric acid to form monolithic gels of disordered, mixed-valent Na-MnOx; incorporated Na(+) is readily exchanged for H(+) by subsequent acid rinsing to form a more crystalline H-MnOx phase. For both Na-MnOx and H-MnOx forms, controlled pore-fluid removal yields either densified, yet still mesoporous, xerogels or low-density aerogels (prepared by drying from supercritical CO2). The performance of these MnOx nanoarchitectures as filtration media is assessed using dynamic-challenge microbreakthrough protocols. We observe technologically relevant sorption capacities under both dry conditions and wet (80% relative humidity) for each of the three toxic industrial chemicals investigated. The Na-MnOx xerogels and aerogels provide optimal performance with the aerogel exhibiting maximum sorption capacities of 39, 200, and 680 mg g(-1) for NH3, SO2, and H2S, respectively. Postbreakthrough characterization using X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms that NH3 is captured and partially protonated within the MnOx structure, while SO2 undergoes oxidation by the redox-active oxide to form adsorbed sulfate at the MnOx surface. Hydrogen sulfide is also oxidized to form a combination of sulfate and sulfur/polysulfide products, concomitant with a decrease in the average Mn oxidation state from 3.43 to 2.94 and generation of a MnOOH phase.

  16. Synthesis and characterization of carbon black/manganese oxide air cathodes for zinc-air batteries: Effects of the crystalline structure of manganese oxides

    Science.gov (United States)

    Li, Po-Chieh; Hu, Chi-Chang; Noda, Hiroyuki; Habazaki, Hiroki

    2015-12-01

    Manganese oxides (MnOx) in α-, β-, γ-, δ-MnO2 phases, Mn3O4, Mn2O3, and MnOOH are synthesized for systematically comparing their electrocatalytic activity of the oxygen reduction reaction (ORR) in the Zn-air battery application. The optimal MnOx/XC-72 mass ratio for the ORR is equal to 1 and the oxide crystalline structure effect on the ORR is compared. The order of composites with respect to decreasing the ORR activity is: α-MnO2/XC-72 > γ-MnO2/XC-72 > β-MnO2/XC-72 > δ-MnO2/XC-72 > Mn2O3/XC-72 > Mn3O4/XC-72 > MnOOH/XC-72. The textural properties of MnOx are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Electrochemical studies include linear sweep voltammetry (LSV), rotating ring-disk electrode (RRDE) voltammetry, and the full-cell discharge test. The discharge peak power density of Zn-air batteries varies from 61.5 mW cm-2 (α-MnO2/XC-72) to 47.1 mW cm-2 (Mn3O4/XC-72). The maximum peak power density is 102 mW cm-2 for the Zn-air battery with an air cathode containing α-MnO2/XC-72 under an oxygen atmosphere when the carbon paper is 10AA. The specific capacity of all full-cell tests is higher than 750 mAh g-1 at all discharge current densities.

  17. Thallium-isotopic compositions of euxinic sediments as a proxy for global manganese-oxide burial

    Science.gov (United States)

    Owens, Jeremy D.; Nielsen, Sune G.; Horner, Tristan J.; Ostrander, Chadlin M.; Peterson, Larry C.

    2017-09-01

    Thallium (Tl) isotopes are a new and potentially powerful paleoredox proxy that may track bottom water oxygen conditions based on the global burial flux of manganese oxides. Thallium has a residence time of ∼20 thousand years, which is longer than the ocean mixing time, and it has been inferred that modern oxic seawater is conservative with respect to both concentration and isotopes. Marine sources of Tl have nearly identical isotopic values. Therefore, the Tl sinks, adsorption onto manganese oxides and low temperature oceanic crust alteration (the dominant seawater output), are the primary controls of the seawater isotopic composition. For relatively short-term, ∼million years, redox events it is reasonable to assume that the dominant mechanism that alters the Tl isotopic composition of seawater is associated with manganese oxide burial because large variability in low temperature ocean crust alteration is controlled by long-term, multi-million years, average ocean crust production rates. This study presents new Tl isotope data for an open ocean transect in the South Atlantic, and depth transects for two euxinic basins (anoxic and free sulfide in the water column), the Cariaco Basin and Black Sea. The Tl isotopic signature of open ocean seawater in the South Atlantic was found to be homogeneous with ε205Tl = -6.0 ± 0.3 (±2 SD, n = 41) while oxic waters from Cariaco and the Black Sea are -5.6 and -2.2, respectively. Combined with existing data from the Pacific and Arctic Oceans, our Atlantic data establish the conservatism of Tl isotopes in the global ocean. In contrast, partially- and predominantly-restricted basins reveal Tl isotope differences that vary between open-ocean (-6) and continental material (-2) ε205Tl, scaling with the degree of restriction. Regardless of the differences between basins, Tl is quantitatively removed from their euxinic waters below the chemocline. The burial of Tl in euxinic sediments is estimated to be an order of magnitude

  18. Structural and optical properties of manganese oxide thin films deposited by pulsed laser deposition at different substrate temperatures

    Science.gov (United States)

    Jamil, H.; Khaleeq-ur-Rahman, M.; Dildar, I. M.; Shaukat, Saima

    2017-09-01

    We report the use of pulsed laser deposition (PLD) to grow manganese oxide thin films at a fixed low oxygen pressure at different temperatures on silicon (1 0 0) substrates. Structural properties of the thin films were examined using x-ray diffraction and Fourier transform infrared spectroscopy. Surface morphology and topography of the films was determined using atomic force microscopy and optical microscopy, while optical properties of the thin films were studied using spectroscopic ellipsometry. It was found that PLD is a convenient technique to deposit different phases of manganese oxide by tuning the deposition temperature. All measured physical properties such as morphology, topography, crystallite size, and optical band gap were clearly dependent on the substrate temperature chosen.

  19. Solution Layer Deposition: A Technique for the Growth of Ultra-Pure Manganese Oxides on Silica at Room Temperature.

    Science.gov (United States)

    Cure, Jérémy; Piettre, Kilian; Coppel, Yannick; Beche, Eric; Esvan, Jérôme; Collière, Vincent; Chaudret, Bruno; Fau, Pierre

    2016-02-24

    With the ever increasing miniaturization in microelectronic devices, new deposition techniques are required to form high-purity metal oxide layers. Herein, we report a liquid route to specifically produce thin and conformal amorphous manganese oxide layers on silicon substrate, which can be transformed into a manganese silicate layer. The undesired insertion of carbon into the functional layers is avoided through a solution metal-organic chemistry approach named Solution Layer Deposition (SLD). The growth of a pure manganese oxide film by SLD takes place through the decoordination of ligands from a metal-organic complex in mild conditions, and coordination of the resulting metal atoms on a silica surface. The mechanism of this chemical liquid route has been elucidated by solid-state (29) Si MAS NMR, XPS, SIMS, and HRTEM.

  20. Recovery of manganese oxides from spent alkaline and zinc–carbon batteries. An application as catalysts for VOCs elimination

    Energy Technology Data Exchange (ETDEWEB)

    Gallegos, María V., E-mail: plapimu@yahoo.com.ar [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina); Falco, Lorena R., E-mail: mlfalco@quimica.unlp.edu.ar [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina); Peluso, Miguel A., E-mail: apelu@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas, “Dr. J. Ronco” CINDECA (CONICET CCT La Plata), 47 N°257, La Plata, Buenos Aires (Argentina); Sambeth, Jorge E., E-mail: sambeth@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas, “Dr. J. Ronco” CINDECA (CONICET CCT La Plata), 47 N°257, La Plata, Buenos Aires (Argentina); Thomas, Horacio J. [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina)

    2013-06-15

    Highlights: • Manganese oxides were synthesized using spent batteries as raw materials. • Spent alkaline and zinc–carbon size AA batteries were used. • A biohydrometallurgical process was employed to bio-lixiviate batteries. • Manganese oxides were active in the oxidation of VOCs (ethanol and heptane). - Abstract: Manganese, in the form of oxide, was recovered from spent alkaline and zinc–carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO{sub 4} solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnO{sub x} synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn{sub 2}O{sub 3} in the EMO and the CMO samples, together with some Mn{sup 4+} cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn{sub 3}O{sub 4}. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200 °C, while heptane requires more than 400 °C. The CMO has the highest oxide selectivity to CO{sub 2}. The results show that manganese oxides obtained using spent alkaline and zinc–carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs.

  1. Behavior of argon gas release from manganese oxide minerals as revealed by 40Ar/39Ar laser incremental heating analysis

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Manganese oxides in association with paleo- weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus andconsistent isochron ages, confirming the feasibility dating very-fined supergene manganese oxides by 40Ar/39Ar technique. Two distinct structural sites hostingAr isotopes can be identified in light of their degassing behaviors obtained byincremental heating analyses. The first site, releasing its gas fraction at thelaser power 0.2-0.4 W, yields primarily 40Aratm, 38Aratm, and 36Aratm (atmospheric Ar isotopes). The second sites yield predominantly 40Ar* (radiogenic 40Ar),39ArK, and 38ArK (nucleogenic components), at ~0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of 40Ar*, 39ArK, and 38ArK suggests that these isotopes occupy the same crystallographic sites and that 39ArK lossfrom the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric 40Ar nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geochronological information by analyzing supergene manganese oxides minerals.

  2. The role of electronic and ionic conductivities in the rate performance of tunnel structured manganese oxides in Li-ion batteries

    Directory of Open Access Journals (Sweden)

    B. W. Byles

    2016-04-01

    Full Text Available Single nanowires of two manganese oxide polymorphs (α-MnO2 and todorokite manganese oxide, which display a controlled size variation in terms of their square structural tunnels, were isolated onto nanofabricated platforms using dielectrophoresis. This platform allowed for the measurement of the electronic conductivity of these manganese oxides, which was found to be higher in α-MnO2 as compared to that of the todorokite phase by a factor of ∼46. Despite this observation of substantially higher electronic conductivity in α-MnO2, the todorokite manganese oxide exhibited better electrochemical rate performance as a Li-ion battery cathode. The relationship between this electrochemical performance, the electronic conductivities of the manganese oxides, and their reported ionic conductivities is discussed for the first time, clearly revealing that the rate performance of these materials is limited by their Li+ diffusivity, and not by their electronic conductivity. This result reveals important new insights relevant for improving the power density of manganese oxides, which have shown promise as a low-cost, abundant, and safe alternative for next-generation cathode materials. Furthermore, the presented experimental approach is suitable for assessing a broader family of one-dimensional electrode active materials (in terms of their electronic and ionic conductivities for both Li-ion batteries and for electrochemical systems utilizing charge-carrying ions beyond Li+.

  3. Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

    Institute of Scientific and Technical Information of China (English)

    DONG De-ming; ZHAO Xing-min; HUA Xiu-yi; ZHANG Jing-jing; WU Shi-ming

    2007-01-01

    Natural surface coatings collected from natural substances(NSCsNS) were employed to study the roles of the main chemical components (iron oxides, manganese oxides, and other components) in controlling the adsorption of lead(Pb) and cadmium(Cd) in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component.Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

  4. Mechanisms of Bond Cleavage during Manganese Oxide and UV Degradation of Glyphosate: Results from Phosphate Oxygen Isotopes and Molecular Simulations.

    Science.gov (United States)

    Jaisi, Deb P; Li, Hui; Wallace, Adam F; Paudel, Prajwal; Sun, Mingjing; Balakrishna, Avula; Lerch, Robert N

    2016-11-16

    Degradation of glyphosate in the presence of manganese oxide and UV light was analyzed using phosphate oxygen isotope ratios and density function theory (DFT). The preference of C-P or C-N bond cleavage was found to vary with changing glyphosate/manganese oxide ratios, indicating the potential role of sorption-induced conformational changes on the composition of intermediate degradation products. Isotope data confirmed that one oxygen atom derived solely from water was incorporated into the released phosphate during glyphosate degradation, and this might suggest similar nucleophilic substitution at P centers and C-P bond cleavage both in manganese oxide- and UV light-mediated degradation. The DFT results reveal that the C-P bond could be cleaved by water, OH(-) or (•)OH, with the energy barrier opposing bond dissociation being lowest in the presence of the radical species, and that C-N bond cleavage is favored by the formation of both nitrogen- and carbon-centered radicals. Overall, these results highlight the factors controlling the dominance of C-P or C-N bond cleavage that determines the composition of intermediate/final products and ultimately the degradation pathway.

  5. The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry.

    Science.gov (United States)

    Wang, Xinghao; Liu, Jiaoqin; Qu, Ruijuan; Wang, Zunyao; Huang, Qingguo

    2017-08-10

    Nanostructured manganese oxides, e.g. MnO2, have shown laccase-like catalytic activities, and are thus promising for pollutant oxidation in wastewater treatment. We have systematically compared the laccase-like reactivity of manganese oxide nanomaterials of different crystallinity, including α-, β-, γ-, δ-, and ɛ-MnO2, and Mn3O4, with 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 17β-estradiol (E2) as the probing substrates. The reaction rate behaviors were examined with regard to substrate oxidation and oxygen reduction to evaluate the laccase-like catalysis of the materials, among which γ-MnO2 exhibits the best performance. Cyclic voltammetry (CV) was employed to assess the six MnOx nanomaterials, and the results correlate well with their laccase-like catalytic activities. The findings help understand the mechanisms of and the factors controlling the laccase-like reactivity of different manganese oxides nanomaterials, and provide a basis for future design and application of MnOx-based catalysts.

  6. Identification and structural analysis of an L-asparaginase enzyme from guinea pig with putative tumor cell killing properties.

    Science.gov (United States)

    Schalk, Amanda M; Nguyen, Hien-Anh; Rigouin, Coraline; Lavie, Arnon

    2014-11-28

    The initial observation that guinea pig serum kills lymphoma cells marks the serendipitous discovery of a new class of anti-cancer agents. The serum cell killing factor was shown to be an enzyme with L-asparaginase (ASNase) activity. As a direct result of this observation, several bacterial L-asparaginases were developed and are currently approved by the Food and Drug Administration for the treatment of the subset of hematological malignancies that are dependent on the extracellular pool of the amino acid asparagine. As drugs, these enzymes act to hydrolyze asparagine to aspartate, thereby starving the cancer cells of this amino acid. Prior to the work presented here, the precise identity of this guinea pig enzyme has not been reported in the peer-reviewed literature. We discovered that the guinea pig enzyme annotated as H0W0T5_CAVPO, which we refer to as gpASNase1, has the required low Km property consistent with that possessed by the cell-killing guinea pig serum enzyme. Elucidation of the ligand-free and aspartate complex gpASNase1 crystal structures allows a direct comparison with the bacterial enzymes and serves to explain the lack of L-glutaminase activity in the guinea pig enzyme. The structures were also used to generate a homology model for the human homolog hASNase1 and to help explain its vastly different kinetic properties compared with gpASNase1, despite a 70% sequence identity. Given that the bacterial enzymes frequently present immunogenic and other toxic side effects, this work suggests that gpASNase1 could be a promising alternative to these bacterial enzymes.

  7. Identification and Structural Analysis of an l-Asparaginase Enzyme from Guinea Pig with Putative Tumor Cell Killing Properties*

    Science.gov (United States)

    Schalk, Amanda M.; Nguyen, Hien-Anh; Rigouin, Coraline; Lavie, Arnon

    2014-01-01

    The initial observation that guinea pig serum kills lymphoma cells marks the serendipitous discovery of a new class of anti-cancer agents. The serum cell killing factor was shown to be an enzyme with l-asparaginase (ASNase) activity. As a direct result of this observation, several bacterial l-asparaginases were developed and are currently approved by the Food and Drug Administration for the treatment of the subset of hematological malignancies that are dependent on the extracellular pool of the amino acid asparagine. As drugs, these enzymes act to hydrolyze asparagine to aspartate, thereby starving the cancer cells of this amino acid. Prior to the work presented here, the precise identity of this guinea pig enzyme has not been reported in the peer-reviewed literature. We discovered that the guinea pig enzyme annotated as H0W0T5_CAVPO, which we refer to as gpASNase1, has the required low Km property consistent with that possessed by the cell-killing guinea pig serum enzyme. Elucidation of the ligand-free and aspartate complex gpASNase1 crystal structures allows a direct comparison with the bacterial enzymes and serves to explain the lack of l-glutaminase activity in the guinea pig enzyme. The structures were also used to generate a homology model for the human homolog hASNase1 and to help explain its vastly different kinetic properties compared with gpASNase1, despite a 70% sequence identity. Given that the bacterial enzymes frequently present immunogenic and other toxic side effects, this work suggests that gpASNase1 could be a promising alternative to these bacterial enzymes. PMID:25320094

  8. Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Brown Jr., G. E.; Chambers, S. A.

    1999-10-31

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

  9. Catalytic ozonation of selected pharmaceuticals over mesoporous alumina-supported manganese oxide.

    Science.gov (United States)

    Yang, Li; Hu, Chun; Nie, Yulun; Qu, Jiuhui

    2009-04-01

    Catalytic ozonation of five pharmaceutical compounds (PhACs)-phenazone, ibuprofen, diphenhydramine, phenytoin, and diclofenac sodium in alumina-supported manganese oxide (MnOx) suspension was carried out with a semicontinuous laboratory reactor. MnOx supported by mesoporous alumina (MnOx/MA) was highly effective in mineralizing the PhACs in aqueous solution. Fourier transform infrared (FTIR) spectroscopy and in situ attenuated total reflection FTIR (ATR-FTIR) spectroscopy were used to examine the interaction of ozone with different catalysts undervarious conditions. The crucial active sites, surface oxide species at 1380 cm(-1), were formed by the interaction of ozone with Lewis acid sites on the alumina surface. New surface hydroxyl groups at 2915 and 2845 cm(-1) were produced by the interaction of the catalyst and ozone in aqueous suspension and became active sites in the presence of MnOx. The introduction of MnOx enhanced the formation and activation of surface hydroxyl groups, causing higher catalytic reactivity. On the basis of these findings, a reaction mechanism is proposed for the catalytic ozonation of PhACs in MnOx/MA suspension.

  10. Platinum nanoparticles–manganese oxide nanorods as novel binary catalysts for formic acid oxidation

    Directory of Open Access Journals (Sweden)

    Mohamed S. El-Deab

    2012-01-01

    Full Text Available The current study proposes a novel binary catalyst system (composed of metal/metal oxide nanoparticles as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt and manganese oxide nanorods (nano-MnOx electrodeposited onto glassy carbon (GC electrodes. Cyclic voltammetric (CV measurements showed that unmodified GC and nano-MnOx/GC electrodes have no catalytic activity. While two oxidation peaks were observed at nano-Pt/GC electrode at ca. 0.2 and 0.55 V (corresponding to the direct oxidation of formic acid and the oxidation of the poisoning CO intermediate, respectively. The combined use of nano-MnOx and nano-Pt results in superb enhancement of the direct oxidation pathway. Nano-MnOx is shown to facilitate the oxidation of CO (to CO2 by providing oxygen at low over-potential. This leads to retrieval of Pt active sites necessary for the direct oxidation of formic acid. The higher catalytic activity of nano-MnOx/nano-Pt/GC electrode (with Pt firstly deposited compared to its mirror image electrode (i.e., with MnOx firstly deposited, nano-Pt/nano-MnOx/GC reveals that the order of the electrodeposition is an essential parameter.

  11. Selective catalytic oxidation of NO over iron and manganese oxides supported on mesoporous silica

    Institute of Scientific and Technical Information of China (English)

    Junfeng Zhang; Yan Huang; Xia Chen

    2008-01-01

    The selective catalytic oxidation (SCO)of NO was studied on a catalyst consisting of iron-manganese oxide supported on mesoporous silica (MPS) with different Mn/Fe ratios.Effects of the amount of manganese and iron,oxygen,and calcination temperature on NO conversion were also investigated.It was found that the Mn-Fe/MPS catalyst with a Mn/Fe molar ratio of l showed the highest activity at the calcination temperature of 400℃.The results showed that over this catalyst,NO conversion reached 70%under the condition of 280℃ and a space velocity of 5000 h-1.SO2 and H2O had no adverse impact on the reaction activity when the SCO reaction temperature was above 240℃.In addition,the SCO activity was suppressed gradually in the presence of SO2 and H2O below 240℃.and such an effect was reversible after heating treatment.

  12. A sodium layered manganese oxides as 3V cathode materials for secondary lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Bach, S.; Pereira-Ramos, J.P. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France); Willmann, P. [CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France)

    2006-10-25

    The synthesis of a new anhydrous sodium manganese oxide {alpha}-Na{sub 0.66}MnO{sub 2.13} obtained via a sol-gel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a=2.84A, c=11.09A) allows to get a high and stable specific capacity of 180mAhg{sup -1} at C/20 in the cycling limits 4.3/2V with a mean working voltage of 3V without the emergence of a spinel phase. By introducing acetylene black in solution during the sol-gel reaction, a composite material containing 8wt.% AB has been obtained. The rate capability is shown to be significantly improved leading to an increase of the available specific capacity with for instance 200 and 90mAhg{sup -1} at C/20 and C rate. This effect is ascribed to a better electronic contact between particles and/or the modification of the oxide surface which makes the intercalation process more homogeneous and more efficient. (author)

  13. A sodium layered manganese oxides as 3 V cathode materials for secondary lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Bach, S. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France)]. E-mail: bach@glvt-cnrs.fr; Pereira-Ramos, J.P. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France); CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France); Willmann, P. [CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France)

    2006-10-25

    The synthesis of a new anhydrous sodium manganese oxide {alpha}-Na{sub 0.66}MnO{sub 2.13} obtained via a sol-gel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a = 2.84 A, c = 11.09 A) allows to get a high and stable specific capacity of 180 mAh g{sup -1} at C/20 in the cycling limits 4.3/2 V with a mean working voltage of 3 V without the emergence of a spinel phase. By introducing acetylene black in solution during the sol-gel reaction, a composite material containing 8 wt.% AB has been obtained. The rate capability is shown to be significantly improved leading to an increase of the available specific capacity with for instance 200 and 90 mAh g{sup -1} at C/20 and C rate. This effect is ascribed to a better electronic contact between particles and/or the modification of the oxide surface which makes the intercalation process more homogeneous and more efficient.

  14. Catalytic ozonation of fenofibric acid over alumina-supported manganese oxide.

    Science.gov (United States)

    Rosal, Roberto; Gonzalo, María S; Rodríguez, Antonio; García-Calvo, Eloy

    2010-11-15

    The catalytic ozonation of fenofibric acid was studied using activated alumina and alumina-supported manganese oxide in a semicontinuous reactor. The rate constants at 20°C for the non-catalytic reaction of fenofibric acid with ozone and hydroxyl radicals were 3.43±0.20 M(-1) s(-1) and (6.55±0.33)×10(9) M(-1) s(-1), respectively. The kinetic constant for the catalytic reaction between fenofibric acid and hydroxyl radicals did not differ significantly from that of homogeneous ozonation, either using Al(2)O(3) or MnO(x)/Al(2)O(3). The results showed a considerable increase in the generation of hydroxyl radicals due to the use of catalysts even in the case of catalytic runs performed using a real wastewater matrix. Both catalysts promoted the decomposition of ozone in homogeneous phase, but the higher production of hydroxyl radicals corresponded to the catalyst with more activity in terms of ozone decomposition. We did not find evidence of the catalysts having any effect on rate constants, which suggests that the reaction may not involve the adsorption of organics on catalyst surface.

  15. Adsorption of {sup 60}Co{sup 2+} on hydrous manganese oxide powder from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Granados Correa, F. [Inst. Nacional de Investigaciones Nucleares, Mexico (Mexico); Univ. Autonoma Metropolitana Iztapalapa, Mexico (Mexico); Jimenez-Becerril, J. [Inst. Nacional de Investigaciones Nucleares, Mexico (Mexico)

    2004-07-01

    Hydrous manganese oxide (HMO) was synthesized and its ability to sorb {sup 60}Co{sup 2+} from aqueous solution was studied under static conditions as a function of contact time, cobalt concentration (10{sup -2}-10{sup -7} M), temperature (303-333 K) and pH of adsorptive solution (2.2-11.4). X-ray diffraction was used in characterization of synthesized HMO. Low concentration of {sup 60}Co{sup 2+} solution, high pH and high temperature were the most favorable conditions for the adsorption process. The results show that the removal process is complete in 40 minutes, obeys a first order rate law and can be described using the Freundlich adsorption model. The standard enthalpy of the system was {delta}H{sup 0} = 12.5 {+-} 0.2 kJ mol{sup -1} and cobalt desorption indicates that the uptake process proceeds via cation exchange. The removal of cobalt ions by HMO appears to be endothermic and irreversible. The values of calculated {delta}G{sup 0} and {delta}S{sup 0} were -17.0 {+-} 3.0 kJ mol{sup -1} and (9.8 {+-} 0.2) x 10{sup -2} kJ K{sup -1} mol{sup -1} respectively, this indicates spontaneity of the process and the degree of freedom of ions is increased by adsorption. (orig.)

  16. Adsorption of Zn2+ from solutions on manganese oxide obtained via ozone precipitation reaction

    Directory of Open Access Journals (Sweden)

    Contreras-Bustos Roberto

    2016-03-01

    Full Text Available Synthesis via ozone precipitation reaction was used to obtain manganese dioxide (OMD and it was probed as an adsorbent for zinc ions. Adsorption was followed along shaking time and increasing ratio [NO3−] / [Zn2+], and isotherms were obtained at different pH values and in the presence of several anions (chloride, nitrate, sulphate, and acetate. It was found that adsorption equilibrium is fast and follows the pseudo-second order model (qe = 34 ±1 mg/g and K = 0.07 ±0.01 g/mg h. Isotherms were fitted to Langmuir, Freundlich, and Langmuir-Freundlich models, and the best fitting was found with the last one. The process is dependent on pH and the efficiency increases from pH 1 to 4. The ratio [NO3−] / [Zn2+] up to 3 does not seem to change the behaviour of the process. Regarding the anions, the efficiency of Zn(II adsorption occurs according to: acetate > nitrate and sulphate > chloride. Manganese oxide obtained via ozonization is an excellent adsorbent for zinc ions.

  17. Green synthesis of manganese oxide nanoparticles for the electrochemical sensing of p-nitrophenol

    Science.gov (United States)

    Kumar, Vineet; Singh, Kulvinder; Panwar, Shaily; Mehta, Surinder Kumar

    2017-03-01

    Manganese oxide (MnO) NPs are widely used in contaminant sensing, drug delivery, data storage, catalysis and biomedical imaging. Green synthesis of NPs is important due to increased concern of environmental pollution. Green chemistry based synthesis of NPs is preferred due to its ecofriendly nature. In this study, MnO NPs of different sizes were synthesized in aqueous medium using clove, i.e., Syzygium aromaticum extract (CE) as reducing and stabilizing agents. These NPs were used for the electrochemical sensing of p-nitrophenol (PNP). The synthesis of MnO NPs was over in 30 min. MnO NPs of different sizes were obtained by varying metal ion concentration, metal ion volume ratio, CE concentration, CE volume ratio, and incubation temperature. Selectively, 4 nm MnO NPs were used for electrochemical sensing of paranitrophenol. The MnO NPs modified gold electrodes detected PNP with good sensitivity, 0.16 µA µM-1 cm2. The limit of PNP detection was 15.65 µM. The MnO NPs prepared using CE based green chemistry approach is useful for PNP sensing. These NPs can also be useful for various in vivo applications in which the NPs come in human contact.

  18. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    Science.gov (United States)

    You, Fu-Tian; Yu, Guang-Wei; Wang, Yin; Xing, Zhen-Jiao; Liu, Xue-Jiao; Li, Jie

    2017-08-01

    Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnOx)-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnOx and the test conditions on the reaction. MLAC with 7.5 wt.% MnOx (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O2, room temperature and GHSV ca. 16000 h-1. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O2 concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnOx loading is assumed to be related to Mn4+/Mn3+ ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnOx lattice O transfer is proposed.

  19. Material characteristics of perovskite manganese oxide thin films for bolometric applications

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, A.; Rajeswari, M.; Shreekala, R.; Lofland, S.E.; Bhagat, S.M.; Boettcher, T.; Kwon, C.; Ramesh, R.; Venkatesan, T. [Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

    1997-10-01

    We are optimizing thin films of perovskite manganese oxides for bolometric applications. We have studied the relevant material characteristics of several members of this family namely, La{sub 0.7}Ba{sub 0.3}MnO{sub 3}, La{sub 0.7}Sr{sub 0.3}MnO{sub 3}, La{sub 0.7}Ca{sub 0.3}MnO{sub 3}, and Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3}. Here, we discuss issues related to the choice of material, the influence of deposition parameters, and postdeposition heat treatments on the relevant characteristics such as the resistivity-peak temperature (T{sub p}) and the temperature coefficient of resistance (TCR). For a given material, a higher peak temperature implies a larger temperature coefficient of resistance. In contrast, on comparing different material systems, the TCR tends to decrease as T{sub p} increases. {copyright} {ital 1997 American Institute of Physics.}

  20. Catalytic ozonation of fenofibric acid over alumina-supported manganese oxide

    Energy Technology Data Exchange (ETDEWEB)

    Rosal, Roberto, E-mail: roberto.rosal@uah.es [Departamento de Quimica Analitica e Ingenieria Quimica, Universidad de Alcala, E-28771 Alcala de Henares (Spain); Gonzalo, Maria S.; Rodriguez, Antonio; Garcia-Calvo, Eloy [Departamento de Quimica Analitica e Ingenieria Quimica, Universidad de Alcala, E-28771 Alcala de Henares (Spain)

    2010-11-15

    The catalytic ozonation of fenofibric acid was studied using activated alumina and alumina-supported manganese oxide in a semicontinuous reactor. The rate constants at 20 deg. C for the non-catalytic reaction of fenofibric acid with ozone and hydroxyl radicals were 3.43 {+-} 0.20 M{sup -1} s{sup -1} and (6.55 {+-} 0.33) x 10{sup 9} M{sup -1} s{sup -1}, respectively. The kinetic constant for the catalytic reaction between fenofibric acid and hydroxyl radicals did not differ significantly from that of homogeneous ozonation, either using Al{sub 2}O{sub 3} or MnO{sub x}/Al{sub 2}O{sub 3}. The results showed a considerable increase in the generation of hydroxyl radicals due to the use of catalysts even in the case of catalytic runs performed using a real wastewater matrix. Both catalysts promoted the decomposition of ozone in homogeneous phase, but the higher production of hydroxyl radicals corresponded to the catalyst with more activity in terms of ozone decomposition. We did not find evidence of the catalysts having any effect on rate constants, which suggests that the reaction may not involve the adsorption of organics on catalyst surface.

  1. Solid-phase photocatalytic degradation of polyethylene film with manganese oxide OMS-2

    Science.gov (United States)

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Cui, Jingzhen; Zhou, Wenbing

    2011-01-01

    Solid-phase photocatalytic degradation of polyethylene (PE) film with cryptomelane-type manganese oxide (OMS-2) as photocatalyst was investigated in the ambient air under ultraviolet and visible light irradiation. The properties of the composite films were compared with those of the pure PE film through performing weight loss monitoring, IR spectroscopy, scanning electron microscopic (SEM) and X-ray photoelectron spectroscopy (XPS). The photoinduced degradation of PE-OMS-2 composite films was higher than that of the pure films, while there has been little change under the visible light irradiation. The weight loss of PE-OMS-2 (1.0 wt%) composite films steadily decreased and reached 16.5% in 288 h under UV light irradiation. Through SEM observation there were some cavities on the surface of composite films, but few change except some surface chalking phenomenon occurred in pure PE film. The degradation rate with ultraviolet irradiation is controllable by adjusting the content of OMS-2 particles in PE plastic. Finally, the mechanism of photocatalytic degradation of the composite films was briefly discussed.

  2. Significantly improved cyclability of lithium manganese oxide under elevated temperature by an easily oxidized electrolyte additive

    Science.gov (United States)

    Zhu, Yunmin; Rong, Haibo; Mai, Shaowei; Luo, Xueyi; Li, Xiaoping; Li, Weishan

    2015-12-01

    Spinel lithium manganese oxide, LiMn2O4, is a promising cathode for lithium ion battery in large-scale applications, because it possesses many advantages compared with currently used layered lithium cobalt oxide (LiCoO2) and olivine phosphate (LiFePO4), including naturally abundant resource, environmental friendliness and high and long work potential plateau. Its poor cyclability under high temperature, however, limits its application. In this work, we report a significant cyclability improvement of LiMn2O4 under elevated temperature by using dimethyl phenylphonite (DMPP) as an electrolyte additive. Charge/discharge tests demonstrate that the application of 0.5 wt.% DMPP yields a capacity retention improvement from 16% to 82% for LiMn2O4 after 200 cycles under 55 °C at 1 C (1C = 148 mAh g-1) between 3 and 4.5 V. Electrochemical and physical characterizations indicate that DMPP is electrochemically oxidized at the potential lower than that for lithium extraction, forming a protective cathode interphase on LiMn2O4, which suppresses the electrolyte decomposition and prevents LiMn2O4 from crystal destruction.

  3. Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Francis, Todd M; Lichty, Paul R; Perkins, Christopher; Tucker, Melinda; Kreider, Peter B; Funke, Hans H; Lewandowski, A; Weimer, Alan W

    2012-10-24

    There are three primary reactions in the sodium manganese oxide high temperature water splitting cycle. In the first reaction, Mn2O3 is decomposed to MnO at 1,500°C and 50 psig. This reaction occurs in a high temperature solar reactor and has a heat of reaction of 173,212 J/mol. Hydrogen is produced in the next step of this cycle. This step occurs at 700°C and 1 atm in the presence of sodium hydroxide. Finally, water is added in the hydrolysis step, which removes NaOH and regenerates the original reactant, Mn2O3. The high temperature solar-driven step for decomposing Mn2O3 to MnO can be carried out to high conversion without major complication in an inert environment. The second step to produce H2 in the presence of sodium hydroxide is also straightforward and can be completed. The third step, the low temperature step to recover the sodium hydroxide is the most difficult. The amount of energy required to essentially distill water to recover sodium hydroxide is prohibitive and too costly. Methods must be found for lower cost recovery. This report provides information on the use of ZnO as an additive to improve the recovery of sodium hydroxide.

  4. Trimethylsilylcyclopentadiene as a novel electrolyte additive for high temperature application of lithium nickel manganese oxide cathode

    Science.gov (United States)

    Tu, Wenqiang; Ye, Changchun; Yang, Xuerui; Xing, Lidan; Liao, Youhao; Liu, Xiang; Li, Weishan

    2017-10-01

    Electrolyte additives are necessary for the application of high potential cathode in high energy density lithium ion batteries, especially at elevated temperature. However, the electrolyte additives that can effectively suppress the dissolution of transition metal ions from cathode have seldom been developed up to date. In this work, we propose a novel electrolyte additive, trimethylsilylcyclopentadiene (SE), for high temperature application of a representative high potential cathode, lithium nickel manganese oxide (LiNi0.5Mn1.5O4). It is found that the dissolution of Mn and Ni from LiNi0.5Mn1.5O4 can be effectively suppressed by applying SE. With applying 0.25% SE, the dissolved amount of Mn and Ni is decreased by 97.4% and 98%, respectively, after 100 cycles at 55 °C. Correspondingly, the cyclic performance of LiNi0.5Mn1.5O4 is significantly improved. Physical characterizations and electrochemical measurements show that SE can be preferentially oxidized and generate a protective film on LiNi0.5Mn1.5O4. The resulting film inhibits the electrolyte decomposition and the transition metal ion dissolution.

  5. Arsenite oxidation by a poorly-crystalline manganese oxide. 3. Arsenic and manganese desorption.

    Science.gov (United States)

    Lafferty, Brandon J; Ginder-Vogel, Matthew; Sparks, Donald L

    2011-11-01

    Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese oxides (Mn oxides) have the ability to decrease overall As mobility both by oxidizing toxic arsenite (As(III)) to less toxic arsenate (As(V)), and by sorbing As. However, the effect of competing ions on the mobility of As sorbed on Mn-oxide surfaces is not well understood. In this study, desorption of As(V) and As(III) from a poorly crystalline phyllomanganate (δ-MnO(2)) by two environmentally significant ions is investigated using a stirred-flow technique and X-ray absorption spectroscopy (XAS). As(III) is not observed in solution after desorption under any conditions used in this study, agreeing with previous studies showing As sorbed on Mn-oxides exists only as As(V). However, some As(V) is desorbed from the δ-MnO(2) surface under all conditions studied, while neither desorptive used in this study completely removes As(V) from the δ-MnO(2) surface.

  6. The kinetics of iodide oxidation by the manganese oxide mineral birnessite

    Science.gov (United States)

    Fox, P.M.; Davis, J.A.; Luther, G. W.

    2009-01-01

    The kinetics of iodide (I-) and molecular iodine (I2) oxidation by the manganese oxide mineral birnessite (??-MnO2) was investigated over the pH range 4.5-6.25. I- oxidation to iodate (IO3-) proceeded as a two-step reaction through an I2 intermediate. The rate of the reaction varied with both pH and birnessite concentration, with faster oxidation occurring at lower pH and higher birnessite concentration. The disappearance of I- from solution was first order with respect to I- concentration, pH, and birnessite concentration, such that -d[I-]/dt = k[I-][H+][MnO2], where k, the third order rate constant, is equal to 1.08 ?? 0.06 ?? 107 M-2 h-1. The data are consistent with the formation of an inner sphere I- surface complex as the first step of the reaction, and the adsorption of I- exhibited significant pH dependence. Both I2, and to a lesser extent, IO3- sorbed to birnessite. The results indicate that iodine transport in mildly acidic groundwater systems may not be conservative. Because of the higher adsorption of the oxidized I species I2 and IO3-, as well as the biophilic nature of I2, redox transformations of iodine must be taken into account when predicting I transport in aquifers and watersheds.

  7. The putative α/β-hydrolases of Dietzia cinnamea P4 strain as potential enzymes for biocatalytic applications.

    Science.gov (United States)

    Procópio, Luciano; Macrae, Andrew; van Elsas, Jan Dirk; Seldin, Lucy

    2013-03-01

    The draft genome of the soil actinomycete Dietzia cinnamea P4 reveals a versatile group of α/β-hydrolase fold enzymes. Phylogenetic and comparative sequence analyses were used to classify the α/β-hydrolases of strain P4 into six different groups: (i) lipases, (ii) esterases, (iii) epoxide hydrolases, (iv) haloacid dehalogenases, (v) C-C breaking enzymes and (vi) serine peptidases. The high number of lipases/esterases (41) and epoxide hydrolase enzymes (14) present in the relatively small (3.6 Mb) P4 genome is unusual; it is likely to be linked to the survival of strain P4 in its natural environment. Strain P4 is thus equipped with a large number of genes which would appear to confer survivability in harsh hot tropical soil. As such, this highly resilient soil bacterial strain provides an interesting genome for enzyme mining for applications in the field of biotransformations of polymeric compounds.

  8. Photo-catalytic Degradation and Sorption of Radio-cobalt from EDTA-Co Complexes Using Manganese Oxide Materials - 12220

    Energy Technology Data Exchange (ETDEWEB)

    Koivula, Risto; Harjula, Risto [University of Helsinki, P.O.Box 55, FI-00014 Helsinki (Finland); Tusa, Esko [Fortum Power and Heat Oy P.O.Box 100, 00048 FORTUM (Finland)

    2012-07-01

    The synthesised cryptomelane-type α-MnO{sub 2} was tested for its Co-57 uptake properties in UV-photo-reactor filled with 10 μM Co-EDTA solution with a background of 10 mM NaNO{sub 3}. High cobalt uptake of 96% was observed after 1 hour of UV irradiation. As for comparison, a well-known TiO{sub 2} (Degussa P25) was tested as reference material that showed about 92% cobalt uptake after six hours of irradiation in identical experiment conditions. It was also noted that the cobalt uptake on cryptomelane with out UV irradiation was modest, only about 10%. Decreasing the pH of the Co-EDTA solution had severe effects on the cobalt uptake mainly due to the rather high point of zero charge of the MnO{sub 2} surface (pzc at pH ∼4.5). Modifying the synthesis procedure we were able to produce a material that functioned well even in solution of pH 3 giving cobalt uptake of almost 99%. The known properties, catalytic and ion exchange, of manganese oxides were simultaneously used for the separation of EDTA complexed Co-57. Tunnel structured cryptomelane -type showed very fast and efficient Co uptake properties outperforming the well known and widely used Degussa P25 TiO{sub 2} in both counts. The layered structured manganese oxide, birnessite, reached also as high Co removal level as the reference material Degussa did but the reaction rate was considerably faster. Since the decontamination solutions are typically slightly acidic and the point of zero charge of the manganese oxides are rather high > pH 4.5 the material had to be modified. This modified material had tolerance to acidic solutions and it's Co uptake performance remained high in the solutions of lower pH (pH 3). Increasing the ion concentration of test solutions, background concentration, didn't affect the final Co uptake level; however, some changes in the uptake kinetics could be seen. The increase in EDTA/MoMO ratio was clearly reflected in the Co uptake curves. The obtained results of manganese

  9. Advance in Studies of Manganese Oxidizing Bacteria%锰氧化细菌研究进展

    Institute of Scientific and Technical Information of China (English)

    井晓欢; 杨季芳; 陈吉刚

    2015-01-01

    Manganese oxidizing bacteria widely occur in nature, which can oxide Mn2+ ions to high manganese oxide (Mn3+,Mn4+,etc.). Manganese oxidizing bacteria not only involved in the formation of the ocean manganese nodules, which played an important role in the cycle of marine manganese element, but also could oxide free manganese ions, adsorb heavy metal, control their transformation and migration, restore the heavy metal pollution and degrade many organic pollutants by oxidation in the environment. This paper mainly reviewed the advances in the studies on the identification methods , classification, biological function, oxidation mechanism, oxidation inhibitor and related oxidases of manganese oxidizing bacteria at home and abroad. The problems existed in the research of manganese oxidizing bacteria were also put forward. Finally, the future study was prospected in this paper.%能够将离子存在的Mn2+氧化成为可沉淀的高价锰(Mn3+、Mn4+等)的锰氧化细菌广泛存在于大自然中。锰氧化细菌不仅参与海洋锰结核的形成,在海洋锰元素的循环中起着举足轻重的作用,而且能够氧化游离的锰离子,吸附多种重金属,控制其在环境中的转化和迁移,修复环境中重金属的污染和氧化降解多种有机污染物。文章主要就国内外对锰氧化细菌的鉴定方法、分类、生物作用、氧化机制、氧化抑制剂以及相关的氧化酶等的研究进展进行了总结,同时提出了锰氧化细菌研究中存在的问题,并对进一步的研究作了展望。

  10. Structure of a putative trans-editing enzyme for prolyl-tRNA synthetase from Aeropyrum pernix K1 at 1.7 Å resolution

    Energy Technology Data Exchange (ETDEWEB)

    Murayama, Kazutaka; Kato-Murayama, Miyuki; Katsura, Kazushige; Uchikubo-Kamo, Tomomi; Yamaguchi-Hirafuji, Machiko; Kawazoe, Masahito; Akasaka, Ryogo; Hanawa-Suetsugu, Kyoko; Hori-Takemoto, Chie [RIKEN Genomic Sciences Center, Yokohama (Japan); Terada, Takaho [RIKEN Genomic Sciences Center, Yokohama (Japan); RIKEN Harima Institute at SPring-8, Hyogo (Japan); Shirouzu, Mikako [RIKEN Harima Institute at SPring-8, Hyogo (Japan); Yokoyama, Shigeyuki, E-mail: yokoyama@biochem.s.u-tokyo.ac.jp [RIKEN Genomic Sciences Center, Yokohama (Japan); RIKEN Harima Institute at SPring-8, Hyogo (Japan); Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo (Japan)

    2005-01-01

    The three-dimensional structure of the APE2540 protein from A. pernix K1 has been determined by the multiple anomalous dispersion method at 1.7 Å resolution. The structure includes two monomers in the asymmetric unit and shares structural similarity with the YbaK protein or cysteinyl-tRNA{sup Pro} deacylase from H. influenzae. The crystal structure of APE2540, the putative trans-editing enzyme ProX from Aeropyrum pernix K1, was determined in a high-throughput manner. The crystal belongs to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 47.4, b = 58.9, c = 53.6 Å, β = 106.8°. The structure was solved by the multiwavelength anomalous dispersion method at 1.7 Å and refined to an R factor of 16.8% (R{sub free} = 20.5%). The crystal structure includes two protein molecules in the asymmetric unit. Each monomer consists of eight β-strands and seven α-helices. A structure-homology search revealed similarity between the trans-editing enzyme YbaK (or cysteinyl-tRNA{sup Pro} deacylase) from Haemophilus influenzae (HI1434; 22% sequence identity) and putative ProX proteins from Caulobacter crescentus (16%) and Agrobacterium tumefaciens (21%)

  11. The putative α/β-hydrolases of Dietzia cinnamea P4 strain as potential enzymes for biocatalytic applications

    NARCIS (Netherlands)

    Procopio da Silva, Luciano; Macrae, Andrew; van Elsas, Jan Dirk; Seldin, Lucy

    2013-01-01

    The draft genome of the soil actinomycete Dietzia cinnamea P4 reveals a versatile group of alpha/beta-hydrolase fold enzymes. Phylogenetic and comparative sequence analyses were used to classify the alpha/beta-hydrolases of strain P4 into six different groups: (i) lipases, (ii) esterases, (iii) epox

  12. Electrodeposition of hierarchical manganese oxide on metal nanoparticles decorated nanoporous gold with enhanced supercapacitor performance

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Zhigang, E-mail: zgzeng@shu.edu.cn [Department of Physics, College of Sciences, Shanghai University, Shanghai 200444 (China); Institute of NanoMicroEnergy, College of Sciences, Shanghai University, Shanghai 200444 (China); Zhou, Haijun; Long, Xiao; Guo, Erjuan [Department of Physics, College of Sciences, Shanghai University, Shanghai 200444 (China); Institute of NanoMicroEnergy, College of Sciences, Shanghai University, Shanghai 200444 (China); Wang, Xiaohong [Department of Chemistry, College of Sciences, Shanghai University, Shanghai 200444 (China); Institute of NanoMicroEnergy, College of Sciences, Shanghai University, Shanghai 200444 (China)

    2015-05-25

    Highlights: • Pt-NPs decorated NPG as current collector for electrodeposition of MnO{sub x} nanosheets. • Pt-NPs facilitate the formation of MnO{sub x} nanosheets and improve the conductivity. • MnO{sub x}/Pt@NPG electrode shows low contact resistance and excellent cycling stability. • Nanosized subunits in hybrid electrode can improve the electrochemical performance. - Abstract: A novel three dimensional nanoarchitecture of manganese oxide nanosheets/Pt@nanoporous gold (MnO{sub x}/Pt@NPG) was designed and synthesized by galvanostatic electrodepositon for supercapacitors application. Nanoporous gold (NPG) membrane was fabricated by a dealloying method as a current collector and discontinuous platinum nanoparticles were pulse electrodeposited on NPG. The morphology and chemical composition of the MnO{sub x}/Pt@NPG products were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the as-prepared MnO{sub x} as an electrode material for supercapacitor were investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy measurements in 1 M Na{sub 2}SO{sub 4} electrolyte. Importantly, the optimized MnO{sub x}/Pt@NPG hybrid electrodes obtain a maximum specific capacitance of 775 F g{sup −1} at 1 A g{sup −1} (about two times larger than that of MnO{sub x}/NPG electrodes with 404 F g{sup −1}), about half of the internal resistance of MnO{sub x}/NPG electrodes and excellent cycling stability, making it a promising candidate for supercapacitors.

  13. Illumina sequencing of fungi associated with manganese oxide deposits in cave systems

    Science.gov (United States)

    Zorn, B. T.; Santelli, C. M.; Carmichael, S. K.; Pepe-Ranney, C. P.; Roble, L.; Carmichael, M.; Bräuer, S.

    2013-12-01

    The environmental cycling of manganese (Mn) remains relatively poorly characterized when compared with other metals such as iron. However, fungi have been observed to produce Mn(III/IV) oxides resembling buserite, birnessite, and todorokite on the periphery of vegetative hyphae, hyphal branching points and at the base of fruiting bodies. Recent studies indicate that some of these oxides may be generated by a two-stage reaction with soluble Mn(II) and biogenic reactive oxygen species for some groups of fungi, in particular the Ascomycota. These oxides can provide a versatile protective barrier or aid in the capture of trace metals in the environment, although the exact evolutionary function and trigger is unclear. In this study, two caves in the southern Appalachians, a pristine cave and an anthropogenically impacted cave, were compared by analyzing fungal community assemblages in manganese oxide rich deposits. Quantitative PCR data indicated that fungi are present in a low abundance (Chytridiomycota, 0.46% of Zygomycota, and 3.65% of Eukarya or Fungi incertae sedis. Using Illumina's MiSeq to sequence amplicons of the fungal ITS1 gene has yielded roughly 100,000-200,000 paired-end reads per sample. These data are currently being analyzed to compare fungal communities before and after induced Mn oxidation in the field. In addition, sites within the pristine cave are being compared with analogous sites in the impacted cave. Culturing efforts have thus far yielded Mn oxide producing members of the orders Glomerales and Pleosporales as well as two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT3, growing on discarded electrical tape) that do not appear to be closely related to any other known Mn oxidizing fungi.

  14. Electrochemical selective ion separation in capacitive deionization with sodium manganese oxide.

    Science.gov (United States)

    Kim, Seonghwan; Yoon, Hansun; Shin, Dongyoon; Lee, Jaehan; Yoon, Jeyong

    2017-11-15

    Electrochemical selective ion separation via capacitive deionization, for example, separation of lithium resource from brine, using lithium ion batteries is proposed and demonstrated to have the potential for separating specific ions selectively from a solution containing diverse ions. This separation method is of great industrial concern because of applicability in various fields such as deionization, water softening, purification, heavy metal removal, and resource recovery. Nevertheless, besides the selectivity of materials for lithium ion batteries toward Li(+), there is very little investigation on the selectivity of the materials for sodium ion batteries toward Na(+). Here, the electrochemical selectivity of sodium manganese oxide (Na0.44MnO2), one of the most widely used material in sodium ion batteries, for Na(+) and other cations (K(+), Mg(2+), and Ca(2+)) is investigated. Selective Na(+) separation using the system consisting of Na0.44MnO2 and a Ag/AgCl electrode is successfully demonstrated from a solution containing diverse cations (Na(+), K(+), Mg(2+), and Ca(2+)) via a two-step process that involves a capturing step (charging process) and a releasing step (discharging process). The results showed that Na0.44-xMnO2 has over 13 times higher selectivity for Na(+) than for K(+) and 6-8times higher selectivity for Na(+) than for Mg(2+) and Ca(2+) in the electrolyte containing equal concentrations of the respective ions. Additionally, as a practical demonstration, Na(+) was successfully separated from an industrial raw material used for pure KOH production (estimated ratio of Na(+):K(+)=1:200). Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Oxidation of AsⅢ by Several Manganese Oxide Minerals in Absence and Presence of Goethite

    Institute of Scientific and Technical Information of China (English)

    FENG Xionghan; TAN Wenfeng; LIU Fan; Huada Daniel RUAN; HE Jizheng

    2006-01-01

    Oxidation of AsⅢ by three types of manganese oxide minerals affected by goethite was investigated by chemical analysis, equilibrium redox, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Three synthesized Mn oxide minerals of different types, birnessite,todorokite, and hausmannite, could actively oxidize AsⅢ to AsⅤ, and greatly varied in their oxidation ability. Layer structured birnessite exhibited the highest capacity of AsⅢ oxidation, followed by the tunnel structured todorokite. Lower oxide hausmannite possessed much low capacity of AsⅢ oxidation,and released more Mn2+ than birnessite and todorokite during the oxidation. The maximum amount of Asv produced during the oxidation of AsⅢ by Mn oxide minerals was in the order: birnessite (480.4mmol/kg) > todorokite (279.6 mmol/kg) > hausmannite (117.9 mmol/kg). The oxidation capacity of the Mn oxide minerals was found to be relative to the composition, crystallinity, and surface properties. In the presence of goethite oxidation of AsⅢ by Mn oxide minerals increased, with maximum amounts of Asv being 651.0 mmol/kg for birnessite, 332.3 mmol/kg for todorokite and 159.4 mmol/kg for hausmannite. Goethite promoted AsⅢ oxidation on the surface of Mn oxide minerals through adsorption of the Asv produced, incurring the decrease of Asv concentration in solutions. Thus, the combined effects of the oxidation (by Mn oxide minerals)-adsorption (by goethite) lead to rapid oxidation and immobilization of As in soils and sediments and alleviation of the AsⅢ toxicity in the environments.

  16. Activity-Based Proteomic Profiling of Deubiquitinating Enzymes in Salmonella-Infected Macrophages Leads to Identification of Putative Function of UCH-L5 in Inflammasome Regulation.

    Directory of Open Access Journals (Sweden)

    Evangel Kummari

    Full Text Available Although protein ubiquitination has been shown to regulate multiple processes during host response to Salmonella enterica serovar Typhimurium infection, specific functions of host deubiquitinating enzymes remain unknown in this bacterial infection. By using chemical proteomics approach, in which deubiquitinating enzymes were labeled by an active-site probe and analyzed by quantitative proteomics, we identified novel deubiquitinases in chicken macrophages based on their reactivity with the probe. Also, we detected down-regulation of UCH-L3, and USP4 as well as up-regulation of USP5 and UCH-L5 deubiquitinating enzymes in macrophages infected with Salmonella Typhimurium. We showed that decrease in either UCH-L5 activity, or in UCH-L5 protein amount in chicken and human macrophages infected or stimulated with LPS/nigericin, led to decreased IL-1β release. These data point towards a putative role of UCH-L5 in inflammasome regulation during Salmonella infection. Because inflammasome activation is important in innate resistance to these bacteria, one would expect that naturally occurring or therapeutically induced alteration in UCH-L5 activation would influence disease outcome and could represent a target for new therapeutic approaches.

  17. Activity-Based Proteomic Profiling of Deubiquitinating Enzymes in Salmonella-Infected Macrophages Leads to Identification of Putative Function of UCH-L5 in Inflammasome Regulation.

    Science.gov (United States)

    Kummari, Evangel; Alugubelly, Navatha; Hsu, Chuan-Yu; Dong, Brittany; Nanduri, Bindu; Edelmann, Mariola J

    2015-01-01

    Although protein ubiquitination has been shown to regulate multiple processes during host response to Salmonella enterica serovar Typhimurium infection, specific functions of host deubiquitinating enzymes remain unknown in this bacterial infection. By using chemical proteomics approach, in which deubiquitinating enzymes were labeled by an active-site probe and analyzed by quantitative proteomics, we identified novel deubiquitinases in chicken macrophages based on their reactivity with the probe. Also, we detected down-regulation of UCH-L3, and USP4 as well as up-regulation of USP5 and UCH-L5 deubiquitinating enzymes in macrophages infected with Salmonella Typhimurium. We showed that decrease in either UCH-L5 activity, or in UCH-L5 protein amount in chicken and human macrophages infected or stimulated with LPS/nigericin, led to decreased IL-1β release. These data point towards a putative role of UCH-L5 in inflammasome regulation during Salmonella infection. Because inflammasome activation is important in innate resistance to these bacteria, one would expect that naturally occurring or therapeutically induced alteration in UCH-L5 activation would influence disease outcome and could represent a target for new therapeutic approaches.

  18. Preparation and structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanocomposite upon intercalating reaction.

    Science.gov (United States)

    Wang, Jianfang; Liu, Zong-Huai; Tang, Xiuhua; Ooi, Kenta

    2007-03-15

    SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid was successfully synthesized by preliminarily expanding the interlayer of H-type layered manganese oxide using dodecylamine, followed by reacting it with a mixture solution of titanium isopropoxide and tetraethylorthosilicate. The basal spacing and the pillared agent content of the obtained materials connected with the length of intercalated n-alkylamine, incorporated Si/Ti molar ratios and the solvothermal treatment temperature. The structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid was characterized by XRD, DSC-TGA, SEM, IR, N(2) adsorption-desorption and element analyses. TiO(2) particles exhibited a stronger affinity for the negatively charged manganese layers, and the TiO(2) particles incorporated were independently intercalated without any distinct chemical bonding with the co-intercalated SiO(2) particles. SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid had a BET surface area of 98 m(2)/g with a gallery height of about 1.43 nm between layers. The obtained SiO(2)-TiO(2) co-pillared layered manganese oxide nanohybrid is expected as a selective catalyst, or an improved battery material.

  19. Coral reef-like polyanaline nanotubes prepared by a reactive template of manganese oxide for supercapacitor electrode

    Institute of Scientific and Technical Information of China (English)

    Ling Ren Wang; Fen Ran; Yong Tao Tan; Lei Zhao; Ling Bin Kong; Long Kang

    2011-01-01

    Coral reef-like PANI nanotubes composed of nanopaticles were successfully synthesized by a reactive template of manganese oxide. The structure was characterized by using SEM, TEM, and FT-IR, and the supercapacitive behaviors of these nanotubes were investigated with cyclic voltammetry (CV), and charge-discharge tests, respectively. A maximum specific capacitance of 533 F/g could be achieved in 1 mol/L aqueous H2SO4 with the potential range of -0.2 to 0.8 V (vs. the saturated calomel electrode) in a half-cell setup configuration for PANI electrode, suggesting its potential application in the electrode material for electrochemical capacitors.

  20. S-Adenosyl-S-carboxymethyl-l-homocysteine: a novel cofactor found in the putative tRNA-modifying enzyme CmoA

    Energy Technology Data Exchange (ETDEWEB)

    Byrne, Robert T.; Whelan, Fiona [University of York, Heslington YO10 5DD (United Kingdom); Aller, Pierre [Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Bird, Louise E. [OPPF-UK, Research Complex at Harwell, R92 Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA (United Kingdom); Oxford University, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Dowle, Adam [University of York, Heslington YO10 5DD (United Kingdom); Lobley, Carina M. C. [Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Reddivari, Yamini; Nettleship, Joanne E.; Owens, Raymond J. [OPPF-UK, Research Complex at Harwell, R92 Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA (United Kingdom); Oxford University, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Antson, Alfred A. [University of York, Heslington YO10 5DD (United Kingdom); Waterman, David G., E-mail: david.waterman@stfc.ac.uk [STFC, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA (United Kingdom); University of York, Heslington YO10 5DD (United Kingdom)

    2013-06-01

    The putative methyltransferase CmoA is involved in the nucleoside modification of transfer RNA. X-ray crystallography and mass spectrometry are used to show that it contains a novel SAM derivative, S-adenosyl-S-carboxymethyl-l-homocysteine, in which the donor methyl group is replaced by a carboxymethyl group. Uridine at position 34 of bacterial transfer RNAs is commonly modified to uridine-5-oxyacetic acid (cmo{sup 5}U) to increase the decoding capacity. The protein CmoA is involved in the formation of cmo{sup 5}U and was annotated as an S-adenosyl-l-methionine-dependent (SAM-dependent) methyltransferase on the basis of its sequence homology to other SAM-containing enzymes. However, both the crystal structure of Escherichia coli CmoA at 1.73 Å resolution and mass spectrometry demonstrate that it contains a novel cofactor, S-adenosyl-S-carboxymethyl-l-homocysteine (SCM-SAH), in which the donor methyl group is substituted by a carboxymethyl group. The carboxyl moiety forms a salt-bridge interaction with Arg199 that is conserved in a large group of CmoA-related proteins but is not conserved in other SAM-containing enzymes. This raises the possibility that a number of enzymes that have previously been annotated as SAM-dependent are in fact SCM-SAH-dependent. Indeed, inspection of electron density for one such enzyme with known X-ray structure, PDB entry http://scripts.iucr.org/cgi-bin/cr.cgi?rm, suggests that the active site contains SCM-SAH and not SAM.

  1. Synthesis of manganese oxide nanocrystal by ultrasonic bath: effect of external magnetic field.

    Science.gov (United States)

    Bastami, Tahereh Rohani; Entezari, Mohammad H

    2012-07-01

    A novel technique was used for the synthesis of manganese oxide nanocrystal by applying an external magnetic field (EMF) on the precursor solution before sonication with ultrasonic bath. The results were compared in the presence and absence of EMF. Manganese acetate solution as precursor was circulated by a pump at constant speed (7 rpm, equal to flow rate of 51.5 mL/min) in an EMF with intensity of 0.38 T in two exposure times (t(MF), 2h and 24h). Then, the magnetized solution was irradiated indirectly by ultrasonic bath in basic and neutral media. One experiment was designed for the effect of oxygen atmosphere in the case of magnetic treated solution in neutral medium. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. In neutral medium, the sonication of magnetized solution (t(MF), 24h) led mainly to a mixture of Mn(3)O(4) (hausmannite) and γ-MnOOH (manganite) and sonication of unmagnetized solution led to a pure Mn(3)O(4). In point of particle size, the larger and smaller size of nanoparticles was obtained with and without magnetic treatment, respectively. In addition, the EMF was retarded the nucleation process, accelerated the growth of the crystal, and increased the amount of rod-like structure especially in oxygen atmosphere. In basic medium, a difference was observed on the composition of the products between magnetic treated and untreated solution. For these samples, the magnetic measurements as a function of temperature were exhibited a reduction in ferrimagnetic temperature to T(c)=39K, and 40K with and without magnetic treatment, respectively. The ferrimagnetic temperature was reported for the bulk at T(c)=43K. A superparamagnetic behavior was observed at room temperature without any saturation magnetization and hysteresis in the measured

  2. Removal and recovery of toxic silver ion using deep-sea bacterial generated biogenic manganese oxides.

    Science.gov (United States)

    Pei, Yuanjun; Chen, Xiao; Xiong, Dandan; Liao, Shuijiao; Wang, Gejiao

    2013-01-01

    Products containing silver ion (Ag(+)) are widely used, leading to a large amount of Ag(+)-containing waste. The deep-sea manganese-oxidizing bacterium Marinobacter sp. MnI7-9 efficiently oxidizes Mn(2+) to generate biogenic Mn oxide (BMO). The potential of BMO for recovering metal ions by adsorption has been investigated for some ions but not for Ag(+). The main aim of this study was to develop effective methods for adsorbing and recovering Ag using BMO produced by Marinobacter sp. MnI7-9. In addition, the adsorption mechanism was determined using X-ray photoelectron spectroscopy analysis, specific surface area analysis, adsorption kinetics and thermodynamics. The results showed that BMO had a higher adsorption capacity for Ag(+) compared to the chemical synthesized MnO2 (CMO). The isothermal absorption curves of BMO and CMO both fit the Langmuir model well and the maximum adsorption capacities at 28°C were 8.097 mmol/g and 0.787 mmol/g, for BMO and CMO, respectively. The change in enthalpy (ΔH(θ)) for BMO was 59.69 kJ/mol indicating that it acts primarily by chemical adsorption. The change in free energy (ΔG(θ)) for BMO was negative, which suggests that the adsorption occurs spontaneously. Ag(+) adsorption by BMO was driven by entropy based on the positive ΔS(θ) values. The Ag(+) adsorption kinetics by BMO fit the pseudo-second order model and the apparent activation energy of Ea is 21.72 kJ/mol. X-ray photoelectron spectroscopy analysis showed that 15.29% Ag(+) adsorbed by BMO was transferred to Ag(0) and meant that redox reaction had happened during the adsorption. Desorption using nitric acid and Na2S completely recovered the Ag. The results show that BMO produced by strain MnI7-9 has potential for bioremediation and reutilization of Ag(+)-containing waste.

  3. Putative role of the malate valve enzyme NADP-malate dehydrogenase in H2O2 signalling in Arabidopsis.

    Science.gov (United States)

    Heyno, Eiri; Innocenti, Gilles; Lemaire, Stéphane D; Issakidis-Bourguet, Emmanuelle; Krieger-Liszkay, Anja

    2014-04-19

    In photosynthetic organisms, sudden changes in light intensity perturb the photosynthetic electron flow and lead to an increased production of reactive oxygen species. At the same time, thioredoxins can sense the redox state of the chloroplast. According to our hypothesis, thioredoxins and related thiol reactive molecules downregulate the activity of H2O2-detoxifying enzymes, and thereby allow a transient oxidative burst that triggers the expression of H2O2 responsive genes. It has been shown recently that upon light stress, catalase activity was reversibly inhibited in Chlamydomonas reinhardtii in correlation with a transient increase in the level of H2O2. Here, it is shown that Arabidopsis thaliana mutants lacking the NADP-malate dehydrogenase have lost the reversible inactivation of catalase activity and the increase in H2O2 levels when exposed to high light. The mutants were slightly affected in growth and accumulated higher levels of NADPH in the chloroplast than the wild-type. We propose that the malate valve plays an essential role in the regulation of catalase activity and the accumulation of a H2O2 signal by transmitting the redox state of the chloroplast to other cell compartments.

  4. Precursor effects on the morphology and crystallinity of manganese oxides and their catalytic application for methylene blue degradation

    Science.gov (United States)

    Awaluddin, Amir; Agustina, Mutia; Aulia, Rizki Rilda; Muhdarina

    2017-03-01

    The cryptomelane-type manganese oxide catalysts have been prepared by sol-gel method based on the redox reaction between potassium permanganate and glucose or oxalic acid. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The SEM results indicated that the marked difference between the morphology of the cyptomelanes produced from glucose and oxalic acid. The glucose precursor produces cotton-shaped morphology, whereas the oxalic acid precursor leads to the formation of the disk-like appearances. The XRD results indicated that the glucose precursor produces more crystalline cryptomelane than that of oxalic acid. The effect of catalyst dosage on methyelene blue degradation was evaluated. Dye-decomposing activity was proportional to the amount of catalyst used, increasing of the catalyst amount leads to higher degradation of methyelene blue at short period of reaction. With different crystalline structures and morphology appearances of the cyptomelanes, however, the total degradation of methylene blue is relatively the same at 120 minute of reaction time with catalyst amount of 100 mg.

  5. Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel

    Science.gov (United States)

    Lee, Hae Ri; Seo, Hyo Ree; Lee, Boeun; Cho, Byung Won; Lee, Kwan-Young; Oh, Si Hyoung

    2017-01-01

    Li-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO4 and LiMg0.5Mn1.5O4 layers on the surface of LiAl0.1Mn1.9O4. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.

  6. Recovery of manganese oxides from spent alkaline and zinc-carbon batteries. An application as catalysts for VOCs elimination.

    Science.gov (United States)

    Gallegos, María V; Falco, Lorena R; Peluso, Miguel A; Sambeth, Jorge E; Thomas, Horacio J

    2013-06-01

    Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200°C, while heptane requires more than 400°C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs.

  7. Influence of dissolved organic matter and manganese oxides on metal speciation in soil solution: A modelling approach.

    Science.gov (United States)

    Schneider, Arnaud R; Ponthieu, Marie; Cancès, Benjamin; Conreux, Alexandra; Morvan, Xavier; Gommeaux, Maxime; Marin, Béatrice; Benedetti, Marc F

    2016-06-01

    Trace element (TE) speciation modelling in soil solution is controlled by the assumptions made about the soil solution composition. To evaluate this influence, different assumptions using Visual MINTEQ were tested and compared to measurements of free TE concentrations. The soil column Donnan membrane technique (SC-DMT) was used to estimate the free TE (Cd, Cu, Ni, Pb and Zn) concentrations in six acidic soil solutions. A batch technique using DAX-8 resin was used to fractionate the dissolved organic matter (DOM) into four fractions: humic acids (HA), fulvic acids (FA), hydrophilic acids (Hy) and hydrophobic neutral organic matter (HON). To model TE speciation, particular attention was focused on the hydrous manganese oxides (HMO) and the Hy fraction, ligands not considered in most of the TE speciation modelling studies in soil solution. In this work, the model predictions of free ion activities agree with the experimental results. The knowledge of the FA fraction seems to be very useful, especially in the case of high DOM content, for more accurately representing experimental data. Finally, the role of the manganese oxides and of the Hy fraction on TE speciation was identified and, depending on the physicochemical conditions of the soil solution, should be considered in future studies.

  8. Electrocatalysis by nanoparticles: Oxidation of formic acid at manganese oxide nanorods-modified Pt planar and nanohole-arrays

    Directory of Open Access Journals (Sweden)

    Mohamed S. El-Deab

    2010-01-01

    Full Text Available The electro-oxidation of formic acid (an essential reaction in direct formic acid fuel cells is a challenging process because of the deactivation of anodes by the adsorption of the poisoning intermediate carbon monoxide (CO. Pt electrodes in two geometries (planar and nanohole-array were modified by the electrodeposition of manganese oxide nanorods (nano-MnOx. The modified Pt electrodes were then tested for their electrocatalytic activity through the electro-oxidation of formic acid in a solution of pH 3.45. Two oxidation peaks (Ipd and Ipind were observed at 0.2 and 0.55 V, respectively; these were assigned to the direct and indirect oxidative pathways. A significant enhancement of the direct oxidation of formic acid to CO2 was observed at the modified electrodes, while the formation of the poisoning intermediate CO was suppressed. Ipd increases with surface coverage (θ of nano-MnOx with a concurrent depression of Ipind. An increase in the ratio Ipd/ν1/2 with decreasing potential scan rate (ν indicates that the oxidation process proceeds via a catalytic mechanism. The modification of Pt anodes with manganese oxide nanorods results in a significant improvement of the electrocatalytic activity along with a higher tolerance to CO. Thus nano-MnOx plays a crucial role as a catalytic mediator which facilitates the charge transfer during the direct oxidation of formic acid to CO2.

  9. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L; Broer, R; Broer-Braam, H.B.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the obse

  10. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  11. A putative gene sbe3-rs for resistant starch mutated from SBE3 for starch branching enzyme in rice (Oryza sativa L..

    Directory of Open Access Journals (Sweden)

    Ruifang Yang

    Full Text Available Foods high in resistant starch (RS are beneficial to prevent various diseases including diabetes, colon cancers, diarrhea and chronic renal or hepatic diseases. Elevated RS in rice is important for public health since rice is a staple food for half of the world population. A japonica mutant 'Jiangtangdao 1' (RS = 11.67% was crossed with an indica cultivar 'Miyang 23' (RS = 0.41%. The mutant sbe3-rs that explained 60.4% of RS variation was mapped between RM6611 and RM13366 on chromosome 2 (LOD = 36 using 178 F(2 plants genotyped with 106 genome-wide polymorphic SSR markers. Using 656 plants from four F(3:4 families, sbe3-rs was fine mapped to a 573.3 Kb region between InDel 2 and InDel 6 using one STS, five SSRs and seven InDel markers. SBE3 which codes for starch branching enzyme was identified as a candidate gene within the putative region. Nine pairs of primers covering 22 exons were designed to sequence genomic DNA of the wild type for SBE3 and the mutant for sbe3-rs comparatively. Sequence analysis identified a missense mutation site where Leu-599 of the wild was changed to Pro-599 of the mutant in the SBE3 coding region. Because the point mutation resulted in the loss of a restriction enzyme site, sbe3-rs was not digested by a CAPS marker for SpeI site while SBE3 was. Co-segregation of the digestion pattern with RS content among 178 F(2 plants further supported sbe3-rs responsible for RS in rice. As a result, the CAPS marker could be used in marker-assisted breeding to develop rice cultivars with elevated RS which is otherwise difficult to accurately assess in crops. Transgenic technology should be employed for a definitive conclusion of the sbe3-rs.

  12. The bacterial cytoskeleton and its putative role in membrane vesicle formation observed in a Gram-positive bacterium producing starch-degrading enzymes.

    Science.gov (United States)

    Mayer, Frank; Gottschalk, Gerhard

    2003-01-01

    Bacteria may possess various kinds of cytoskeleton. In general, bacterial cytoskeletons may play a role in the control and preservation of the cell shape. Such functions become especially evident when the bacteria do not possess a true wall and are nevertheless elongated (e.g. Mycoplasma spp.) or under extreme cultivation conditions whereby loss of the entire bacterial cell wall takes place. Bacterial cytoskeletons may control and preserve the cell shape only if a number of preconditions are fulfilled. They should be present not only transiently, but permanently, they should be located as a lining close to the inner face of the cytoplasmic membrane, enclosing the entire cytoplasm, and they should comprise structural elements (fibrils) crossing the inner volume of the cell in order to provide the necessary stability for the lining. Complete loss of the cell wall layers had earlier been observed to occur during extensive production of bacterial starch-degrading enzymes in an optimized fermentation process by a Gram-positive bacterium. Even under these conditions, the cells had maintained their elongated shape and full viability. Which of the various kinds of bacterial cytoskeleton might have been responsible for shape preservation? Only one of them, the primary or basic cytoskeleton turns out to fulfil the necessary preconditions listed above. Its structural features now provided a first insight into a possible mechanism of formation of membrane blebs and vesicles as observed in the Gram-positive eubacterium Thermoanaerobacterium thermosulfurogenes EM1, and the putative role of the cytoskeletal web in this process.

  13. Preparation of manganese oxide immobilized on SBA-15 by atomic layer deposition as an efficient and reusable catalyst for selective oxidation of benzyl alcohol in the liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Mahdavi, Vahid, E-mail: v-mahdavi@araku.ac.ir; Mardani, Mahdieh

    2015-04-01

    Manganese oxide supported on mesoporous silica SBA-15 catalyst (Mn-SBA-15) was tested with Mn contents in the range of 0.8–23 wt%. Samples were prepared by the controlled grafting process of atomic layer deposition (ALD). Other sample was prepared for comparisons by the wet impregnation method. These samples were characterized by the techniques of ICP, XRD, SEM, Raman, FT-IR spectroscopy, diffuse reflectance UV–Vis, TGA-DSC, and N{sub 2} absorption–desorption surface area measurement. Results indicated that anchored manganese oxide particles have been successfully synthesized over the surface of SBA-15. These samples contained Red-Ox ion pairs of Mn{sup 2+} and Mn{sup 3+} highly dispersed on the mesoporous silica surface. The impregnated sample exhibited lower surface area and contained Red-Ox ion pairs of Mn{sup 3+} and Mn{sup 4+} more aggregated particles on the SBA-15 surface. Results determined Mn-SBA-15 as an efficient and selective catalyst for oxidation of benzyl alcohol with tert-butylhydroperoxide in liquid phase. In accordance with expectations, there was a negligible amount of leaching of immobilized manganese oxide from the support during the reaction, because of strong surface interaction between manganese oxide and hydroxyls groups. The influences of reaction temperature, reaction time, solvent, TBHP/benzyl alcohol molar ratio, amount of catalyst and reusability were investigated. Under optimized conditions (0.2 g catalyst, TBHP/benzyl alcohol molar ratio 1, solvent acetonitrile; T = 90 °C; reaction time 8 h), results achieved 70% conversion of benzyl alcohol and 100% selectivity to benzaldehyde. - Highlights: • Manganese oxide immobilized on SBA-15 were prepared by atomic layer deposition (ALD). • Oxidation of benzyl alcohol to benzaldehyde over this catalyst were investigated. • Effects of loading of manganese oxide, T, oxidant/alcohol ratio were investigated. • The leaching of manganese oxide from support during the reaction was

  14. Enzyme

    Science.gov (United States)

    Enzymes are complex proteins that cause a specific chemical change in all parts of the body. For ... use them. Blood clotting is another example of enzymes at work. Enzymes are needed for all body ...

  15. The key role of biogenic manganese oxides in enhanced removal of highly recalcitrant 1,2,4-triazole from bio-treated chemical industrial wastewater.

    Science.gov (United States)

    Wu, Ruiqin; Wu, Haobo; Jiang, Xinbai; Shen, Jinyou; Faheem, Muhammad; Sun, Xiuyun; Li, Jiansheng; Han, Weiqing; Wang, Lianjun; Liu, Xiaodong

    2017-04-01

    The secondary effluent from biological treatment process in chemical industrial plant often contains refractory organic matter, which deserves to be further treated in order to meet the increasingly stringent environmental regulations. In this study, the key role of biogenic manganese oxides (BioMnOx) in enhanced removal of highly recalcitrant 1,2,4-triazole from bio-treated chemical industrial wastewater was investigated. BioMnOx production by acclimated manganese-oxidizing bacterium (MOB) consortium was confirmed through scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis. Pseudomonas and Bacillus were found to be the most predominant species in acclimated MOB consortium. Mn(2+) could be oxidized optimally at neutral pH and initial Mn(2+) concentration below 33 mg L(-1). However, 1,2,4-triazole removal by BioMnOx produced occurred optimally at slightly acidic pH. High dosage of both Mn(2+) and 1,2,4-triazole resulted in decreased 1,2,4-triazole removal. In a biological aerated filter (BAF) coupled with manganese oxidation, 1,2,4-triazole and total organic carbon removal could be significantly enhanced compared to the control system without the participation of manganese oxidation, confirming the key role of BioMnOx in the removal of highly recalcitrant 1,2,4-triazole. This study demonstrated that the biosystem coupled with manganese oxidation had a potential for the removal of various recalcitrant contaminants from bio-treated chemical industrial wastewater.

  16. Preparation of polyacrylnitrile (PAN)/ Manganese oxide based activated carbon nanofibers (ACNFs) for adsorption of Cadmium (II) from aqueous solution

    Science.gov (United States)

    Abdullah, N.; Yusof, N.; Jaafar, J.; Ismail, AF; Che Othman, F. E.; Hasbullah, H.; Salleh, W. N. W.; Misdan, N.

    2016-06-01

    In this work, activated carbon nanofibers (ACNFs) from precursor polyacrylnitrile (PAN) and manganese oxide (MnO2) were prepared via electrospinning process. The electrospun PAN/MnO2-based ACNFs were characterised in term of its morphological structure and specific surface area using SEM and BET analysis respectively. The comparative adsorption study of cadmium (II) ions from aqueous solution between the neat ACNFs, composite ACNFs and commercial granular activated carbon was also conducted. SEM analysis illustrated that composite ACNFs have more compact fibers with presence of MnO2 beads with smaller fiber diameter of 437.2 nm as compared to the neat ACNFs which is 575.5 nm. BET analysis elucidated specific surface area of ACNFs/MnO2 to be 67 m2/g. Under adsorption study, it was found out that Cd (II) removal by ACNFs/MnO2 was the highest (97%) followed by neat ACNFs (96%) and GAC (74%).

  17. Gold & silver nanoparticles supported on manganese oxide: Synthesis, characterization and catalytic studies for selective oxidation of benzyl alcohol

    Directory of Open Access Journals (Sweden)

    Saad Alabbad

    2014-12-01

    Full Text Available Nano-gold and silver particles supported on manganese oxide were synthesized by the co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as a source of oxygen. The catalyst was calcined at 300, 400 and 500 °C. They were characterized by electron microscopy, powder X-ray diffraction (XRD and surface area. It was observed that the calcination temperature affects the size of the nanoparticle, which plays a significant role in the catalytic process. The catalyst calcined at 400 °C, gave a 100% conversion and >99% selectivity, whereas catalysts calcined at 300 and 500 °C gave a conversion of 69.51% and 19.90% respectively, although the selectivity remains >99%.

  18. Recent Advancements in the Cobalt Oxides, Manganese Oxides, and Their Composite As an Electrode Material for Supercapacitor: A Review

    Directory of Open Access Journals (Sweden)

    Santosh J. Uke

    2017-08-01

    Full Text Available Recently, our modern society demands the portable electronic devices such as mobile phones, laptops, smart watches, etc. Such devices demand light weight, flexible, and low-cost energy storage systems. Among different energy storage systems, supercapacitor has been considered as one of the most potential energy storage systems. This has several significant merits such as high power density, light weight, eco-friendly, etc. The electrode material is the important part of the supercapacitor. Recent studies have shown that there are many new advancement in electrode materials for supercapacitors. In this review, we focused on the recent advancements in the cobalt oxides, manganese oxides, and their composites as an electrode material for supercapacitor.

  19. High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn{sub 3}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Laffont, L., E-mail: Lydia.laffont@ensiacet.fr [Institut Carnot, Laboratoire CIRIMAT (equipe MEMO), CNRS UMR 5085, ENSIACET, 4 allee Emile Monso, BP 74233, 31432 Toulouse cedex 4 (France); Gibot, P. [Laboratoire de Reactivite et Chimie des Solides CNRS UMR 6007, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens cedex 9 (France)

    2010-11-15

    Manganese oxides particularly Mn{sub 3}O{sub 4} Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn{sub 3}O{sub 4}, a bivalent oxide, for which a precise characterization is necessary and for which the determination of the valency proves to be essential. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and particularly High Resolution Electron Energy Loss Spectroscopy (HREELS) allow us to perform these measurements on the nanometer scale. Well crystallized 10-20 nm sized Mn{sub 3}O{sub 4} particles with sphere-shaped morphology were thus successfully synthesized. Meticulous EELS investigations allowed the determination of a Mn{sup 3+}/Mn{sup 2+} ratio of 1.5, i.e. slightly lower than the theoretical value of 2 for the bulk Hausmannite manganese oxide. This result emphasizes the presence of vacancies on the tetrahedral sites in the structure of the as-synthesized nanomaterial. - Research Highlights: {yields}Mn{sub 3}O{sub 4} bulk and nano were studied by XRD, TEM and EELS. {yields}XRD and TEM determine the degree of crystallinity and the narrow grain size. {yields}HREELS gave access to the Mn{sup 3+}/Mn{sup 2+} ratio. {yields}Mn{sub 3}O{sub 4} nano have vacancies on the tetrahedral sites.

  20. 锂离子电池纳米锂锰氧化物正极材料的研究进展%Research Progress in Nano-scale Lithium Manganese Oxide as Cathode Material for Lithium Ion Batteries

    Institute of Scientific and Technical Information of China (English)

    曾丽珍

    2012-01-01

    综述了近年来锂离子电池正极材料锂锰氧化物的研究现状,重点对锂锰氧化物的结构和性能的关系,尖晶石锂锰氧化物的制备以及其改性研究进行了阐述。%New progress of nanotechnology applied in lithium ion battery of lithium manganese oxide as cathode material was summarized during recent years,focusing on the relationship between structure and properties of lithium manganese oxide,the preparation methods of nanometer lithium manganese oxide materials cathode material and modification of spinel lithium manganese oxide materials were described.

  1. 钾锰氧化物:电化学控制合成及其电容器性质%Potassium Manganese Oxides: Electrochemically Controlled Synthesis and Capacitor Properties

    Institute of Scientific and Technical Information of China (English)

    冯良东; 石建军; 姜立萍; 朱俊杰

    2010-01-01

    Potassium manganese oxides were prepared by cathodic deposition from aqueous KMnO4 solution on an indium tin oxide slide. The products were characterized by XRD, XPS and SEM techniques. The as-prepared products were potassium manganese oxides with different manganese valence states. The component, morphology and size of the products could be controlled through adjusting the preparation parameters such as deposition potential, deposition time and acidity of the electrolyte. The results show that the deposition of potassium manganese oxide from aqueous KMnO4 is a pH value dependent procedure. Due to the facilitating of intercalation and deintercalation of cations, the specific capacitance of the products deposited for 500 s is higher than that indicate that the reversibility and performance of these potassium manganese oxides are also changed with the deposition time.

  2. 云南某氧化锰矿选矿试验研究%Mineral processing research for manganese oxide ores from Yunnan

    Institute of Scientific and Technical Information of China (English)

    李宁钧; 兰健; 梁怀文

    2014-01-01

    云南某氧化锰矿属于半风化型沉积锰矿,原矿锰品位16.17%,选矿试验研究表明:采用“洗矿-跳汰-跳汰尾矿强磁选”选矿工艺流程,锰总回收率达到了92.26%,选别指标理想。%Manganese oxide ores from Yunnan is part of semi weathering type of sedimentary manganese oxide ores;the raw ores contains 16.17%manganese. The test results show that the mineral processing flow sheet was carried out by washed ore-jigging-high intensity magnetic separation of jigging tailing can achieve good dressing index of the recovery 0f manganese is 92.26%in total.

  3. Role of Reactive Intermediates in Manganese Oxide Formation By Filamentous Ascomycete Fungi

    Science.gov (United States)

    Zeiner, C. A.; Anderton, C.; Wu, S.; Purvine, S.; Zink, E.; Paša-Tolić, L.; Santelli, C. M.; Hansel, C. M.

    2014-12-01

    Biogenic manganese (Mn) oxide minerals are ubiquitous in the environment, and their high reactivity can profoundly impact the fate of contaminants and cycling of carbon and nutrients. In contrast to bacteria, the pathways utilized by fungi to oxidize Mn(II) to Mn(III,IV) oxides remain largely unknown. Here, we explore the mechanisms of Mn(II) oxidation by a phylogenetically diverse group of filamentous Ascomycete fungi using a combination of chemical assays and bulk and spatially-resolved mass spectrometry. We show that the mechanisms of Mn(II) oxidation vary with fungal species, over time during secretome compositional changes, and in the presence of other fungi. Specifically, our work implicates a dynamic transition in Mn(II) oxidation pathways that varies between species. In particular, while reactive oxygen species (ROS) produced via transmembrane NADPH oxidases are involved in initial oxidation, over time, secreted enzymes become important Mn(II) oxidation mediators for some species. In addition, the overall secretome oxidation capacity varies with time and fungal species. Secretome analysis reveals a surprising absence of enzymes currently considered to be Mn(II)-oxidizing enzymes in these organisms, and instead highlights a wide variety of redox-active enzymes. Furthermore, we implicate fungal cell defense mechanisms in the formation of distinct Mn oxide patterns when fungi are grown in head-to-head competition. The identification and regulation of these secreted enzymes are under current investigation within the bulk secretome and within the interaction zone of structured fungal communities. Overall, our findings illustrate that Ascomycete Mn(II) oxidation mechanisms are highly variable and are dictated by complex environmental and ecological interactions. Future work will explore the connection between Ascomycete Mn(II) oxidation and the ability to degrade cellulose, a key carbon reservoir for biofuel production.

  4. A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

    Science.gov (United States)

    Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

    2005-05-04

    A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

  5. A study of a ceria-zirconia-supported manganese oxide catalyst for combustion of Diesel soot particles

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Escribano, V.; Fernandez Lopez, E.; del Hoyo Martinez, C. [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Pa. de la Merced s/n, E-37008 Salamanca (Spain); Gallardo-Amores, J.M. [Lab. Complutense de Altas Presiones, Departamento de Quimica Inorganica I, Universidad Complutense, Ciudad Universitaria, E-28040 Madrid (Spain); Pistarino, C.; Panizza, M.; Resini, C.; Busca, G. [Dipartimento di Ingegneria Chimica e di Processo, Universita di Genova, P.le J.F. Kennedy, Pad. D, I-16129 Genoa (Italy)

    2008-04-15

    A study has been conducted on the structural and morphological characterization of a Ce-Zr mixed oxide-supported Mn oxide as well as on its catalytic activity in the oxidation of particulate matter arising from Diesel engines. X-ray powder diffraction analysis (XRD) and FT-IR and FT-Raman spectroscopy evidence that the support is a fluorite-like ceria-zirconia solid solution, whereas the supported phase corresponds to the manganese oxide denoted as bixbyite ({alpha}-Mn{sub 2}O{sub 3}). Thermal analyses and FT-IR spectra in air at varying temperatures of soot mechanically mixed with the catalyst evidence that the combustion takes place to a total extent in the range 420-720 K, carboxylic species being detected as intermediate compounds. Moreover, the soot oxidation was studied in a flow reactor and was found to be selective to CO{sub 2}, with CO as by-product in the range 420-620 K. The amount of the generated CO decreases significantly with increasing O{sub 2} concentration in the feed. (author)

  6. Electrical characterization of a laminar manganese oxide type birnessite; Caracterizacion electrica de un oxido de manganeso laminar tipo birnesita

    Energy Technology Data Exchange (ETDEWEB)

    Arias, N. P.; Becerra, M. E.; Giraldo, O., E-mail: ohgiraldoo@unal.edu.co [Universidad Nacional de Colombia, Sede Manizales, Facultad de Ciencias Exactas y Naturales, Laboratorio de Materiales Nanoestructurados y Funcionales, Carrera 27 No. 64-60, 170004 Manizales (Colombia)

    2015-07-01

    This paper records the characterization of a manganese oxide synthesized by solid state routes which is analogous to natural mineral called birnessite. The analysis of X-ray diffraction and average oxidation state of manganese show that the material has a lamellar structure containing manganese in oxidation states (+4) and (+3). The results of electron microscopy along with surface area and pore size measurements reveal the presence of micro and meso pores in the material. Impedance spectroscopy suggests that high frequency electrical conduction occurs in the volume and on the border of the aggregates; in contrast, ionic conductivity at low frequencies was associated with potassium ions located in the interlaminar region. Ac conductivity values at low frequencies were 1.599 x 10{sup -6} Ω{sup -1} cm{sup -1} and 6.416 x 10{sup -5} Ω{sup -1} cm{sup -1} at high frequencies. These values are associated with an increased probability of electron jumping as frequency increases. These findings contribute to the understanding of electrical conduction processes and provides important information about its potential applications. As a result, this research will prove relevant in the field of batteries, super capacitors and heterogeneous catalysis, among others. (Author)

  7. Durability tests and up-scaling of selective absorbers based on copper-manganese oxide deposited by dip-coating

    Energy Technology Data Exchange (ETDEWEB)

    Bayon, Rocio; San Vicente, Gema; Morales, Angel [Unidad de Concentracion Solar, Plataforma Solar de Almeria, Departamento de Energia, CIEMAT, Avd. Complutense 22, 28040 Madrid (Spain)

    2010-06-15

    Selective absorbers based on copper-manganese oxide were prepared by dip-coating method. The optical properties of the 2-layer configuration (Al/CuMnO{sub x}/SiO{sub 2}) were improved by introducing an additional absorber-protective layer directly in contact with the aluminium substrate (i.e. 3-layer absorber), for which solar absorptance up to 0.950 was achieved. Long-term durability of these absorbers was investigated by applying both thermal stability and humidity tests established by the IEA-SHC Task X. All the analyzed samples qualified for both tests leading to similar or even better results than some commercial absorbers. In order to prove the feasibility of the up-scaling process, 3-layer absorber samples of 30 x 30 cm{sup 2} size were prepared. It was observed that sintering process was determinant for obtaining fully homogenous films within the whole large-area surface. By using a sintering process with increasing temperature, 30 x 30 cm{sup 2} samples with {alpha}{sub s}=0.935{+-}0.005 (100 measurements) could be obtained. This study reveals that it is possible to deposit CuMn-oxide absorbers on large-area substrates and that they could be a good alternative to the materials present today in the market, not only in terms of optical properties but also in terms of long term durability. (author)

  8. Rational design of coaxial structured carbon nanotube-manganese oxide (CNT-MnO2) for energy storage application

    Science.gov (United States)

    Salunkhe, Rahul R.; Ahn, Heejoon; Kim, Jung Ho; Yamauchi, Yusuke

    2015-05-01

    Recently, there has been great research interest in the development of composites (core-shell structures) of carbon nanotubes (CNTs) with metal oxides for improved electrochemical energy storage, photonics, electronics, catalysis, etc. Currently, the synthetic strategies for metal oxides/hydroxides are well established, but the development of core-shell structures by robust, cost-effective chemical methods is still a challenge. The main drawbacks for obtaining such electrodes are the very complex synthesis methods which ultimately result in high production costs. Alternatively, the solution based method offers the advantages of simple and cost effective synthesis, as well as being easy to scale up. Here, we report on the development of multi-walled carbon nanotube-manganese oxide (CNT-MnO2) core-shell structures. These samples were directly utilized for asymmetric supercapacitor (ASC) applications, where the CNT-MnO2 composite was used as the positive electrode and ZIF-8 (zeolitic imidazolate framework, ZIF) derived nanoporous carbon was used as the negative electrode. This unconventional ASC shows a high energy density of 20.44 W h kg-1 and high power density of 16 kW kg-1. The results demonstrate that these are efficient electrodes for supercapacitor application.

  9. Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

    Science.gov (United States)

    Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

    2013-08-01

    Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 °C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.

  10. Manganese Oxide-Coated Carbon Nanotubes As Dual-Modality Lymph Mapping Agents for Photothermal Therapy of Tumor Metastasis.

    Science.gov (United States)

    Wang, Sheng; Zhang, Qin; Yang, Peng; Yu, Xiangrong; Huang, Li-Yong; Shen, Shun; Cai, Sanjun

    2016-02-17

    Lymph node (LN) status is a major indicator of stage and survival of lung cancer patients. LN dissection is a primary option for lung cancer LN metastasis; however, this strategy elicits adverse effects and great trauma. Therefore, developing a minimally invasive technique to cure LN metastasis of lung cancer is desired. In this study, multiwalled carbon nanotubes (MWNTs) coated with manganese oxide (MnO) and polyethylene glycol (PEG) (namely MWNTs-MnO-PEG) was employed as a lymphatic theranostic agent to diagnose and treat metastatic LNs. After single local injection and lymph drainage were performed, regional LNs were clearly mapped by T1-weighted magnetic resonance (MR) of MnO and dark dye imaging of MWNTs. Meanwhile, metastatic LNs could be simultaneously ablated by near-infrared (NIR) irradiation under the guidance of dual-modality mapping. The excellent result was obtained in mice bearing LNs metastasis models, showing that MWNTs-MnO-PEG as a multifunctional theranostic agent was competent for dual-modality mapping guided photothermal therapy of metastatic LNs.

  11. Binder-free graphene and manganese oxide coated carbon felt anode for high-performance microbial fuel cell.

    Science.gov (United States)

    Zhang, Changyong; Liang, Peng; Yang, Xufei; Jiang, Yong; Bian, Yanhong; Chen, Chengmeng; Zhang, Xiaoyuan; Huang, Xia

    2016-07-15

    A novel anode was developed by coating reduced graphene oxide (rGO) and manganese oxide (MnO2) composite on the carbon felt (CF) surface. With a large surface area and excellent electrical conductivity, this binder-free anode was found to effectively enhance the enrichment and growth of electrochemically active bacteria and facilitate the extracellular electron transfer from the bacteria to the anode. A microbial fuel cell (MFC) equipped with the rGO/MnO2/CF anode delivered a maximum power density of 2065mWm(-2), 154% higher than that with a bare CF anode. The internal resistance of the MFC with this novel anode was 79Ω, 66% lower than the regular one's (234Ω). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses affirmed that the rGO/MnO2 composite significantly increased the anodic reaction rates and facilitated the electron transfer from the bacteria to the anode. The findings from this study suggest that the rGO/MnO2/CF anode, fabricated via a simple dip-coating and electro-deposition process, could be a promising anode material for high-performance MFC applications.

  12. Production of zinc and manganese oxide particles by pyrolysis of alkaline and Zn-C battery waste.

    Science.gov (United States)

    Ebin, Burçak; Petranikova, Martina; Steenari, Britt-Marie; Ekberg, Christian

    2016-05-01

    Production of zinc and manganese oxide particles from alkaline and zinc-carbon battery black mass was studied by a pyrolysis process at 850-950°C with various residence times under 1L/minN2(g) flow rate conditions without using any additive. The particular and chemical properties of the battery waste were characterized to investigate the possible reactions and effects on the properties of the reaction products. The thermodynamics of the pyrolysis process were studied using the HSC Chemistry 5.11 software. The carbothermic reduction reaction of battery black mass takes place and makes it possible to produce fine zinc particles by a rapid condensation, after the evaporation of zinc from a pyrolysis batch. The amount of zinc that can be separated from the black mass is increased by both pyrolysis temperature and residence time. Zinc recovery of 97% was achieved at 950°C and 1h residence time using the proposed alkaline battery recycling process. The pyrolysis residue is mainly MnO powder with a low amount of zinc, iron and potassium impurities and has an average particle size of 2.9μm. The obtained zinc particles have an average particle size of about 860nm and consist of hexagonal crystals around 110nm in size. The morphology of the zinc particles changes from a hexagonal shape to s spherical morphology by elevating the pyrolysis temperature.

  13. One-pot synthesis of co-substituted manganese oxide nanosheets and physical properties of lamellar aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Kai, Kazuya [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan); Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Cuisinier, Marine [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan); Institut des Materiaux Jean Rouxel (IMN), CNRS UMR 6502, Universite de Nantes, 2 Rue de la Houssiniere, BP32229, 44322 Nantes Cedex 3 (France); Yoshida, Yukihiro; Saito, Gunzi [Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Research Institute, Meijo University, Shiogamaguchi 1-501 Tempaku-ku, Nagoya 468-8502 (Japan); Kobayashi, Yoji [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan); Kageyama, Hiroshi, E-mail: kage@scl.kyoto-u.ac.jp [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan); Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► Solid solution nanosheets, (Mn{sub 1−x}Co{sub x})O{sub 2}, synthesized via facile one-pot process. ► The structural characterization of nanosheets revealing a single (Mn,Co)O{sub 2} layer and the solubility limit as x ∼ 0.20. ► The invariant charge density of the layer upon Co substitution. ► Systematic dependence of magnetic and optical properties of the lamellar aggregates. -- Abstract: Co-substituted manganese oxide nanosheets, (Mn{sub 1−x}Co{sub x})O{sub 2} have been synthesized in the form of a colloidal suspension via a simple one-pot method. Substitution effects on the structural, optical absorption, and magnetic properties are investigated for the nanosheets and their lamellar aggregates. The composition of the (Mn{sub 1−x}Co{sub x})O{sub 2} nanosheets can be controlled continuously by adjusting the molar ratio of the starting materials. The solubility limit is x ∼ 0.20 based on the cell volume. In the 0.00 ≤ x ≤ 0.20 range, the band gap energy, magnetic moment, and Weiss temperature change systematically with x. The charge density of the (Mn,Co)O{sub 2} layer is independent of x (i.e., [(Mn,Co)O{sub 2}]{sup 0.2−}) and the cobalt ions are trivalent in low-spin state.

  14. Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

    Directory of Open Access Journals (Sweden)

    Oyedotun K.O.

    2015-12-01

    Full Text Available Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS, UV-Vis spectrophotometry, X-ray diffraction (XRD spectroscopy, atomic force microscopy (AFM and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2 and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8 thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26 film.

  15. Graphite coated with manganese oxide/multiwall carbon nanotubes composites as anodes in marine benthic microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yubin, E-mail: ffyybb@ouc.edu.cn; Yu, Jian; Zhang, Yelong; Meng, Yao

    2014-10-30

    Highlights: • MnO{sub 2}/MWCNTs composites anode exhibits faster reaction kinetics. • The surfaces of MnO{sub 2}/MWCNTs composites anode exhibits better wettability. • A BMFC using the modified anode have excellent power output. - Abstract: Improving anode performance is of great significance to scale up benthic microbial fuel cells (BMFCs) for its marine application to drive oceanography instruments. In this study, manganese oxide (MnO{sub 2})/multiwall carbon nanotubes (MWCNTs) composites are prepared to be as novel anodes in the BMFCs via a direct redox reaction between permanganate ions (MnO{sub 4}{sup −}) and MWCNTs. The results indicate that the MnO{sub 2}/MWCNTs anode has a better wettability, greater kinetic activity and higher power density than that of the plain graphite (PG) anode. It is noted that the MnO{sub 2} (50% weight percent)/MWCNTs anode shows the highest electrochemical performance among them and will be a promising material for improving bioelectricity production of the BMFCs. Finally, a synergistic mechanism of electron transfer shuttle of Mn ions and their redox reactions in the interface between modified anode and bacteria biofilm are proposed to explain its excellent electrochemical performance.

  16. Selective hydrogenation of halogenated arenes using porous manganese oxide (OMS-2) and platinum supported OMS-2 catalysts.

    Science.gov (United States)

    McManus, Iain J; Daly, Helen; Manyar, Haresh G; Taylor, S F Rebecca; Thompson, Jillian M; Hardacre, Christopher

    2016-07-04

    Porous manganese oxide (OMS-2) and platinum supported on OMS-2 catalysts have been shown to facilitate the hydrogenation of the nitro group in chloronitrobenzene to give chloroaniline with no dehalogenation. Complete conversion was obtained within 2 h at 25 °C and, although the rate of reaction increased with increasing temperature up to 100 °C, the selectivity to chloroaniline remained at 99.0%. Use of Pd/OMS-2 or Pt/Al2O3 resulted in significant dechlorination even at 25 °C and 2 bar hydrogen pressure giving a selectivity to chloroaniline of 34.5% and 77.8%, respectively, at complete conversion. This demonstrates the potential of using platinum group metal free catalysts for the selective hydrogenation of halogenated aromatics. Two pathways were observed for the analogous nitrobenzene hydrogenation depending on the catalyst used. The hydrogenation of nitrobenzene was found to follow a direct pathway to aniline and nitrosobenzene over Pd/OMS-2 in contrast to the OMS and Pt/OMS-2 catalysts which resulted in formation of nitrosobenzene, azoxybenzene and azobenzene/hydrazobenzene intermediates before complete conversion to aniline. These results indicate that for Pt/OMS-2 the hydrogenation proceeds predominantly over the support with the metal acting to dissociate hydrogen. In the case of Pd/OMS-2 both the hydrogenation and hydrogen adsorption occur on the metal sites.

  17. Catalytic degradation of Acid Orange 7 by manganese oxide octahedral molecular sieves with peroxymonosulfate under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Lian; Sun, Binzhe; Wei, Mingyu; Luo, Shilu; Pan, Fei; Xu, Aihua [School of Environmental Engineering, Wuhan Textile University, Wuhan 430073 (China); Li, Xiaoxia, E-mail: lixxwh@163.com [School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073 (China)

    2015-03-21

    Highlights: • OMS-2/PMS/Vis system could efficiently catalyze the degradation of organic dyes. • The system showed much higher activity than that of OMS-2/PMS and OMS-2/Vis. • The OMS-2 catalyst exhibited stable performance for multiple runs. • Sulfate radicals were suggested to be the major reactive species in the system. • The radicals production might involve the redox cycle of Mn(IV)/Mn(III) and Mn(III)/Mn(II). - Abstract: In this paper, the photodegradation of Acid Orange 7 (AO7) in aqueous solutions with peroxymonosulfate (PMS) was studied with manganese oxide octahedral molecular sieves (OMS-2) as the catalyst. The activities of different systems including OMS-2 under visible light irradiation (OMS-2/Vis), OMS-2/PMS and OMS-2/PMS/Vis were evaluated. It was found that the efficiency of OMS-2/PMS was much higher than that of OMS-2/Vis and could be further enhanced by visible light irradiation. The catalyst also exhibited stable performance for multiple runs. Results from ESR and XPS analyses suggested that the highly catalytic activity of the OMS-2/PMS/Vis system possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) and Mn(III)/Mn(II), while in the OMS-2/PMS system, only the redox reaction between Mn(IV)/Mn(III) occurred. Several operational parameters, such as dye concentration, catalyst load, PMS concentration and solution pH, affected the degradation of AO7.

  18. The effects of manganese oxide octahedral molecular sieve chitosan microspheres on sludge bacterial community structures during sewage biological treatment

    Science.gov (United States)

    Pan, Fei; Liu, Wen; Yu, Yang; Yin, Xianze; Wang, Qingrong; Zheng, Ziyan; Wu, Min; Zhao, Dongye; Zhang, Qiu; Lei, Xiaoman; Xia, Dongsheng

    2016-11-01

    This study examines the effects of manganese oxide octahedral molecular sieve chitosan microspheres (Fe3O4@OMS-2@CTS) on anaerobic and aerobic microbial communities during sewage biological treatment. The addition of Fe3O4@OMS-2@CTS (0.25 g/L) resulted in enhanced levels of operational performance for decolourization dye X-3B. However, degradation dye X-3B inhibition in the presence of Fe3O4@OMS-2@CTS was recorded as greater than or equal to 1.00 g/L. Illumina MiSeq high throughput sequencing of the 16 S rRNA gene showed that 108 genera were observed during the anaerobic process, while only 71 genera were observed during the aerobic process. The largest genera (Aequorivita) decreased from 21.14% to 12.65% and the Pseudomonas genera increased from 10.57% to 12.96% according to the abundance in the presence of 0.25 g/L Fe3O4@OMS-2@CTS during the anaerobic process. The largest Gemmatimonas genera decreased from 21.46% to 11.68% and the Isosphaerae genera increased from 5.8% to 11.98% according to the abundance in the presence of 0.25 g/L Fe3O4@OMS-2@CTS during the aerobic process. Moreover, the X-ray photoelectron spectroscopy results show that the valence states of Mn and Fe in Fe3O4@OMS-2@CTS changed during sewage biological treatment.

  19. Validation of In-Situ Iron-Manganese Oxide Coated Stream Pebbles as Sensors for Arsenic Source Monitoring

    Science.gov (United States)

    Blake, J.; Peters, S. C.; Casteel, A.

    2013-12-01

    Locating nonpoint source contaminant fluxes can be challenging due to the inherent heterogeneity of source and of the subsurface. Contaminants such as arsenic are a concern for drinking water quality and ecosystem health. Arsenic contamination can be the result of several natural and anthropogenic sources, and therefore it can be difficult to trace and identify major areas of arsenic in natural systems. Identifying a useful source indicator for arsenic is a crucial step for environmental remediation efforts. Previous studies have found iron-manganese oxide coated streambed pebbles as useful source indicators due to their high attraction for heavy metals in water. In this study, pebbles, surface water at baseflow and nearby rocks were sampled from the Pennypack Creek and its tributaries, in southwestern Pennsylvania, to test the ability of coated streambed pebbles as environmental source indicators for arsenic. Quartz pebbles, 5-7 cm in diameter, were sampled to minimize elemental contamination from rock chemistry. In addition, quartz provides an excellent substrate for iron and manganese coatings to form. These coatings were leached from pebbles using 4M nitric acid with 0.1% concentrated hydrochloric acid. Following sample processing, analyses were performed using an ICP-MS and the resulting data were spatially organized using ArcGIS software. Arsenic, iron and manganese concentrations in the leachate are normalized to pebble surface area and each location is reported as a ratio of arsenic to iron and manganese. Results suggest that iron-manganese coated stream pebbles are useful indicators of arsenic location within a watershed.

  20. Complete genome sequence of Arthrobacter sp. ERGS1:01, a putative novel bacterium with prospective cold active industrial enzymes, isolated from East Rathong glacier in India.

    Science.gov (United States)

    Kumar, Rakshak; Singh, Dharam; Swarnkar, Mohit Kumar; Singh, Anil Kumar; Kumar, Sanjay

    2015-11-20

    We report the complete genome sequence of Arthrobacter sp. ERGS1:01, a novel bacterium which produces industrial enzymes at low temperature. East Rathong glacier in Sikkim Himalayas is untouched and unexplored for microbial diversity though it has a rich source of glaciers, alpine and meadows. Genome sequence has provided the basis for understanding its adaptation under harsh condition of Himalayan glacier, its ability to produce cold active industrial enzymes and has unlocked opportunities for microbial bioprospection from East Rathong glacier.

  1. Physicochemical factors for affecting the efficiency of Arthrobacter chlorophenolicus MN1409 on manganese oxidation%理化因素对锰细菌Arthrobacter chlorophenolicus MN1409氧化Mn2+的影响

    Institute of Scientific and Technical Information of China (English)

    冯福鑫; 王芳; 许旭萍

    2012-01-01

    Arthrobacter chlorophenolicus MN1409是1株分离自锰矿样品的高效锰氧化细菌.为了建立该菌株氧化Mn2+的适宜条件,研究了接种量、装液量、摇床转速、温度、pH值、Fe2+初始质量浓度和Mn2+初始质量浓度等理化因素对其锰氧化效率的影响.结果表明,接种量、装液量、转速和Mn2+初始质量浓度在一定范围内变化对锰氧化率影响不大;而温度、pH值和Fe2+初始质量浓度变化对锰氧化率有较大影响.当接种量为4%,装液量为60mL,温度为25℃,摇床转速为100r/min,pH值为7,且有一定的Fe2+存在时,Arthrobacter chlorophenolicus MN1409对锰的氧化效率最高.%The physicochemical factors for affecting the manganese oxidation efficiency of an manganese oxidizing bacteria named Arthrobacter chlorophennlicus MN1409 which was isolated from manganese ore sample were studied. The identified factors include inoculum volume, liquid volume, temperature, shaking speed, pH as well as the concentration of Fe2+ and Mn2+ . The results showed that there was no significant effect on the biological manganese oxidation rate and chemical manganese oxidation rate during 2% - 10% inoculum volumes. 4% inoculum volume was the optimum condition according to its highest total manganese oxidation rate. Similarly, biological and chemical manganese oxidation rale have no significant difference for the liquid volume ranging from 50 mL to 100 mL in 250 mL triangular flask , the highest total manganese oxidation rate occurred in 60 mL liquid volume. Nevertheless, temperature showed an positive effect on manganese oxidation rate. By increasing the temperature from 15 ℃ to 35 ℃, highest biological and chemical manganese oxidation rate could be reached at 25 ℃ and 35 ℃ , respectively, plus the total oxidation rate could achieved 81.52% as well in 35 ℃ . In addition, the effect of shaker speed on manganese oxidation efficiency (MOE) showed that the oxidation rates were similar for

  2. Lithium carbonate as an electrolyte additive for enhancing the high-temperature performance of lithium manganese oxide spinel cathode

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Renheng [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Li, Xinhai, E-mail: 703131039@qq.com [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Wang, Zhixing; Guo, Huajun [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Hou, Tao [Jiangxi Youli New Materials Co., Ltd, Pingxiang 337000 (China); Yan, Guochun; Huang, Bin [School of Metallurgy and Environment, Central South University, Changsha 410083 (China)

    2015-01-05

    Highlights: • The addition of Li{sub 2}CO{sub 3} to the electrolyte can suppress the contents of HF in the electrolyte. • The low self-discharge rate of the LiMn{sub 2}O{sub 4} cells with Li{sub 2}CO{sub 3} is lower than that of no additive. • The LiMn{sub 2}O{sub 4} cells with Li{sub 2}CO{sub 3} exhibit better rate capability and excellent cycle stability than that without Li{sub 2}CO{sub 3}. • A stable film can be formed on the LiMn{sub 2}O{sub 4} cathode using containing-Li{sub 2}CO{sub 3} electrolyte. - Abstract: The effect of lithium carbonate (Li{sub 2}CO{sub 3}) as an additive on the stability of the electrolyte and cycling performance of lithium manganese oxide spinel (LiMn{sub 2}O{sub 4}) batteries at elevated temperature was studied. The addition of Li{sub 2}CO{sub 3} to the electrolyte can suppress the capacity fading of LiMn{sub 2}O{sub 4} batteries. The linear sweep voltammetry (LSV) and the cyclic voltammetry (CV) indicate that Li{sub 2}CO{sub 3} has a lower oxidation potential in the mixed solvents of ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), participating in the formation process of the stable cathode electrolyte interface (CEI) film. In addition, the results of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrate that the stable CEI film of the cells with Li{sub 2}CO{sub 3} can be formed, which can effectively reduce the dissolution of Mn{sup 2+} from LiMn{sub 2}O{sub 4} into the electrolyte at elevated temperature. It is concluded that the addition of Li{sub 2}CO{sub 3} to a solution of 1 M LiPF{sub 6}–EC/EMC/DEC = 1/1/1 (weight ratio) may decrease solvent decomposition and change the structure of the passivation film on the LiMn{sub 2}O{sub 4} cathode.

  3. Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Hameed, R.M., E-mail: randa311eg@yahoo.com [Chemistry Department, Faculty of Science, Cairo University, Giza (Egypt); Fetohi, Amani E.; Amin, R.S.; El-Khatib, K.M. [Chemical Engineering Department, National Research Center, Dokki, Giza (Egypt)

    2015-12-30

    Graphical abstract: Physical and electrochemical properties of Pt/C, Pt–MnO{sub 2}/C-1 and Pt–MnO{sub 2}/C-2 electrocatalysts. - Highlights: • Adding MnO{sub 2} to Pt/C improved the dispersion of Pt nanoparticles. • The existence of MnO{sub 2} improved the kinetics of methanol oxidation reaction. • R{sub ct} value of Pt–MnO{sub 2}/C was about 10 times as low as that at Pt/C. • The removal of CO{sub ads} poisoning species was facilitated at Pt–MnO{sub 2}/C. - Abstract: The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt–MnO{sub 2}/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO{sub 2} improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt–MnO{sub 2}/C towards methanol oxidation in H{sub 2}SO{sub 4} solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO{sub 2} is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt–MnO{sub 2}/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt–MnO{sub 2}/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).

  4. Application of manganese oxidizing bacteria and biogenic manganese oxide in remediation of environmental pollution:a review%锰氧化菌及其生物锰氧化物在环境污染修复中的应用研究进展

    Institute of Scientific and Technical Information of China (English)

    廖水姣; 王革娇

    2013-01-01

    目前,重金属和有毒有机污染物的环境污染受到社会广泛的关注.已有的研究表明,环境中广泛存在的锰氧化菌能修复环境中的Mn(Ⅱ)污染及生产锰氧化物(简称生物锰氧化物);生物锰氧化物较化学合成氧化锰矿物结晶弱,粒径小,Mn价态高,结构中八面体空穴多,比表面积大,具有比化学合成锰氧化物更强的吸附、氧化和光还原溶解特性;生物锰氧化物能吸附Cu(Ⅱ)、Zn(Ⅱ)、Pb(Ⅱ)、Co(Ⅲ)、Cd(Ⅱ)、Hg(Ⅱ)等多种重金属,氧化Co(Ⅱ)、As(Ⅲ)、Cr(Ⅲ)、U(Ⅳ)、Ce(Ⅲ)等低价重金属离子,降解乙炔基雌二醇等有机污染物,是具有广泛应用前景的环境材料.%At present,the environmental pollution of heavy metals and toxic organic pollutants has been widely concerned in the community.Some researches indicated that manganese-oxidizing bacteria widely existed in the environment can remediate Mn (Ⅱ) pollution and produce biogenic manganese oxides.The biogenic manganese oxides have weaker crystalline,smaller particle size,higher Mn valence,more cavity structure in octahedral,larger specific surface area,stronger adsorption,oxidation and photochemical reductive dissolution characteristics than that of the chemical Mn oxides.The biogenic manganese oxides can absorb Cu (Ⅱ),Zn (Ⅱ),Pb (Ⅱ),Co (Ⅲ),Cd (Ⅱ),Hg (Ⅱ),oxidize Co (Ⅱ),As (Ⅲ),Cr(Ⅲ),U(Ⅳ),Ce(Ⅲ),degrade ethynylestradiol and other organic pollutants.The biogenic manganese oxides are environmental materials with wide application prospect.

  5. The putative endoglucanase PcGH61D from Phanerochaete chrysosporium is a metal-dependent oxidative enzyme that cleaves cellulose.

    Directory of Open Access Journals (Sweden)

    Bjørge Westereng

    Full Text Available Many fungi growing on plant biomass produce proteins currently classified as glycoside hydrolase family 61 (GH61, some of which are known to act synergistically with cellulases. In this study we show that PcGH61D, the gene product of an open reading frame in the genome of Phanerochaete chrysosporium, is an enzyme that cleaves cellulose using a metal-dependent oxidative mechanism that leads to generation of aldonic acids. The activity of this enzyme and its beneficial effect on the efficiency of classical cellulases are stimulated by the presence of electron donors. Experiments with reduced cellulose confirmed the oxidative nature of the reaction catalyzed by PcGH61D and indicated that the enzyme may be capable of penetrating into the substrate. Considering the abundance of GH61-encoding genes in fungi and genes encoding their functional bacterial homologues currently classified as carbohydrate binding modules family 33 (CBM33, this enzyme activity is likely to turn out as a major determinant of microbial biomass-degrading efficiency.

  6. A-site substitution effect of perovskite-type cobalt and manganese oxides on two-step water splitting reaction for solar hydrogen production

    Science.gov (United States)

    Kaneko, Hiroshi; Hasegawa, Takumi; Mori, Kohei

    2017-06-01

    The perovskite type metal oxides (ABO3: A and B are metal elements) are attractive material for the two-step water splitting process to produce solar hydrogen, because the diversity of perovskite compound with substitution of metal ion makes its reducibility changeable. The perovskite-type cobalt and manganese oxides are prepared with substitution of metal ion in the A-site, and the performance of two-step water splitting reaction is investigated. The LaCoO3 and Ca0.45Sr0.4La0.15MnO3-δ, containing more trivalent metal ions in the A-site of perovskite structure, are most promising materials for solar hydrogen production. It is found that the two-step water-splitting reaction with Ca0.45Sr0.4La0.15MnO3-δ of the perovskite-type manganese oxide proceed stoichiometrically and Ca0.45Sr0.4La0.15MnO3-δ can produce much H2 gas (4cm3/g-sample) at the reduction temperature of 1400 °C.

  7. Enhanced catalytic toluene oxidation by interaction between copper oxide and manganese oxide in Cu-O-Mn/γ-Al2O3 catalysts

    Science.gov (United States)

    Wang, Hongpei; Lu, Yiyuan; Han, YuXiang; Lu, Chunliang; Wan, Haiqin; Xu, Zhaoyi; Zheng, Shourong

    2017-10-01

    Toward catalytic oxidation of toluene, Cu-O-Mn/γ-Al2O3 catalysts with series molar ratios of Cu/Mn were prepared using an impregnation method. The surface structure and chemical state of the as-prepared catalysts were characterized by the combination of X-ray diffraction (XRD), N2 adsorption/desorption, UV-vis spectroscopy (UV-vis), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR). The results demonstrated that copper oxide and manganese oxide were highly dispersed on the γ-Al2O3 support. Meanwhile, there is an interaction between copper oxide and manganese oxide, depending on the atomic ratio of Cu/Mn. At the ratio of Cu/Mn = 1:1.5, the interaction between Cu and Mn oxides reached the strongest, thus leading to the highest catalytic activity and turn over frequency among all of the ratios. The temperature for complete combustion of toluene over the strongest interaction sample could be 350 °C, which could further decrease to 300 °C when tuning the loading amount of Cu and Mn. Findings in this work are important for the design of efficient catalyst by tuning the interaction between each components.

  8. Immobilization of iron- and manganese-oxidizing bacteria with a biofilm-forming bacterium for the effective removal of iron and manganese from groundwater.

    Science.gov (United States)

    Li, Chunyan; Wang, Shuting; Du, Xiaopeng; Cheng, Xiaosong; Fu, Meng; Hou, Ning; Li, Dapeng

    2016-11-01

    In this study, three bacteria with high Fe- and Mn-oxidizing capabilities were isolated from groundwater well sludge and identified as Acinetobacter sp., Bacillus megaterium and Sphingobacterium sp. The maximum removal ratios of Fe and Mn (99.75% and 96.69%) were obtained by an optimal combination of the bacteria at a temperature of 20.15°C, pH 7.09 and an inoculum size of 2.08%. Four lab-scale biofilters were tested in parallel for the removal of iron and manganese ions from groundwater. The results indicated that the Fe/Mn removal ratios of biofilter R4, which was inoculated with iron- and manganese-oxidizing bacteria and a biofilm-forming bacterium, were approximately 95% for each metal during continuous operation and were better than the other biofilters. This study demonstrated that the biofilm-forming bacterium could promote the immobilization of the iron- and manganese-oxidizing bacteria on the biofilters and enhance the removal efficiency of iron and manganese ions from groundwater.

  9. Pseudouridine synthases: four families of enzymes containing a putative uridine-binding motif also conserved in dUTPases and dCTP deaminases.

    Science.gov (United States)

    Koonin, E V

    1996-06-15

    Using a combination of several methods for protein sequence comparison and motif analysis, it is shown that the four recently described pseudouridine syntheses with different specificities belong to four distinct families. Three of these families share two conserved motifs that are likely to be directly involved in catalysis. One of these motifs is detected also in two other families of enzymes that specifically bind uridine, namely deoxycitidine triphosphate deaminases and deoxyuridine triphosphatases. It is proposed that this motif is an essential part of the uridine-binding site. Two of the pseudouridine syntheses, one of which modifies the anticodon arm of tRNAs and the other is predicted to modify a portion of the large ribosomal subunit RNA belonging to the peptidyltransferase center, are encoded in all extensively sequenced genomes, including the 'minimal' genome of Mycoplasma genitalium. These particular RNA modifications and the respective enzymes are likely to be essential for the functioning of any cell.

  10. Flavonoid inhibitors as novel antimycobacterial agents targeting Rv0636, a putative dehydratase enzyme involved in Mycobacterium tuberculosis fatty acid synthase II.

    Science.gov (United States)

    Brown, Alistair K; Papaemmanouil, Athina; Bhowruth, Veemal; Bhatt, Apoorva; Dover, Lynn G; Besra, Gurdyal S

    2007-10-01

    Flavonoids comprise a large group of bioactive polyphenolic plant secondary metabolites. Several of these possess potent in vivo activity against Escherichia coli and Plasmodium falciparum, targeting enzymes involved in fatty acid biosynthesis, such as enoyl-ACP-reductase, beta-ketoacyl-ACP reductase and beta-hydroxyacyl-ACP dehydratase. Herein, we report that butein, isoliquirtigenin, 2,2',4'-trihydroxychalcone and fisetin inhibit the growth of Mycobacterium bovis BCG. Furthermore, in vitro inhibition of the mycolic-acid-producing fatty acid synthase II (FAS-II) of Mycobacterium smegmatis suggests a mode of action related to those observed in E. coli and P. falciparum. Through a bioinformatic approach, we have established the product of Rv0636 as a candidate for the unknown mycobacterial dehydratase, and its overexpression in M. bovis BCG conferred resistance to growth inhibition by butein and isoliquirtigenin, and relieved inhibition of fatty acid and mycolic acid biosynthesis in vivo. Furthermore, after overexpression of Rv0636 in M. smegmatis, FAS-II was less sensitive to these inhibitors in vitro. Overall, the data suggest that these flavonoids are inhibitors of mycobacterial FAS-II and in particular Rv0636, which represents a strong candidate for the beta-hydroxyacyl-ACP dehydratase enzyme of M. tuberculosis FAS-II.

  11. Manganese extraction from high-iron-content manganese oxide ores by selective reduction roasting-acid leaching process using black charcoal as reductant

    Institute of Scientific and Technical Information of China (English)

    张元波; 赵熠; 游志雄; 段道显; 李光辉; 姜涛

    2015-01-01

    Reduction roasting-acid leaching process was utilized to process high-iron-content manganese oxide ore using black charcoal as reductant. The results indicate that, compared with the traditional reductant of anthracite, higher manganese extraction efficiency is achieved at lower roasting temperature and shorter residence time. The effects of roasting parameters on the leaching efficiency of Mn and Fe were studied, and the optimal parameters are determined as follows: roasting temperature is 650 °C, residence time is 40 min, and black charcoal dosage is 10% (mass fraction). Under these conditions, the leaching efficiency of Mn reaches 82.37% while that of Fe is controlled below 7%. XRD results show that a majority of MnO2 and Fe2O3in the raw ore are reduced to MnO and Fe3O4, respectively.

  12. Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples

    Science.gov (United States)

    Serra, Antonio; Monteduro, Anna Grazia; Padmanabhan, Sanosh Kunjalukkal; Licciulli, Antonio; Bonfrate, Valentina; Salvatore, Luca; Calcagnile, Lucio

    2017-01-01

    Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the pores volume ten times. This feature was crucial to decontaminate both aqueous samples and food extracts from nickel ion. Efficient removal of Ni2+ was highlighted by the well-known dimethylglyoxime test and by ICP-MS analysis and the possibility of regenerating the nanostructure was obtained by a washing treatment in disodium ethylenediaminetetraacetate solution. PMID:28804670

  13. Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis

    DEFF Research Database (Denmark)

    Su, Hai-Yan; Gorlin, Yelena; Man, Isabela Costinela

    2012-01-01

    Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen...... and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface...... intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis...

  14. Size-controlled synthesis and formation mechanism of manganese oxide OMS-2 nanowires under reflux conditions with KMnO4 and inorganic acids

    Science.gov (United States)

    Zhang, Qin; Cheng, Xiaodi; Qiu, Guohong; Liu, Fan; Feng, Xionghan

    2016-05-01

    This study presents a simplified approach for size-controlled synthesis of manganese oxide octahedral molecular sieve (OMS-2) nanowires using potassium permanganate (KMnO4) and different inorganic acids (HCl, HNO3, and H2SO4) under reflux conditions. The morphology and nanostructure of the synthesized products are characterized by X-ray diffraction, Ar adsorption, and electron microscopy analysis, in order to elucidate the controlling effects of acid concentration and type as well as the formation mechanism of OMS-2 nanowires. The concentration of inorganic acid is a crucial factor controlling the phase of the synthesized products. OMS-2 nanowires are obtained with HCl at the concentration ≥0.96 mol/L or with HNO3 and H2SO4 at the concentrations ≥0.72 mol/L. Differently, the type of inorganic acid effectively determines the particle size of OMS-2 nanowires. When the acid is changed from HCl to HNO3 and H2SO4 in the reflux system, the average length of OMS-2 declines significantly by 60-70% (1104-442 and 339 nm), with minor decreased in the average width (43-39 and 34 nm). The formation of OMS-2 nanowires under reflux conditions with KMnO4 and inorganic acids involves a two-step process, i.e., the initial formation of layered manganese oxides, and subsequent transformation to OMS-2 via a dissolution-recrystallization process under acidic conditions. The proposed reflux route provides an alternative approach for synthesizing OMS-2 nanowires as well as other porous nano-crystalline OMS materials.

  15. Effects of Helicobacter suis γ-glutamyl transpeptidase on lymphocytes: modulation by glutamine and glutathione supplementation and outer membrane vesicles as a putative delivery route of the enzyme.

    Directory of Open Access Journals (Sweden)

    Guangzhi Zhang

    Full Text Available Helicobacter (H. suis colonizes the stomach of the majority of pigs as well as a minority of humans worldwide. Infection causes chronic inflammation in the stomach of the host, however without an effective clearance of the bacteria. Currently, no information is available about possible mechanisms H. suis utilizes to interfere with the host immune response. This study describes the effect on various lymphocytes of the γ-glutamyl transpeptidase (GGT from H. suis. Compared to whole cell lysate from wild-type H. suis, lysate from a H. suis ggt mutant strain showed a decrease of the capacity to inhibit Jurkat T cell proliferation. Incubation of Jurkat T cells with recombinantly expressed H. suis GGT resulted in an impaired proliferation, and cell death was shown to be involved. A similar but more pronounced inhibitory effect was also seen on primary murine CD4(+ T cells, CD8(+ T cells, and CD19(+ B cells. Supplementation with known GGT substrates was able to modulate the observed effects. Glutamine restored normal proliferation of the cells, whereas supplementation with reduced glutathione strengthened the H. suis GGT-mediated inhibition of proliferation. H. suis GGT treatment abolished secretion of IL-4 and IL-17 by CD4(+ T cells, without affecting secretion of IFN-γ. Finally, H. suis outer membrane vesicles (OMV were identified as a possible delivery route of H. suis GGT to lymphocytes residing in the deeper mucosal layers. Thus far, this study is the first to report that the effects on lymphocytes of this enzyme, not only important for H. suis metabolism but also for that of other Helicobacter species, depend on the degradation of two specific substrates: glutamine and reduced glutatione. This will provide new insights into the pathogenic mechanisms of H. suis infection in particular and infection with gastric helicobacters in general.

  16. Altered alkaline phosphatase activity in obese Zucker rats liver respect to lean Zucker and Wistar rats discussed in terms of all putative roles ascribed to the enzyme

    Directory of Open Access Journals (Sweden)

    V. Bertone

    2011-02-01

    most hepatocytes were devoid of AlkP activity with the exception of clusters of macrosteatotic hepatocytes in the mid-zone, where the reaction was intense in basolateral domains and in distorted canaliculi, a typical pattern of cholestasis. The interpretation of these data was hindered by the fact that the physiological role of AlkP is still under debate. In the present study, the various functions proposed for the role of the enzyme in bile canaliculi and in cholangiocytes are reviewed. Independently of the AlkP role, our data suggest that AlkP does not seem to be a reliable marker to study the initial step of bile production during OLT of fatty livers, but may still be used to investigate the behaviour of bile ductules and small bile ducts.

  17. Putative Enzymes of UV Photoproduct Repair

    Directory of Open Access Journals (Sweden)

    Cynthia J. Sakofsky

    2011-01-01

    Full Text Available In order to determine the biological relevance of two S. acidocaldarius proteins to the repair of UV photoproducts, the corresponding genes (Saci_1227 and Saci_1096 were disrupted, and the phenotypes of the resulting mutants were examined by various genetic assays. The disruption used integration by homologous recombination of a functional but heterologous pyrE gene, promoted by short sequences attached to both ends via PCR. The phenotypic analyses of the disruptants confirmed that ORF Saci_1227 encodes a DNA photolyase which functions in vivo, but they could not implicate ORF Saci_1096 in repair of UV- or other externally induced DNA damage despite its similarity to genes encoding UV damage endonucleases. The success of the gene-disruption strategy, which used 5′ extensions of PCR primers to target cassette integration, suggests potential advantages for routine construction of Sulfolobus strains.

  18. 四种用于降低三价砷毒性的锰氧化物合成及表征%Synthesis and Characterization of Four Manganese Oxides to Reduce Trivalent Arsenic Toxicity

    Institute of Scientific and Technical Information of China (English)

    李秀娟; 张雅莉; 崔月梅

    2014-01-01

    Four kinds of manganese oxides was synthesized in this paper to study the oxidation and ad-sorption of trivalent arsenic. A variety of methods were used to characterized the morphology of manganese oxides and make the preparation for the next step to reduce the toxicity of trivalent arsenic.%为了研究不同形态的锰氧化物对三价砷的氧化及吸附,本文合成了四种锰氧化物,并用多种方法对其形态进行了表征,以用于后续研究中对三价砷毒性降低的研究。

  19. 系列纳米结构锰氧化物的水热合成%Synthesis of Various Nanostructured Manganese Oxides via Facile Hydrothermal Reaction

    Institute of Scientific and Technical Information of China (English)

    杨则恒; 周晨旭; 宋新民; 张卫新; 张娜

    2008-01-01

    以KMnO4为锰源、抗坏血酸(AA)为还原剂,采用水热法制备系列纳米结构锰氧化物.通过调节反应物的物质的量的比、水溶液的pH值、反应温度和反应时间,制备出了不同纳米结构的锰氧化物,包括Mn3O4纳米粒子、MnOOH、α-MnO2和β-MnO2纳米棒.采用XRD和TEM测试技术对合成产物进行了表征,同时对其反应机理进行了探讨.%A versatile hydrothermal reaction between KMnO4 and ascorbic acid (AA) was developed to synthesizemanganese compounds. A variety of nanostructured manganese oxides including Mn3O4 nanoparticles, MnOOH, α-MnO2 and β-MnO2 nanorods have been prepared through adjusting the molar ratio of the reactants, pH value of theaqueous solution, reaction temperature and reaction time. The products were characterized by X-ray powderdiffraction(XRD) and transmission electron microscopy(TEM). The possible reaction mechanism was discussed.

  20. Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries.

    Science.gov (United States)

    Wu, Xuehang; Xu, Gui-Liang; Zhong, Guiming; Gong, Zhengliang; McDonald, Matthew J; Zheng, Shiyao; Fu, Riqiang; Chen, Zonghai; Amine, Khalil; Yang, Yong

    2016-08-31

    P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ X-ray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SS-NMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na0.66Ni0.33-xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni(4+)/Ni(3+)/Ni(2+) redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.

  1. Lithium manganese oxide (LiMn2O4) nanoparticles synthesized by hydrothermal method as adsorbent of lithium recovery process from geothermal fluid of Lumpur Sidoarjo

    Science.gov (United States)

    Noerochim, Lukman; Sapputra, Gede Panca Ady; Widodo, Amien

    2016-04-01

    Lumpur Sidoarjo is one of geothermal fluid types which has a great potential as source of lithium. Adsorption method with Lithium Manganese Oxide (LiMn2O4) as an adsorbent has been chosen for lithium recovery process due to low production cost and environmental friendly. LiMn2O4 was synthesized by hydrothermal method at 200 °C for 24 hrs, 48 hrs, and 72 hrs. As prepared LiMn2O4 powder is treated by acid treatment with 0.5 M HCl solution for 24 hrs. XRD test result reveals that all of as-prepared samples are indexed as spinel structure of LiMn2O4 (JCPDS card no 35-0782) with no impurity peaks detected. SEM images show that LiMn2O4 has nanoparticles morphology with particle size around 25 nm. The highest adsorption efficiency of adsorbent is obtained by sample hydrothermal for 72 hrs with 42.76%.

  2. Facile one-step template-free synthesis of uniform hollow microstructures of cryptomelane-type manganese oxide K-OMS-2.

    Science.gov (United States)

    Galindo, Hugo M; Carvajal, Yadira; Njagi, Eric; Ristau, Roger A; Suib, Steven L

    2010-08-17

    Hollow microstructures of cryptomelane-type manganese oxide were produced in a template-free one-step process based on the fine-tuning of the oxidation rate of manganese species during the synthesis. The tuning of the reaction rate brought about by a mixture of the oxidants oxone and potassium nitrate becomes apparent from the gradual physical changes taking place in the reaction medium at early times of the synthesis. The successful synthesis of the hollow uniform structures could be performed in the ranges 120-160 degrees C and 8.2-10.7 for temperature and mass ratio oxone/potassium nitrate, respectively. Independent of the conditions of the synthesis, all of the complex microstructures showed the same pattern for the array of very long nanofibers in which some of these elongated around the surface confining the cavity and the other fibers grew normal to the surface created by the previous arrangement. A mechanism based on the heterogeneous nucleation of the cryptomelane phase on the surface of an amorphous precursor and the growth of the nanoscale fibers by processes such as dissolution-crystallization and lateral attachment of primary nanocrystalline fibers is proposed to explain the formation of the hollow structures.

  3. Effects of manganese oxide-modified biochar composites on arsenic speciation and accumulation in an indica rice (Oryza sativa L.) cultivar.

    Science.gov (United States)

    Yu, Zhihong; Qiu, Weiwen; Wang, Fei; Lei, Ming; Wang, Di; Song, Zhengguo

    2017-02-01

    A pot experiment was used to investigate arsenic (As) speciation and accumulation in rice, as well as its concentration in both heavily contaminated and moderately contaminated soils amended with manganese oxide-modified biochar composites (MBC) and biochar alone (BC). In heavily As-contaminated soil, application of BC and MBC improved the weight of above-ground part and rice root, whereas in moderately As-contaminated soil, the application of MBC and low rate BC amendment increased rice root, grain weight and the biomass of the plant. Arsenic reduction in different parts of rice grown in MBC-amended soils was greater than that in plants cultivated in BC-amended soils. Such reduction can be attributed to the oxidation of arsenite, As(III), to arsenate, As(V), by Mn-oxides, which also had a strong adsorptive capacity for As(V). MBC amended to As-contaminated soil had a positive effect on amino acids. The Fe and Mn levels in the iron-manganese plaque that formed on the rice root surface differed among the treatments. MBC addition significantly increased Mn content (p < 0.05); the application of 2.0% MBC increased Mn content 36- and 10-fold compared to the control in heavily and moderately As-contaminated soils, respectively. The results indicate that application of Mn oxide-modified biochar to As-contaminated paddy soil could effectively remediate contaminated soil and reduce As accumulation in edible parts of rice.

  4. One-step sonochemical synthesis of a graphene oxide-manganese oxide nanocomposite for catalytic glycolysis of poly(ethylene terephthalate).

    Science.gov (United States)

    Park, Gle; Bartolome, Leian; Lee, Kyoung G; Lee, Seok Jae; Kim, Do Hyun; Park, Tae Jung

    2012-07-07

    Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn(3)O(4)) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn(3)O(4). An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn(3)O(4) phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn(3)O(4) were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene terephthalate) (PET) depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET). The highest monomer yield of 96.4% was obtained with the nanocomposite containing the lowest amount of Mn(3)O(4), while PET glycolysis with the Mn(3)O(4) without GO yielded 82.7% BHET.

  5. Citreicella manganoxidans sp. nov., a novel manganese oxidizing bacterium isolated from a shallow water hydrothermal vent in Espalamaca (Azores)

    Digital Repository Service at National Institute of Oceanography (India)

    Rajasabapathy, R.; Mohandass, C.; Dastager, S.G.; Liu, Q.; Li, W.-J.; Colaco, A.

    and phylogenetic analyses Genomic DNA was extracted with a DNeasy Blood and Tissue Kit (Qiagen) following the manufacturer’s instructions and the 16S rRNA gene was PCR amplified with eubacterial primers 27F/1492R (Lane 1991). The PCR amplified 16S rRNA gene... determined as described previously (Rajasabapathy et al. 2014b) on MA. Other enzyme activities were tested using API ZYM kits (bioMérieux) according to the manufacturer’s protocol. Acid production from carbohydrates was determined using the API 50CH kit...

  6. Culture-Independent Identification of Manganese-Oxidizing Genes from Deep-Sea Hydrothermal Vent Chemoautotrophic Ferromanganese Microbial Communities Using a Metagenomic Approach

    Science.gov (United States)

    Davis, R.; Tebo, B. M.

    2013-12-01

    Microbial activity has long been recognized as being important to the fate of manganese (Mn) in hydrothermal systems, yet we know very little about the organisms that catalyze Mn oxidation, the mechanisms by which Mn is oxidized or the physiological function that Mn oxidation serves in these hydrothermal systems. Hydrothermal vents with thick ferromanganese microbial mats and Mn oxide-coated rocks observed throughout the Pacific Ring of Fire are ideal models to study the mechanisms of microbial Mn oxidation, as well as primary productivity in these metal-cycling ecosystems. We sampled ferromanganese microbial mats from Vai Lili Vent Field (Tmax=43°C) located on the Eastern Lau Spreading Center and Mn oxide-encrusted rhyolytic pumice (4°C) from Niua South Seamount on the Tonga Volcanic Arc. Metagenomic libraries were constructed and assembled from these samples and key genes known to be involved in Mn oxidation and carbon fixation pathways were identified in the reconstructed genomes. The Vai Lili metagenome assembled to form 121,157 contiguous sequences (contigs) greater than 1000bp in length, with an N50 of 8,261bp and a total metagenome size of 593 Mbp. Contigs were binned using an emergent self-organizing map of tetranucleotide frequencies. Putative homologs of the multicopper Mn-oxidase MnxG were found in the metagenome that were related to both the Pseudomonas-like and Bacillus-like forms of the enzyme. The bins containing the Pseudomonas-like mnxG genes are most closely related to uncultured Deltaproteobacteria and Chloroflexi. The Deltaproteobacteria bin appears to be an obligate anaerobe with possible chemoautotrophic metabolisms, while the Chloroflexi appears to be a heterotrophic organism. The metagenome from the Mn-stained pumice was assembled into 122,092 contigs greater than 1000bp in length with an N50 of 7635 and a metagenome size of 385 Mbp. Both forms of mnxG genes are present in this metagenome as well as the genes encoding the putative Mn

  7. Chemical versus Enzymatic Digestion of Contaminated Estuarine Sediment: Relative Importance of Iron and Manganese Oxides in Controlling Trace Metal Bioavailability

    Science.gov (United States)

    Turner, A.; Olsen, Y. S.

    2000-12-01

    Chemical and enzymatic reagents have been employed to determine available concentrations of Fe, Mn, Cu and Zn in contaminated estuarine sediment. Gastric and intestinal enzymes (pepsin, pH 2, and trypsin, pH 7·6, respectively) removed significantly more metal than was water-soluble or exchangeable (by seawater or ammonium acetate), while gastro-intestinal fluid of the demersal teleost, Pleuronectes platessa L. (plaice), employed to operationally define a bioavailable fraction of contaminants, generally solubilized more metal than the model enzymes. Manganese was considerably more available than Fe under these conditions and it is suggested that the principal mechanism of contaminant release is via surface complexation and reductive solubilization of Mn oxides, a process which is enhanced under conditions of low pH. Of the chemical reagents tested, acetic acid best represents the fraction of Mn (as well as Cu and Zn) which is available under gastro-intestinal conditions, suggesting that the reducing tendency of acetate is similar to that of the ligands encountered in the natural digestive environment. Although the precise enzymatic and non-enzymatic composition of plaice gastro-intestinal fluid may be different to that encountered in more representative, filter-feeding or burrowing organisms, a general implication of this study is that contaminants associated with Mn oxides are significantly more bioavailable than those associated with Fe oxides, and that contaminant bioavailability may be largely dictated by the oxidic composition of contaminated sediment.

  8. Reductive leaching of manganese oxide ores using waste tea as reductant in sulfuric acid solution%以废茶叶为还原剂在硫酸溶液中还原浸出氧化锰矿

    Institute of Scientific and Technical Information of China (English)

    唐清; 钟宏; 王帅; 李进中; 刘广义

    2014-01-01

    Manganese oxide ores from Gabon and Xiangxi were leached with waste tea as reductant in dilute sulfuric acid solution. The effects of waste tea dosage, concentration of sulfuric acid, liquid-to-solid ratio, leaching temperature and reaction time on leaching process were explored. The leaching efficiency of Gabonese manganese oxide ore reached almost 100%under the optimal condition which was determined as follows:manganese oxide ore to waste tea mass ratio of 10:1, sulfuric acid concentration of 2.5 mol/L, liquid-to-solid ratio of 7.5:1, leaching temperature of 368 K, time of 8 h. The leaching efficiency of Xiangxi manganese oxide ore reached 99.8%under the optimal condition which was determined as follows:manganese oxide ore to waste tea mass ratio of 10:1, sulfuric acid concentration of 1.7 mol/L, liquid-to-solid ratio of 7.5:1, leaching temperature of 368 K, time of 8 h. The leaching process followed the internal diffusion controlled kinetic model, and the apparent activation energies of Gabonese manganese oxide ore and Xiangxi manganese oxide ore were calculated to be 38.2 kJ/mol and 20.4 kJ/mol, respectively. The morphological changes and mineralogical forms of the ore before and after the chemical treatment were discussed with the support of XRD analysis and SEM analysis.%采用废茶叶在硫酸溶液中还原浸出加蓬和湘西氧化锰矿石,探索废茶叶用量、硫酸浓度、固液比、浸出温度和反应时间对浸出过程的影响。对加蓬氧化锰矿,优化的浸出条件为:氧化锰矿与废茶叶的质量比10:4、硫酸浓度2.5 mol/L、固液比7.5:1、浸出温度368 K、浸出时间8 h;在此条件下,加蓬氧化锰矿的浸出率几乎达100%。对于湘西氧化锰矿,优化浸出条件为:氧化锰矿与废茶叶的质量比10:1、硫酸浓度1.7 mol/L、液固比7.5:1、温度368 K、浸出时间8 h;在此条件下,锰的浸出率达到99.8%。氧化锰矿的还原浸出过程符合内扩散控制模

  9. Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xuehang; Xu, Gui-Liang; Zhong, Guiming; Gong, Zhengliang; McDonald, Matthew J.; Zheng, Shiyao; Fu, Riqiang; Chen, Zonghai; Amine, Khalil; Yang, Yong

    2016-08-31

    P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ Xray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SSNMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na0.66Ni0.33-xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni4+/Ni3+/ Ni2+ redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.

  10. New insight into the origin of manganese oxide ore deposits in the Appalachian Valley and Ridge of northeastern Tennessee and northern Virginia, USA

    Science.gov (United States)

    Carmichael, Sarah K.; Doctor, Daniel H.; Wilson, Crystal G.; Feierstein, Joshua; McAleer, Ryan

    2017-01-01

    Manganese oxide deposits have long been observed in association with carbonates within the Appalachian Mountains, but their origin has remained enigmatic for well over a century. Ore deposits of Mn oxides from several productive sites located in eastern Tennessee and northern Virginia display morphologies that include botryoidal and branching forms, massive nodules, breccia matrix cements, and fracture fills. The primary ore minerals include hollandite, cryptomelane, and romanèchite. Samples of Mn oxides from multiple localities in these regions were analyzed using electron microscopy, X-ray analysis, Fourier transform infrared spectroscopy, and trace and rare earth element (REE) geochemistry. The samples from eastern Tennessee have biological morphologies, contain residual biopolymers, and exhibit REE signatures that suggest the ore formation was due to supergene enrichment (likely coupled with microbial activity). In contrast, several northern Virginia ores hosted within quartz-sandstone breccias exhibit petrographic relations, mineral morphologies, and REE signatures indicating inorganic precipitation, and a likely hydrothermal origin with supergene overprinting. Nodular accumulations of Mn oxides within weathered alluvial deposits that occur close to breccia-hosted Mn deposits in Virginia show geochemical signatures that are distinct from the breccia matrices and appear to reflect remobilization of earlier-emplaced Mn and concentration within supergene traps. Based on the proximity of all of the productive ore deposits to mapped faults or other zones of deformation, we suggest that the primary source of all of the Mn may have been deep seated, and that Mn oxides with supergene and/or biological characteristics resulted from the local remobilization and concentration of this primary Mn.

  11. Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NO{sub x} reduction with NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pourkhalil, Mahnaz [Chemical Engineering Faculty, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Moghaddam, Abdolsamad Zarringhalam, E-mail: zarrin@modares.ac.ir [Chemical Engineering Faculty, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Rashidi, Alimorad [Nanotechnology Research Center, Research Institute of the Petroleum Industry (RIPI), P.O. Box 18745-4163, Tehran (Iran, Islamic Republic of); Towfighi, Jafar [Chemical Engineering Faculty, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Mortazavi, Yadollah [Catalysis and Nanostructured Materials Lab, Chemical Engineering Faculty, Tehran University, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of)

    2013-08-15

    Manganese oxide catalysts (MnO{sub x}) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NO{sub x}) with NH{sub 3} in the presence of excess O{sub 2} were prepared by the incipient wetness impregnation method. These catalysts were characterized by N{sub 2} adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H{sub 2}-temperature programmed reduction (H{sub 2}-TPR) methods. The effects of reaction temperature, MnO{sub x} loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NO{sub x} with NH{sub 3}. Under the reaction conditions of 200 °C, 1 bar, NO = NH{sub 3} = 900 ppm, O{sub 2} = 5 vol%, GHSV = 30,000 h{sup −1} and 12 wt% MnO{sub x}, NO{sub x} conversion and N{sub 2} selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO{sub 2} and 2.5 vol% H{sub 2}O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.

  12. Charge storage mechanisms of manganese oxide nanosheets and N-doped reduced graphene oxide aerogel for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Seubsai, Anusorn; Chanlek, Narong; Kidkhunthod, Pinit; Sangthong, Winyoo; Maensiri, Santi; Yimnirun, Rattikorn; Nilmoung, Sukanya; Pannopard, Panvika; Ittisanronnachai, Somlak; Kongpatpanich, Kanokwan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-11-01

    Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGOae) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO2 during the charging process is 7.4 μg cm-2. Whilst, the mass change of the solvated ions at the N-rGOae electrode is 8.4 μg cm-2. An asymmetric supercapacitor of MnO2//N-rGOae (CR2016) provides a maximum specific capacitance of ca. 467 F g-1 at 1 A g-1, a maximum specific power of 39 kW kg-1 and a specific energy of 40 Wh kg-1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO2//N-rGOae supercapacitor may be practically used in high power and energy applications.

  13. 铁锰菌和硝化菌同步去除铁、锰和氨氮的研究%Simultaneous Removal of Iron, Manganese and Ammonia Nitrogen by Iron and Manganese Oxidizing Bacteria and Nitrobacteria

    Institute of Scientific and Technical Information of China (English)

    唐玉兰; 武卫斌; 赵玉华; 傅金祥; 郜玉楠; 王小兰

    2013-01-01

    在实验室条件下,提取人工挂膜启动后运行效果良好的除铁、锰和氨氮的BAF滤料上的混合菌,将其分离富集培养出铁锰菌和硝化菌,研究了铁锰菌、硝化菌和混合茵各自同步去除铁、锰和氨氮的效能.结果表明,铁锰菌不仅对铁和锰具有去除作用,对氨氮也有去除作用,且主要为亚硝化作用;硝化菌仅对氨氮有去除作用,对铁和锰则几乎无去除作用;混合菌同步去除铁、锰和氨氮的效果最好,铁锰菌和硝化菌共存对同步去除铁、锰和氨氮具有协同作用.%Mixed bacteria for removal of iron, manganese and ammonia nitrogen were extracted in laboratory from the ceramic media in a well-operated BAF after artificial biofilm formation. Iron and manganese oxidizing bacteria and nitrobacteria were separated and enriched from the mixed bacteria. The respective efficiencies of three types of bacteria for simultaneous removal of iron, manganese and ammonia nitrogen were investigated. The results showed that iron and manganese oxidizing bacteria not only simultaneously removed iron and manganese, but also ammonia nitrogen via nitrosation. Nitrobacteria removed ammonia nitrogen, but not iron and manganese. Mixed bacteria showed the highest efficiency in simultaneous removal of iron, manganese and ammonia nitrogen. Iron and manganese oxidizing bacteria and nitrobacteria had a synergistic effect in simultaneous removal of iron, manganese and ammonia nitrogen.

  14. Effects of properties of manganese oxide-impregnated catalysts and flue gas condition on multipollutant control of Hg{sup 0} and NO

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Chun-Hsiang [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China); Hsi, Hsing-Cheng, E-mail: hchsi@ntu.edu.tw [Graduate Institute of Environmental Engineering, National Taiwan University, No. 71, Chou-Shan Rd., Taipei 106, Taiwan (China); Lin, Hong-Ping [Department of Chemistry, National Cheng-Kung University, No. 1, University Rd., Tainan 701, Taiwan (China); Chang, Tien-Chin [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China)

    2015-06-30

    Highlights: • MnO{sub x} impregnation caused changes in physical/chemical properties of catalyst. • Mn{sup 4+} was the main valence state of impregnated MnO{sub x}. • MnO{sub x} impregnation enhanced the removal of Hg{sup 0}/NO/SO{sub 2} with SCR catalyst. • HCl, O{sub 2}, and SO{sub 2} at ≤200 ppm and elevating temperature promoted Hg{sup 0} oxidation. • Increasing NO and NH{sub 3} concentrations reduced Hg{sup 0} oxidation. - Abstract: This research investigated the effects of manganese oxide (MnO{sub x}) impregnation on the physical/chemical properties and multi pollutant control effectiveness of Hg{sup 0} and NO using a V{sub 2}O{sub 5}–WO{sub 3}/TiO{sub 2}–SiO{sub 2} selective catalytic reduction (SCR) catalyst. Raw and MnO{sub x}-treated SCR samples were bean-shaped nanoparticles with sizes within 10–30 nm. Impregnating MnO{sub x} of ≤5 wt% caused limited changes in physical properties of the catalyst. The decrease in surface area when the impregnated MnO{sub x} amount was 10 wt% may stem from the pore blockage and particle growth or aggregation of the catalyst. Mn{sup 4+} was the main valence state of impregnated MnO{sub x}. Apparent crystallinity of MnO{sub x} was not observed based on X-ray diffraction. MnO{sub x} impregnation enhanced the Hg{sup 0} oxidation and NO/SO{sub 2} removal of SCR catalyst. The 5 and 10% MnO{sub x}-impregnated samples had the greatest multi pollutant control potentials for Hg{sup 0} oxidation and NO removal; however, the increasing SO{sub 2} removal that may be mainly due to SO{sub 2}–SO{sub 3} conversion should be cautioned. HCl and O{sub 2} greatly promoted Hg{sup 0} oxidation. SO{sub 2} enhanced Hg{sup 0} oxidation at ≤200 ppm while NO and NH{sub 3} consistently inhibited Hg{sup 0} oxidation. Elevating flue gas temperature enhanced Hg{sup 0} oxidation. Overall, MnO{sub x}-impregnated catalysts show stable and consistent multi pollutant removal effectiveness under the test conditions.

  15. Supported manganese oxide on TiO{sub 2} for total oxidation of toluene and polycyclic aromatic hydrocarbons (PAHs): Characterization and catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Aboukaïs, Antoine, E-mail: aboukais@univ-littoral.fr [Univ Lille Nord de France, 59000 Lille (France); Equipe Catalyse, UCEIV, EA 4492, MREI, ULCO, 59140 Dunkerque (France); Abi-Aad, Edmond [Univ Lille Nord de France, 59000 Lille (France); Equipe Catalyse, UCEIV, EA 4492, MREI, ULCO, 59140 Dunkerque (France); Taouk, Bechara [Laboratoire de Sécurité des procédés Chimiques (LSPC), EA 4704, INSA Rouen, Avenue de l' Université, 76801 Saint Etienne du Rouvray (France)

    2013-11-01

    Manganese oxide catalysts supported on titania (TiO{sub 2}) were prepared by incipient wetness impregnation method in order to elaborate catalysts for total oxidation of toluene and PAHs. These catalysts have been characterized by means of X-ray diffraction (XRD), electron paramagnetic resonance (EPR), temperature programmed reduction (TPR) and temperature programmed desorption (TPD). It has been shown that for the 5%Mn/TiO{sub 2} catalyst the reducibility and the mobility of oxygen are higher compared, in one side, to other x%Mn/TiO{sub 2} samples and, in another side, to catalysts where TiO{sub 2} support was replaced by γ-Al{sub 2}O{sub 3} or SiO{sub 2}. It has been shown that the content of manganese loading on TiO{sub 2} has an effect on the catalytic activity in the toluene oxidation. A maximum of activity was obtained for the 5%Mn/TiO{sub 2} catalyst where the total conversion of toluene was reached at 340 °C. This activity seems to be correlated to the presence of the Mn{sup 3+}/Mn{sup 4+} redox couple in the catalyst. When the Mn content increases, large particles of Mn{sub 2}O{sub 3} appear leading then to the decrease in the corresponding activity. In addition, compared to both other supports, TiO{sub 2} seems to be the best to give the best catalytic activity for the oxidation of toluene when it is loaded with 5% of manganese. For this reason, the latter catalyst was tested for the abatement of some PAHs. The light off temperature of PAHs compounds increases with increasing of benzene rings number and with decreasing of H/C ratio. All of PAHs are almost completely oxidized and converted at temperatures lower than 500 °C. - Highlights: • Preparation of x%MnO{sub 2}/TiO{sub 2} catalysts. • Catalytic oxidation tests of toluene and PAHs. • EPR, TPR and TPD characterizations of Mn(II) and Mn(IV) ions.

  16. Adsorption of antimony(V) onto Mn(II)-enriched surfaces of manganese-oxide and FeMn binary oxide.

    Science.gov (United States)

    Liu, Ruiping; Xu, Wei; He, Zan; Lan, Huachun; Liu, Huijuan; Qu, Jiuhui; Prasai, Tista

    2015-11-01

    Manganese(IV) oxide [Mn(IV)] potentially oxidizes antimony(III) [Sb(III)] to antimony(V) [Sb(V)] and improves Sb removal by FeMn binary oxide (FMBO) through an oxidation-adsorption mechanism. This study focused on the effect of Mn(IV) reductive dissolution by potassium sulfite (K2SO3) on Sb(V) adsorption onto manganese oxide (Mn-oxide) and FMBO. The maximum Sb(V) adsorption (Qmax,Sb(V)) increased from 1.0 to 1.1 mmol g(-1) for FMBO and from 0.4 to 0.6 mmol g(-1) for Mn-oxide after pretreatment with 10 mmol L(-1) K2SO3. The addition of 2.5 mmol L(-1) Mn(2+) also significantly improved Sb(V) adsorption, and the observed Qmax,Sb(V) increased to 1.4 and 1.0 mmol g(-1) for FMBO and Mn-oxide, respectively, with pre-adsorbed Mn(2+). Neither K2SO3 nor Mn(2+) addition had any effect on Sb(V) adsorption onto iron oxide (Fe-oxide). Mn(2+) introduced by either Mn(IV) dissolution or addition tended to form outer-sphere surface complexes with hydroxyl groups on Mn-oxide surfaces (MnOOH). Mn(2+) at 2.5 mmol L(-1) shifted the isoelectric point (pHiep) from 7.5 to 10.2 for FMBO and from 4.8 to 9.2 for Mn-oxide and hence benefited Sb(V) adsorption. The adsorption of Sb(V) onto Mn(2+)-enriched surfaces contributed to the release of Mn(2+), and the X-ray photoelectron spectra also indicated increased binding energy of Mn 2p3/2 after the adsorption of Sb(V) onto K2SO3-pretreated FMBO and Mn-oxide. Sb(V) adsorption involved the formation of inner-sphere complexes and contributed to the release of Mn(2+). In the removal of Sb(III) by Mn-based oxides, the oxidation of Sb(III) to Sb(V) by Mn(IV) oxides had an effect; however, Mn(IV) dissolution and Mn(2+)-enrichment also played an important role.

  17. Reaproveitamento de óxidos de manganês de pilhas descartadas para eletrocatálise da reação de redução de oxigênio em meio básico Use of manganese oxides recovered from spent batteries in electrocatalysis of oxygen reduction reaction in alkaline medium

    Directory of Open Access Journals (Sweden)

    Daniel C. Rascio

    2010-01-01

    Full Text Available The oxygen reduction reaction was studied in alkaline media using manganese oxides obtained from spent batteries as electrocatalysts. Three processes were used to recover manganese oxides from spent batteries. The particles obtained were in the range from 8 to 11 nm. The electrochemical experiments indicated a good electrocatalytic activity toward oxygen reduction using the different samples and showing approximately a direct transference of 4 electrons during the process. Even though all the processes were efficient, the best result was observed for the prepared sample using reactants of low cost.

  18. 锰氧化细菌的分离鉴定及其锰氧化特性的分析%Isolation and identification of manganese-oxidizing bacterium and its manganes-oxidation characteristics

    Institute of Scientific and Technical Information of China (English)

    张璐; 李婷婷; 王芳; 许旭萍

    2011-01-01

    The selective media were used to isolate and screen the manganese-oxidizing bacteria. A high efficiency manganese-oxidizing bacterium (MN1405) was selected from manganese ores. According to the morphological features, physiological and biochemical characteristics and the sequence analysis of 16S rRNA gene, MN1405 was identified as Arthrobacter echigonensis. Under the cultural conditions,the manganese removal rate in the medium by MN1405 was reached 93.38%. The culture that was obtained from the bacterium also had a good manganese removal effects.%利用选择性培养基对锰矿样品进行分离、筛选,得到一株高效锰氧化细菌(MN1405).经形态特征、生理生化特征以及16S rRNA基因序列分析,将菌株MN1405鉴定为Arthrobacter echigonensis.在培养条件下,MN1405对培养基中的锰离子去除率可达93.38%,且其培养所获得的培养液也具有良好的除锰效果.

  19. 掺铌尖晶石型锰酸锂烧结工艺的优化%Optimization of Sintering Process of Nb-doped Spinel Lithium Manganese Oxide

    Institute of Scientific and Technical Information of China (English)

    胡柳泉; 张瑾瑾; 周友元

    2015-01-01

    The Nb⁃doped lithium manganese oxides with homogenous spinel phase and high energy density were mass⁃synthesized by an optimized high⁃temperature solid⁃state synthetic method. Through various characterizing methods, such as XRD, SEM, SSA, and PSD, it was found that the cycle performance of the Nb⁃doped lithium manganese oxide synthesized by sintering at a constant temperature of 760℃ for 15 h was the best with an initial capacity of 109.9 mAh/g, a capacity retention of 95.3% after 50 cycles, and the maximum tapped density reaching 3.3 g/cm3 .%采用高温固相法,通过优化烧结工艺,批量合成了具有高能量密度、单一尖晶石相的掺铌锰酸锂,并采用XRD、SEM、SSA、PSD等表征手段对其性能进行了分析,结果表明,在760℃下恒温烧结15 h,烧结制备的掺铌尖晶石锰酸锂综合性能较好,在1C倍率下,最高初始放电容量可达109.9 mAh/g,循环50周后的容量保持率达95.3%,最大压实密度可达3.3 g/cm3。

  20. A copal-8-ol diphosphate synthase from the angiosperm Cistus creticus subsp. creticus is a putative key enzyme for the formation of pharmacologically active, oxygen-containing labdane-type diterpenes.

    Science.gov (United States)

    Falara, Vasiliki; Pichersky, Eran; Kanellis, Angelos K

    2010-09-01

    The resin of Cistus creticus subsp. creticus, a plant native to Crete, is rich in labdane-type diterpenes with significant antimicrobial and cytotoxic activities. The full-length cDNA of a putative diterpene synthase was isolated from a C. creticus trichome cDNA library. The deduced amino acid sequence of this protein is highly similar (59%-70% identical) to type B diterpene synthases from other angiosperm species that catalyze a protonation-initiated cyclization. The affinity-purified recombinant Escherichia coli-expressed protein used geranylgeranyl diphosphate as substrate and catalyzed the formation of copal-8-ol diphosphate. This diterpene synthase, therefore, was named CcCLS (for C. creticus copal-8-ol diphosphate synthase). Copal-8-ol diphosphate is likely to be an intermediate in the biosynthesis of the oxygen-containing labdane-type diterpenes that are abundant in the resin of this plant. RNA gel-blot analysis revealed that CcCLS is preferentially expressed in the trichomes, with higher transcript levels found in glands on young leaves than on fully expanded leaves, while CcCLS transcript levels increased after mechanical wounding. Chemical analyses revealed that labdane-type diterpene production followed a similar pattern, with higher concentrations in trichomes of young leaves and increased accumulation upon wounding.

  1. A Copal-8-ol Diphosphate Synthase from the Angiosperm Cistus creticus subsp. creticus Is a Putative Key Enzyme for the Formation of Pharmacologically Active, Oxygen-Containing Labdane-Type Diterpenes1[OA

    Science.gov (United States)

    Falara, Vasiliki; Pichersky, Eran; Kanellis, Angelos K.

    2010-01-01

    The resin of Cistus creticus subsp. creticus, a plant native to Crete, is rich in labdane-type diterpenes with significant antimicrobial and cytotoxic activities. The full-length cDNA of a putative diterpene synthase was isolated from a C. creticus trichome cDNA library. The deduced amino acid sequence of this protein is highly similar (59%–70% identical) to type B diterpene synthases from other angiosperm species that catalyze a protonation-initiated cyclization. The affinity-purified recombinant Escherichia coli-expressed protein used geranylgeranyl diphosphate as substrate and catalyzed the formation of copal-8-ol diphosphate. This diterpene synthase, therefore, was named CcCLS (for C. creticus copal-8-ol diphosphate synthase). Copal-8-ol diphosphate is likely to be an intermediate in the biosynthesis of the oxygen-containing labdane-type diterpenes that are abundant in the resin of this plant. RNA gel-blot analysis revealed that CcCLS is preferentially expressed in the trichomes, with higher transcript levels found in glands on young leaves than on fully expanded leaves, while CcCLS transcript levels increased after mechanical wounding. Chemical analyses revealed that labdane-type diterpene production followed a similar pattern, with higher concentrations in trichomes of young leaves and increased accumulation upon wounding. PMID:20595348

  2. The structure at 2.4 Å resolution of the protein from gene locus At3g21360, a putative FeII/2-oxo­glutarate-dependent enzyme from Arabidopsis thaliana

    Science.gov (United States)

    Bitto, Eduard; Bingman, Craig A.; Allard, Simon T. M.; Wesenberg, Gary E.; Aceti, David J.; Wrobel, Russell L.; Frederick, Ronnie O.; Sreenath, Hassan; Vojtik, Frank C.; Jeon, Won Bae; Newman, Craig S.; Primm, John; Sussman, Michael R.; Fox, Brian G.; Markley, John L.; Phillips, George N.

    2005-01-01

    The crystal structure of the gene product of At3g21360 from Arabidopsis thaliana was determined by the single-wavelength anomalous dispersion method and refined to an R factor of 19.3% (R free = 24.1%) at 2.4 Å resolution. The crystal structure includes two monomers in the asymmetric unit that differ in the conformation of a flexible domain that spans residues 178–230. The crystal structure confirmed that At3g21360 encodes a protein belonging to the clavaminate synthase-like superfamily of iron(II) and 2-oxoglutarate-dependent enzymes. The metal-binding site was defined and is similar to the iron(II) binding sites found in other members of the superfamily. PMID:16511070

  3. The structure at 2.4 Å resolution of the protein from gene locus At3g21360, a putative Fe{sup II}/2-oxoglutarate-dependent enzyme from Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Bitto, Eduard; Bingman, Craig A.; Allard, Simon T. M.; Wesenberg, Gary E.; Aceti, David J.; Wrobel, Russell L.; Frederick, Ronnie O.; Sreenath, Hassan; Vojtik, Frank C.; Jeon, Won Bae; Newman, Craig S.; Primm, John; Sussman, Michael R.; Fox, Brian G.; Markley, John L.; Phillips, George N. Jr, E-mail: phillips@biochem.wisc.edu [Center for Eukaryotic Structural Genomics, Department of Biochemistry, University of Wisconsin-Madison (United States)

    2005-05-01

    The crystal structure of the 37.2 kDa At3g21360 gene product from A. thaliana was determined at 2.4 Å resolution. The structure establishes that this protein binds a metal ion and is a member of a clavaminate synthase-like superfamily in A. thaliana. The crystal structure of the gene product of At3g21360 from Arabidopsis thaliana was determined by the single-wavelength anomalous dispersion method and refined to an R factor of 19.3% (R{sub free} = 24.1%) at 2.4 Å resolution. The crystal structure includes two monomers in the asymmetric unit that differ in the conformation of a flexible domain that spans residues 178–230. The crystal structure confirmed that At3g21360 encodes a protein belonging to the clavaminate synthase-like superfamily of iron(II) and 2-oxoglutarate-dependent enzymes. The metal-binding site was defined and is similar to the iron(II) binding sites found in other members of the superfamily.

  4. Effect of Precipitation Method and Ce Doping on the Catalytic Activity of Copper Manganese Oxide Catalysts for CO Oxidation%沉淀方法及铈掺杂对铜锰氧化物催化剂催化氧化CO性能的影响

    Institute of Scientific and Technical Information of China (English)

    张学彬; 马扩颜; 张灵辉; 雍国平; 戴亚; 刘少民

    2011-01-01

    The influence of Ce doping and the precipitation method on structural properties and the catalytic activity of copper manganese oxides for CO oxidation at ambient temperature have been investigated. The catalysts were characterized by means of the powder X-ray diffraction and N2 adsorption-desorption, the inductively coupled plasma atomic emission spectrometry, the temperature programmed reduction, diffuse reflectance UV-Vis spectra,and the X-ray photoelectron spectroscopy. It was found that after doping little amount of Ce in copper manganese oxide, CeO2 phase was highly dispersed and could prevent sintering and aggregating of the catalyst, the size of the catalytic material was decreased, the reducibility was enhanced, the specific surface area was increased and the formation of the active sites for the oxidation of CO was improved significantly. Therefore, the activity of the rare earth promoted catalyst was enhanced remarkably.

  5. 微波辅助氧化锰改性竹质活性炭的工艺%Study on Microwave Auxiliary Modification of Activated Carbon by Manganese Oxide

    Institute of Scientific and Technical Information of China (English)

    赵小红

    2016-01-01

    In order to improve the adsorption and specific capacitance properties of activated carbon,promote its application in environmental protection and electronic industry,modification of the activated carbon from bambusa sinospinosa by zinc chloride method was carried out with microwave auxiliary and manganese oxide method. In the modification process,the effects of five factors such as immersing time,concentration,microwave power,heating time and light-wave irradiation time on the property of modified activated carbon were studied. The results showed that the optimal conditions were:the immersing time 4h,the impregnation concentration 1.0215mol/L,the microwave power 640W,the heating time 18 minutes and the light-wave radiation 24 minutes. Under these conditions,the decolorization of methylene blue was 94.0441ml/ 0.1g,the decolorization effect of modified active carbon was improved by 43.07% compared with the unmodified one. Microwave auxiliary modification of activated carbon by manganese oxide can reduce the modification time and improve the performance effectively.%为了提高活性炭吸附和比电容性能,促进其在环保和电子产业应用,以氧化锰为改性剂,对氯化锌法竹质活性炭进行微波辅助改性,考察浸渍时间、浸渍液浓度、微波功率、加热时间、光波辐射时间五个因素对改性活性炭性能的影响。结果表明最佳工艺条件为:浸渍时间4h,浸渍液浓度1.00mol/L,微波功率640W,加热时间18min,光波辐射时间24min。此条件下亚甲蓝脱色力为94.0441ml/0.1g,比改性前提高了43.07%。微波辅助氧化锰改性竹质活性炭能大大缩短改性时间,有效提高其性能。

  6. 聚乙烯醇二次交联固定锰氧化细菌的试验%Test of Manganese-Oxidizing Bacteria Immobilized in Polyvinyl Alcohol by Second Cross-Linking Process

    Institute of Scientific and Technical Information of China (English)

    王景晶; 张长利; 杨宏

    2013-01-01

    To overcome the shortcomings of expansion,low mechanical strength and toxicity in traditional PVA-boric acid method,the manganese-oxidizing bacteria were embedded in polyvinyl alcohol made by secondary cross-linking method.In the single-factor experiment,the effect of concentration of PVA,pH value,time in secondary cross linking process,different co-composite matters and the amount of embedded bacteria on the immobilized manganese-oxidizing bacteria were studied.The results show that improving the concentration of PVA is benefit for the mechanical strength,and lowers bacteria activity.When pH value in secondary process changes in 8~10,PVA has better mechanical strength and the highest bacteria activity,when pH is 8 or 9.The time of the secondary process should not be shorter than 8 h and longer than 48 h.Activated carbon is useful for improving bioactivity and calcium carbonate for mechanical strength.The manganese removing rate improves with the amount of embedded bacteria.%针对传统聚乙烯醇-硼酸法固定化颗粒粘连膨胀、机械强度差、硼酸对细菌具有毒性等缺点,该文采用二次交联法固定锰氧化细菌.分别考察了聚乙烯醇(PVA)浓度、二次交联pH值、二次交联时间、添加剂、包菌量对固定细菌膨胀性、机械强度、活性的影响.结果表明聚乙烯醇浓度的提高有利于机械强度的提高并降低膨胀率,但是会降低固定细菌活性;二次交联pH在8~10时机械强度较好,pH为8和9时活性最高;二次交联时间应大于8h,不宜超过48 h;碳酸钙、活性炭有利于降低膨胀率,但是碳酸钙会降低细菌活性,活性炭会使机械强度降低;当包菌量大于4%时机械强度有明显的下降趋势,锰去除率随着包菌量的增加而增加.

  7. Construction and screening of a functional metagenomic library to identify novel enzymes produced by Antarctic bacteria

    Institute of Scientific and Technical Information of China (English)

    Ignacio Ferrés; Vanesa Amarelle; Francisco Noya; Elena Fabiano

    2015-01-01

    A metagenomic fosmid library of approximately 52 000 clones was constructed to identify functional genes encoding cold-adapted enzymes. Metagenomic DNA was extracted from a sample of glacial meltwater, collected on the Antarctic Peninsula during the ANTARKOS XXIX Expedition during the austral summer of 2012–2013. Each clone contained an insert of about 35–40 kb, so the library represented almost 2 Gb of genetic information from metagenomic DNA. Activity-driven screening was used to detect the cold-adapted functions expressed by the library. Fifty lipase/esterase and two cellulase-producing clones were isolated, and two clones able to grow on Avicel® as the sole carbon source. Interestingly, three clones formed a brown precipitate in the presence of manganese (II). Accumulation of manganese oxides was determined with a leucoberbelin blue assay, indicating that these three clones had manganese-oxidizing activity. To the best of our knowledge, this is the first report of a manganese oxidase activity detected with a functional metagenomic strategy.

  8. Molecular Cloning and Heterologous Expression of Putative Berberine Bridge Enzymes from Arabidopsis thaliana%拟南芥基因组中注释为小檗碱桥环酶基因的分子克隆及异源表达

    Institute of Scientific and Technical Information of China (English)

    张翔; 马磊; 田永强; 张国林; 罗应刚

    2012-01-01

    Berberine bridge enzyme ( BBE ) , one member of bi - covalent flavoprotein family, catalyzes the convereion of ( S) -reticuline to (S) -scoulerine via the formation of a new carbon-carbon bond between the carbon of N-methyl group and the intramolecular aromatic carbon ortho to the phenolic hydroxyl group in the benzyl motif. BBE is a key enzyme in the biosynthetic pathway of berberine alkaloids. No complex alkaloids have been detected in Arabidopsis thaliana. However, bioinformatics analysis of the whole genome sequences of A. thaliana indicated that many genes were annotated as enzymes for the biosynthesis of complex alkaloids. For instance, 12 genes were annotated as BBE involved in the biosynthesis of berberine alkaloids. To investigate on the possible function of these genes ,4 putative AtBbes is selected out of 12 genes on the basis of bioinformatics analysis of known functional EcBBE and AtBBEs. The four putative AtBbe genes were obtained by RT-PCR u-sing total RNA as template. The plasmid containing AtBbes were screened and then confirmed by DNA sequencing. The target genes such as AT2G34810, AT5C44400, AT5G44410 and AT5G44440 are obtained. The expression plasmids were transformed into Escherichia coli Rosette ( DE3) for protein overexpression. Induced by IPTG.the AtBBEs were overexpressed in the prokaryotic host.%小檗碱桥环酶(BBE)催化(S)-牛心果碱((S)-reticuline)中N-CH3与分子内苄基部分中羟基的邻位芳香碳之间C-C键的形成,该酶属于双共价黄素蛋白家族,是苄基异喹啉类生物碱向小檗碱类生物碱转化的关键酶.迄今,在拟南芥(Arabidopsis thaliana)中尚未发现复杂生物碱,但其基因组测序结果表明拟南芥含有众多可能与复杂生物碱生物合成相关的基因,其中与BBE类似的基因有12个.基于与已知功能的BBE及拟南芥中BBE序列的分析,选定拟南芥中4个注释为BBE的编码基因为目的基因,设计特异引物,从拟南芥cDNA中扩增并克隆到pGM

  9. Removal of Cadmium and Copper from Aqueous Solution by the Adsorption Resin Coated Manganese Oxide%吸附树脂负载锰氧化物去除水中镉和铜

    Institute of Scientific and Technical Information of China (English)

    鲁雪梅; 熊鹰; 张广之; 倪晋仁

    2012-01-01

    A new hybrid material (Mn-SD300) was prepared by coating manganese oxide onto the adsorption resin SD300, which adopted the method of in-suit potassium permanganate oxidation and reduction. The adsorption ability of Mn-SD300 for Cd2+ and Cu2+ was studied. The results of TEM, XRD and XPS demonstrated that the form of manganese oxide loaded on the resin was MnO2. A good adsorption property of Cd2+ and Cu2+ onto Mn-SD300 was indicated by the batch experiments. The adsorption behavior of Cd2+ and Cu2+ on Mn-SD300 was well described by pseudo-first-order kinetic model and Langmuir isotherm model (P2>0.99), and the maximum adsorption capacity of Mn-SD300 towards Cd2+ and Cu2+, were up to 76.92 mg/g and 142.86 mg/g respectively at 303 K. Compared to the conventional cation exchange resin D001, Mn-SD300 had a better adsorption selectivity to Cd2+ and Cu2+, when Ca2+, Mg2+ and Na+ coexisted at high concentration.%以大孔吸附树脂SD300为载体,采用原位高锰酸钾氧化还原法将锰氧化物负载其上,制备了新型锰氧化物-吸附树脂复合材料Mn-SD300,并对其吸附水中Cd2+和Cu2+的性能进行了研究.TEM,XRD以及XPS的分析结果表明,负载的锰氧化物以MnO2的形态存在.静态吸附实验结果表明Mn-SD300对Cd2+和Cu2+具有良好的吸附性能.吸附行为均符合准一级动力学模型(R2>0.99)和Langmuir吸附等温线模型(R2>0.99),温度为303 K时,Mn-SD300对Cd2+和Cu2+的饱和吸附容量可分别达到76.92mg/g和142.86 mg/g.在高浓度竞争离子Ca2+,Mg2+和Na+共存的情况下,Mn-SD300对Cd2+和Cu2+的吸附选择性要强于传统阳离子交换树脂D001.

  10. Putative respiratory chain of Porphyromonas gingivalis.

    Science.gov (United States)

    Meuric, Vincent; Rouillon, Astrid; Chandad, Fatiha; Bonnaure-Mallet, Martine

    2010-05-01

    The electron transfer chain in Porphyromonas gingivalis, or periodontopathogens, has not yet been characterized. P. gingivalis, a strict anaerobic bacteria and the second colonizer of the oral cavity, is considered to be a major causal agent involved in periodontal diseases. Primary colonizers create a favorable environment for P. gingivalis growth by decreasing oxygen pressure. Oxygen does not appear to be the final electron acceptor of the respiratory chain. Fumarate and cytochrome b have been implicated as major components of the respiratory activity. However, the P. gingivalis genome shows many other enzymes that could be implicated in aerobic or nitrite respiration. Using bioinformatic tools and literature studies of respiratory pathways, the ATP synthesis mechanism from the sodium cycle and nutrients metabolism, the putative respirasome of P. gingivalis has been proposed.

  11. 泡沫陶瓷负载锰氧化物的制备及催化臭氧化苯酚研究%Preparation of manganese oxide coated foam ceramic and research on catalytic ozonation phenol

    Institute of Scientific and Technical Information of China (English)

    廖润华; 李月明; 成岳; 王竹梅

    2014-01-01

    采用泡沫陶瓷为载体,利用浸渍法制备了锰氧化物固相催化剂,研究了浸渍溶液种类与浓度对固相催化剂负载量及稳定性的影响,利用SEM、EDS对固相催化剂进行表征,并结合臭氧对苯酚进行降解实验研究。研究结果表明:采用0.5 mol/L Mn(NO3)2浸渍液负载率最大,达到2.32%,且稳定性最佳;制备的载锰固相催化剂对苯酚降解率达到89.6%,对应的COD降解率达到79.2%。%Using foam ceramics as carrier,manganese oxide solid phase catalyst has been prepared by impregnation method. The effects of different species and concentrations of the dipping solution on the loading capacity and stability of solid phase catalyst are investigated. The solid catalyst is characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). And combined with ozone,experimental research on catalytic degradation of phenol has been conducted. The results show that the load rate of using 0.5 mol/L Mn (NO3)2 of impregnation liquid is the highest,reaching 2.32%,and its stability is the best. The phenol degradation rate by using the prepared man-ganese-loaded solid phase catalyst can reach 89.6%and the corresponding COD degradation rate reaches 79.2%.

  12. In-situ Collapse Self-assembly Route to Synthesize Manganese Oxide Nanostructured Materials%原位塌陷自组装法制备氧化锰纳米结构材料

    Institute of Scientific and Technical Information of China (English)

    周丽; 胡玉才; 贺军辉

    2011-01-01

    A straightforward in-situ collapse self-assembly route has been used to fabricate hierarchical manganese oxide nanostructures using ethyl ether (EE) as co-solvent. In the emulsion, the “Baeyer test for unsaturation” reaction quickly occurs between KMnO4 and oleic acid at the O/W interface. The main advantage of adding ethyl ether is to reduce the amount of oleic acid and to simplify greatly the washing process of the products. The as-obtained products were characterized by SEM, TEM and XRD measurements. The morphology and size of products could be controlled by adjusting the volume ratio of OA/EE, the molar ratio of KMnO4/OA, the volume ratio of oil phase/water phase and the reaction temperature. When the volume ratio of OA/EE fell in between 10 : 0~3 : 7, the molar ratio of KMnO4/OA and the volume ratio of oil phase/water phase were less than 1: 1 and 2: 45, respectively, honeycomb manganese oxide nanoparticles were obtained. In contrast, when the OA/EE volume ratio was less than 3: 7, the molar ratio of KMnO4/OA and the volume ratio of oil phase/water phase were greater than 0.67; 1 and 2: 75, respectively, manganese oxide nanoplatelets were produced. When the reaction temperature increased from 25 to 33 ℃, the morphology and size of product did not have significant changes. However, the obtained nanoparticles contained less nanoplatelets when the reaction temperature further increased to 45 ℃. Based on the experimental observations, a plausible formation mechanism via continuous collapse self-assembly of nanoplatelets was proposed.%采用一种简单的原位塌陷自组装法利用高锰酸钾(KMnO4)和油酸(OA)在O/W乳液界面上发生的"Baeyer test for unsaturation"反应,用乙醚作为共溶剂来制备氧化锰纳米结构.与之前相比,加入乙醚(EE)最大的优点是减少了反应过程中油酸的用量,大大简化了产品的洗涤过程,降低了制备成本.得到的产品分别用SEM,TEM和XRD进行了表征.产品的形貌和

  13. Manganese Oxidation by Bacteria: Biogeochemical Aspects

    Digital Repository Service at National Institute of Oceanography (India)

    Sujith, P.P.; LokaBharathi, P.A.

    Manganese is an essential trace metal that is not as readily oxidizable like iron. Several bacterial groups posses the ability to oxidize Mn effectively competing with chemical oxidation. The oxides of Mn are the strongest of the oxidants, next...

  14. Spin dependent calculation of calcium manganese oxide

    Science.gov (United States)

    Rathod, Ruchi; Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

    2017-05-01

    Particularly interesting as candidates for technological applications are the manganese perovskites with AMnO3 formula. In this paper, we investigated the ground states properties of the CaMnO3 perovskite oxide. Our structural properties are given using GGA in the aim to introduce the exchange correlation potential using density functional calculation. Generally, the perovskites materials of ABO3-type are well known with their anti/ferroelectric, piezoelectric and anti/ferromagnetism properties applied in remarkable technological studies.

  15. Biological Superoxide In Manganese Oxide Formation

    Science.gov (United States)

    Hansel, C.; Learman, D.; Zeiner, C.; Santelli, C. M.

    2011-12-01

    Manganese (Mn) oxides are among the strongest sorbents and oxidants within the environment, controlling the fate and transport of numerous elements and the degradation of recalcitrant carbon. Both bacteria and fungi mediate the oxidation of Mn(II) to Mn(III/IV) oxides but the genetic and biochemical mechanisms responsible remain poorly understood. Furthermore, the physiological basis for microbial Mn(II) oxidation remains an enigma. We have recently reported that a common marine bacterium (Roseobacter sp. AzwK-3b) oxidizes Mn(II) via reaction with extracellular superoxide (O2-) produced during exponential growth. Here we expand this superoxide-mediated Mn(II) oxidation pathway to fungi, introducing a surprising homology between prokaryotic and eukaryotic metal redox processes. For instance, Stibella aciculosa, a common soil Ascomycete filamentous fungus, precipitates Mn oxides at the base of asexual reproductive structures (synnemata) used to support conidia (Figure 1). This distribution is a consequence of localized production of superoxide (and it's dismutation product hydrogen peroxide, H2O2), leading to abiotic oxidation of Mn(II) by superoxide. Disruption of NADPH oxidase activity using the oxidoreductase inhibitor DPI leads to diminished cell differentiation and subsequent Mn(II) oxidation inhibition. Addition of Cu(II) (an effective superoxide scavenger) leads to a concentration dependent decrease in Mn oxide formation. We predict that due to the widespread production of extracellular superoxide within the fungal and likely bacterial kingdoms, biological superoxide may be an important contributor to the cycling of Mn, as well as other metals (e.g., Hg, Fe). Current and future explorations of the genes and proteins involved in superoxide production and Mn(II) oxidation will ideally lend insight into the physiological and biochemical basis for these processes.

  16. Manganese Oxidation State Assignment for Manganese Catalase.

    Science.gov (United States)

    Beal, Nathan J; O'Malley, Patrick J

    2016-04-06

    The oxidation state assignment of the manganese ions present in the superoxidized manganese (III/IV) catalase active site is determined by comparing experimental and broken symmetry density functional theory calculated (14)N, (17)O, and (1)H hyperfine couplings. Experimental results have been interpreted to indicate that the substrate water is coordinated to the Mn(III) ion. However, by calculating hyperfine couplings for both scenarios we show that water is coordinated to the Mn(IV) ion and that the assigned oxidation states of the two manganese ions present in the site are the opposite of that previously proposed based on experimental measurements alone.

  17. Manganese oxide composite electrodes for lithium batteries

    Science.gov (United States)

    Thackeray, Michael M.; Johnson, Christopher S.; Li, Naichao

    2007-12-04

    An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor of a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0

  18. Pectic enzymes

    NARCIS (Netherlands)

    Benen, J.A.E.; Voragen, A.G.J.; Visser, J.

    2003-01-01

    The pectic enzymes comprise a diverse group of enzymes. They consist of main-chain depolymerases and esterases active on methyl- and acetylesters of galacturonosyl uronic acid residues. The depolymerizing enzymes comprise hydrolases as wel as lyases

  19. Pectic enzymes

    NARCIS (Netherlands)

    Benen, J.A.E.; Voragen, A.G.J.; Visser, J.

    2003-01-01

    The pectic enzymes comprise a diverse group of enzymes. They consist of main-chain depolymerases and esterases active on methyl- and acetylesters of galacturonosyl uronic acid residues. The depolymerizing enzymes comprise hydrolases as wel as lyases

  20. Enzyme assays.

    Science.gov (United States)

    Reymond, Jean-Louis; Fluxà, Viviana S; Maillard, Noélie

    2009-01-07

    Enzyme assays are analytical tools to visualize enzyme activities. In recent years a large variety of enzyme assays have been developed to assist the discovery and optimization of industrial enzymes, in particular for "white biotechnology" where selective enzymes are used with great success for economically viable, mild and environmentally benign production processes. The present article highlights the aspects of fluorogenic and chromogenic substrates, sensors, and enzyme fingerprinting, which are our particular areas of interest.

  1. Moonlighting enzymes in parasitic protozoa.

    Science.gov (United States)

    Collingridge, Peter W; Brown, Robert W B; Ginger, Michael L

    2010-08-01

    Enzymes moonlight in a non-enzymatic capacity in a diverse variety of cellular processes. The discovery of these non-enzymatic functions is generally unexpected, and moonlighting enzymes are known in both prokaryotes and eukaryotes. Importantly, this unexpected multi-functionality indicates that caution might be needed on some occasions in interpreting phenotypes that result from the deletion or gene-silencing of some enzymes, including some of the best known enzymes from classic intermediary metabolism. Here, we provide an overview of enzyme moonlighting in parasitic protists. Unequivocal and putative examples of moonlighting are discussed, together with the possibility that the unusual biological characteristics of some parasites either limit opportunities for moonlighting to arise or perhaps contribute to the evolution of novel proteins with clear metabolic ancestry.

  2. Isolation and characterization of 17 different genes encoding putative endopolygalacturonase genes from Rhizopus oryzae

    Science.gov (United States)

    Polygalacturonase enzymes are a valuable aid in the retting of flax for production of linens and, more recently, production of biofuels from citrus wastes. In a search of the recently sequenced Rhizopus oryzae strain 99-880 genome database, 18 putative endopolygalacturonase genes were identified, w...

  3. 反应温度对隐甲锰矿型MnO2微纳结构和超级电容性能的影响∗%The effect of reaction temperature on the micro-nano structure and the capacitance properties of cryptomelane-type manganese oxide

    Institute of Scientific and Technical Information of China (English)

    冉奋; 康龙; 刘影; 王翎任; 刘卯成; 张宣宣; 范会利; 宋海明; 申魁文; 孔令斌

    2015-01-01

    采用简单的水热法制备了具有均一八面分子筛(OMS-2)结构的隐甲锰矿型二氧化锰(MnO2);通过水热反应温度控制 Mn O 2的微纳结构,研究反应温度对其超级电容器性能的影响。采用扫描电子显微镜(SEM)、X 射线衍射(XRD)和透射电子显微镜(TEM)表征材料的结构特点;采用循环伏安和恒流充放电测试其电化学电容性能。结果表明,制备的Mn O 2具有纳米刺或纳米棒形成放射状结构,随着反应温度的增加,Mn O 2晶体逐渐生长完全,从针状纳米刺转变成四方形纳米棒;制备的 Mn O 2具有双电层电容和法拉第准电容的双重特征,在5 mA/cm2的电流密度下,最高比电容达到了603 F/g;在100~180℃的范围内,比容量随着反应温度的升高而逐渐降低。%In this article,the uniform cryptomelane-type manganese oxide with an octahedral molecular sieves structure was prepared under mild hydrothermal condition;the effects of hydrothermal temperature on the mi-cro-nanostructure and supercapacitance properties of manganese dioxide were studied in detail.The structures were characterized by SEM,XRD and TEM;and the supercapacitive behaviors were investigated with cyclic voltammetry,galvanostatic charge and discharge tests.The experiment results suggested that:the prepared nanoparticles can be self-organized into dendritic nanostructures,and the nanocluster arrays are composed of nanoneedles or tetragonal prism nanorods;with the increase of reaction temprature,the crystal morphology of manganese oxide was gradually improving,and was trasformed from nanoneedles to tetragonal prism nanorods;the capacitance of MnO2 electrode was a combined contribution of electrical double-layer capacitance and pseud-ocapacitance,and the best specific capacitance value of MnO2 electrode was 603 F/g corresponding to the charge/discharge current density of 5 mA/cm2;with the increase of reaction temperature ranging from 100-180℃,the specific capacitance

  4. 生物遗态氧化锰基镁铝水滑石的制备及铅吸附性能∗%Preparation and Pb2+adsorption property of MgAl Layered double hydroxides(LDHs) based on biomorphic manganese oxide

    Institute of Scientific and Technical Information of China (English)

    高乐乐; 李秋荣; 韩璐; 胡晓辉; 王馨培; 宋河儒; 燕丽

    2016-01-01

    In this paper, biomorphic manganese oxide was prepared by the method of impregnation and calcination using cotton as the template. MgAl Layered double hydroxides ( LDHs ) based on biomorphic manganese oxide was synthesized by a hydrothermal synthetic method. The structure of MgAl LDHs based on manganese oxide was characterized by thermogravimetric⁃differential thermal analysis ( TG⁃DTA) , X⁃ray diffraction ( XRD) and scanning electron microscopy ( SEM) . The as⁃prepared sample was calcined at 500 ℃, and its adsorption properties for lead ions from aqueous solution were investigated. The adsorbent dosage, initial concentration, temperature, time and other factors on the adsorption properties were examined in detail. It was shown that the adsorption reaction reached the equilibrium within 2 h and the remove efficiency reached more than 99% with 50 mg adsorbent, 50 mg·L-1 pb2+at 25℃. The kinetic data fit the pseudo⁃second⁃order kinetic model. The adsorption isotherm was fit to the D⁃R model and the adsorption mechanism was physical adsorption. Moreover, the temperature was favorable for the adsorption.%本文以棉花为模板,浸渍醋酸锰溶液进而再煅烧的方法制备出具有棉花生物遗态的氧化锰。以氧化锰为基底,采用水热合成法制备出氧化锰基镁铝水滑石。利用热重差热( TG⁃DTA)分析、X射线衍射( XRD)和扫描电镜( SEM)对其进行表征。将所得样品在500℃下煅烧,研究所得氧化物对铅离子的吸附性能,对吸附剂用量、初始浓度、温度、时间等对吸附有影响的因素进行了系统的研究。结果表明,在25℃下,50 mg生物遗态氧化锰基镁铝氧化物吸附浓度为50 mg·L-1的铅离子溶液,去除率可达99%以上,吸附可在120 min基本达到平衡,吸附动力学模型符合准二级动力学。吸附等温线符合D⁃R模型,吸附属于物理吸附,且升温有利于吸附。

  5. Characterization of putative effectors from the cereal cyst nematode Heterodera avenae.

    Science.gov (United States)

    Cui, Jiangkuan; Peng, Huan; Qiao, Fen; Wang, Gaofeng; Huang, Wenkun; Wu, Duqign; Peng, Deliang

    2017-09-20

    Few molecular details of effectors of Heterodera avenae parasitism are known. We performed a high-throughput sequencing analysis of the H. avenae transcriptome at five developmental stages. A total of 82,549 unigenes were ultimately obtained, and 747 transcripts showed best hits to genes putatively encoding carbohydrate-active enzymes in plant parasitic nematodes that play an important role in the invasion process. A total of 1480 unigenes were homologous to known phytonematode effectors, and 63 putative novel effectors were identified in the H. avenae transcriptomes. Twenty-three unigenes were analyzed by qRT-PCR and confirmed to be highly expressed during at least one developmental stage. For in situ hybridization, 17 of the 22 tested putative effectors were specifically expressed and located in the subventral gland cells, and five putative novel effectors were specifically expressed in the dorsal gland. Furthermore, 115 transcripts were found to have putative lethal RNA interference (RNAi) phenotypes. Three target genes with lethal RNAi phenotypes and two of the four tested putative effectors were associated with a decrease in the number of cysts through in vitro RNAi technology. These transcriptomic data lay a foundation for further studies of interactions of H. avenae with cereal and H. avenae parasitic control.

  6. CRYSTAL STRUCTURE ANALYSIS OF A PUTATIVE OXIDOREDUCTASE FROM KLEBSIELLA PNEUMONIAE

    Energy Technology Data Exchange (ETDEWEB)

    Baig, M.; Brown, A.; Eswaramoorthy, S.; Swaminathan, S.

    2009-01-01

    Klebsiella pneumoniae, a gram-negative enteric bacterium, is found in nosocomial infections which are acquired during hospital stays for about 10% of hospital patients in the United States. The crystal structure of a putative oxidoreductase from K. pneumoniae has been determined. The structural information of this K. pneumoniae protein was used to understand its function. Crystals of the putative oxidoreductase enzyme were obtained by the sitting drop vapor diffusion method using Polyethylene glycol (PEG) 3350, Bis-Tris buffer, pH 5.5 as precipitant. These crystals were used to collect X-ray data at beam line X12C of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The crystal structure was determined using the SHELX program and refi ned with CNS 1.1. This protein, which is involved in the catalysis of an oxidation-reduction (redox) reaction, has an alpha/beta structure. It utilizes nicotinamide adenine dinucleotide phosphate (NADP) or nicotine adenine dinucleotide (NAD) to perform its function. This structure could be used to determine the active and co-factor binding sites of the protein, information that could help pharmaceutical companies in drug design and in determining the protein’s relationship to disease treatment such as that for pneumonia and other related pathologies.

  7. Characterization of three putative xylulose 5-phosphate/fructose 6-phosphate phosphoketolases in the cyanobacterium Anabaena sp. PCC 7120.

    Science.gov (United States)

    Moriyama, Takashi; Tajima, Naoyuki; Sekine, Kohsuke; Sato, Naoki

    2015-01-01

    Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) is a key enzyme in the central carbohydrate metabolism in heterofermentative bacteria, in which enzymatic property of Xfps is well characterized. This is not the case in other microbes. The cyanobacterium Anabaena sp. PCC 7120 possesses three putative genes encoding Xfp, all1483, all2567, and alr1850. We purified three putative Xfps as recombinant proteins. The results of gel filtration indicated that these proteins form homomultimer complex. All1483 and All2567 showed phosphoketolase activity, whereas Alr1850 did not show the activity. Kinetic analyses demonstrated that substrates, fructose 6-phosphate and inorganic phosphate, are cooperatively bound to enzymes positively and negatively, respectively.

  8. Removal of Uranium (Ⅵ) by Fixed Bed Ion-exchange Column Using Natural Zeolite Coated with Manganese Oxide%锰氧化物负载沸石固定床离子交换柱去除铀(VI)的研究

    Institute of Scientific and Technical Information of China (English)

    邹卫华; 赵蕾; 韩润平

    2009-01-01

    The adsorption of uranium (Ⅵ) on the manganese oxide coated zeolite (MOCZ) from aqueous solution was investigated in a fixed-bed column. The experiments were conducted to investigate the effects of bed height, flow rate, particle size, initial concentration of uranium (Ⅵ), initial pH, presence of salt and competitive ions. The U-uptake by MOCZ increased with initial uranium (Ⅵ) concentration and bed height, but decreased as the flow rate and particle size increased. In the presence of salt and competitive ions, the breakthrough time was shorter. The ad-sorption capacity reached a maximum at pH of 6.3. The Thomas model was applied to the experimental data to de-termine the characteristic parameters of the column for process design using linear regression. The breakthrough curves calculated from the model were in good agreement with the experimental data. The BDST model was used to study the influence of bed height on the adsorption of uranium (Ⅵ). Desorption of uranium (Ⅵ) in the MOCZ column was investigated. The column could be used for at least four adsorption-desorption cycles using 0.1 mol'L-1 NaHCO3 solution as the elution. After desorption and regeneration with deionized water, MOCZ could be reused to adsorb uranium (Ⅵ) at a comparable capacity. Compared to raw zeolite, MOCZ showed better capacity for uranium (Ⅵ) removal.

  9. Phosphoglycerate Dehydrogenase: Potential Therapeutic Target and Putative Metabolic Oncogene

    Directory of Open Access Journals (Sweden)

    Cheryl K. Zogg

    2014-01-01

    Full Text Available Exemplified by cancer cells’ preference for glycolysis, for example, the Warburg effect, altered metabolism in tumorigenesis has emerged as an important aspect of cancer in the past 10–20 years. Whether due to changes in regulatory tumor suppressors/oncogenes or by acting as metabolic oncogenes themselves, enzymes involved in the complex network of metabolic pathways are being studied to understand their role and assess their utility as therapeutic targets. Conversion of glycolytic intermediate 3-phosphoglycerate into phosphohydroxypyruvate by the enzyme phosphoglycerate dehydrogenase (PHGDH—a rate-limiting step in the conversion of 3-phosphoglycerate to serine—represents one such mechanism. Forgotten since classic animal studies in the 1980s, the role of PHGDH as a potential therapeutic target and putative metabolic oncogene has recently reemerged following publication of two prominent papers near-simultaneously in 2011. Since that time, numerous studies and a host of metabolic explanations have been put forward in an attempt to understand the results observed. In this paper, I review the historic progression of our understanding of the role of PHGDH in cancer from the early work by Snell through its reemergence and rise to prominence, culminating in an assessment of subsequent work and what it means for the future of PHGDH.

  10. Putative archaeal viruses from the mesopelagic ocean.

    Science.gov (United States)

    Vik, Dean R; Roux, Simon; Brum, Jennifer R; Bolduc, Ben; Emerson, Joanne B; Padilla, Cory C; Stewart, Frank J; Sullivan, Matthew B

    2017-01-01

    Oceanic viruses that infect bacteria, or phages, are known to modulate host diversity, metabolisms, and biogeochemical cycling, while the viruses that infect marine Archaea remain understudied despite the critical ecosystem roles played by their hosts. Here we introduce "MArVD", for Metagenomic Archaeal Virus Detector, an annotation tool designed to identify putative archaeal virus contigs in metagenomic datasets. MArVD is made publicly available through the online iVirus analytical platform. Benchmarking analysis of MArVD showed it to be >99% accurate and 100% sensitive in identifying the 127 known archaeal viruses among the 12,499 viruses in the VirSorter curated dataset. Application of MArVD to 10 viral metagenomes from two depth profiles in the Eastern Tropical North Pacific (ETNP) oxygen minimum zone revealed 43 new putative archaeal virus genomes and large genome fragments ranging in size from 10 to 31 kb. Network-based classifications, which were consistent with marker gene phylogenies where available, suggested that these putative archaeal virus contigs represented six novel candidate genera. Ecological analyses, via fragment recruitment and ordination, revealed that the diversity and relative abundances of these putative archaeal viruses were correlated with oxygen concentration and temperature along two OMZ-spanning depth profiles, presumably due to structuring of the host Archaea community. Peak viral diversity and abundances were found in surface waters, where Thermoplasmata 16S rRNA genes are prevalent, suggesting these archaea as hosts in the surface habitats. Together these findings provide a baseline for identifying archaeal viruses in sequence datasets, and an initial picture of the ecology of such viruses in non-extreme environments.

  11. Food Enzymes

    Science.gov (United States)

    McBroom, Rachel; Oliver-Hoyo, Maria T.

    2007-01-01

    Many students view biology and chemistry as two unrelated, separate sciences; how these courses are generally taught in high schools may do little to change that impression. The study of enzymes provide a great opportunity for both biology and chemistry teachers to share with students the interdisciplinary nature of science. This article describes…

  12. Food Enzymes

    Science.gov (United States)

    McBroom, Rachel; Oliver-Hoyo, Maria T.

    2007-01-01

    Many students view biology and chemistry as two unrelated, separate sciences; how these courses are generally taught in high schools may do little to change that impression. The study of enzymes provide a great opportunity for both biology and chemistry teachers to share with students the interdisciplinary nature of science. This article describes…

  13. Enzyme immunoassay

    DEFF Research Database (Denmark)

    Feldt-Rasmussen, B; Dinesen, B; Deckert, M

    1985-01-01

    An enzyme linked immunoadsorbent assay for urinary albumin using commercially available reagents is described. The assay range is 2.5-120 micrograms/l. When samples are analysed in two standard dilutions, the assayable albumin concentration range is 2.5-240 mg/l, covering the clinical range from...

  14. Complete Genome Sequence of the Filamentous Fungus Aspergillus westerdijkiae Reveals the Putative Biosynthetic Gene Cluster of Ochratoxin A

    Science.gov (United States)

    Chakrabortti, Alolika; Li, Jinming

    2016-01-01

    Ochratoxin A (OTA) is a common mycotoxin that contaminates food and agricultural products. Sequencing of the complete genome of Aspergillus westerdijkiae, a major producer of OTA, reveals more than 50 biosynthetic gene clusters, including a putative OTA biosynthetic gene cluster that encodes a dozen of enzymes, transporters, and regulatory proteins. PMID:27635003

  15. Characterization of the Entamoeba histolytica ornithine decarboxylase-like enzyme.

    Directory of Open Access Journals (Sweden)

    Anupam Jhingran

    Full Text Available BACKGROUND: The polyamines putrescine, spermidine, and spermine are organic cations that are required for cell growth and differentiation. Ornithine decarboxylase (ODC, the first and rate-limiting enzyme in the polyamine biosynthetic pathway, is a highly regulated enzyme. METHODOLOGY AND RESULTS: To use this enzyme as a potential drug target, the gene encoding putative ornithine decarboxylase (ODC-like sequence was cloned from Entamoeba histolytica, a protozoan parasite causing amoebiasis. DNA sequence analysis revealed an open reading frame (ORF of approximately 1,242 bp encoding a putative protein of 413 amino acids with a calculated molecular mass of 46 kDa and a predicted isoelectric point of 5.61. The E. histolytica putative ODC-like sequence has 33% sequence identity with human ODC and 36% identity with the Datura stramonium ODC. The ORF is a single-copy gene located on a 1.9-Mb chromosome. The recombinant putative ODC protein (48 kDa from E. histolytica was heterologously expressed in Escherichia coli. Antiserum against recombinant putative ODC protein detected a band of anticipated size approximately 46 kDa in E. histolytica whole-cell lysate. Difluoromethylornithine (DFMO, an enzyme-activated irreversible inhibitor of ODC, had no effect on the recombinant putative ODC from E. histolytica. Comparative modeling of the three-dimensional structure of E. histolytica putative ODC shows that the putative binding site for DFMO is disrupted by the substitution of three amino acids-aspartate-332, aspartate-361, and tyrosine-323-by histidine-296, phenylalanine-305, and asparagine-334, through which this inhibitor interacts with the protein. Amino acid changes in the pocket of the E. histolytica enzyme resulted in low substrate specificity for ornithine. It is possible that the enzyme has evolved a novel substrate specificity. CONCLUSION: To our knowledge this is the first report on the molecular characterization of putative ODC-like sequence from

  16. Reductive dissolution of MnO2 and manganese oxides in soils by low-molecular-weight organic compounds%低分子量有机化合物对MnO2和土壤氧化锰的还原溶解作用∗

    Institute of Scientific and Technical Information of China (English)

    刘源; 徐仁扣

    2015-01-01

    In order to get an insight into the reductive dissolution behaviors of manganese oxides in soils, eight organic acids ( cysteine, ascorbic acid, vanillic acid, citric acid, oxalate acid, tartaric acid, salicylic acid and phthalic acid) and one phenolic compound (catechol), synthetic MnO2, and five types of high⁃manganese oxides⁃containing soils ( three latosols from Xuwen of Guangdong Province, Chengmai of Hainan Province and Kunming of Yunnan province, respectively, one red soil from Shengxian of Zhejiang Province and one yellow⁃brown soil from Nanjing of Jiangsu Province) were used to investigate the reductive dissolution of manganese oxides by these organic compounds. The results showed that low pH and high temperature favoured the reductive dissolution of MnO2 by the organic compounds. In the range of pH 4. 5—5. 5 and 5—45 ℃, the reductive dissolution of MnO2 by the organic compounds followed the order: catechol > cysteine > ascorbic acid > vanillic acid > citric acid > oxalate acid ≈ tartaric acid > salicylic acid ≈ phthalic acid. Catechol, cysteine and ascorbic acid showed stronger ability to reduce and dissolve MnO2 . Among the five soils, the highest amount of Mn2+ was reductively dissolved from the latosol from Xuwen, followed by the latosol of Kunming, and the least amount of Mn2+was reductively dissolved from the red soil from Shengxian. The results presented in this study suggest that the manganese oxides in the latosols from Xuwen, Kunming and Chengmai were easy to be reduced by reducing organic compounds, which increased the contents of soluble and exchangeable Mn2+in these soils and could cause manganese toxicity to plants in the soils.%为考察土壤锰氧化物的还原溶解行为,本文选取常见的根系分泌的8种有机酸(抗坏血酸、香草酸、柠檬酸、草酸、酒石酸、水杨酸、半胱氨酸和邻苯二甲酸)和1种酚类化合物(邻苯二酚),人工合成的MnO2和5种富含氧化锰的土壤

  17. Ten Putative Contributors to the Obesity Epidemic

    Science.gov (United States)

    McAllister, Emily J.; Dhurandhar, Nikhil V.; Keith, Scott W.; Aronne, Louis J.; Barger, Jamie; Baskin, Monica; Benca, Ruth M.; Biggio, Joseph; Boggiano, Mary M.; Eisenmann, Joe C.; Elobeid, Mai; Fontaine, Kevin R.; Gluckman, Peter; Hanlon, Erin C.; Katzmarzyk, Peter; Pietrobelli, Angelo; Redden, David T.; Ruden, Douglas M.; Wang, Chenxi; Waterland, Robert A.; Wright, Suzanne M.; Allison, David B.

    2010-01-01

    The obesity epidemic is a global issue and shows no signs of abating, while the cause of this epidemic remains unclear. Marketing practices of energy-dense foods and institutionally-driven declines in physical activity are the alleged perpetrators for the epidemic, despite a lack of solid evidence to demonstrate their causal role. While both may contribute to obesity, we call attention to their unquestioned dominance in program funding and public efforts to reduce obesity, and propose several alternative putative contributors that would benefit from equal consideration and attention. Evidence for microorganisms, epigenetics, increasing maternal age, greater fecundity among people with higher adiposity, assortative mating, sleep debt, endocrine disruptors, pharmaceutical iatrogenesis, reduction in variability of ambient temperatures, and intrauterine and intergenerational effects, as contributing factors to the obesity epidemic are reviewed herein. While the evidence is strong for some contributors such as pharmaceutical-induced weight gain, it is still emerging for other reviewed factors. Considering the role of such putative etiological factors of obesity may lead to comprehensive, cause specific, and effective strategies for prevention and treatment of this global epidemic. PMID:19960394

  18. Putative Nitrogen Sensing Systems in Higher Plants

    Institute of Scientific and Technical Information of China (English)

    Hon-Ming Lam; Ying Ann Chiao; Man-Wah Li; Yuk-Kwong Yung; Sang Ji

    2006-01-01

    Nitrogen (N) metabolism is essential for the biosynthesis of vital biomolecules. N status thus exerts profound effects on plant growth and development, and must be closely monitored. In bacteria and fungi, a few sophisticated N sensing systems have been extensively studied. In animals, the ability to receive amino acid signals has evolved to become an integral part of the nervous coordination system. In this review, we will summarize recent developments in the search for putative N sensing systems in higher plants based on homologous systems in bacteria, fungi, and animals. Apparently, although plants have separated and diversified from other organisms during the evolution process, striking similarities can be found in their N sensing systems compared with those of their counterparts; however, our understanding of these systems is still incomplete. Significant modifications of the N sensing systems (including cross-talk with other signal transduction pathways) in higher plants may be a strategy of adaptation to their unique mode of life.

  19. Enrichment of putative stem cells from adipose tissue using dielectrophoretic field-flow fractionation

    Science.gov (United States)

    Vykoukal, Jody; Vykoukal, Daynene M.; Freyberg, Susanne; Alt, Eckhard U.; Gascoyne, Peter R. C.

    2009-01-01

    We have applied the microfluidic cell separation method of dielectrophoretic field-flow fractionation (DEP-FFF) to the enrichment of a putative stem cell population from an enzyme-digested adipose tissue derived cell suspension. A DEP-FFF separator device was constructed using a novel microfluidic-microelectronic hybrid flex-circuit fabrication approach that is scaleable and anticipates future low-cost volume manufacturing. We report the separation of a nucleated cell fraction from cell debris and the bulk of the erythrocyte population, with the relatively rare (<2% starting concentration) NG2-positive cell population (pericytes and/or putative progenitor cells) being enriched up to 14-fold. This work demonstrates a potential clinical application for DEP-FFF and further establishes the utility of the method for achieving label-free fractionation of cell subpopulations. PMID:18651083

  20. Putative bronchopulmonary flagellated protozoa in immunosuppressed patients.

    Science.gov (United States)

    Kilimcioglu, Ali Ahmet; Havlucu, Yavuz; Girginkardesler, Nogay; Celik, Pınar; Yereli, Kor; Özbilgin, Ahmet

    2014-01-01

    Flagellated protozoa that cause bronchopulmonary symptoms in humans are commonly neglected. These protozoal forms which were presumed to be "flagellated protozoa" have been previously identified in immunosuppressed patients in a number of studies, but have not been certainly classified so far. Since no human cases of bronchopulmonary flagellated protozoa were reported from Turkey, we aimed to investigate these putative protozoa in immunosuppressed patients who are particularly at risk of infectious diseases. Bronchoalveolar lavage fluid samples of 110 immunosuppressed adult patients who were admitted to the Department of Chest Diseases, Hafsa Sultan Hospital of Celal Bayar University, Manisa, Turkey, were examined in terms of parasites by light microscopy. Flagellated protozoal forms were detected in nine (8.2%) of 110 cases. Metronidazole (500 mg b.i.d. for 30 days) was given to all positive cases and a second bronchoscopy was performed at the end of the treatment, which revealed no parasites. In conclusion, immunosuppressed patients with bronchopulmonary symptoms should attentively be examined with regard to flagellated protozoa which can easily be misidentified as epithelial cells.

  1. The Biogeography of Putative Microbial Antibiotic Production.

    Directory of Open Access Journals (Sweden)

    Hélène Morlon

    Full Text Available Understanding patterns in the distribution and abundance of functional traits across a landscape is of fundamental importance to ecology. Mapping these distributions is particularly challenging for species-rich groups with sparse trait measurement coverage, such as flowering plants, insects, and microorganisms. Here, we use likelihood-based character reconstruction to infer and analyze the spatial distribution of unmeasured traits. We apply this framework to a microbial dataset comprised of 11,732 ketosynthase alpha gene sequences extracted from 144 soil samples from three continents to document the spatial distribution of putative microbial polyketide antibiotic production. Antibiotic production is a key competitive strategy for soil microbial survival and performance. Additionally, novel antibiotic discovery is highly relevant to human health, making natural antibiotic production by soil microorganisms a major target for bioprospecting. Our comparison of trait-based biogeographical patterns to patterns based on taxonomy and phylogeny is relevant to our basic understanding of microbial biogeography as well as the pressing need for new antibiotics.

  2. Mechanosensory neurons, cutaneous mechanoreceptors, and putative mechanoproteins.

    Science.gov (United States)

    Del Valle, M E; Cobo, T; Cobo, J L; Vega, J A

    2012-08-01

    The mammalian skin has developed sensory structures (mechanoreceptors) that are responsible for different modalities of mechanosensitivity like touch, vibration, and pressure sensation. These specialized sensory organs are anatomically and functionally connected to a special subset of sensory neurons called mechanosensory neurons, which electrophysiologically correspond with Aβ fibers. Although mechanosensory neurons and cutaneous mechanoreceptors are rather well known, the biology of the sense of touch still remains poorly understood. Basically, the process of mechanosensitivity requires the conversion of a mechanical stimulus into an electrical signal through the activation of ion channels that gate in response to mechanical stimuli. These ion channels belong primarily to the family of the degenerin/epithelium sodium channels, especially the subfamily acid-sensing ion channels, and to the family of transient receptor potential channels. This review compiles the current knowledge on the occurrence of putative mechanoproteins in mechanosensory neurons and mechanoreceptors, as well as the involvement of these proteins on the biology of touch. Furthermore, we include a section about what the knock-out mice for mechanoproteins are teaching us. Finally, the possibilities for mechanotransduction in mechanoreceptors, and the common involvement of the ion channels, extracellular membrane, and cytoskeleton, are revisited.

  3. Constraints on superoxide mediated formation of manganese oxides

    Directory of Open Access Journals (Sweden)

    Deric R. Learman

    2013-09-01

    Full Text Available Manganese (Mn oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2- (both of biogenic and abiogenic origin as an effective oxidant of Mn(II leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III and Mn(III/IV oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide, a product of the reaction of O2- with Mn(II, inhibits the oxidation process presumably through the reduction of Mn(III. Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III-ligand complexes. While complexing ligands played a role in stabilizing Mn(III, they did not eliminate the inhibition of net Mn(III formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

  4. Transformation kinetics and pathways of tetracycline antibiotics with manganese oxide

    Energy Technology Data Exchange (ETDEWEB)

    Chen Wanru [School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Huang, Ching-Hua, E-mail: ching-hua.huang@ce.gatech.edu [School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

    2011-05-15

    Tetracycline antibiotics including tetracycline (TTC), oxytetracycline (OTC) and chlorotetracycline (CTC) undergo rapid transformation to yield various products in the presence of MnO{sub 2} at mild conditions (pH 4-9 and 22 {sup o}C). Reaction rates follow the trend of CTC > TTC > OTC, and are affected by pH and complexation of TCs with Mg{sup 2+} or Ca{sup 2+}. Experimental results of TTC indicate that MnO{sub 2} promotes isomerization at the C ring to form iso-TTC and oxidizes the phenolic-diketone and tricarbonylamide groups, leading to insertion of up to 2 O most likely at the C9 and C2 positions. In contrast, reactions of OTC with MnO{sub 2} generate little iso-OTC, but occur mainly at the A ring's dimethylamine group to yield N-demethylated products. CTC yields the most complicated products upon reactions with MnO{sub 2}, encompassing transformation patterns observed with both TTC and OTC. The identified product structures suggest lower antibacterial activity than that of the parent tetracyclines. - Highlights: > Tetracyclines transform rapidly by MnO{sub 2} to yield complicated products. > Isomerized, (hydr)oxygenated and N-demethylated products are formed. > Transformation product structures may suggest lowered antibacterial activity. - The complex transformation pathways of three popular tetracycline antibiotics (tetracycline, oxytetracycline and chlorotetracycline) with MnO{sub 2} under environmental conditions are systematically evaluated and elucidated.

  5. Smart Radiation Device based on a perovskite manganese oxide

    Science.gov (United States)

    Tachikawa, Sumitaka; Shimazaki, Kazunori; Ohnishi, Akira; Hirosawa, Haruto; Shimakawa, Yuichi; Ochi, Atsushi; Okamoto, Akira; Nakamura, Yasuyuki

    2003-09-01

    A new thermal control material named the Smart Radiation Device (SRD) was studied and improved. An SRD can be used as a variable emittance radiator; it controls the heat radiated to deep space without electrical instruments or mechanical parts, simply by changing emissivity. This device reduces the energy consumption of the on-board electrical heater, and decreases the weight and the cost of the thermal control system on the spacecraft. Three types of SRD were tried in the process of improving optical properties. In order to reduce solar absorptance, we designed and applied multilayer films for SRDs to reflect solar radiation while retaining its infrared radiative properties. In this paper, we introduce the optical properties of the SRD, a space environmental simulation test on ground, and environmental tests in space. In addition, we report the optical properties of the value-added SRD.

  6. Manganese-oxidizing photosynthesis before the rise of cyanobacteria

    Science.gov (United States)

    Johnson, Jena E.; Webb, Samuel M.; Thomas, Katherine; Ono, Shuhei; Kirschvink, Joseph L.; Fischer, Woodward W.

    2013-07-01

    The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ∼17 wt %) well before those associated with the rise of oxygen such as the ∼2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O2-multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains-reveal that the original Mn-oxide phases were not produced by reactions with O2, which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn.

  7. Manganese oxidation by bacterial isolates from the Indian Ridge System

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Krishnan, K.P.; Khedekar, V.D.; LokaBharathi, P.A.

    Ridge waters during the cruise SK194 onboard ORV Sagar Kanya (July, 2003). A total of 25 samples along the ridge axis and flanks were collected in 100 ml sterile polypropylene bottles and analyzed immediately onboard. An inoculum of 100 ll was used... twice with sterile saline and resuspended by vortexing. The inoculum size was calculated by direct cell counts in a cell counting chamber. Triphenyl tetrazolium chloride (TTC; 0.025%) was added to every tube prior to incubation. For heterotrophic or amen...

  8. Electromagnetic Properties of Lanthanum Manganese Oxides Doped with Iron

    Energy Technology Data Exchange (ETDEWEB)

    Oda, Katsuro; Miwa, Yasunari [University of Tokyo, Institute of Industrial Science (Japan); Ohtsuka, Hideyuki [National Research Institute for Metals (Japan)

    2002-03-15

    The mechanism of GMR effects in La(Mn{sub 1-x}Fe{sub x})O{sub 3} (x=0, 0.01, 0.03) oxides has been investigated by means of magnetic measurements, resistivity measurements in magnetic field and Moessbauer spectroscopy. For the x=0.01 sample, the GMR behavior is similar to that of the conventional (La, A)MnO{sub 3} (A: divalent cations) oxides. For the x=0.03 sample, even though the temperature dependence of the Moessbauer spectra was similar to that of the x=0.01 sample, the mechanism for the occurrence of the GMR effect seems to be different. The x=0 sample shows a similar behavior to the x=0.03 sample. A thermal stabilization of spin fluctuation is proposed for the x=0 and x=0.03 sample.

  9. Oxidation of phenolic acids by soil iron and manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, R.G.; Cheng, H.H.; Harsh, J.B.

    Phenolic acids are intermediary metabolites of many aromatic chemicals and may be involved in humus formation, allelopathy, and nutrient availability. Depending on their structures, six phenolic acids were shown to react at different rates with oxidized forms of Fe and Mn in a Palouse soil (fine-silty, mixed, mesic Pachic Ultic Haploxeroll). Increasing methoxy substitution on the aromatic ring of phenolic acids increased the reaction rate. Reaction rate was also increased for longer carboxyl-containing side chains. After 4 h reaction, little of the applied (10 mg kg/sup -1/ soil) p-hydroxybenzoic or p-coumaric acids had reacted, while 0 to 5, 70, 90, and 100% of the vanillic, ferulic, syringic, and sinapic acids, respectively, had reacted. After 72 h under conditions limiting microbial growth, none of the p-hydroxybenzoic, 30% of the p-coumaric, and 50% of the vanillic acids had reacted. The reaction was shown to be predominantly chemical, and not biological, since phenolic acid extractabilities were similar for Palouse soil and for Palouse soil pretreated with LiOBr to remove organic matter. When the Palouse soil was pretreated with a sodium dithionite-citrate solution to remove Fe and Mn oxides, none of the phenolic acids reacted after 1 h. The reaction of sinapic acid with Palouse soil was shown to produce Fe(II) and soluble Mn as reaction products. The reaction of phenolic acids with soil was thus shown to be an oxidation of the phenolic acids, coupled with a reduction of soil Fe and Mn oxides.

  10. Ageing behaviour of zirconia stabilised by yttria and manganese oxide

    DEFF Research Database (Denmark)

    Appel, C.C.; Bonanos, N.; Horsewell, Andy

    2001-01-01

    The effect of Mn on the structure, lattice parameter and conductivity has been investigated for near-cubic YSZ with an yttrium content slightly under 8 mol% Y2O3. The structure and chemistry of the material were studied both as sintered, and also after prolonged heat treatments at 850 and 1000 de...

  11. Tissue factor residues that putatively interact with membrane phospholipids.

    Directory of Open Access Journals (Sweden)

    Ke Ke

    Full Text Available Blood clotting is initiated by the two-subunit enzyme consisting of the plasma protease, factor VIIa (the catalytic subunit, bound to the integral membrane protein, tissue factor (the regulatory subunit. Molecular dynamics simulations have predicted that certain residues in the tissue factor ectodomain interact with phosphatidylserine headgroups to ensure optimal positioning of the tissue factor/factor VIIa complex relative to its membrane-bound protein substrates, factors IX and X. In this study, we individually mutated to alanine all the putative phosphatidylserine-interactive residues in the tissue factor ectodomain and measured their effects on tissue factor cofactor function (activation of factors IX and X by tissue factor/factor VIIa, and clotting of plasma. Some tissue factor mutants exhibited decreased activity in all three assays, with the most profound defects observed from mutations in or near the flexible loop from Lys159 to Gly164. The decreased activity of all of these tissue factor mutants could be partially or completely overcome by increasing the phosphatidylserine content of tissue factor-liposomes. Additionally, yeast surface display was used to screen a random library of tissue factor mutants for enhanced factor VIIa binding. Surprisingly, mutations at a single amino acid (Lys165 predominated, with the Lys165→Glu mutant exhibiting a 3-fold enhancement in factor VIIa binding affinity. Our studies reveal the functional contributions of residues in the C-terminal half of the tissue factor ectodomain that are implicated in interacting with phosphatidylserine headgroups to enhance tissue factor cofactor activity, possibly by allosterically modulating the conformation of the adjacent substrate-binding exosite region of tissue factor.

  12. A survey of orphan enzyme activities

    Directory of Open Access Journals (Sweden)

    Pouliot Yannick

    2007-07-01

    Full Text Available Abstract Background Using computational database searches, we have demonstrated previously that no gene sequences could be found for at least 36% of enzyme activities that have been assigned an Enzyme Commission number. Here we present a follow-up literature-based survey involving a statistically significant sample of such "orphan" activities. The survey was intended to determine whether sequences for these enzyme activities are truly unknown, or whether these sequences are absent from the public sequence databases but can be found in the literature. Results We demonstrate that for ~80% of sampled orphans, the absence of sequence data is bona fide. Our analyses further substantiate the notion that many of these enzyme activities play biologically important roles. Conclusion This survey points toward significant scientific cost of having such a large fraction of characterized enzyme activities disconnected from sequence data. It also suggests that a larger effort, beginning with a comprehensive survey of all putative orphan activities, would resolve nearly 300 artifactual orphans and reconnect a wealth of enzyme research with modern genomics. For these reasons, we propose that a systematic effort to identify the cognate genes of orphan enzymes be undertaken.

  13. Enzyme detection by microfluidics

    DEFF Research Database (Denmark)

    2013-01-01

    Microfluidic-implemented methods of detecting an enzyme, in particular a DNA-modifying enzyme, are provided, as well as methods for detecting a cell, or a microorganism expressing said enzyme. The enzyme is detected by providing a nucleic acid substrate, which is specifically targeted...... by that enzyme...

  14. Immunodiagnosis of episomal Banana streak MY virus using polyclonal antibodies to an expressed putative coat protein.

    Science.gov (United States)

    Sharma, Susheel Kumar; Kumar, P Vignesh; Baranwal, Virendra Kumar

    2014-10-01

    A cryptic Badnavirus species complex, known as banana streak viruses (BSV) poses a serious threat to banana production and genetic improvement worldwide. Due to the presence of integrated BSV sequences in the banana genome, routine detection is largely based on serological and nucleo-serological diagnostic methods which require high titre specific polyclonal antiserum. Viral structural proteins like coat protein (CP) are the best target for in vitro expression, to be used as antigen for antiserum production. However, in badnaviruses precise CP sequences are not known. In this study, two putative CP coding regions (p48 and p37) of Banana streak MY virus (BSMYV) were identified in silico by comparison with caulimoviruses, retroviruses and Rice tungro bacilliform virus. The putative CP coding region (p37) was in vitro expressed in pMAL system and affinity purified. The purified fusion protein was used as antigen for raising polyclonal antiserum in rabbit. The specificity of antiserum was confirmed in Western blots, immunosorbent electron microscopy (ISEM) and antigen coated plate-enzyme linked immunosorbent assay (ACP-ELISA). The antiserum (1:2000) was successfully used in ACP-ELISA for specific detection of BSMYV infection in field and tissue culture raised banana plants. The antiserum was also utilized in immuno-capture PCR (IC-PCR) based indexing of episomal BSMYV infection. This is the first report of in silico identification of putative CP region of BSMYV, production of polyclonal antiserum against recombinant p37 and its successful use in immunodetection.

  15. Phylogeny of algal sequences encoding carbohydrate sulfotransferases, formylglycine-dependent sulfatases and putative sulfatase modifying factors

    Directory of Open Access Journals (Sweden)

    Chai-Ling eHo

    2015-11-01

    Full Text Available Many algae are rich sources of sulfated polysaccharides with biological activities. The physicochemical/rheological properties and biological activities of sulfated polysaccharides are affected by the pattern and number of sulfate moieties. Sulfation of carbohydrates is catalyzed by carbohydrate sulfotransferases (CHSTs while modification of sulfate moieties on sulfated polysaccharides was presumably catalyzed by sulfatases including formylglycine-dependent sulfatases (FGly-SULFs. Post-translationally modification of Cys to FGly in FGly-SULFs by sulfatase modifiying factors (SUMFs is necessary for the activity of this enzyme. The aims of this study are to mine for sequences encoding algal CHSTs, FGly-SULFs and putative SUMFs from the fully sequenced algal genomes and to infer their phylogenetic relationships to their well characterized counterparts from other organisms. Algal sequences encoding CHSTs, FGly-SULFs, SUMFs and SUMF-like proteins were successfully identified from green and brown algae. However, red algal FGly-SULFs and SUMFs were not identified. In addition, a group of SUMF-like sequences with different gene structure and possibly different functions were identified for green, brown and red algae. The phylogeny of these putative genes contributes to the corpus of knowledge of an unexplored area. The analyses of these putative genes contribute towards future production of existing and new sulfated carbohydrate polymers through enzymatic synthesis and metabolic engineering.

  16. Elevated Liver Enzymes

    Science.gov (United States)

    Symptoms Elevated liver enzymes By Mayo Clinic Staff Elevated liver enzymes may indicate inflammation or damage to cells in the liver. Inflamed or ... than normal amounts of certain chemicals, including liver enzymes, into the bloodstream, which can result in elevated ...

  17. Identification and functional analysis of Penicillium digitatum genes putatively involved in virulence towards citrus fruit.

    Science.gov (United States)

    López-Pérez, Mario; Ballester, Ana-Rosa; González-Candelas, Luis

    2015-04-01

    The fungus Penicillium digitatum, the causal agent of green mould rot, is the most destructive post-harvest pathogen of citrus fruit in Mediterranean regions. In order to identify P. digitatum genes up-regulated during the infection of oranges that may constitute putative virulence factors, we followed a polymerase chain reaction (PCR)-based suppression subtractive hybridization and cDNA macroarray hybridization approach. The origin of expressed sequence tags (ESTs) was determined by comparison against the available genome sequences of both organisms. Genes coding for fungal proteases and plant cell wall-degrading enzymes represent the largest categories in the subtracted cDNA library. Northern blot analysis of a selection of P. digitatum genes, including those coding for proteases, cell wall-related enzymes, redox homoeostasis and detoxification processes, confirmed their up-regulation at varying time points during the infection process. Agrobacterium tumefaciens-mediated transformation was used to generate knockout mutants for two genes encoding a pectin lyase (Pnl1) and a naphthalene dioxygenase (Ndo1). Two independent P. digitatum Δndo1 mutants were as virulent as the wild-type. However, the two Δpnl1 mutants analysed were less virulent than the parental strain or an ectopic transformant. Together, these results provide a significant advance in our understanding of the putative determinants of the virulence mechanisms of P. digitatum.

  18. Five putative nucleoside triphosphate diphosphohydrolase genes are expressed in Trichomonas vaginalis.

    Science.gov (United States)

    Frasson, Amanda Piccoli; Dos Santos, Odelta; Meirelles, Lúcia Collares; Macedo, Alexandre José; Tasca, Tiana

    2016-01-01

    Trichomonas vaginalis is a protozoan that parasitizes the human urogenital tract causing trichomoniasis, the most common non-viral sexually transmitted disease. The parasite has unique genomic characteristics such as a large genome size and expanded gene families. Ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) is an enzyme responsible for hydrolyzing nucleoside tri- and diphosphates and has already been biochemically characterized in T. vaginalis. Considering the important role of this enzyme in the production of extracellular adenosine for parasite uptake, we evaluated the gene expression of five putative NTPDases in T. vaginalis. We showed that all five putative TvNTPDase genes (TvNTPDase1-5) were expressed by both fresh clinical and long-term grown isolates. The amino acid alignment predicted the presence of the five crucial apyrase conserved regions, transmembrane domains, signal peptides, phosphorylation and catalytic sites. Moreover, a phylogenetic analysis showed that TvNTPDase sequences make up a clade with NTPDases intracellularly located. Biochemical NTPDase activity (ATP and ADP hydrolysis) is responsive to the serum-restrictive conditions and the gene expression of TvNTPDases was mostly increased, mainly TvNTPDase2 and TvNTPDase4, although there was not a clear pattern of expression among them. In summary, the present report demonstrates the gene expression patterns of predicted NTPDases in T. vaginalis.

  19. Putative Corneal Neuralgia Responding to Vitamin D Supplementation

    Directory of Open Access Journals (Sweden)

    Eric L. Singman

    2013-09-01

    Full Text Available A patient with putative corneal neuralgia was incidentally discovered to have hypovitaminosis D. Supplementation of vitamin D appears to have led to a resolution of the patient's pain, whereas other efforts to treat the patient were unsuccessful.

  20. Enzyme detection by microfluidics

    DEFF Research Database (Denmark)

    2013-01-01

    Microfluidic-implemented methods of detecting an enzyme, in particular a DNA-modifying enzyme, are provided, as well as methods for detecting a cell, or a microorganism expressing said enzyme. The enzyme is detected by providing a nucleic acid substrate, which is specifically targeted...

  1. Putative SF2 helicases of the early-branching eukaryote Giardia lamblia are involved in antigenic variation and parasite differentiation into cysts.

    Science.gov (United States)

    Gargantini, Pablo R; Serradell, Marianela C; Torri, Alessandro; Lujan, Hugo D

    2012-11-28

    Regulation of surface antigenic variation in Giardia lamblia is controlled post-transcriptionally by an RNA-interference (RNAi) pathway that includes a Dicer-like bidentate RNase III (gDicer). This enzyme, however, lacks the RNA helicase domain present in Dicer enzymes from higher eukaryotes. The participation of several RNA helicases in practically all organisms in which RNAi was studied suggests that RNA helicases are potentially involved in antigenic variation, as well as during Giardia differentiation into cysts. An extensive in silico analysis of the Giardia genome identified 32 putative Super Family 2 RNA helicases that contain almost all the conserved RNA helicase motifs. Phylogenetic studies and sequence analysis separated them into 22 DEAD-box, 6 DEAH-box and 4 Ski2p-box RNA helicases, some of which are homologs of well-characterized helicases from higher organisms. No Giardia putative helicase was found to have significant homology to the RNA helicase domain of Dicer enzymes. Additionally a series of up- and down-regulated putative RNA helicases were found during encystation and antigenic variation by qPCR experiments. Finally, we were able to recognize 14 additional putative helicases from three different families (RecQ family, Swi2/Snf2 and Rad3 family) that could be considered DNA helicases. This is the first comprehensive analysis of the Super Family 2 helicases from the human intestinal parasite G. lamblia. The relative and variable expression of particular RNA helicases during both antigenic variation and encystation agrees with the proposed participation of these enzymes during both adaptive processes. The putatives RNA and DNA helicases identified in this early-branching eukaryote provide initial information regarding the biological role of these enzymes in cell adaptation and differentiation.

  2. Identification and characterization of a gene encoding a putative lysophosphatidyl acyltransferase from Arachis hypogaea

    Indian Academy of Sciences (India)

    Si-Long Chen; Jia-Quan Huang; Lei Yong; Yue-Ting Zhang; Xiao-Ping Ren; Yu-Ning Chen; Hui-Fang Jiang; Li-Ying Yan; Yu-Rong Li; Bo-Shou Liao

    2012-12-01

    Lysophosphatidyl acyltransferase (LPAT) is the important enzyme responsible for the acylation of lysophosphatidic acid (LPA), leading to the generation of phosphatidic acid (PA) in plant. Its encoding gene is an essential candidate for oil crops to improve oil composition and increase seed oil content through genetic engineering. In this study, a full-length AhLPAT4 gene was isolated via cDNA library screening and rapid amplification of cDNA ends (RACE); our data demonstrated that AhLPAT4 had 1631 nucleotides, encoding a putative 43.8 kDa protein with 383 amino acid residues. The deduced protein included a conserved acyltransferase domain and four motifs (I–IV) with putative LPA and acyl-CoA catalytic and binding sites. Bioinformatic analysis indicated that AhLPAT4 contained four transmembrane domains (TMDs), localized to the endoplasmic reticulum (ER) membrane; detailed analysis indicated that motif I and motifs II–III in AhLPAT4 were separated by the third TMD, which located on cytosolic and ER luminal side respectively, and hydrophobic residues on the surface of AhLPAT4 protein fold to form a hydrophobic tunnel to accommodate the acyl chain. Subcellular localization analysis confirmed that AhLPAT4 was a cytoplasm protein. Phylogenetic analysis revealed that AhLPAT4 had a high homology (63.7–78.3%) with putative LPAT4 proteins from Glycine max, Arabidopsis thaliana and Ricinus communis. AhLPAT4 was ubiquitously expressed in diverse tissues except in flower, which is almost undetectable. The expression analysis in different developmental stages in peanut seeds indicated that AhLPAT4 did not coincide with oil accumulation.

  3. Identification of putative rhamnogalacturonan-II specific glycosyltransferases in Arabidopsis using a combination of bioinformatics approaches.

    Science.gov (United States)

    Voxeur, Aline; André, Aurélie; Breton, Christelle; Lerouge, Patrice

    2012-01-01

    Rhamnogalacturonan-II (RG-II) is a complex plant cell wall polysaccharide that is composed of an α(1,4)-linked homogalacturonan backbone substituted with four side chains. It exists in the cell wall in the form of a dimer that is cross-linked by a borate di-ester. Despite its highly complex structure, RG-II is evolutionarily conserved in the plant kingdom suggesting that this polymer has fundamental functions in the primary wall organisation. In this study, we have set up a bioinformatics strategy aimed at identifying putative glycosyltransferases (GTs) involved in RG-II biosynthesis. This strategy is based on the selection of candidate genes encoding type II membrane proteins that are tightly coexpressed in both rice and Arabidopsis with previously characterised genes encoding enzymes involved in the synthesis of RG-II and exhibiting an up-regulation upon isoxaben treatment. This study results in the final selection of 26 putative Arabidopsis GTs, including 10 sequences already classified in the CAZy database. Among these CAZy sequences, the screening protocol allowed the selection of α-galacturonosyltransferases involved in the synthesis of α4-GalA oligogalacturonides present in both homogalacturonans and RG-II, and two sialyltransferase-like sequences previously proposed to be involved in the transfer of Kdo and/or Dha on the pectic backbone of RG-II. In addition, 16 non-CAZy GT sequences were retrieved in the present study. Four of them exhibited a GT-A fold. The remaining sequences harbored a GT-B like fold and a fucosyltransferase signature. Based on homologies with glycosyltransferases of known functions, putative roles in the RG-II biosynthesis are proposed for some GT candidates.

  4. Non-homologous isofunctional enzymes: a systematic analysis of alternative solutions in enzyme evolution.

    Science.gov (United States)

    Omelchenko, Marina V; Galperin, Michael Y; Wolf, Yuri I; Koonin, Eugene V

    2010-04-30

    Evolutionarily unrelated proteins that catalyze the same biochemical reactions are often referred to as analogous - as opposed to homologous - enzymes. The existence of numerous alternative, non-homologous enzyme isoforms presents an interesting evolutionary problem; it also complicates genome-based reconstruction of the metabolic pathways in a variety of organisms. In 1998, a systematic search for analogous enzymes resulted in the identification of 105 Enzyme Commission (EC) numbers that included two or more proteins without detectable sequence similarity to each other, including 34 EC nodes where proteins were known (or predicted) to have distinct structural folds, indicating independent evolutionary origins. In the past 12 years, many putative non-homologous isofunctional enzymes were identified in newly sequenced genomes. In addition, efforts in structural genomics resulted in a vastly improved structural coverage of proteomes, providing for definitive assessment of (non)homologous relationships between proteins. We report the results of a comprehensive search for non-homologous isofunctional enzymes (NISE) that yielded 185 EC nodes with two or more experimentally characterized - or predicted - structurally unrelated proteins. Of these NISE sets, only 74 were from the original 1998 list. Structural assignments of the NISE show over-representation of proteins with the TIM barrel fold and the nucleotide-binding Rossmann fold. From the functional perspective, the set of NISE is enriched in hydrolases, particularly carbohydrate hydrolases, and in enzymes involved in defense against oxidative stress. These results indicate that at least some of the non-homologous isofunctional enzymes were recruited relatively recently from enzyme families that are active against related substrates and are sufficiently flexible to accommodate changes in substrate specificity.

  5. Non-homologous isofunctional enzymes: A systematic analysis of alternative solutions in enzyme evolution

    Directory of Open Access Journals (Sweden)

    Wolf Yuri I

    2010-04-01

    Full Text Available Abstract Background Evolutionarily unrelated proteins that catalyze the same biochemical reactions are often referred to as analogous - as opposed to homologous - enzymes. The existence of numerous alternative, non-homologous enzyme isoforms presents an interesting evolutionary problem; it also complicates genome-based reconstruction of the metabolic pathways in a variety of organisms. In 1998, a systematic search for analogous enzymes resulted in the identification of 105 Enzyme Commission (EC numbers that included two or more proteins without detectable sequence similarity to each other, including 34 EC nodes where proteins were known (or predicted to have distinct structural folds, indicating independent evolutionary origins. In the past 12 years, many putative non-homologous isofunctional enzymes were identified in newly sequenced genomes. In addition, efforts in structural genomics resulted in a vastly improved structural coverage of proteomes, providing for definitive assessment of (nonhomologous relationships between proteins. Results We report the results of a comprehensive search for non-homologous isofunctional enzymes (NISE that yielded 185 EC nodes with two or more experimentally characterized - or predicted - structurally unrelated proteins. Of these NISE sets, only 74 were from the original 1998 list. Structural assignments of the NISE show over-representation of proteins with the TIM barrel fold and the nucleotide-binding Rossmann fold. From the functional perspective, the set of NISE is enriched in hydrolases, particularly carbohydrate hydrolases, and in enzymes involved in defense against oxidative stress. Conclusions These results indicate that at least some of the non-homologous isofunctional enzymes were recruited relatively recently from enzyme families that are active against related substrates and are sufficiently flexible to accommodate changes in substrate specificity. Reviewers This article was reviewed by Andrei

  6. Non-homologous isofunctional enzymes: A systematic analysis of alternative solutions in enzyme evolution

    Science.gov (United States)

    2010-01-01

    Background Evolutionarily unrelated proteins that catalyze the same biochemical reactions are often referred to as analogous - as opposed to homologous - enzymes. The existence of numerous alternative, non-homologous enzyme isoforms presents an interesting evolutionary problem; it also complicates genome-based reconstruction of the metabolic pathways in a variety of organisms. In 1998, a systematic search for analogous enzymes resulted in the identification of 105 Enzyme Commission (EC) numbers that included two or more proteins without detectable sequence similarity to each other, including 34 EC nodes where proteins were known (or predicted) to have distinct structural folds, indicating independent evolutionary origins. In the past 12 years, many putative non-homologous isofunctional enzymes were identified in newly sequenced genomes. In addition, efforts in structural genomics resulted in a vastly improved structural coverage of proteomes, providing for definitive assessment of (non)homologous relationships between proteins. Results We report the results of a comprehensive search for non-homologous isofunctional enzymes (NISE) that yielded 185 EC nodes with two or more experimentally characterized - or predicted - structurally unrelated proteins. Of these NISE sets, only 74 were from the original 1998 list. Structural assignments of the NISE show over-representation of proteins with the TIM barrel fold and the nucleotide-binding Rossmann fold. From the functional perspective, the set of NISE is enriched in hydrolases, particularly carbohydrate hydrolases, and in enzymes involved in defense against oxidative stress. Conclusions These results indicate that at least some of the non-homologous isofunctional enzymes were recruited relatively recently from enzyme families that are active against related substrates and are sufficiently flexible to accommodate changes in substrate specificity. Reviewers This article was reviewed by Andrei Osterman, Keith F. Tipton

  7. Enzyme inhibition by iminosugars

    DEFF Research Database (Denmark)

    López, Óscar; Qing, Feng-Ling; Pedersen, Christian Marcus

    2013-01-01

    Imino- and azasugar glycosidase inhibitors display pH dependant inhibition reflecting that both the inhibitor and the enzyme active site have groups that change protonation state with pH. With the enzyme having two acidic groups and the inhibitor one basic group, enzyme-inhibitor complexes...

  8. Transcriptome Analysis Reveals Putative Genes Involved in Iridoid Biosynthesis in Rehmannia glutinosa

    Directory of Open Access Journals (Sweden)

    Xianen Li

    2012-10-01

    Full Text Available Rehmannia glutinosa, one of the most widely used herbal medicines in the Orient, is rich in biologically active iridoids. Despite their medicinal importance, no molecular information about the iridoid biosynthesis in this plant is presently available. To explore the transcriptome of R. glutinosa and investigate genes involved in iridoid biosynthesis, we used massively parallel pyrosequencing on the 454 GS FLX Titanium platform to generate a substantial EST dataset. Based on sequence similarity searches against the public sequence databases, the sequences were first annotated and then subjected to Gene Ontology (GO and Kyoto Encyclopedia of Genes and Genomes (KEGG based analysis. Bioinformatic analysis indicated that the 454 assembly contained a set of genes putatively involved in iridoid biosynthesis. Significantly, homologues of the secoiridoid pathway genes that were only identified in terpenoid indole alkaloid producing plants were also identified, whose presence implied that route II iridoids and route I iridoids share common enzyme steps in the early stage of biosynthesis. The gene expression patterns of four prenyltransferase transcripts were analyzed using qRT-PCR, which shed light on their putative functions in tissues of R. glutinosa. The data explored in this study will provide valuable information for further studies concerning iridoid biosynthesis.

  9. Biochemical Characterization of Putative Adenylate Dimethylallyltransferase and Cytokinin Dehydrogenase from Nostoc sp. PCC 7120.

    Science.gov (United States)

    Frébortová, Jitka; Greplová, Marta; Seidl, Michael F; Heyl, Alexander; Frébort, Ivo

    2015-01-01

    Cytokinins, a class of phytohormones, are adenine derivatives common to many different organisms. In plants, these play a crucial role as regulators of plant development and the reaction to abiotic and biotic stress. Key enzymes in the cytokinin synthesis and degradation in modern land plants are the isopentyl transferases and the cytokinin dehydrogenases, respectively. Their encoding genes have been probably introduced into the plant lineage during the primary endosymbiosis. To shed light on the evolution of these proteins, the genes homologous to plant adenylate isopentenyl transferase and cytokinin dehydrogenase were amplified from the genomic DNA of cyanobacterium Nostoc sp. PCC 7120 and expressed in Escherichia coli. The putative isopentenyl transferase was shown to be functional in a biochemical assay. In contrast, no enzymatic activity was detected for the putative cytokinin dehydrogenase, even though the principal domains necessary for its function are present. Several mutant variants, in which conserved amino acids in land plant cytokinin dehydrogenases had been restored, were inactive. A combination of experimental data with phylogenetic analysis indicates that adenylate-type isopentenyl transferases might have evolved several times independently. While the Nostoc genome contains a gene coding for protein with characteristics of cytokinin dehydrogenase, the organism is not able to break down cytokinins in the way shown for land plants.

  10. Comparative genomics study for identification of putative drug targets in Salmonella typhi Ty2.

    Science.gov (United States)

    Batool, Nisha; Waqar, Maleeha; Batool, Sidra

    2016-01-15

    Typhoid presents a major health concern in developing countries with an estimated annual infection rate of 21 million. The disease is caused by Salmonella typhi, a pathogenic bacterium acquiring multiple drug resistance. We aim to identify proteins that could prove to be putative drug targets in the genome of S. typhi str. Ty2. We employed comparative and subtractive genomics to identify targets that are absent in humans and are essential to S. typhi Ty2. We concluded that 46 proteins essential to pathogen are absent in the host genome. Filtration on the basis of drug target prioritization singled out 20 potentially therapeutic targets. Their absence in the host and specificity to S. typhi Ty2 makes them ideal targets for treating typhoid in Homo sapiens. 3D structures of two of the final target enzymes, MurA and MurB have been predicted via homology modeling which are then used for a docking study.

  11. A new generation of versatile chromogenic substrates for high-throughput analysis of biomass-degrading enzymes

    DEFF Research Database (Denmark)

    Kracun, Stjepan Kresimir; Schückel, Julia; Westereng, Bjørge;

    2015-01-01

    Background: Enzymes that degrade or modify polysaccharides are widespread in pro- and eukaryotes and have multiple biological roles and biotechnological applications. Recent advances in genome and secretome sequencing, together with associated bioinformatic tools, have enabled large numbers...... of carbohydrate-acting enzymes to be putatively identified. However, there is a paucity of methods for rapidly screening the biochemical activities of these enzymes, and this is a serious bottleneck in the development of enzyme-reliant bio-refining processes. Results: We have developed a new generation of multi...... carbohydrate-acting enzymes, and the assays have the potential to be incorporated into fully or semi-automated robotic enzyme screening systems...

  12. Amplification of tumor inducing putative cancer stem cells (CSCs) by vitamin A/retinol from mammary tumors

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Rohit B. [Department of Microbiology and Molecular Genetics, University of Pittsburgh, PA 15261 (United States); Wang, Qingde [Department of Surgery, University of Pittsburgh, PA 15261 (United States); Khillan, Jaspal S., E-mail: khillan@pitt.edu [Department of Microbiology and Molecular Genetics, University of Pittsburgh, PA 15261 (United States)

    2013-07-12

    Highlights: •Vitamin A supports self renewal of putative CSCs from mammary tumors. •These cells exhibit impaired retinol metabolism into retinoic acid. •CSCs from mammary tumors differentiate into mammary specific cell lineages. •The cells express mammary stem cell specific CD29 and CD49f markers. •Putative CSCs form highly metastatic tumors in NOD SCID mouse. -- Abstract: Solid tumors contain a rare population of cancer stem cells (CSCs) that are responsible for relapse and metastasis. The existence of CSC however, remains highly controversial issue. Here we present the evidence for putative CSCs from mammary tumors amplified by vitamin A/retinol signaling. The cells exhibit mammary stem cell specific CD29{sup hi}/CD49f{sup hi}/CD24{sup hi} markers, resistance to radiation and chemo therapeutic agents and form highly metastatic tumors in NOD/SCID mice. The cells exhibit indefinite self renewal as cell lines. Furthermore, the cells exhibit impaired retinol metabolism and do not express enzymes that metabolize retinol into retinoic acid. Vitamin A/retinol also amplified putative CSCs from breast cancer cell lines that form highly aggressive tumors in NOD SCID mice. The studies suggest that high purity putative CSCs can be isolated from solid tumors to establish patient specific cell lines for personalized therapeutics for pre-clinical translational applications. Characterization of CSCs will allow understanding of basic cellular and molecular pathways that are deregulated, mechanisms of tumor metastasis and evasion of therapies that has direct clinical relevance.

  13. Putative glycosyltransferases and other plant Golgi apparatus proteins are revealed by LOPIT proteomics.

    Science.gov (United States)

    Nikolovski, Nino; Rubtsov, Denis; Segura, Marcelo P; Miles, Godfrey P; Stevens, Tim J; Dunkley, Tom P J; Munro, Sean; Lilley, Kathryn S; Dupree, Paul

    2012-10-01

    The Golgi apparatus is the central organelle in the secretory pathway and plays key roles in glycosylation, protein sorting, and secretion in plants. Enzymes involved in the biosynthesis of complex polysaccharides, glycoproteins, and glycolipids are located in this organelle, but the majority of them remain uncharacterized. Here, we studied the Arabidopsis (Arabidopsis thaliana) membrane proteome with a focus on the Golgi apparatus using localization of organelle proteins by isotope tagging. By applying multivariate data analysis to a combined data set of two new and two previously published localization of organelle proteins by isotope tagging experiments, we identified the subcellular localization of 1,110 proteins with high confidence. These include 197 Golgi apparatus proteins, 79 of which have not been localized previously by a high-confidence method, as well as the localization of 304 endoplasmic reticulum and 208 plasma membrane proteins. Comparison of the hydrophobic domains of the localized proteins showed that the single-span transmembrane domains have unique properties in each organelle. Many of the novel Golgi-localized proteins belong to uncharacterized protein families. Structure-based homology analysis identified 12 putative Golgi glycosyltransferase (GT) families that have no functionally characterized members and, therefore, are not yet assigned to a Carbohydrate-Active Enzymes database GT family. The substantial numbers of these putative GTs lead us to estimate that the true number of plant Golgi GTs might be one-third above those currently annotated. Other newly identified proteins are likely to be involved in the transport and interconversion of nucleotide sugar substrates as well as polysaccharide and protein modification.

  14. Olanzapine-induced hepatopathy in albino rats: A newer model for screening putative hepatoprotective agents, namely silymarin

    Directory of Open Access Journals (Sweden)

    Sengupta Parama

    2010-01-01

    Full Text Available Backgrounds: This study was conducted to establish olanzapine-induced hepatopathy in Wistar albino rats as a newer model to screen putative hepatoprotective agents namely silymarin. Materials and Methods: Albino rats were divided into three groups, namely vehicle control group (CG, olanzapine-treated group (OZ, and olanzapine plus silymarin (OZS treated groups. Both the OZ and OZS groups were treated with the same dose of intraperitoneal olanzapine for 6 weeks and group OZS additionally received oral silymarin. Baseline and terminal hepatic enzymes (SGOT, SGPT, and ALP were measured in all three groups. Results: Histopathological examination of livers of both OZ and OZS groups showed degenerative changes, whereas those of control group showed normal architecture. Liver enzyme levels showed statistically significant rise in comparison to the control group as well as the respective base line values in both the test groups, but the differences in the rise of liver enzymes between the two test groups were not statistically significant. Conclusion: Olanzapine-induced hepatopathy in rats can be used as a model for screening putative hepatoprotective agents and in our setting silymarin has failed to provide any hepatoprotection.

  15. A putative viral defence mechanism in archaeal cells

    DEFF Research Database (Denmark)

    Lillestøl, Reidun K; Redder, Peter; Garrett, Roger Antony

    2006-01-01

    in cells, and that both the mode of inhibition of viral propagation and the mechanism of adding spacer-repeat units to clusters, are dependent on RNAs transcribed from the clusters. Moreover, the putative inhibitory apparatus (piRNA-based) may be evolutionarily related to the interference RNA systems (si...

  16. Putative Lineage of Novel African Usutu Virus, Central Europe

    Centers for Disease Control (CDC) Podcasts

    2015-10-15

    Sarah Gregory reads an abridged version of "Putative Lineage of Novel African Usutu Virus, Central Europe.".  Created: 10/15/2015 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 10/15/2015.

  17. Putative golden proportions as predictors of facial esthetics in adolescents.

    NARCIS (Netherlands)

    Kiekens, R.M.A.; Kuijpers-Jagtman, A.M.; Hof, M.A. van 't; Hof, BE van 't; Maltha, J.C.

    2008-01-01

    INTRODUCTION: In orthodontics, facial esthetics is assumed to be related to golden proportions apparent in the ideal human face. The aim of the study was to analyze the putative relationship between facial esthetics and golden proportions in white adolescents. METHODS: Seventy-six adult laypeople

  18. Enzyme kinetics of conjugating enzymes: PAPS sulfotransferase.

    Science.gov (United States)

    James, Margaret O

    2014-01-01

    The sulfotransferase (SULT) enzymes catalyze the formation of sulfate esters or sulfamates from substrates that contain hydroxy or amine groups, utilizing 3'-phosphoadenosyl-5'-phosphosulfate (PAPS) as the donor of the sulfonic group. The rate of product formation depends on the concentrations of PAPS and substrate as well as the sulfotransferase enzyme; thus, if PAPS is held constant while varying substrate concentration (or vice versa), the kinetic constants derived are apparent constants. When studied over a narrow range of substrate concentrations, classic Michaelis-Menten kinetics can be observed with many SULT enzymes and most substrates. Some SULT enzymes exhibit positive or negative cooperativity during conversion of substrate to product, and the kinetics fit the Hill plot. A characteristic feature of most sulfotransferase-catalyzed reactions is that, when studied over a wide range of substrate concentrations, the rate of product formation initially increases as substrate concentration increases, then decreases at high substrate concentrations, i.e., they exhibit substrate inhibition or partial substrate inhibition. This chapter gives an introduction to sulfotransferases, including a historical note, the nomenclature, a description of the function of SULTs with different types of substrates, presentation of examples of enzyme kinetics with SULTs, and a discussion of what is known about mechanisms of substrate inhibition in the sulfotransferases.

  19. Enzymes for improved biomass conversion

    Science.gov (United States)

    Brunecky, Roman; Himmel, Michael E.

    2016-02-02

    Disclosed herein are enzymes and combinations of the enzymes useful for the hydrolysis of cellulose and the conversion of biomass. Methods of degrading cellulose and biomass using enzymes and cocktails of enzymes are also disclosed.

  20. Enzymes for improved biomass conversion

    Energy Technology Data Exchange (ETDEWEB)

    Brunecky, Roman; Himmel, Michael E.

    2016-02-02

    Disclosed herein are enzymes and combinations of the enzymes useful for the hydrolysis of cellulose and the conversion of biomass. Methods of degrading cellulose and biomass using enzymes and cocktails of enzymes are also disclosed.

  1. Profiling the orphan enzymes

    Science.gov (United States)

    2014-01-01

    The emergence of Next Generation Sequencing generates an incredible amount of sequence and great potential for new enzyme discovery. Despite this huge amount of data and the profusion of bioinformatic methods for function prediction, a large part of known enzyme activities is still lacking an associated protein sequence. These particular activities are called “orphan enzymes”. The present review proposes an update of previous surveys on orphan enzymes by mining the current content of public databases. While the percentage of orphan enzyme activities has decreased from 38% to 22% in ten years, there are still more than 1,000 orphans among the 5,000 entries of the Enzyme Commission (EC) classification. Taking into account all the reactions present in metabolic databases, this proportion dramatically increases to reach nearly 50% of orphans and many of them are not associated to a known pathway. We extended our survey to “local orphan enzymes” that are activities which have no representative sequence in a given clade, but have at least one in organisms belonging to other clades. We observe an important bias in Archaea and find that in general more than 30% of the EC activities have incomplete sequence information in at least one superkingdom. To estimate if candidate proteins for local orphans could be retrieved by homology search, we applied a simple strategy based on the PRIAM software and noticed that candidates may be proposed for an important fraction of local orphan enzymes. Finally, by studying relation between protein domains and catalyzed activities, it appears that newly discovered enzymes are mostly associated with already known enzyme domains. Thus, the exploration of the promiscuity and the multifunctional aspect of known enzyme families may solve part of the orphan enzyme issue. We conclude this review with a presentation of recent initiatives in finding proteins for orphan enzymes and in extending the enzyme world by the discovery of new

  2. Unhairing with enzymes

    OpenAIRE

    Crispim, A.; Mota, M.

    2003-01-01

    The use of enzymes in the leather industry is increasing and their application is being widened to include operations such as de-greasing, unhairing and other wet-end operations. Enzymes can also be used to assist with recycling leather wastes as well as to avoid pollution. The present work is devoted to illustrate the potential application of enzymes in unhairing without hair destruction. Enzymatic unhairing is based upon the weakening of the epidermis basal layer to which the hair is at...

  3. Adenylate-forming enzymes

    Science.gov (United States)

    Schmelz, Stefan; Naismith, James H.

    2012-01-01

    Thioesters, amides and esters are common chemical building blocks in a wide array of natural products. The formation of these bonds can be catalyzed in a variety of ways. For chemists, the use of an activating group is a common strategy and adenylate enzymes are exemplars of this approach. Adenylating enzymes activate the otherwise unreactive carboxylic acid by transforming the normal hydroxyl leaving group into adenosine monophosphate. Recently there have been a number of studies of such enzymes and in this review we suggest a new classification scheme. The review highlights the diversity in enzyme fold, active site architecture and metal coordination that has evolved to catalyze this particular reaction. PMID:19836944

  4. Food and feed enzymes.

    Science.gov (United States)

    Fraatz, Marco Alexander; Rühl, Martin; Zorn, Holger

    2014-01-01

    Humans have benefited from the unique catalytic properties of enzymes, in particular for food production, for thousands of years. Prominent examples include the production of fermented alcoholic beverages, such as beer and wine, as well as bakery and dairy products. The chapter reviews the historic background of the development of modern enzyme technology and provides an overview of the industrial food and feed enzymes currently available on the world market. The chapter highlights enzyme applications for the improvement of resource efficiency, the biopreservation of food, and the treatment of food intolerances. Further topics address the improvement of food safety and food quality.

  5. Microbial amylolytic enzymes.

    Science.gov (United States)

    Vihinen, M; Mäntsälä, P

    1989-01-01

    Starch-degrading, amylolytic enzymes are widely distributed among microbes. Several activities are required to hydrolyze starch to its glucose units. These enzymes include alpha-amylase, beta-amylase, glucoamylase, alpha-glucosidase, pullulan-degrading enzymes, exoacting enzymes yielding alpha-type endproducts, and cyclodextrin glycosyltransferase. Properties of these enzymes vary and are somewhat linked to the environmental circumstances of the producing organisms. Features of the enzymes, their action patterns, physicochemical properties, occurrence, genetics, and results obtained from cloning of the genes are described. Among all the amylolytic enzymes, the genetics of alpha-amylase in Bacillus subtilis are best known. Alpha-Amylase production in B. subtilis is regulated by several genetic elements, many of which have synergistic effects. Genes encoding enzymes from all the amylolytic enzyme groups dealt with here have been cloned, and the sequences have been found to contain some highly conserved regions thought to be essential for their action and/or structure. Glucoamylase appears usually in several forms, which seem to be the results of a variety of mechanisms, including heterogeneous glycosylation, limited proteolysis, multiple modes of mRNA splicing, and the presence of several structural genes.

  6. Putative molecular mechanism underlying sperm chromatin remodelling is regulated by reproductive hormones

    Directory of Open Access Journals (Sweden)

    Gill-Sharma Manjeet Kaur

    2012-12-01

    Full Text Available Abstract Background The putative regulatory role of the male reproductive hormones in the molecular mechanism underlying chromatin condensation remains poorly understood. In the past decade, we developed two adult male rat models wherein functional deficits of testosterone or FSH, produced after treatments with 20 mg/Kg/d of cyproterone acetate (CPA per os, for a period of 15 days or 3 mg/Kg/d of fluphenazine decanoate (FD subcutaneously, for a period of 60 days, respectively, affected the rate of sperm chromatin decondensation in vitro. These rat models have been used in the current study in order to delineate the putative roles of testosterone and FSH in the molecular mechanism underlying remodelling of sperm chromatin. Results We report that deficits of both testosterone and FSH affected the turnover of polyubiquitylated histones and led to their accumulation in the testis. Functional deficits of testosterone reduced expression of MIWI, the 5-methyl cap binding RNA-binding protein (PIWIlike murine homologue of the Drosophila protein PIWI/P-element induced wimpy testis containing a PAZ/Piwi-Argonaut-Zwille domain and levels of histone deacetylase1 (HDAC1, ubiquitin ligating enzyme (URE-B1/E3, 20S proteasome α1 concomitant with reduced expression of ubiquitin activating enzyme (ube1, conjugating enzyme (ube2d2, chromodomain Y like protein (cdyl, bromodomain testis specific protein (brdt, hdac6 (histone deacetylase6, androgen-dependent homeobox placentae embryonic protein (pem/RhoX5, histones h2b and th3 (testis-specific h3. Functional deficits of FSH reduced the expression of cdyl and brdt genes in the testis, affected turnover of ubiquitylated histones, stalled the physiological DNA repair mechanism and culminated in spermiation of DNA damaged sperm. Conclusions We aver that deficits of both testosterone and FSH differentially affected the process of sperm chromatin remodelling through subtle changes in the ‘chromatin condensation

  7. Putative melatonin receptors in a human biological clock

    Energy Technology Data Exchange (ETDEWEB)

    Reppert, S.M.; Weaver, D.R.; Rivkees, S.A.; Stopa, E.G.

    1988-10-07

    In vitro autoradiography with /sup 125/I-labeled melatonin was used to examine melatonin binding sites in human hypothalamus. Specific /sup 125/I-labeled melatonin binding was localized to the suprachiasmatic nuclei, the site of a putative biological clock, and was not apparent in other hypothalamic regions. Specific /sup 125/I-labeled melatonin binding was consistently found in the suprachiasmatic nuclei of hypothalami from adults and fetuses. Densitometric analysis of competition experiments with varying concentrations of melatonin showed monophasic competition curves, with comparable half-maximal inhibition values for the suprachiasmatic nuclei of adults (150 picomolar) and fetuses (110 picomolar). Micromolar concentrations of the melatonin agonist 6-chloromelatonin completely inhibited specific /sup 125/I-labeled melatonin binding, whereas the same concentrations of serotonin and norepinephrine caused only a partial reduction in specific binding. The results suggest that putative melatonin receptors are located in a human biological clock.

  8. Trypanosoma brucei: a putative RNA polymerase II promoter.

    Science.gov (United States)

    Bayele, Henry K

    2009-12-01

    RNA polymerase II (pol II) promoters are rare in the African trypanosome Trypanosoma brucei because gene regulation in the parasite is complex and polycistronic. Here, we describe a putative pol II promoter and its structure-function relationship. The promoter has features of an archetypal eukaryotic pol II promoter including putative canonical CCAAT and TATA boxes, and an initiator element. However, the spatial arrangement of these elements is only similar to yeast pol II promoters. Deletion mapping and transcription assays enabled delineation of a minimal promoter that could drive orientation-independent reporter gene expression suggesting that it may be a bidirectional promoter. In vitro transcription in a heterologous nuclear extract revealed that the promoter can be recognized by the basal eukaryotic transcription complex. This suggests that the transcription machinery in the parasite may be very similar to those of other eukaryotes.

  9. Chromosomal Abnormalities and Putative Susceptibility Genes in Autism Spectrum Disorders

    DEFF Research Database (Denmark)

    Nielsen, Mette Gilling

    Autism spectrum disorders (ASDs) is a heterogeneous group of neurodevelopmental disorders with a significant genetic component as shown by family and twin studies. However, only a few genes have repeatedly been shown to be involved in the development of ASDs. The aim of this study has been...... to identify possible ASD susceptibility genes. Genome screens in ASD patients suggest possible susceptibility gene regions on almost every chromosome. We identified four ASD patients with chromosomal rearrangements, two of which were familial rearrangements involving one of these putative susceptibility gene......) was performed for all four patients. By combination of these methods we identified several putative susceptibility genes for ASDs. Expression patterns were established for several of these genes by Quantitative PCR (Q-PCR) or in situ hybridization and one gene was sequenced in 157 ASD patients. Our results...

  10. Cloning of partial putative gonadotropin hormone receptor sequence from fish

    Indian Academy of Sciences (India)

    G Kumaresan; T Venugopal; A Vikas; T J Pandian; S M Athavan

    2000-03-01

    A search for the presence of mariner-like elements in the Labeo rohita genome by polymerase chain reaction led to the amplification of a partial DNA sequence coding for a putative transmembrane domain of gonadotropin hormone receptor. The amplified DNA sequence shows a high degree of homology to the available turkey and human luteinizing and follicle stimulating hormone receptor coding sequences. This is the first report on cloning such sequences of piscine origin.

  11. A putative role for apelin in the etiology of obesity.

    Science.gov (United States)

    Rayalam, Srujana; Della-Fera, Mary Anne; Krieg, Paul A; Cox, Christopher M; Robins, Allan; Baile, Clifton A

    2008-04-11

    Apelin, the endogenous ligand of the G protein-coupled APJ receptor has been shown to promote tumor angiogenesis. However, the effect of apelin on inducing angiogenesis in adipose tissue has not been investigated. In this review, we propose a putative role for apelin in promoting angiogenesis in adipose tissue. We further propose that targeting adipose tissue vasculature by blocking apelin signaling with anti-apelin antibodies will lead not only to inhibition of angiogenesis in adipose tissue but also to decreased adiposity.

  12. Magnetically responsive enzyme powders

    Energy Technology Data Exchange (ETDEWEB)

    Pospiskova, Kristyna, E-mail: kristyna.pospiskova@upol.cz [Regional Centre of Advanced Technologies and Materials, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Safarik, Ivo, E-mail: ivosaf@yahoo.com [Regional Centre of Advanced Technologies and Materials, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, Na Sadkach 7, 370 05 Ceske Budejovice (Czech Republic)

    2015-04-15

    Powdered enzymes were transformed into their insoluble magnetic derivatives retaining their catalytic activity. Enzyme powders (e.g., trypsin and lipase) were suspended in various liquid media not allowing their solubilization (e.g., saturated ammonium sulfate and highly concentrated polyethylene glycol solutions, ethanol, methanol, 2-propanol) and subsequently cross-linked with glutaraldehyde. Magnetic modification was successfully performed at low temperature in a freezer (−20 °C) using magnetic iron oxides nano- and microparticles prepared by microwave-assisted synthesis from ferrous sulfate. Magnetized cross-linked enzyme powders were stable at least for two months in water suspension without leakage of fixed magnetic particles. Operational stability of magnetically responsive enzymes during eight repeated reaction cycles was generally without loss of enzyme activity. Separation of magnetically modified cross-linked powdered enzymes from reaction mixtures was significantly simplified due to their magnetic properties. - Highlights: • Cross-linked enzyme powders were prepared in various liquid media. • Insoluble enzymes were magnetized using iron oxides particles. • Magnetic iron oxides particles were prepared by microwave-assisted synthesis. • Magnetic modification was performed under low (freezing) temperature. • Cross-linked powdered trypsin and lipase can be used repeatedly for reaction.

  13. Artificial Enzymes, "Chemzymes"

    DEFF Research Database (Denmark)

    Bjerre, Jeannette; Rousseau, Cyril Andre Raphaël; Pedersen, Lavinia Georgeta M

    2008-01-01

    Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models that successf......Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models...... that successfully perform Michaelis-Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called...... "Chemzymes", based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well...

  14. Enzymes in Fermented Fish.

    Science.gov (United States)

    Giyatmi; Irianto, H E

    Fermented fish products are very popular particularly in Southeast Asian countries. These products have unique characteristics, especially in terms of aroma, flavor, and texture developing during fermentation process. Proteolytic enzymes have a main role in hydrolyzing protein into simpler compounds. Fermentation process of fish relies both on naturally occurring enzymes (in the muscle or the intestinal tract) as well as bacteria. Fermented fish products processed using the whole fish show a different characteristic compared to those prepared from headed and gutted fish. Endogenous enzymes like trypsin, chymotrypsin, elastase, and aminopeptidase are the most involved in the fermentation process. Muscle tissue enzymes like cathepsins, peptidases, transaminases, amidases, amino acid decarboxylases, glutamic dehydrogenases, and related enzymes may also play a role in fish fermentation. Due to the decreased bacterial number during fermentation, contribution of microbial enzymes to proteolysis may be expected prior to salting of fish. Commercial enzymes are supplemented during processing for specific purposes, such as quality improvement and process acceleration. In the case of fish sauce, efforts to accelerate fermentation process and to improve product quality have been studied by addition of enzymes such as papain, bromelain, trypsin, pepsin, and chymotrypsin. © 2017 Elsevier Inc. All rights reserved.

  15. High-throughput screening of carbohydrate-degrading enzymes using novel insoluble chromogenic substrate assay kits

    DEFF Research Database (Denmark)

    Schückel, Julia; Kracun, Stjepan Kresimir; Willats, William George Tycho

    2016-01-01

    of CAZymes exist in nature (especially in microorganisms) and hundreds of thousands have been cataloged and described in the carbohydrate active enzyme database (CAZy). However, the rate of discovery of putative enzymes has outstripped our ability to biochemically characterize their activities. One reason...... kit based on insoluble chromogenic substrates is described here. Two distinct substrate types were produced: Chromogenic Polymer Hydrogel (CPH) substrates (made from purified polysaccharides and proteins) and Insoluble Chromogenic Biomass (ICB) substrates (made from complex biomass materials). Both...

  16. Isolation and Identification of Putative Oral Cancer Stem Cells

    Institute of Scientific and Technical Information of China (English)

    ZHANG Min; ZHAO Yan-Hua; TANG Xiao-Fei

    2011-01-01

    Objective: To isolate and characterize putative cancer stem cells in Tea8113 oral squmous cell carcinoma cell line. Methods: Putative cancer stem cells were isolated by limited dilution assay in Tea8113 cell line. Biological features of putative cancer stem cells were detected by MTT assay, flow cytometry, immunofluorescence, Colony Forming Efficiency assays, cell motility assay and in vivo tumor formation experiment. Results: Compared with untreated Tea8113 cells, the putative cancer stem cells proliferated more quickly and showed heteroploid cell cycle,higher G0/G1-arrested cells, higher CFE and higher expression levels of ABCG2 belonged to tumor stem cell phenotypes. The putative cancer stem cells had stronger capacity to generate tumors in vivo. Conclusion: The holoclone cells have higher proliferation and self-renewal abilities, which may be cancer stem cells existed in Tea8113 oral squmous cell carcinoma cell line.%目的:分离鉴定口腔鳞癌细胞系Tca8113中的肿瘤干细胞.方法:利用有限稀释的方法分离Tca8113细胞系中的肿瘤干细胞.通过MTT法、流式细胞技术、细胞免疫荧光、克隆形成率分析、细胞迁移能力检测和裸鼠皮下成瘤实验确定分离得到的肿瘤干细胞的生物学特点.结果:分离得到的紧密型克隆肿瘤细胞表现为异倍体样细胞周期,大部分细胞处于G0/G1期,增殖能力、克隆形成率和体外迁移能力都明显高于未分离的肿瘤细胞.紧密型克隆肿瘤细胞肿瘤干细胞标记物ABCG2表达也高于未分离的肿瘤细胞,并且具有更强的裸鼠皮下成瘤能力.结论:我们分离得到的紧密型克隆细胞具有较强的细胞增殖和自我更新能力,可能就是口腔鳞癌细胞系Tca8113中的肿瘤干细胞.

  17. Cotton cellulose: enzyme adsorption and enzymic hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Beltrame, P.L.; Carniti, P.; Focher, B.; Marzetti, A.; Cattaneo, M.

    1982-01-01

    The adsorption of a crude cellulase complex from Trichoderma viride on variously pretreated cotton cellulose samples was studied in the framework of the Langmuir approach at 2-8 degrees. The saturation amount of adsorbed enzyme was related to the susceptibility of the substrates to hydrolysis. In every case the adsorption process was faster by 2-3 orders of magnitude than the hydrolysis step to give end products. For ZnCl/sub 2/-treated cotton cellulose the Langmuir parameters correlated fairly well with the value of the Michaelis constant, measured for its enzymic hydrolysis, and the adsorptive complex was indistinguishable from the complex of the Michaelis-Menten model for the hydrolysis.

  18. Application of a Colorimetric Assay to Identify Putative Ribofuranosylaminobenzene 5'-Phosphate Synthase Genes Expressed with Activity in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Bechard Matthew E.

    2003-01-01

    Full Text Available Tetrahydromethanopterin (H4MPT is a tetrahydrofolate analog originally discovered in methanogenic archaea, but later found in other archaea and bacteria. The extent to which H4MPT occurs among living organisms is unknown. The key enzyme which distinguishes the biosynthetic pathways of H4MPT and tetrahydrofolate is ribofuranosylaminobenzene 5'-phosphate synthase (RFAP synthase. Given the importance of RFAP synthase in H4MPT biosynthesis, the identification of putative RFAP synthase genes and measurement of RFAP synthase activity would provide an indication of the presence of H4MPT in untested microorganisms. Investigation of putative archaeal RFAP synthase genes has been hampered by the tendency of the resulting proteins to form inactive inclusion bodies in Escherichia coli. The current work describes a colorimetric assay for measuring RFAP synthase activity, and two modified procedures for expressing recombinant RFAP synthase genes to produce soluble, active enzyme. By lowering the incubation temperature during expression, RFAP synthase from Archaeoglobus fulgidus was produced in E. coli and purified to homogeneity. The production of active RFAP synthase from Methanothermobacter thermautotrophicus was achieved by coexpression of the gene MTH0830 with a molecular chaperone. This is the first direct biochemical identification of a methanogen gene that codes for an active RFAP synthase.

  19. The V-ATPase a2-subunit as a putative endosomal pH-sensor.

    Science.gov (United States)

    Marshansky, V

    2007-11-01

    V-ATPase (vesicular H(+)-ATPase)-driven intravesicular acidification is crucial for vesicular trafficking. Defects in vesicular acidification and trafficking have recently been recognized as essential determinants of various human diseases. An important role of endosomal acidification in receptor-ligand dissociation and in activation of lysosomal hydrolytic enzymes is well established. However, the molecular mechanisms by which luminal pH information is transmitted to the cytosolic small GTPases that control trafficking events such as budding, coat formation and fusion are unknown. Here, we discuss our recent discovery that endosomal V-ATPase is a pH-sensor regulating the degradative pathway. According to our model, V-ATPase is responsible for: (i) the generation of a pH gradient between vesicular membranes; (ii) sensing of intravesicular pH; and (iii) transmitting this information to the cytosolic side of the membrane. We also propose the hypothetical molecular mechanism involved in function of the V-ATPase a2-subunit as a putative pH-sensor. Based on extensive experimental evidence on the crucial role of histidine residues in the function of PSPs (pH-sensing proteins) in eukaryotic cells, we hypothesize that pH-sensitive histidine residues within the intra-endosomal loops and/or C-terminal luminal tail of the a2-subunit could also be involved in the pH-sensing function of V-ATPase. However, in order to identify putative pH-sensitive histidine residues and to test this hypothesis, it is absolutely essential that we increase our understanding of the folding and transmembrane topology of the a-subunit isoforms of V-ATPase. Thus the crucial role of intra-endosomal histidine residues in pH-dependent conformational changes of the V-ATPase a2-isoform, its interaction with cytosolic small GTPases and ultimately in its acidification-dependent regulation of the endosomal/lysosomal protein degradative pathway remain to be determined.

  20. The EBI enzyme portal.

    Science.gov (United States)

    Alcántara, Rafael; Onwubiko, Joseph; Cao, Hong; Matos, Paula de; Cham, Jennifer A; Jacobsen, Jules; Holliday, Gemma L; Fischer, Julia D; Rahman, Syed Asad; Jassal, Bijay; Goujon, Mikael; Rowland, Francis; Velankar, Sameer; López, Rodrigo; Overington, John P; Kleywegt, Gerard J; Hermjakob, Henning; O'Donovan, Claire; Martín, María Jesús; Thornton, Janet M; Steinbeck, Christoph

    2013-01-01

    The availability of comprehensive information about enzymes plays an important role in answering questions relevant to interdisciplinary fields such as biochemistry, enzymology, biofuels, bioengineering and drug discovery. At the EMBL European Bioinformatics Institute, we have developed an enzyme portal (http://www.ebi.ac.uk/enzymeportal) to provide this wealth of information on enzymes from multiple in-house resources addressing particular data classes: protein sequence and structure, reactions, pathways and small molecules. The fact that these data reside in separate databases makes information discovery cumbersome. The main goal of the portal is to simplify this process for end users.

  1. Enzyme molecules as nanomotors.

    Science.gov (United States)

    Sengupta, Samudra; Dey, Krishna K; Muddana, Hari S; Tabouillot, Tristan; Ibele, Michael E; Butler, Peter J; Sen, Ayusman

    2013-01-30

    Using fluorescence correlation spectroscopy, we show that the diffusive movements of catalase enzyme molecules increase in the presence of the substrate, hydrogen peroxide, in a concentration-dependent manner. Employing a microfluidic device to generate a substrate concentration gradient, we show that both catalase and urease enzyme molecules spread toward areas of higher substrate concentration, a form of chemotaxis at the molecular scale. Using glucose oxidase and glucose to generate a hydrogen peroxide gradient, we induce the migration of catalase toward glucose oxidase, thereby showing that chemically interconnected enzymes can be drawn together.

  2. The biosynthesis of N-arachidonoyl dopamine (NADA), a putative endocannabinoid and endovanilloid, via conjugation of arachidonic acid with dopamine.

    Science.gov (United States)

    Hu, Sherry Shu-Jung; Bradshaw, Heather B; Benton, Valery M; Chen, Jay Shih-Chieh; Huang, Susan M; Minassi, Alberto; Bisogno, Tiziana; Masuda, Kim; Tan, Bo; Roskoski, Robert; Cravatt, Benjamin F; Di Marzo, Vincenzo; Walker, J Michael

    2009-10-01

    N-arachidonoyl dopamine (NADA) is an endogenous ligand that activates the cannabinoid type 1 receptor and the transient receptor potential vanilloid type 1 channel. Two potential biosynthetic pathways for NADA have been proposed, though no conclusive evidence exists for either. The first is the direct conjugation of arachidonic acid with dopamine and the other is via metabolism of a putative N-arachidonoyl tyrosine (NA-tyrosine). In the present study we investigated these biosynthetic mechanisms and report that NADA synthesis requires TH in dopaminergic terminals; however, NA-tyrosine, which we identify here as an endogenous lipid, is not an intermediate. We show that NADA biosynthesis primarily occurs through an enzyme-mediated conjugation of arachidonic acid with dopamine. While this conjugation likely involves a complex of enzymes, our data suggest a direct involvement of fatty acid amide hydrolase in NADA biosynthesis either as a rate-limiting enzyme that liberates arachidonic acid from AEA, or as a conjugation enzyme, or both.

  3. Enzymes in Analytical Chemistry.

    Science.gov (United States)

    Fishman, Myer M.

    1980-01-01

    Presents tabular information concerning recent research in the field of enzymes in analytic chemistry, with methods, substrate or reaction catalyzed, assay, comments and references listed. The table refers to 128 references. Also listed are 13 general citations. (CS)

  4. Enzymic lactose hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.J.; Brand, J.C.

    1980-01-01

    Acid or enzymic hydrolysis can be used to hydrolyze lactose. Advantages of both are compared and details of enzymic hydrolysis using yeast or fungal enzymes given. The new scheme outlined involves recycling lactase. Because lactose and lactase react to ultrafiltration (UF) membranes differently separation is possible. Milk or milk products are ultrafiltered to separate a concentrate from a lactose-rich permeate which is treated with lactase in a reactor until hydrolysis reaches a required level. The lactase can be removed by UF as it does not permeate the membrane, and it is recycled back to the reactor. Permeate from the second UF stage may or may not be recombined with the concentrate from the first stage to produce a low lactose product (analysis of a typical low-lactose dried whole milk is given). Batch or continuous processes are explained and a batch process without enzyme recovery is discussed. (Refs. 4).

  5. Membrane Assisted Enzyme Fractionation

    DEFF Research Database (Denmark)

    Yuan, Linfeng

    . In this thesis, separations using crossflow elecro-membrane filtration (EMF) of amino acids, bovine serum albumin (BSA) and industrial enzymes from Novozymes were performed. The main objective of this study was to investigate the technological feasibility of EMF in the application of industrial enzyme...... fractionation, such as removal of a side activity from the main enzyme activity. As a proof-of-concept, amino acids were used as model solution to test the feasibility of EMF in the application of amphoteric molecule separation. A single amino acid was used to illustrate the effect of an electric field...... on the separation performance were very small in the investigated range. The mass transport of each enzyme can be well explained by the Extended-Nernst-Planck equation. Better separation was observed at lower feed concentration, higher solution pH in the investigated range and with a polysulfone (PS) MF membrane...

  6. Indicators: Sediment Enzymes

    Science.gov (United States)

    Sediment enzymes are proteins that are produced by microorganisms living in the sediment or soil. They are indicators of key ecosystem processes and can help determine which nutrients are affecting the biological community of a waterbody.

  7. Starch Biorefinery Enzymes.

    Science.gov (United States)

    Läufer, Albrecht

    2017-03-07

    Nature uses enzymes to build and convert biomass; mankind uses the same enzymes and produces them on a large scale to make optimum use of biomass in biorefineries. Bacterial α-amylases and fungal glucoamylases have been the workhorses of starch biorefineries for many decades. Pullulanases were introduced in the 1980s. Proteases, cellulases, hemicellulases, and phytases have been on the market for a few years as process aids, improving yields, performance, and costs. Detailed studies of the complex chemical structures of biomass and of the physicochemical limitations of industrial biorefineries have led enzyme developers to produce novel tailor-made solutions for improving yield and profitability in the industry. This chapter reviews the development of enzyme applications in the major starch biorefining processes.

  8. Membrane Assisted Enzyme Fractionation

    DEFF Research Database (Denmark)

    Yuan, Linfeng

    . In this thesis, separations using crossflow elecro-membrane filtration (EMF) of amino acids, bovine serum albumin (BSA) and industrial enzymes from Novozymes were performed. The main objective of this study was to investigate the technological feasibility of EMF in the application of industrial enzyme...... fractionation, such as removal of a side activity from the main enzyme activity. As a proof-of-concept, amino acids were used as model solution to test the feasibility of EMF in the application of amphoteric molecule separation. A single amino acid was used to illustrate the effect of an electric field...... on the separation performance were very small in the investigated range. The mass transport of each enzyme can be well explained by the Extended-Nernst-Planck equation. Better separation was observed at lower feed concentration, higher solution pH in the investigated range and with a polysulfone (PS) MF membrane...

  9. RNA-modifying enzymes.

    Science.gov (United States)

    Ferré-D'Amaré, Adrian R

    2003-02-01

    A bewildering number of post-transcriptional modifications are introduced into cellular RNAs by enzymes that are often conserved among archaea, bacteria and eukaryotes. The modifications range from those with well-understood functions, such as tRNA aminoacylation, to widespread but more mysterious ones, such as pseudouridylation. Recent structure determinations have included two types of RNA nucleobase modifying enzyme: pseudouridine synthases and tRNA guanine transglycosylases.

  10. Overproduction of ligninolytic enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Elisashvili, Vladimir; Kachlishvili, Eva; Torok, Tamas

    2014-06-17

    Methods, compositions, and systems for overproducing ligninolytic enzymes from the basidiomycetous fungus are described herein. As described, the method can include incubating a fungal strain of Cerrena unicolor IBB 303 in a fermentation system having growth medium which includes lignocellulosic material and then cultivating the fungal strain in the fermentation system under conditions wherein the fungus expresses the ligninolytic enzymes. In some cases, the lignocellulosic material is mandarin peel, ethanol production residue, walnut pericarp, wheat bran, wheat straw, or banana peel.

  11. Activity-based protein profiling of hydrolytic enzymes induced by gibberellic acid in isolated aleurone layers of malting barley.

    Science.gov (United States)

    Daneri-Castro, Sergio N; Chandrasekar, Balakumaran; Grosse-Holz, Friederike M; van der Hoorn, Renier A L; Roberts, Thomas H

    2016-09-01

    During barley germination, the aleurone layer secretes most of the enzymes required to degrade the endosperm, many of which are yet to be characterized. We used activity-based protein profiling (ABPP) to detect a range of active enzymes extracted from aleurone layers isolated from grains of a commercial malting barley variety incubated with or without gibberellic acid (GA). Enzymes found to be induced by GA were putative aleurains, cathepsin-B-like proteases and serine hydrolases. By using an inhibitory sugar panel, a specific active retaining β-glycosidase in the barley aleurone was identified as a putative xylanase. Our results show that ABPP can be used rapidly to identify a variety of active enzyme isoforms in cereal aleurone without the need for enzyme purification.

  12. Molecular genetics: DNA analysis of a putative dog clone.

    Science.gov (United States)

    Parker, Heidi G; Kruglyak, Leonid; Ostrander, Elaine A

    2006-03-09

    In August 2005, Lee et al. reported the first cloning of a domestic dog from adult somatic cells. This putative dog clone was the result of somatic-cell nuclear transfer from a fibroblast cell of a three-year-old male Afghan hound into a donor oocyte provided by a dog of mixed breed. In light of recent concerns regarding the creation of cloned human cell lines from the same institution, we have undertaken an independent test to determine the validity of the claims made by Lee et al..

  13. Pyrosequencing of the Camptotheca acuminata transcriptome reveals putative genes involved in camptothecin biosynthesis and transport

    Directory of Open Access Journals (Sweden)

    Sun Yongzhen

    2011-10-01

    Full Text Available Abstract Background Camptotheca acuminata is a Nyssaceae plant, often called the "happy tree", which is indigenous in Southern China. C. acuminata produces the terpenoid indole alkaloid, camptothecin (CPT, which exhibits clinical effects in various cancer treatments. Despite its importance, little is known about the transcriptome of C. acuminata and the mechanism of CPT biosynthesis, as only few nucleotide sequences are included in the GenBank database. Results From a constructed cDNA library of young C. acuminata leaves, a total of 30,358 unigenes, with an average length of 403 bp, were obtained after assembly of 74,858 high quality reads using GS De Novo assembler software. Through functional annotation, a total of 21,213 unigenes were annotated at least once against the NCBI nucleotide (Nt, non-redundant protein (Nr, Uniprot/SwissProt, Kyoto Encyclopedia of Genes and Genomes (KEGG, and Arabidopsis thaliana proteome (TAIR databases. Further analysis identified 521 ESTs representing 20 enzyme genes that are involved in the backbone of the CPT biosynthetic pathway in the library. Three putative genes in the upstream pathway, including genes for geraniol-10-hydroxylase (CaPG10H, secologanin synthase (CaPSCS, and strictosidine synthase (CaPSTR were cloned and analyzed. The expression level of the three genes was also detected using qRT-PCR in C. acuminata. With respect to the branch pathway of CPT synthesis, six cytochrome P450s transcripts were selected as candidate transcripts by detection of transcript expression in different tissues using qRT-PCR. In addition, one glucosidase gene was identified that might participate in CPT biosynthesis. For CPT transport, three of 21 transcripts for multidrug resistance protein (MDR transporters were also screened from the dataset by their annotation result and gene expression analysis. Conclusion This study produced a large amount of transcriptome data from C. acuminata by 454 pyrosequencing. According to

  14. PIERO ontology for analysis of biochemical transformations: effective implementation of reaction information in the IUBMB enzyme list.

    Science.gov (United States)

    Kotera, Masaaki; Nishimura, Yosuke; Nakagawa, Zen-ichi; Muto, Ai; Moriya, Yuki; Okamoto, Shinobu; Kawashima, Shuichi; Katayama, Toshiaki; Tokimatsu, Toshiaki; Kanehisa, Minoru; Goto, Susumu

    2014-12-01

    Genomics is faced with the issue of many partially annotated putative enzyme-encoding genes for which activities have not yet been verified, while metabolomics is faced with the issue of many putative enzyme reactions for which full equations have not been verified. Knowledge of enzymes has been collected by IUBMB, and has been made public as the Enzyme List. To date, however, the terminology of the Enzyme List has not been assessed comprehensively by bioinformatics studies. Instead, most of the bioinformatics studies simply use the identifiers of the enzymes, i.e. the Enzyme Commission (EC) numbers. We investigated the actual usage of terminology throughout the Enzyme List, and demonstrated that the partial characteristics of reactions cannot be retrieved by simply using EC numbers. Thus, we developed a novel ontology, named PIERO, for annotating biochemical transformations as follows. First, the terminology describing enzymatic reactions was retrieved from the Enzyme List, and was grouped into those related to overall reactions and biochemical transformations. Consequently, these terms were mapped onto the actual transformations taken from enzymatic reaction equations. This ontology was linked to Gene Ontology (GO) and EC numbers, allowing the extraction of common partial reaction characteristics from given sets of orthologous genes and the elucidation of possible enzymes from the given transformations. Further future development of the PIERO ontology should enhance the Enzyme List to promote the integration of genomics and metabolomics.

  15. Comparative Investigation of Copper Tolerance and Identification of Putative Tolerance Related Genes in Tardigrades

    Science.gov (United States)

    Hygum, Thomas L.; Fobian, Dannie; Kamilari, Maria; Jørgensen, Aslak; Schiøtt, Morten; Grosell, Martin; Møbjerg, Nadja

    2017-01-01

    Tardigrades are microscopic aquatic animals renowned for their tolerance toward extreme environmental conditions. The current study is the first to investigate their tolerance toward heavy metals and we present a novel tardigrade toxicant tolerance assay based on activity assessments as a measure of survival. Specifically, we compare tolerance toward copper in four species representing different evolutionary lineages, habitats and adaptation strategies, i.e., a marine heterotardigrade, Echiniscoides sigismundi, a limno-terrestrial heterotardigrade, Echiniscus testudo, a limno-terrestrial eutardigrade, Ramazzottius oberhaeuseri, and a marine eutardigrade, Halobiotus crispae. The latter was sampled at a time of year, when the population is predominantly represented by aberrant P1 cysts, while the other species were in normal active states prior to exposure. Based on volume measurements and a general relation between body mass and copper tolerance, expected tardigrade EC50 values were estimated at 0.5–2 μg l−1. Following 24 h of exposure, tolerance was high with no apparent link to lineage or habitat. EC50s (95% CI), 24 h after exposure, were estimated at 178 (168–186) and 310 (295–328) μg l−1, respectively, for E. sigismundi and R. oberhaeuseri, whereas E. testudo and H. crispae were less affected. Highest tolerance was observed in H. crispae with a mean ± s.e.m. activity of 77 ± 2% (n = 3) 24 h after removal from ~3 mg l−1 copper, suggesting that tardigrade cysts have increased tolerance toward toxicants. In order to identify putative tolerance related genes, an E. sigismundi transcriptome was searched for key enzymes involved in osmoregulation, antioxidant defense and copper metabolism. We found high expression of Na/K ATPase and carbonic anhydrase, known targets for copper. Our transcriptome, furthermore, revealed high expression of antioxidant enzymes, copper transporters, ATOX1, and a Cu-ATPase. In summary, our results indicate that tardigrades

  16. Putative cryptoendolithic life in Devonian pillow basalt, Rheinisches Schiefergebirge, Germany.

    Science.gov (United States)

    Peckmann, J; Bach, W; Behrens, K; Reitner, J

    2008-03-01

    Middle Devonian (Givetian) pillow basalt and inter-pillow breccia from the Rheinisches Schiefergebirge in Germany were found to contain putative biogenic filaments that indicate that life once proliferated within these volcanic rocks. Mineralized filaments are found in carbonate amygdules (vesicles filled by carbonate cement) in the volcanic rock, where they started to form on the internal surface of the once water-filled vesicles. Biogenicity of the filaments is indicated by (1) their size and shape resembling modern microorganisms including a constant diameter along the length of curved filaments, (2) their independence of crystal faces or cleavage planes, (3) branching patterns reminiscent of modern microorganisms, and (4) their spatial clustering and preferential occurrence close to the margin of pillows and in the inter-pillow breccias. A time lag between the deposition of pillow basalt and the activity of endoliths is revealed by the sequence of carbonate cements filling the amygdules. The putative filamentous microorganisms thrived after the formation of early fibrous rim cement, but before later equant calcite spar filled most of the remaining porosity. Microbial clay authigenesis analogous to the encrustation of prokaryotes in modern iron-rich environments led to the preservation of filaments. The filaments predominantly consist of the clay minerals chamosite and illite. Having dwelled in water-filled vesicles, the Devonian basalt-hosted filaments apparently represent cryptoendoliths. This finding suggests that a previously unrecognized niche for life exists within volcanic rock.

  17. Putative golden proportions as predictors of facial esthetics in adolescents.

    Science.gov (United States)

    Kiekens, Rosemie M A; Kuijpers-Jagtman, Anne Marie; van 't Hof, Martin A; van 't Hof, Bep E; Maltha, Jaap C

    2008-10-01

    In orthodontics, facial esthetics is assumed to be related to golden proportions apparent in the ideal human face. The aim of the study was to analyze the putative relationship between facial esthetics and golden proportions in white adolescents. Seventy-six adult laypeople evaluated sets of photographs of 64 adolescents on a visual analog scale (VAS) from 0 to 100. The facial esthetic value of each subject was calculated as a mean VAS score. Three observers recorded the position of 13 facial landmarks included in 19 putative golden proportions, based on the golden proportions as defined by Ricketts. The proportions and each proportion's deviation from the golden target (1.618) were calculated. This deviation was then related to the VAS scores. Only 4 of the 19 proportions had a significant negative correlation with the VAS scores, indicating that beautiful faces showed less deviation from the golden standard than less beautiful faces. Together, these variables explained only 16% of the variance. Few golden proportions have a significant relationship with facial esthetics in adolescents. The explained variance of these variables is too small to be of clinical importance.

  18. New lipolytic enzymes identified by screening two metagenomic libraries derived from the soil of a winter wheat field

    Directory of Open Access Journals (Sweden)

    Stroobants, A.

    2015-01-01

    Full Text Available Description of the subject. Lipolytic enzymes are widely distributed and fulfil important physiological functions in the microorganisms inhabiting diverse environments. Soils are rich, diversified environments containing microbial communities that remain largely unknown. Objectives. This work aimed to discover new lipolytic enzymes. Method. New enzymes were found by functional screening of two seasonal metagenomic libraries (a winter and a spring library constructed from an agricultural soil. Screens were performed on 2xYT medium supplemented with 3% lipase reagent. Results. Nineteen positive clones were isolated. Analysis of the corresponding inserts led to identifying 23 putative lipolytic enzymes (13 for the winter library and 10 for the spring library displaying between 31% and 62% identity to known enzymes and belonging to seven different families. Conclusions. As enzymes show low identity to known enzymes, the encoded enzymes may display novel biochemical features.

  19. Random-walk enzymes.

    Science.gov (United States)

    Mak, Chi H; Pham, Phuong; Afif, Samir A; Goodman, Myron F

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C→U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  20. Random-walk enzymes

    Science.gov (United States)

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C →U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  1. Random-walk enzymes

    Science.gov (United States)

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-01-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C → U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics. PMID:26465508

  2. Enzyme recycling in lignocellulosic biorefineries

    DEFF Research Database (Denmark)

    Jørgensen, Henning; Pinelo, Manuel

    2017-01-01

    platform. Cellulases are the most important enzymes required in this process, but the complex nature of lignocellulose requires several other enzymes (hemicellulases and auxiliary enzymes) for efficient hydrolysis. Enzyme recycling increases the catalytic productivity of the enzymes by reusing them...... upscaled and tested in industrial settings, mainly because of many difficulties with recycling of enzymes from the complex lignocellulose hydrolyzate at industrially relevant conditions, i.e., high solids loadings. The challenges are associated with the large number of different enzymes required...... for efficient hydrolysis, enzyme stability, and the detrimental interaction between enzyme and lignin. This review provides a comprehensive overview of the various methods for enzyme recovery and recycling, for example recycling of free enzymes, readsorption to fresh material, recycling of solids, membrane...

  3. ANTIBIOTICS RESISTANCE AND PUTATIVE VIRULENCE FACTORS OF AEROMONAS HYDROPHILA ISOLATED FROM ESTUARY

    Directory of Open Access Journals (Sweden)

    Olumide Adedokun Odeyemi

    2012-06-01

    Full Text Available This study aim to investigate antibiotics resistance profile and putative virulence factors of Aeromonas hydrophila isolated from estuary. Bacteria used for this study were isolated from water and sediment samples obtained from Sungai Melayu, Johor, Malaysia. Serially diluted 100 µL water and 1g sediment were inoculated on modified Rimler - Shott (mRS agar. Colonies with distinct cultural characteristics were picked for further studies. Isolates were tested for biofilm productions, protease enzyme and antibiotics resistance profile using agar well diffusion method against 10 commercial antibiotics. Congo Red Agar (CRA, Microplate and Standard Tube (ST methods were used for assessment of biofilm formation among the isolates while Skim Milk Agar was used for protease production. Sw.KMJ 3 and Sw.KMJ 9 produced black crystalline colonies on CRA. Six of the isolates were biofilm producers in ST method. Result of Microplate method, helped in grouping the isolates into weak (n = 8, moderate (n = 3 and strong producers (n = 4 at 540 nm wavelength. All the isolates were classified as weak ODc  ODi 0.1, moderate ODi = 0.1  0.12 and strong producers ODi  0.12 respectively at 540 nm wavelength. Antibiotics susceptibility test also revealed that all the isolates were resistant to between 6 and 10 antibiotics. Two isolates each were resistant to 6 (60 %, 7 (70 % and 9 (90 % antibiotics respectively. Eight of the isolates showed resistance to 8 (80 % antibiotics while only isolate Sw.KMJ-7 showed resistance to all the tested antibiotics. Sw.KMJ-3, Sw.KMJ-8 and Sw.KMJ-9 produced protease enzyme on SMA. The isolates were also found to be resistant to both antibiotics and heavy metals.

  4. Structure determination and biochemical characterization of a putative HNH endonuclease from Geobacter metallireducens GS-15.

    Directory of Open Access Journals (Sweden)

    Shuang-yong Xu

    Full Text Available The crystal structure of a putative HNH endonuclease, Gmet_0936 protein from Geobacter metallireducens GS-15, has been determined at 2.6 Å resolution using single-wavelength anomalous dispersion method. The structure contains a two-stranded anti-parallel β-sheet that are surrounded by two helices on each face, and reveals a Zn ion bound in each monomer, coordinated by residues Cys38, Cys41, Cys73, and Cys76, which likely plays an important structural role in stabilizing the overall conformation. Structural homologs of Gmet_0936 include Hpy99I endonuclease, phage T4 endonuclease VII, and other HNH endonucleases, with these enzymes sharing 15-20% amino acid sequence identity. An overlay of Gmet_0936 and Hpy99I structures shows that most of the secondary structure elements, catalytic residues as well as the zinc binding site (zinc ribbon are conserved. However, Gmet_0936 lacks the N-terminal domain of Hpy99I, which mediates DNA binding as well as dimerization. Purified Gmet_0936 forms dimers in solution and a dimer of the protein is observed in the crystal, but with a different mode of dimerization as compared to Hpy99I. Gmet_0936 and its N77H variant show a weak DNA binding activity in a DNA mobility shift assay and a weak Mn²⁺-dependent nicking activity on supercoiled plasmids in low pH buffers. The preferred substrate appears to be acid and heat-treated DNA with AP sites, suggesting Gmet_0936 may be a DNA repair enzyme.

  5. Isolation and characterization of the glnD gene of Gluconacetobacter diazotrophicus, encoding a putative uridylyltransferase/uridylyl-removing enzyme.

    Science.gov (United States)

    Perlova, Olena; Nawroth, Roman; Zellermann, Eva-Maria; Meletzus, Dietmar

    2002-09-04

    The glnD gene of Gluconacetobacter diazotrophicus was isolated by complementation of the Azotobacter vinelandii glnD (nfrX) mutant strain MV17 using a pLAFR3 cosmid library. The 5 kb chromosomal DNA region encoding the glnD gene on cosmid pAD401 was identified by introduction of deletions as well as subcloning of restriction fragments followed by subsequent DNA sequencing. Three open reading frames were identified with the deduced amino acid sequence of ORF1 showing significant homologies to known GlnD proteins of other proteobacteria such as Sinorhizobium meliloti, Rhizobium tropici, Escherichia coli and Azotobacter vinelandii.A mutagenesis of the chromosomal glnD gene was carried out by insertion of an interposon carrying the kanamycin resistance gene of Tn5. Mutants carrying the cassette inserted into a central region of glnD could not be isolated, while an interposon mutation at the 3' end of glnD was successful. The resulting strain showed a prolonged generation time in complex growth medium and was unable to utilize ammonium as sole nitrogen source. This phenotype appears to be pleiotropic, since the addition of single amino acids to the minimal medium was not sufficient to allow growth. Furthermore, the glnD mutant was able to express nitrogenase under diazotrophic as well as repressing growth conditions.

  6. Angiotensin converting enzyme 2 and atherosclerosis.

    Science.gov (United States)

    Wang, Yutang; Tikellis, Chris; Thomas, Merlin C; Golledge, Jonathan

    2013-01-01

    Angiotensin converting enzyme 2 (ACE2) is a homolog of angiotensin converting enzyme (ACE) which generates angiotensin II from angiotensin I. ACE, its product angiotensin II and the downstream angiotensin type I receptor are important components of the renin-angiotensin system (RAS). Angiotensin II, the most important component of the RAS, promotes the development of atherosclerosis. The identification of ACE2 in 2000 opened a new chapter of research on the regulation of the RAS. ACE2 degrades pro-atherosclerotic angiotensin II and generates anti-atherosclerotic angiotensin 1-7. In this review, we explored the importance of ACE2 in protecting experimental animals from developing atherosclerosis and its involvement in human atherosclerosis. We also examined the published evidence assessing the importance of ACE2 in different cell types relevant to atherosclerosis and putative underlying cellular and molecular mechanisms linking ACE2 with protection from atherosclerosis. ACE2 shifts the balance from angiotensin II to angiotensin 1-7 inhibiting the progression of atherosclerosis in animal models.

  7. Entropy and Enzyme Catalysis.

    Science.gov (United States)

    Åqvist, Johan; Kazemi, Masoud; Isaksen, Geir Villy; Brandsdal, Bjørn Olav

    2017-02-21

    The role played by entropy for the enormous rate enhancement achieved by enzymes has been debated for many decades. There are, for example, several confirmed cases where the activation free energy is reduced by around 10 kcal/mol due to entropic effects, corresponding to a rate enhancement of ∼10(7) compared to the uncatalyzed reaction. However, despite substantial efforts from both the experimental and theoretical side, no real consensus has been reached regarding the origin of such large entropic contributions to enzyme catalysis. Another remarkable instance of entropic effects is found in enzymes that are adapted by evolution to work at low temperatures, near the freezing point of water. These cold-adapted enzymes invariably show a more negative entropy and a lower enthalpy of activation than their mesophilic orthologs, which counteracts the exponential damping of reaction rates at lower temperature. The structural origin of this universal phenomenon has, however, remained elusive. The basic problem with connecting macroscopic thermodynamic quantities, such as activation entropy and enthalpy derived from Arrhenius plots, to the 3D protein structure is that the underlying detailed (microscopic) energetics is essentially inaccessible to experiment. Moreover, attempts to calculate entropy contributions by computer simulations have mostly focused only on substrate entropies, which do not provide the full picture. We have recently devised a new approach for accessing thermodynamic activation parameters of both enzyme and solution reactions from computer simulations, which turns out to be very successful. This method is analogous to the experimental Arrhenius plots and directly evaluates the temperature dependence of calculated reaction free energy profiles. Hence, by extensive molecular dynamics simulations and calculations of up to thousands of independent free energy profiles, we are able to extract activation parameters with sufficient precision for making

  8. Angiotensin-converting enzyme

    DEFF Research Database (Denmark)

    Sørensen, P G; Rømer, F K; Cortes, D

    1984-01-01

    In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical or radiolog......In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical...

  9. Exceptional error minimization in putative primordial genetic codes

    Directory of Open Access Journals (Sweden)

    Koonin Eugene V

    2009-11-01

    Full Text Available Abstract Background The standard genetic code is redundant and has a highly non-random structure. Codons for the same amino acids typically differ only by the nucleotide in the third position, whereas similar amino acids are encoded, mostly, by codon series that differ by a single base substitution in the third or the first position. As a result, the code is highly albeit not optimally robust to errors of translation, a property that has been interpreted either as a product of selection directed at the minimization of errors or as a non-adaptive by-product of evolution of the code driven by other forces. Results We investigated the error-minimization properties of putative primordial codes that consisted of 16 supercodons, with the third base being completely redundant, using a previously derived cost function and the error minimization percentage as the measure of a code's robustness to mistranslation. It is shown that, when the 16-supercodon table is populated with 10 putative primordial amino acids, inferred from the results of abiotic synthesis experiments and other evidence independent of the code's evolution, and with minimal assumptions used to assign the remaining supercodons, the resulting 2-letter codes are nearly optimal in terms of the error minimization level. Conclusion The results of the computational experiments with putative primordial genetic codes that contained only two meaningful letters in all codons and encoded 10 to 16 amino acids indicate that such codes are likely to have been nearly optimal with respect to the minimization of translation errors. This near-optimality could be the outcome of extensive early selection during the co-evolution of the code with the primordial, error-prone translation system, or a result of a unique, accidental event. Under this hypothesis, the subsequent expansion of the code resulted in a decrease of the error minimization level that became sustainable owing to the evolution of a high

  10. Immunodiagnosis of Citrus leprosis virus C using a polyclonal antibody to an expressed putative coat protein.

    Science.gov (United States)

    Choudhary, Nandlal; Roy, Avijit; Guillermo, Leon M; Picton, D D; Wei, G; Nakhla, M K; Levy, L; Brlansky, R H

    2013-11-01

    Citrus leprosis virus C (CiLV-C), a causal agent for citrus leprosis disease, is present in South and Central America and is a threat for introduction into the U.S. citrus industry. A specific, inexpensive and reliable antibody based detection system is needed for the rapid identification of CiLV-C. The CiLV-C is very labile and has not been purified in sufficient amount for antibody production. The p29 gene of CiLV-C genome that codes for the putative coat protein (PCP) was codon optimized for expression in Escherichia coli and synthesized in vitro. The optimized gene was sub-cloned into the bacterial expression vector pDEST17 and transferred into E. coli BL21AI competent cells. The expression of PCP containing N-terminal His-tag was optimized by induction with l-arabinose. Induced cells were disrupted by sonication and expressed PCP was purified by affinity chromatography using Ni-NTA agarose. The purified expressed PCP was then used as an immunogen for injections into rabbits to produce polyclonal antibody (PAb). The PAb specific to the expressed PCP was identified using Western blotting. The antibody was successfully used to detect CiLV-C in the symptomatic CiLV-C infected tissues using double antibody sandwich-enzyme-linked-immunosorbent (DAS-ELISA), indirect ELISA and dot-blot immunoassay (DBIA) formats. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. The Pun1 gene for pungency in pepper encodes a putative acyltransferase.

    Science.gov (United States)

    Stewart, Charles; Kang, Byoung-Cheorl; Liu, Kede; Mazourek, Michael; Moore, Shanna L; Yoo, Eun Young; Kim, Byung-Dong; Paran, Ilan; Jahn, Molly M

    2005-06-01

    Pungency in Capsicum fruits is due to the accumulation of the alkaloid capsaicin and its analogs. The biosynthesis of capsaicin is restricted to the genus Capsicum and results from the acylation of an aromatic moiety, vanillylamine, by a branched-chain fatty acid. Many of the enzymes involved in capsaicin biosynthesis are not well characterized and the regulation of the pathway is not fully understood. Based on the current pathway model, candidate genes were identified in public databases and the literature, and genetically mapped. A published EST co-localized with the Pun1 locus which is required for the presence of capsaicinoids. This gene, AT3, has been isolated and its nucleotide sequence has been determined in an array of genotypes within the genus. AT3 showed significant similarity to acyltransferases in the BAHD superfamily. The recessive allele at this locus contains a deletion spanning the promoter and first exon of the predicted coding region in every non-pungent accession tested. Transcript and protein expression of AT3 was tissue-specific and developmentally regulated. Virus-induced gene silencing of AT3 resulted in a decrease in the accumulation of capsaicinoids, a phenotype consistent with pun1. In conclusion, gene mapping, allele sequence data, expression profile and silencing analysis collectively indicate that the Pun1 locus in pepper encodes a putative acyltransferase, and the pun1 allele, used in pepper breeding for nearly 50 000 years, results from a large deletion at this locus.

  12. Structure and functional annotation of hypothetical proteins having putative Rubisco activase function from Vitis vinifera.

    Science.gov (United States)

    Kumar, Suresh

    2015-01-01

    Rubisco is a very large, complex and one of the most abundant proteins in the world and comprises up to 50% of all soluble protein in plants. The activity of Rubisco, the enzyme that catalyzes CO2 assimilation in photosynthesis, is regulated by Rubisco activase (Rca). In the present study, we searched for hypothetical protein of Vitis vinifera which has putative Rubisco activase function. The Arabidopsis and tobacco Rubisco activase protein sequences were used as seed sequences to search against Vitis vinifera in UniprotKB database. The selected hypothetical proteins of Vitis vinifera were subjected to sequence, structural and functional annotation. Subcellular localization predictions suggested it to be cytoplasmic protein. Homology modelling was used to define the three-dimensional (3D) structure of selected hypothetical proteins of Vitis vinifera. Template search revealed that all the hypothetical proteins share more than 80% sequence identity with structure of green-type Rubisco activase from tobacco, indicating proteins are evolutionary conserved. The homology modelling was generated using SWISS-MODEL. Several quality assessment and validation parameters computed indicated that homology models are reliable. Further, functional annotation through PFAM, CATH, SUPERFAMILY, CDART suggested that selected hypothetical proteins of Vitis vinifera contain ATPase family associated with various cellular activities (AAA) and belong to the AAA+ super family of ring-shaped P-loop containing nucleoside triphosphate hydrolases. This study will lead to research in the optimization of the functionality of Rubisco which has large implication in the improvement of plant productivity and resource use efficiency.

  13. Characterization of the putative tryptophan synthase β-subunit from Mycobacterium tuberculosis

    Institute of Scientific and Technical Information of China (English)

    Hongbo Shen; Yanping Yang; Feifei Wang; Ying Zhang; Naihao Ye; Shengfeng Xu; Honghai Wang

    2009-01-01

    The increasing emergence of drug-resistant tuberculosis (TB)poses a serious threat to the control of this disease.It is in urgent need to develop new TB drugs.Tryptophan biosynthetic pathway plays an important role in the growth and replication of Mycobacterium tuberculosis(Mtb).The β-subunit of tryptophan synthase(TrpB)catalyzes the last step of the tryptophan biosynthetic pathway,and it might be a potential target for TB drug design.In this study,we overexpressed,purified,and characterized the putative TrpB-encoding gene Rv1612 in Mtb H37Rv.Results showed that Mtb His-TrpB optimal enzymatic activity is at pH 7.8 with 0.15 M Na+or 0.18 M Mg2+ at 37℃.Structure analysis indicated that Mtb TrpB exhibited a typical β/α barrel structure.The amino acid residues believed to interact with the enzyme cofactor pyridoxal-5'-phosphate were predicted by homology modeling and structure alignment.The role of these residues in catalytic activity of the Mtb His-TrpB was confirmed by site-directed mutagenesis.These results provided reassuring structural information for drug design based on TrpB.

  14. The putative RNA helicase HELZ promotes cell proliferation, translation initiation and ribosomal protein S6 phosphorylation.

    Directory of Open Access Journals (Sweden)

    Philippe A Hasgall

    Full Text Available The hypoxia-inducible transcription factor (HIF is a key component of the cellular adaptation mechanisms to hypoxic conditions. HIFα subunits are degraded by prolyl-4-hydroxylase domain (PHD enzyme-dependent prolyl-4-hydroxylation of LxxLAP motifs that confer oxygen-dependent proteolytic degradation. Interestingly, only three non-HIFα proteins contain two conserved LxxLAP motifs, including the putative RNA helicase with a zinc finger domain HELZ. However, HELZ proteolytic regulation was found to be oxygen-independent, supporting the notion that a LxxLAP sequence motif alone is not sufficient for oxygen-dependent protein destruction. Since biochemical pathways involving RNA often require RNA helicases to modulate RNA structure and activity, we used luciferase reporter gene constructs and metabolic labeling to demonstrate that HELZ overexpression activates global protein translation whereas RNA-interference mediated HELZ suppression had the opposite effect. Although HELZ interacted with the poly(A-binding protein (PABP via its PAM2 motif, PABP was dispensable for HELZ function in protein translation. Importantly, downregulation of HELZ reduced translational initiation, resulting in the disassembly of polysomes, in a reduction of cell proliferation and hypophosphorylation of ribosomal protein S6.

  15. Basal ganglia calcification as a putative cause for cognitive decline

    Directory of Open Access Journals (Sweden)

    João Ricardo Mendes de Oliveira

    Full Text Available ABSTRACT Basal ganglia calcifications (BGC may be present in various medical conditions, such as infections, metabolic, psychiatric and neurological diseases, associated with different etiologies and clinical outcomes, including parkinsonism, psychosis, mood swings and dementia. A literature review was performed highlighting the main neuropsychological findings of BGC, with particular attention to clinical reports of cognitive decline. Neuroimaging studies combined with neuropsychological analysis show that some patients have shown progressive disturbances of selective attention, declarative memory and verbal perseveration. Therefore, the calcification process might represent a putative cause for dementia syndromes, suggesting a probable link among calcinosis, the aging process and eventually with neuronal death. The increasing number of reports available will foster a necessary discussion about cerebral calcinosis and its role in determining symptomatology in dementia patients

  16. Probing the putative active site of YjdL

    DEFF Research Database (Denmark)

    Jensen, Johanne Mørch; Ismat, Fouzia; Szakonyi, Gerda;

    2012-01-01

    YjdL from E. coli is an unusual proton-coupled oligopeptide transporter (POT). Unlike prototypical POTs, dipeptides are preferred over tripeptides, in particular dipeptides with a positively charged C-terminal residue. To further understand this difference in peptide specificity, the sequences...... of YjdL and YdgR, a prototypical E. coli POT, were compared in light of the crystal structure of a POT from Shewanella oneidensis. Several residues found in the putative active site were mutated and the activities of the mutated variants were assessed in terms of substrate uptake assays, and changes...... pocket that opens towards the extracellular space. The C-terminal side chain faces in the opposite direction into a sub pocket that faces the cytoplasm. These data indicated a stabilizing effect on a bulky N-terminal residue by an Ala281Phe variant and on the dipeptide backbone by Trp278...

  17. Novel putative mechanisms to link circadian clocks to healthy aging.

    Science.gov (United States)

    Popa-Wagner, Aurel; Catalin, Bogdan; Buga, Ana-Maria

    2015-08-01

    The circadian clock coordinates the internal physiology to increase the homeostatic capacity thereby providing both a survival advantage to the system and an optimization of energy budgeting. Multiple-oscillator circadian mechanisms are likely to play a role in regulating human health and may contribute to the aging process. Our aim is to give an overview of how the central clock in the hypothalamus and peripheral clocks relate to aging and metabolic disorders, including hyperlipidemia and hyperglycemia. In particular, we unravel novel putative mechanisms to link circadian clocks to healthy aging. This review may lead to the design of large-scale interventions to help people stay healthy as they age by adjusting daily activities, such as feeding behavior, and or adaptation to age-related changes in individual circadian rhythms.

  18. Ballistic gelatin as a putative substrate for EEG phantom devices

    CERN Document Server

    Hairston, W David; Yu, Alfred B

    2016-01-01

    Phantom devices allow the human variable to be controlled for in order to allow clear comparison and validation of biomedical imaging hardware and software. There is currently no standard phantom for electroencephalography (EEG). To be useful, such a device would need to: (a) accurately recreate the real and imaginary components of scalp electrical impedance, (b) contain internal emitters to create electrical dipoles, and (c) be easily replicable across various labs and research groups. Cost-effective materials, which are conductive, repeatable, and easily formed are a missing key enabler for EEG phantoms. Here, we explore the use of ballistics gelatin, an inexpensive, easily-formable and repeatable material, as a putative substrate by examining its electrical properties and physical stability over time. We show that varied concentrations of NaCl salt relative to gelatin powder shifts the phase/frequency response profile, allowing for selective tuning of the material electrical properties.

  19. Putative benefits of microalgal astaxanthin on exercise and human health

    Directory of Open Access Journals (Sweden)

    Marcelo P. Barros

    2011-04-01

    Full Text Available Astaxanthin (ASTA is a pinkish-orange carotenoid produced by microalgae, but also commonly found in shrimp, lobster and salmon, which accumulate ASTA from the aquatic food chain. Numerous studies have addressed the benefits of ASTA for human health, including the inhibition of LDL oxidation, UV-photoprotection and prophylaxis of bacterial stomach ulcers. ASTA is recognized as a powerful scavenger of reactive oxygen species (ROS, especially those involved in lipid peroxidation. Both aerobic and anaerobic exercise are closely related to overproduction of ROS in muscle tissue. Post-exercise inflammatory processes can even exacerbate the oxidative stress imposed by exercise. Thus, ASTA is suggested here as a putative nutritional alternative/coadjutant for antioxidant therapy to afford additional protection to muscle tissues against oxidative damage induced by exercise, as well as for an (overall integrative redox re-balance and general human health.

  20. Cryptic species in putative ancient asexual darwinulids (Crustacea, Ostracoda.

    Directory of Open Access Journals (Sweden)

    Isa Schön

    Full Text Available BACKGROUND: Fully asexually reproducing taxa lack outcrossing. Hence, the classic Biological Species Concept cannot be applied. METHODOLOGY/PRINCIPAL FINDINGS: We used DNA sequences from the mitochondrial COI gene and the nuclear ITS2 region to check species boundaries according to the evolutionary genetic (EG species concept in five morphospecies in the putative ancient asexual ostracod genera, Penthesilenula and Darwinula, from different continents. We applied two methods for detecting cryptic species, namely the K/θ method and the General Mixed Yule Coalescent model (GMYC. We could confirm the existence of species in all five darwinulid morphospecies and additional cryptic diversity in three morphospecies, namely in Penthesilenula brasiliensis, Darwinula stevensoni and in P. aotearoa. The number of cryptic species within one morphospecies varied between seven (P. brasiliensis, five to six (D. stevensoni and two (P. aotearoa, respectively, depending on the method used. Cryptic species mainly followed continental distributions. We also found evidence for coexistence at the local scale for Brazilian cryptic species of P. brasiliensis and P. aotearoa. Our ITS2 data confirmed that species exist in darwinulids but detected far less EG species, namely two to three cryptic species in P. brasiliensis and no cryptic species at all in the other darwinulid morphospecies. CONCLUSIONS/SIGNIFICANCE: Our results clearly demonstrate that both species and cryptic diversity can be recognized in putative ancient asexual ostracods using the EG species concept, and that COI data are more suitable than ITS2 for this purpose. The discovery of up to eight cryptic species within a single morphospecies will significantly increase estimates of biodiversity in this asexual ostracod group. Which factors, other than long-term geographic isolation, are important for speciation processes in these ancient asexuals remains to be investigated.

  1. Putative regulatory factors associated with intramuscular fat content.

    Directory of Open Access Journals (Sweden)

    Aline S M Cesar

    Full Text Available Intramuscular fat (IMF content is related to insulin resistance, which is an important prediction factor for disorders, such as cardiovascular disease, obesity and type 2 diabetes in human. At the same time, it is an economically important trait, which influences the sensorial and nutritional value of meat. The deposition of IMF is influenced by many factors such as sex, age, nutrition, and genetics. In this study Nellore steers (Bos taurus indicus subspecies were used to better understand the molecular mechanisms involved in IMF content. This was accomplished by identifying differentially expressed genes (DEG, biological pathways and putative regulatory factors. Animals included in this study had extreme genomic estimated breeding value (GEBV for IMF. RNA-seq analysis, gene set enrichment analysis (GSEA and co-expression network methods, such as partial correlation coefficient with information theory (PCIT, regulatory impact factor (RIF and phenotypic impact factor (PIF were utilized to better understand intramuscular adipogenesis. A total of 16,101 genes were analyzed in both groups (high (H and low (L GEBV and 77 DEG (FDR 10% were identified between the two groups. Pathway Studio software identified 13 significantly over-represented pathways, functional classes and small molecule signaling pathways within the DEG list. PCIT analyses identified genes with a difference in the number of gene-gene correlations between H and L group and detected putative regulatory factors involved in IMF content. Candidate genes identified by PCIT include: ANKRD26, HOXC5 and PPAPDC2. RIF and PIF analyses identified several candidate genes: GLI2 and IGF2 (RIF1, MPC1 and UBL5 (RIF2 and a host of small RNAs, including miR-1281 (PIF. These findings contribute to a better understanding of the molecular mechanisms that underlie fat content and energy balance in muscle and provide important information for the production of healthier beef for human consumption.

  2. Crystal structure of a putative exo-β-1,3-galactanase from Bifidobacterium bifidum S17.

    Science.gov (United States)

    Godoy, Andre S; de Lima, Mariana Z T; Camilo, Cesar M; Polikarpov, Igor

    2016-04-01

    Given the current interest in second-generation biofuels, carbohydrate-active enzymes have become the most important tool to overcome the structural recalcitrance of the plant cell wall. While some glycoside hydrolase families have been exhaustively described, others remain poorly characterized, especially with regard to structural information. The family 43 glycoside hydrolases are a diverse group of inverting enzymes; the available structure information on these enzymes is mainly from xylosidases and arabinofuranosidase. Currently, only one structure of an exo-β-1,3-galactanase is available. Here, the production, crystallization and structure determination of a putative exo-β-1,3-galactanase from Bifidobacterium bifidum S17 (BbGal43A) are described. BbGal43A was successfully produced and showed activity towards synthetic galactosides. BbGal43A was subsequently crystallized and data were collected to 1.4 Å resolution. The structure shows a single-domain molecule, differing from known homologues, and crystal contact analysis predicts the formation of a dimer in solution. Further biochemical studies are necessary to elucidate the differences between BbGal43A and its characterized homologues.

  3. The surface science of enzymes

    DEFF Research Database (Denmark)

    Rod, Thomas Holm; Nørskov, Jens Kehlet

    2002-01-01

    One of the largest challenges to science in the coming years is to find the relation between enzyme structure and function. Can we predict which reactions an enzyme catalyzes from knowledge of its structure-or from its amino acid sequence? Can we use that knowledge to modify enzyme function......? To solve these problems we must understand in some detail how enzymes interact with reactants from its surroundings. These interactions take place at the surface of the enzyme and the question of enzyme function can be viewed as the surface science of enzymes. In this article we discuss how to describe...... catalysis by enzymes, and in particular the analogies between enzyme catalyzed reactions and surface catalyzed reactions. We do this by discussing two concrete examples of reactions catalyzed both in nature (by enzymes) and in industrial reactors (by inorganic materials), and show that although analogies...

  4. Amperometric Enzyme Electrodes

    Science.gov (United States)

    1989-12-01

    form of carbon (glascy carbon, graphite, reticulated vitreous carbon, carbon paste, fiber or foil). Carbon is favored for enzyme immoblization...interference from spurious electroactive species in blood, t proprietary multilayer membranie that includes a cellulose acetate memirane and a Nucleopore

  5. ISFET based enzyme sensors

    NARCIS (Netherlands)

    van der Schoot, Bart H.; Bergveld, Piet

    1987-01-01

    This paper reviews the results that have been reported on ISFET based enzyme sensors. The most important improvement that results from the application of ISFETs instead of glass membrane electrodes is in the method of fabrication. Problems with regard to the pH dependence of the response and the

  6. Computational enzyme design

    Science.gov (United States)

    Bolon, Daniel N.

    2002-08-01

    The long-term objective of computational enzyme design is the ability to generate efficient protein catalysts for any chemical reaction. This thesis develops and experimentally validates a general computational approach for the design of enzymes with novel function. In order to include catalytic mechanism in protein design, a high-energy state (HES) rotamer (side chain representation) was constructed. In this rotamer, substrate atoms are in a HES. In addition, at least one amino acid side chain is positioned to interact favorably with substrate atoms in their HES and facilitate the reaction. Including an amino acid side chain in the HES rotamer automatically positions substrate relative to a protein scaffold and allows protein design algorithms to search for sequences capable of interacting favorably with the substrate. Because chemical similarity exists between the transition state and the high-energy state, optimizing the protein sequence to interact favorably with the HES rotamer should lead to transition state stabilization. In addition, the HES rotamer model focuses the subsequent computational active site design on a relevant phase space where an amino acid is capable of interacting in a catalytically active geometry with substrate. Using a HES rotamer model of the histidine mediated nucleophilic hydrolysis of p-nitrophenyl acetate, the catalytically inert 108 residue E. coli thioredoxin as a scaffold, and the ORBIT protein design software to compute sequences, an active site scan identified two promising active site designs. Experimentally, both candidate ?protozymes? demonstrated catalytic activity significantly above background. In addition, the rate enhancement of one of these ?protozymes? was the same order of magnitude as the first catalytic antibodies. Because polar groups are frequently buried at enzyme-substrate interfaces, improved modeling of buried polar interactions may benefit enzyme design. By studying native protein structures, rules have been

  7. Experimental Evidence for a Revision in the Annotation of Putative Pyridoxamine 5'-Phosphate Oxidases P(N/MP from Fungi.

    Directory of Open Access Journals (Sweden)

    Tatiana Domitrovic

    Full Text Available Pyridoxinamine 5'-phosphate oxidases (P(N/MP oxidases that bind flavin mononucleotide (FMN and oxidize pyridoxine 5'-phosphate or pyridoxamine 5'-phosphate to form pyridoxal 5'-phosphate (PLP are an important class of enzymes that play a central role in cell metabolism. Failure to generate an adequate supply of PLP is very detrimental to most organisms and is often clinically manifested as a neurological disorder in mammals. In this study, we analyzed the function of YLR456W and YPR172W, two homologous genes of unknown function from S. cerevisiae that have been annotated as putative P(N/MP oxidases based on sequence homology. Different experimental approaches indicated that neither protein catalyzes PLP formation nor binds FMN. On the other hand, our analysis confirmed the enzymatic activity of Pdx3, the S. cerevisiae protein previously implicated in PLP biosynthesis by genetic and structural characterization. After a careful sequence analysis comparing the putative and confirmed P(N/MP oxidases, we found that the protein domain (PF01243 that led to the YLR456W and YPR172W annotation is a poor indicator of P(N/MP oxidase activity. We suggest that a combination of two Pfam domains (PF01243 and PF10590 present in Pdx3 and other confirmed P(N/MP oxidases would be a stronger predictor of this molecular function. This work exemplifies the importance of experimental validation to rectify genome annotation and proposes a revision in the annotation of at least 400 sequences from a wide variety of fungal species that are homologous to YLR456W and are currently misrepresented as putative P(N/MP oxidases.

  8. Screening for Genes Coding for Putative Antitumor Compounds, Antimicrobial and Enzymatic Activities from Haloalkalitolerant and Haloalkaliphilic Bacteria Strains of Algerian Sahara Soils

    Directory of Open Access Journals (Sweden)

    Okba Selama

    2014-01-01

    Full Text Available Extreme environments may often contain unusual bacterial groups whose physiology is distinct from those of normal environments. To satisfy the need for new bioactive pharmaceuticals compounds and enzymes, we report here the isolation of novel bacteria from an extreme environment. Thirteen selected haloalkalitolerant and haloalkaliphilic bacteria were isolated from Algerian Sahara Desert soils. These isolates were screened for the presence of genes coding for putative antitumor compounds using PCR based methods. Enzymatic, antibacterial, and antifungal activities were determined by using cultural dependant methods. Several of these isolates are typical of desert and alkaline saline soils, but, in addition, we report for the first time the presence of a potential new member of the genus Nocardia with particular activity against the yeast Saccharomyces cerevisiae. In addition to their haloalkali character, the presence of genes coding for putative antitumor compounds, combined with the antimicrobial activity against a broad range of indicator strains and their enzymatic potential, makes them suitable for biotechnology applications.

  9. Screening for genes coding for putative antitumor compounds, antimicrobial and enzymatic activities from haloalkalitolerant and haloalkaliphilic bacteria strains of Algerian Sahara Soils.

    Science.gov (United States)

    Selama, Okba; Amos, Gregory C A; Djenane, Zahia; Borsetto, Chiara; Laidi, Rabah Forar; Porter, David; Nateche, Farida; Wellington, Elizabeth M H; Hacène, Hocine

    2014-01-01

    Extreme environments may often contain unusual bacterial groups whose physiology is distinct from those of normal environments. To satisfy the need for new bioactive pharmaceuticals compounds and enzymes, we report here the isolation of novel bacteria from an extreme environment. Thirteen selected haloalkalitolerant and haloalkaliphilic bacteria were isolated from Algerian Sahara Desert soils. These isolates were screened for the presence of genes coding for putative antitumor compounds using PCR based methods. Enzymatic, antibacterial, and antifungal activities were determined by using cultural dependant methods. Several of these isolates are typical of desert and alkaline saline soils, but, in addition, we report for the first time the presence of a potential new member of the genus Nocardia with particular activity against the yeast Saccharomyces cerevisiae. In addition to their haloalkali character, the presence of genes coding for putative antitumor compounds, combined with the antimicrobial activity against a broad range of indicator strains and their enzymatic potential, makes them suitable for biotechnology applications.

  10. The Moderately Efficient Enzyme: Futile Encounters and Enzyme Floppiness.

    Science.gov (United States)

    Bar-Even, Arren; Milo, Ron; Noor, Elad; Tawfik, Dan S

    2015-08-18

    The pioneering model of Henri, Michaelis, and Menten was based on the fast equilibrium assumption: the substrate binds its enzyme reversibly, and substrate dissociation is much faster than product formation. Here, we examine this assumption from a somewhat different point of view, asking what fraction of enzyme-substrate complexes are futile, i.e., result in dissociation rather than product formation. In Knowles' notion of a "perfect" enzyme, all encounters of the enzyme with its substrate result in conversion to product. Thus, the perfect enzyme's catalytic efficiency, kcat/KM, is constrained by only the diffusion on-rate, and the fraction of futile encounters (defined as φ) approaches zero. The available data on >1000 different enzymes suggest that for ≥90% of enzymes φ > 0.99 and for the "average enzyme" φ ≥ 0.9999; namely, <1 of 10(4) encounters is productive. Thus, the "fast equilibrium" assumption holds for the vast majority of enzymes. We discuss possible molecular origins for the dominance of futile encounters, including the coexistence of multiple sub-states of an enzyme's active site (enzyme floppiness) and/or its substrate. Floppiness relates to the inherent flexibility of proteins, but also to conflicting demands, or trade-offs, between rate acceleration (the rate-determining chemical step) and catalytic turnover, or between turnover rate and accuracy. The study of futile encounters and active-site floppiness may contribute to a better understanding of enzyme catalysis, enzyme evolution, and improved enzyme design.

  11. Sequence analysis and gene expression of putative exo- and endo-glucanases from oil palm (Elaeis guineensis) during fungal infection.

    Science.gov (United States)

    Yeoh, Keat-Ai; Othman, Abrizah; Meon, Sariah; Abdullah, Faridah; Ho, Chai-Ling

    2012-10-15

    Glucanases are enzymes that hydrolyze a variety β-d-glucosidic linkages. Plant β-1,3-glucanases are able to degrade fungal cell walls; and promote the release of cell-wall derived fungal elicitors. In this study, three full-length cDNA sequences encoding oil palm (Elaeis guineensis) glucanases were analyzed. Sequence analyses of the cDNA sequences suggested that EgGlc1-1 is a putative β-d-glucan exohydolase belonging to glycosyl hydrolase (GH) family 3 while EgGlc5-1 and EgGlc5-2 are putative glucan endo-1,3-β-glucosidases belonging to GH family 17. The transcript abundance of these genes in the roots and leaves of oil palm seedlings treated with Ganoderma boninense and Trichoderma harzianum was profiled to investigate the involvement of these glucanases in oil palm during fungal infection. The gene expression of EgGlc1-1 in the root of oil palm seedlings was increased by T. harzianum but suppressed by G. boninense; while the gene expression of both EgGlc5-1 and EgGlc5-2 in the roots of oil palm seedlings was suppressed by G. boninense or/and T. harzianum. Copyright © 2012 Elsevier GmbH. All rights reserved.

  12. A new versatile microarray-based method for high-throughput screening of carbohydrate-active enzymes

    DEFF Research Database (Denmark)

    Vidal Melgosa, Silvia; Pedersen, Henriette Lodberg; Schückel, Julia;

    2015-01-01

    Carbohydrate-active enzymes have multiple biological roles and industrial applications. Advances in genome and transcriptome sequencing, together with associated bioinformatic tools have identified vast numbers of putative carbohydrate degrading and modifying enzymes including glycoside hydrolases...... and lytic polysaccharide monooxygenases. However, there is a paucity of methods for rapidly screening the activities of these enzymes. By combining the multiplexing capacity of carbohydrate microarrays with the specificity of molecular probes, we have developed a sensitive, high-throughput and versatile...... semi-quantitative enzyme-screening technique which requires low amounts of enzyme and substrate. The method can be used to assess the activities of single enzymes, enzyme cocktails and crude culture broths against single substrates, substrate mixtures and biomass samples. Moreover, we show...

  13. Engineered protein nano-compartments for targeted enzyme localization.

    Directory of Open Access Journals (Sweden)

    Swati Choudhary

    Full Text Available Compartmentalized co-localization of enzymes and their substrates represents an attractive approach for multi-enzymatic synthesis in engineered cells and biocatalysis. Sequestration of enzymes and substrates would greatly increase reaction efficiency while also protecting engineered host cells from potentially toxic reaction intermediates. Several bacteria form protein-based polyhedral microcompartments which sequester functionally related enzymes and regulate their access to substrates and other small metabolites. Such bacterial microcompartments may be engineered into protein-based nano-bioreactors, provided that they can be assembled in a non-native host cell, and that heterologous enzymes and substrates can be targeted into the engineered compartments. Here, we report that recombinant expression of Salmonella enterica ethanolamine utilization (eut bacterial microcompartment shell proteins in E. coli results in the formation of polyhedral protein shells. Purified recombinant shells are morphologically similar to the native Eut microcompartments purified from S. enterica. Surprisingly, recombinant expression of only one of the shell proteins (EutS is sufficient and necessary for creating properly delimited compartments. Co-expression with EutS also facilitates the encapsulation of EGFP fused with a putative Eut shell-targeting signal sequence. We also demonstrate the functional localization of a heterologous enzyme (β-galactosidase targeted to the recombinant shells. Together our results provide proof-of-concept for the engineering of protein nano-compartments for biosynthesis and biocatalysis.

  14. Carbohydrate-related enzymes of important Phytophthora plant pathogens.

    Science.gov (United States)

    Brouwer, Henk; Coutinho, Pedro M; Henrissat, Bernard; de Vries, Ronald P

    2014-11-01

    Carbohydrate-Active enZymes (CAZymes) form particularly interesting targets to study in plant pathogens. Despite the fact that many CAZymes are pathogenicity factors, oomycete CAZymes have received significantly less attention than effectors in the literature. Here we present an analysis of the CAZymes present in the Phytophthora infestans, Ph. ramorum, Ph. sojae and Pythium ultimum genomes compared to growth of these species on a range of different carbon sources. Growth on these carbon sources indicates that the size of enzyme families involved in degradation of cell-wall related substrates like cellulose, xylan and pectin is not always a good predictor of growth on these substrates. While a capacity to degrade xylan and cellulose exists the products are not fully saccharified and used as a carbon source. The Phytophthora genomes encode larger CAZyme sets when compared to Py. ultimum, and encode putative cutinases, GH12 xyloglucanases and GH10 xylanases that are missing in the Py. ultimum genome. Phytophthora spp. also encode a larger number of enzyme families and genes involved in pectin degradation. No loss or gain of complete enzyme families was found between the Phytophthora genomes, but there are some marked differences in the size of some enzyme families.

  15. Isolation and characterization of a new chemokine receptor gene, the putative chicken CXCR1.

    Science.gov (United States)

    Li, Q J; Lu, S; Ye, R D; Martins-Green, M

    2000-10-31

    This study delineates the isolation and characterization of a novel chemokine receptor gene, the putative chicken CXC receptor 1 (cCXCR1). Using a human CXCR1 probe, we isolated several positive clones from a chicken genomic library. One of the clones contained a fragment of approximately 5000bp that hybridized strongly with the hCXCR1 probe. This fragment was sequenced and subjected to a variety of computer analyses. The open reading frame for this gene predicts a seven transmembrane domain protein with all the characteristics of a chemokine receptor and with 67% sequence homology to hCXCR1, 65% to hCXCR2 and also with considerable sequence homology to other human chemokine receptors such as hCXCR4 (50%), hCCR2 (49%) and hCCR1 (49%). However, the homology to a previously isolated potential G-protein-coupled receptor for chickens (AvCRL1) is only 47%. Using 5' RACE, two transcription initiation sites were identified suggesting the potential for the expression of two protein isoforms (I and II) in vivo. The promoter for the putative cCXCR1 contains a variety of consensus transcription factor binding elements that can potentially be involved in the expression of this chicken receptor upon stimulation by stress-inducing agents. RT-PCR analysis was used to determine the pattern of expression of the larger isoform (I) of this receptor in a variety of tissues. This form of the receptor is expressed primarily in the organs of the gastrointestinal tract, tissues that are frequently exposed to stress-inducing agents, but not in the central nervous system, tissues that are protected from insult by the blood barrier. Using the same RT-PCR approach we show that stress-inducing agents, such as 'first-hand' and 'second-hand' cigarette smoke components, tumor promoters and thrombin, differentially stimulate the expression of the isoform I in primary fibroblasts. Thrombin is an enzyme that plays many important roles in thrombosis, angiogenesis and wound healing and exposure to

  16. Molecular cloning of a novel glucuronokinase/putative pyrophosphorylase from zebrafish acting in an UDP-glucuronic acid salvage pathway.

    Directory of Open Access Journals (Sweden)

    Roman Gangl

    Full Text Available In animals, the main precursor for glycosaminoglycan and furthermore proteoglycan biosynthesis, like hyaluronic acid, is UDP-glucuronic acid, which is synthesized via the nucleotide sugar oxidation pathway. Mutations in this pathway cause severe developmental defects (deficiency in the initiation of heart valve formation. In plants, UDP-glucuronic acid is synthesized via two independent pathways. Beside the nucleotide sugar oxidation pathway, a second minor route to UDP-glucuronic acid exist termed the myo-inositol oxygenation pathway. Within this myo-inositol is ring cleaved into glucuronic acid, which is subsequently converted to UDP-glucuronic acid by glucuronokinase and UDP-sugar pyrophosphorylase. Here we report on a similar, but bifunctional enzyme from zebrafish (Danio rerio which has glucuronokinase/putative pyrophosphorylase activity. The enzyme can convert glucuronic acid into UDP-glucuronic acid, required for completion of the alternative pathway to UDP-glucuronic acid via myo-inositol and thus establishes a so far unknown second route to UDP-glucuronic acid in animals. Glucuronokinase from zebrafish is a member of the GHMP-kinase superfamily having unique substrate specificity for glucuronic acid with a Km of 31 ± 8 µM and accepting ATP as the only phosphate donor (Km: 59 ± 9 µM. UDP-glucuronic acid pyrophosphorylase from zebrafish has homology to bacterial nucleotidyltransferases and requires UTP as nucleosid diphosphate donor. Genes for bifunctional glucuronokinase and putative UDP-glucuronic acid pyrophosphorylase are conserved among some groups of lower animals, including fishes, frogs, tunicates, and polychaeta, but are absent from mammals. The existence of a second pathway for UDP-glucuronic acid biosynthesis in zebrafish likely explains some previous contradictory finding in jekyll/ugdh zebrafish developmental mutants, which showed residual glycosaminoglycans and proteoglycans in knockout mutants of UDP

  17. Characterization of five putative aspartate aminotransferase genes in the N2-fixing heterocystous cyanobacterium Anabaena sp. strain PCC 7120.

    Science.gov (United States)

    Xu, Xinyi; Gu, Liping; He, Ping; Zhou, Ruanbao

    2015-06-01

    Aspartate and glutamate are two key amino acids used in biosynthesis of many amino acids that play vital role in cellular metabolism. Aspartate aminotransferases (AspATs) are required for channelling nitrogen (N(2)) between Glu and Asp in all life forms. Biochemical and genetic characterization of AspATs have been lacking in N(2)-fixing cyanobacteria. In this report, five putative AspAT genes (alr1039, all2340, alr2765, all4327 and alr4853) were identified in the N(2)-fixing heterocystous cyanobacterium Anabaena sp. PCC 7120. Five recombinant C-terminal hexahistidine-tagged AspATs (AspAT-H(6)) were overexpressed in Escherichia coli and purified to homogeneity. Biochemical analysis demonstrated that these five putative AspATs have authentic AspAT activity in vitro using aspartate as an amino donor. However, the enzymic activities of the five AspATs differed in vitro. Alr4853-H(6) showed the highest AspAT activity, while the enzymic activity for the other four AspATs ranged from 6.5 to 53.7 % activity compared to Alr4853 (100 %). Genetic characterization of the five AspAT genes was also performed by inactivating each individual gene. All of the five AspAT knockout mutants exhibited reduced diazotrophic growth, and alr4853 was further identified to be a Fox gene (requiring fixed N(2) for growth in the presence of oxygen). Four out of five P(aspAT)-gfp transcriptional fusions were constitutively expressed in both diazotrophic and nitrate-dependent growth conditions. Quantitative reverse transcriptase PCR showed that alr4853 expression was increased by 2.3-fold after 24 h of N(2) deprivation. Taken together, these findings add to our understanding of the role of AspATs in N(2)-fixing within heterocystous cyanobacteria.

  18. Halophilic adaptation of enzymes.

    Science.gov (United States)

    Madern, D; Ebel, C; Zaccai, G

    2000-04-01

    It is now clear that the understanding of halophilic adaptation at a molecular level requires a strategy of complementary experiments, combining molecular biology, biochemistry, and cellular approaches with physical chemistry and thermodynamics. In this review, after a discussion of the definition and composition of halophilic enzymes, the effects of salt on their activity, solubility, and stability are reviewed. We then describe how thermodynamic observations, such as parameters pertaining to solvent-protein interactions or enzyme-unfolding kinetics, depend strongly on solvent composition and reveal the important role played by water and ion binding to halophilic proteins. The three high-resolution crystal structures now available for halophilic proteins are analyzed in terms of haloadaptation, and finally cellular response to salt stress is discussed briefly.

  19. Immobilized enzymes in organic synthesis.

    Science.gov (United States)

    Mosbach, K

    1985-01-01

    The immobilization of enzymes and cells by different methods and the possible stabilization of immobilized preparations are discussed. An outlook on 'second generation enzyme technology', which involves immobilized multi-enzyme systems and coenzymes, is given with examples: the immobilization of dehydrogenases with their active sites facing one another, and systems containing NAD(H) coenzymes immobilized by coupling to dextran (in an enzyme electrode), to polyethylene glycol (in a membrane reactor), or to enzymes themselves. The use of immobilized enzymes to synthesize peptides and disaccharides is described.

  20. Putative uremic encephalopathy in horses: five cases (1978-1998).

    Science.gov (United States)

    Frye, M A; Johnson, J S; Traub-Dargatz, J L; Savage, C J; Fettman, M J; Gould, D H

    2001-02-15

    To determine historical, physical examination, clinicopathologic, and postmortem findings in horses with putative uremic encephalopathy. Design-Retrospective study. Animals-5 horses with renal failure and neurologic disease not attributable to abnormalities in any other organ system. Medical records from 1978 to 1998 were examined for horses with renal disease and neurologic signs not attributable to primary neurologic, hepatic, or other diseases. Signalment, history, physical examination findings, clinicopathologic data, renal ultrasonographic findings, and postmortem data were reviewed. Of 332 horses with renal disease, 5 met selection criteria. Historical findings, physical examination findings, clinicopathologic data, ultrasonographic data, and postmortem findings were consistent with chronic renal failure. Swollen astrocytes were detected in all 4 horses examined at necropsy. A single criterion was not determined to be pathognomonic for uremic encephalopathy in horses. Uremic encephalopathy should be considered as a differential diagnosis in horses with evidence of chronic renal failure and encephalopathic neurologic sign not attributable to other causes. Astrocyte swelling, which was common to all 4 horses examined at necropsy, may serve as a microscopic indicator of uremic encephalopathy in horses.

  1. Phytophthora infestans specific phosphorylation patterns and new putative control targets.

    Science.gov (United States)

    Frades, Itziar; Andreasson, Erik

    2016-04-01

    In this study we applied biomathematical searches of gene regulatory mechanisms to learn more about oomycete biology and to identify new putative targets for pesticides or biological control against Phytophthora infestans. First, oomycete phylum-specific phosphorylation motifs were found by discriminative n-gram analysis. We found 11.600 P. infestans specific n-grams, mapping 642 phosphoproteins. The most abundant group among these related to phosphatidylinositol metabolism. Due to the large number of possible targets found and our hypothesis that multi-level control is a sign of usefulness as targets for intervention, we identified overlapping targets with a second screen. This was performed to identify proteins dually regulated by small RNA and phosphorylation. We found 164 proteins to be regulated by both sRNA and phosphorylation and the dominating functions where phosphatidylinositol signalling/metabolism, endocytosis, and autophagy. Furthermore we performed a similar regulatory study and discriminative n-gram analysis of proteins with no clear orthologs in other species and proteins that are known to be unique to P. infestans such as the RxLR effectors, Crinkler (CRN) proteins and elicitins. We identified CRN proteins with specific phospho-motifs present in all life stages. PITG_12626, PITG_14042 and PITG_23175 are CRN proteins that have species-specific phosphorylation motifs and are subject to dual regulation.

  2. Rapid Discrimination Among Putative Mechanistic Models of Biochemical Systems.

    Science.gov (United States)

    Lomnitz, Jason G; Savageau, Michael A

    2016-08-31

    An overarching goal in molecular biology is to gain an understanding of the mechanistic basis underlying biochemical systems. Success is critical if we are to predict effectively the outcome of drug treatments and the development of abnormal phenotypes. However, data from most experimental studies is typically noisy and sparse. This allows multiple potential mechanisms to account for experimental observations, and often devising experiments to test each is not feasible. Here, we introduce a novel strategy that discriminates among putative models based on their repertoire of qualitatively distinct phenotypes, without relying on knowledge of specific values for rate constants and binding constants. As an illustration, we apply this strategy to two synthetic gene circuits exhibiting anomalous behaviors. Our results show that the conventional models, based on their well-characterized components, cannot account for the experimental observations. We examine a total of 40 alternative hypotheses and show that only 5 have the potential to reproduce the experimental data, and one can do so with biologically relevant parameter values.

  3. Putative role of Tat-Env interaction in HIV infection.

    Science.gov (United States)

    Poon, Selina; Moscoso, Carlos G; Xing, Li; Kan, Elaine; Sun, Yide; Kolatkar, Prasanna R; Vahlne, Anders G; Srivastava, Indresh K; Barnett, Susan W; Cheng, R Holland

    2013-09-24

    To study the complex formed between Tat protein and Env soluble trimeric immunogen, and compare with previously determined structures of Env native trimers and Env-CD4m complexes. The soluble Env trimer was used to mimic the spike glycoprotein on the virus surface for the study. To overcome limitations of other structural determination methods, cryoelectron microscopy was employed to image the complex, and single particle reconstruction was utilized to reconstruct the structure of the complex from collected micrographs. Molecular modeling of gp120-Tat was performed to provide atomic coordinates for docking. Images were preprocessed by multivariate statistical analysis to identify principal components of variation then submitted for reconstruction. Reconstructed structures were docked with modeled gp120-Tat atomic coordinates to study the positions of crucial epitopes. Analysis of the Env-Tat complex demonstrated an intermediate structure between Env native trimers and Env-CD4m structures. Docking results indicate that the CD4-binding site and the V3 loop are exposed in the Env-Tat complex. The integrin-binding sequence in Tat was also exposed in Env-Tat docking. The intermediate structure induced by Tat-interaction with Env could potentially provide an explanation for increased virus infection in the presence of Tat protein. Consequently, exposure of CD4-binding sites and a putative integrin-binding sequence on Tat in the complex may provide a new avenue for rational design of an effective HIV vaccine. © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

  4. Small intestinal mucosa expression of putative chaperone fls485

    Directory of Open Access Journals (Sweden)

    Raupach Kerstin

    2010-03-01

    Full Text Available Abstract Background Maturation of enterocytes along the small intestinal crypt-villus axis is associated with significant changes in gene expression profiles. fls485 coding a putative chaperone protein has been recently suggested as a gene involved in this process. The aim of the present study was to analyze fls485 expression in human small intestinal mucosa. Methods fls485 expression in purified normal or intestinal mucosa affected with celiac disease was investigated with a molecular approach including qRT-PCR, Western blotting, and expression strategies. Molecular data were corroborated with several in situ techniques and usage of newly synthesized mouse monoclonal antibodies. Results fls485 mRNA expression was preferentially found in enterocytes and chromaffine cells of human intestinal mucosa as well as in several cell lines including Rko, Lovo, and CaCo2 cells. Western blot analysis with our new anti-fls485 antibodies revealed at least two fls485 proteins. In a functional CaCo2 model, an increase in fls485 expression was paralleled by cellular maturation stage. Immunohistochemistry demonstrated fls485 as a cytosolic protein with a slightly increasing expression gradient along the crypt-villus axis which was impaired in celiac disease Marsh IIIa-c. Conclusions Expression and synthesis of fls485 are found in surface lining epithelia of normal human intestinal mucosa and deriving epithelial cell lines. An interdependence of enterocyte differentiation along the crypt-villus axis and fls485 chaperone activity might be possible.

  5. Small intestinal mucosa expression of putative chaperone fls485.

    Science.gov (United States)

    Reinartz, Andrea; Ehling, Josef; Franz, Susanne; Simon, Verena; Bravo, Ignacio G; Tessmer, Claudia; Zentgraf, Hanswalter; Lyer, Stefan; Schneider, Ursula; Köster, Jan; Raupach, Kerstin; Kämmerer, Elke; Klaus, Christina; Tischendorf, Jens J W; Kopitz, Jürgen; Alonso, Angel; Gassler, Nikolaus

    2010-03-07

    Maturation of enterocytes along the small intestinal crypt-villus axis is associated with significant changes in gene expression profiles. fls485 coding a putative chaperone protein has been recently suggested as a gene involved in this process. The aim of the present study was to analyze fls485 expression in human small intestinal mucosa. fls485 expression in purified normal or intestinal mucosa affected with celiac disease was investigated with a molecular approach including qRT-PCR, Western blotting, and expression strategies. Molecular data were corroborated with several in situ techniques and usage of newly synthesized mouse monoclonal antibodies. fls485 mRNA expression was preferentially found in enterocytes and chromaffine cells of human intestinal mucosa as well as in several cell lines including Rko, Lovo, and CaCo2 cells. Western blot analysis with our new anti-fls485 antibodies revealed at least two fls485 proteins. In a functional CaCo2 model, an increase in fls485 expression was paralleled by cellular maturation stage. Immunohistochemistry demonstrated fls485 as a cytosolic protein with a slightly increasing expression gradient along the crypt-villus axis which was impaired in celiac disease Marsh IIIa-c. Expression and synthesis of fls485 are found in surface lining epithelia of normal human intestinal mucosa and deriving epithelial cell lines. An interdependence of enterocyte differentiation along the crypt-villus axis and fls485 chaperone activity might be possible.

  6. Putative impact of RNA editing on drug discovery.

    Science.gov (United States)

    Decher, Niels; Netter, Michael F; Streit, Anne K

    2013-01-01

    Virtually all organisms use RNA editing as a powerful post-transcriptional mechanism to recode genomic information and to increase functional protein diversity. The enzymatic editing of pre-mRNA by ADARs and CDARs is known to change the functional properties of neuronal receptors and ion channels regulating cellular excitability. However, RNA editing is also an important mechanism for genes expressed outside the brain. The fact that RNA editing breaks the 'one gene encodes one protein' hypothesis is daunting for scientists and a probable drawback for drug development, as scientists might search for drugs targeting the 'wrong' protein. This possible difficulty for drug discovery and development became more evident from recent publications, describing that RNA editing events have profound impact on the pharmacology of some common drug targets. These recent studies highlight that RNA editing can cause massive discrepancies between the in vitro and in vivo pharmacology. Here, we review the putative impact of RNA editing on drug discovery, as RNA editing has to be considered before using high-throughput screens, rational drug design or choosing the right model organism for target validation.

  7. Epigenetic regulation of putative tumor suppressor TGFBI in human leukemias

    Institute of Scientific and Technical Information of China (English)

    Fang Hongbo; Liu Jing; Guo Dan; Liu Peixiang; Zhao Yongliang

    2014-01-01

    Background Both in vitro and in vivo data have demonstrated the TGFBI gene functions as a putative tumor suppressor and is frequently downregulated in human tumors of different histological types.The hypermethylation of the TGFBI promoter,as one of the main regulatory mechanisms,is associated with TGFBI silencing.In this study,we used a methylation-specific PCR (MSP) method to evaluate the methylation status of the TGFBI promoter in human leukemias.Methods Real-time RT-PCR and methylation-specific PCR approaches were performed to define the TGFBI expression and promoter methylation in human leukemia call lines and clinical samples.Genomic DNA was isolated from peripheral blood mononuclear cells from leukemia patients,bisulfite-converted,and analyzed by the MSP method.Results Hypermethylation of the TGFBI promoter occurred in leukemia cell lines and demethylation treatment reexpressed TGFBI at a substantially increased level in most of leukemia cell lines tested.Furthermore,a much higher level of CpG island methylation and a significantly lower TGFBI expression were also identified in clinical leukemia samples.Conclusion The results suggest an important role of promoter methylation in regulating TGFBI expression in leukemia,which provides a useful diagnostic marker for clinical management of human leukemias.

  8. Expression and characterization of rice putative PAUSED gene

    Institute of Scientific and Technical Information of China (English)

    Chengguo Yao; Liangfa Ge; Wei Li; Botao Zhao; Chaoqun Li; Kangcheng Ruan; Hongxuan Lin; Youxin Jin

    2008-01-01

    In Arab idopsis, PA USED ( PSD ) encodes the ortholog of loslp/ exportin-t, which mediates the nuclear export of transfer RNA (tRNA) in yeast and mammals. However, in monocot plants such as rice, knowledge of the corresponding ortholog is limited, and its effects on growth development and productivity remain unknown. In this study, we verified a rice transfer-DNA insertional mutantpsd line and analyzed its phenotypes;the mutant displayed severe morphological defects including retarded development and low fertility compared with wild-type rice. Examining intronless tRNA-Tyr and intron-containing pre-tRNA-Ala expression levels in cytoplasmic and nuclear fraction with Northern blot analysis between wild -type and mutant leaf tissue suggested that rice PSD might be involved in tRNA export from the nucleus to the cytoplasm.Additionally, reverse transcription-polymerase chain reaction analysis revealed that PSD transcript was expressed throughout normal rice plant development, and subcellular localization assays showed that rice PSD protein was present in both the nucleus and cytoplasm. In summary, our data implied that the putative PSD gene might be indispensable for normal rice development and its function might be the same as that ofArabidopsis PSD.

  9. Conformational study of a putative HLTV-1 retroviral protease inhibitor.

    Science.gov (United States)

    Llido, S; d'Estaintot, B L; Dautant, A; Geoffre, S; Picard, P; Precigoux, G

    1993-05-01

    The crystal structure of prolyl-glutaminyl-valyl-statyl-alanyl-leucine (Pro-Gln-Val-Sta-Ala-Leu, C(32)H(57)N(7)0(9).5H(2)0, M(r) = 683.9 + 90.1), a putative HTLV-1 protease inhibitor based on one of the consensus retroviral protease cleavage sequences, and containing the statine residue [(4S,3S)-4-amino-3-hydroxy-6-methylheptanoic acid], has been determined by X-ray diffraction. The same molecule has been modelled in the active site of the HTLV-1 protease and both conformations have been compared. The peptide crystallizes as a pentahydrate in space group P2(1) with a = 10.874(2), b = 9.501(2), c = 21.062(5) A, beta = 103.68 (1) degrees, Z = 2, V= 2114.3 A(3), D(x) = 1.21 g cm(-3), micro = 8.02 cm(-1), T= 293 K, lambda(Cu Kalpha) = 1.5418 A. The structure has been refined to an R value of 0.070 for 2152 observed reflections. The peptide main chain can be described as extended and adopts the usual zigzag conformation from the prolyl to the statyl residue. The main difference in conformation between the individual observed and modelled molecules is located on the Sta, Ala and Leu residues with the main chain of the modelled molecule rotated by about 180 degrees as compared to the observed conformation in the crystal state.

  10. A new putative sigma factor of Myxococcus xanthus.

    Science.gov (United States)

    Apelian, D; Inouye, S

    1993-06-01

    A third putative sigma factor gene, sigC, has been isolated from Myxococcus xanthus by using the sigA gene (formerly rpoD of M. xanthus) as a probe. The nucleotide sequence of sigC has been determined, and an open reading frame of 295 residues (M(r) = 33,430) has been identified. The deduced amino acid sequence of sigC exhibits the features which are characteristic of other bacterial sigma factors. The characterization of a sigC-lacZ strain has demonstrated that sigC expression is induced immediately after cells enter into the developmental cycle and is dramatically reduced at the onset of sporulation. A deletion mutant of sigC grows normally in vegetative culture and is able to develop normally. However, in contrast to the wild-type cells, the sigC deletion mutant cells became capable of forming fruiting bodies and myxospores on semirich agar plates. This suggests that sigC may play a role in expression of genes involved in negatively regulating the initiation of fruiting body formation.

  11. Cloning and expression of the catalase-peroxidase gene from the hyperthermophilic archaeon Archaeoglobus fulgidus and characterization of the enzyme

    NARCIS (Netherlands)

    Kengen, S.W.M.; Bikker, F.; Vos, de W.M.; Oost, van der J.

    2001-01-01

    A putative perA gene from Archaeoglobus fulgidus was cloned and expressed in Escherichia coli BL21(DE3), and the recombinant catalase-peroxidase was purified to homogeneity. The enzyme is a homodimer with a subunit molecular mass of 85 kDa. UV-visible spectroscopic analysis indicated the presence of

  12. Treating Wastewater With Immobilized Enzymes

    Science.gov (United States)

    Jolly, Clifford D.

    1991-01-01

    Experiments show enzymes are immobilized on supporting materials to make biocatalyst beds for treatment of wastewater. With suitable combination of enzymes, concentrations of various inorganic and organic contaminants, including ammonia and urea, reduced significantly.

  13. Putative neuroprotective actions of N-acyl-ethanolamines

    DEFF Research Database (Denmark)

    Hansen, Harald S.; Moesgaard, B.; Petersen, G.

    2002-01-01

    and monounsaturated fatty acids. Formation of NAPE and NAE is catalyzed by an N-acyltransferase and an NAPE-hydrolyzing phospholipase D, respectively, two enzymes that have been characterized only preliminary. Interestingly, NAPEs and NAEs accumulate in the brain in response to neurodegenerative insults at a time...... when other phospholipids are subjected to rapid degradation. This is an important biosynthetic aspect of NAPE and NAE, as NAEs may be neuroprotective by a number of different mechanisms involving both receptor activation and non-receptor-mediated effects, e.g. by binding to cannabinoid receptors...

  14. The Catalytic Function of Enzymes.

    Science.gov (United States)

    Splittgerber, Allan G.

    1985-01-01

    Discusses: structure of the enzyme molecule; active site; reaction mechanism; transition state; factors affecting enzyme reaction rates, concentration of enzyme; concentration of substrate; product concentration; temperature effects and pH effects; factors causing a lowering of activation energy; proximity and orientation effects; substrate strain…

  15. The evolution and putative function of phosducin-like proteins in the malaria parasite Plasmodium.

    Science.gov (United States)

    Putonti, Catherine; Quach, Bryan; Kooistra, Rachel L; Kanzok, Stefan M

    2013-01-01

    Ubiquitous to the proteomes of all living species is the presence of proteins containing the thioredoxin (Trx)-domain. The best characterized Trx-domain containing proteins include the enzymes involved in cellular redox metabolism facilitated by their cysteine-containing active site. But not all members of the Trx-fold superfamily exhibit this catalytic motif, e.g., the phosducin-like (PhLP) family of proteins. Genome sequencing efforts have uncovered new Trx-domain containing proteins, and their redox activity and cellular functions have yet to be determined. The genome of the malaria parasite Plasmodium contains multiple thioredoxins and thioredoxin-like proteins which are of considerable interest given their role in the parasite's antioxidant defense. While adaptations within the Trx-domain have been studied, primarily with respect to redox active structures, PhLP proteins have not been examined. Using the uncharacterized phosducin-like protein from Plasmodium berghei PhLP-1, we investigated the evolution of PhLP proteins across all branches of the tree of life. As a result of our analysis, we have discovered the presence of two additional PhLP proteins in Plasmodium, PhLP-2 and PhLP-3. Sequence homology with annotated PhLP proteins in other species confirms that the Plasmodium PhLP-2 and PhLP-3 belong to the PhLP family of proteins. Furthermore, as a result of our analysis we hypothesize that the PhLP-2 thioredoxin was lost over time given its absence from higher-order eukaryotes. Probing deeper into the putative function of these proteins, inspection of the active sites indicate that PbPhLP-1 and PbPhLP-2 may be redox active while PbPhLP-3 is very likely not. The results of this phylogenetic study provide insight into the emergence of this family of Trx-domain containing proteins.

  16. Functional Characterization of Four Putative δ1-Pyrroline-5-Carboxylate Reductases from Bacillus subtilis

    Directory of Open Access Journals (Sweden)

    Giuseppe Forlani

    2017-08-01

    Full Text Available In most living organisms, the amino acid proline is synthesized starting from both glutamate and ornithine. In prokaryotes, in the absence of an ornithine cyclodeaminase that has been identified to date only in a small number of soil and plant bacteria, these pathways share the last step, the reduction of δ1-pyrroline-5-carboxylate (P5C catalyzed by P5C reductase (EC 1.5.1.2. In several species, multiple forms of P5C reductase have been reported, possibly reflecting the dual function of proline. Aside from its common role as a building block of proteins, proline is indeed also involved in the cellular response to osmotic and oxidative stress conditions. Genome analysis of Bacillus subtilis identifies the presence of four genes (ProH, ProI, ProG, and ComER that, based on bioinformatic and phylogenic studies, were defined as respectively coding a putative P5C reductase. Here we describe the cloning, heterologous expression, functional analysis and small-angle X-ray scattering studies of the four affinity-purified proteins. Results showed that two of them, namely ProI and ComER, lost their catalytic efficiency or underwent subfunctionalization. In the case of ComER, this could be likely explained by the loss of the ability to form a dimer, which has been previously shown to be an essential structural feature of the catalytically active P5C reductase. The properties of the two active enzymes are consistent with a constitutive role for ProG, and suggest that ProH expression may be beneficial to satisfy an increased need for proline.

  17. Functional Characterization of Four Putative d1-Pyrroline-5-Carboxylate Reductases from Bacillus subtilis

    Energy Technology Data Exchange (ETDEWEB)

    Forlani, Giuseppe; Nocek, Boguslaw; Chakravarthy, Srinivas; Joachimiak, Andrzej

    2017-08-02

    In most living organisms, the amino acid proline is synthesized starting from both glutamate and ornithine. In prokaryotes, in the absence of an ornithine cyclodeaminase that has been identified to date only in a small number of soil and plant bacteria, these pathways share the last step, the reduction of delta(1)-pyrroline-5-carboxylate (P5C) catalyzed by P5C reductase (EC 1.5.1.2). In several species, multiple forms of P5C reductase have been reported, possibly reflecting the dual function of proline. Aside from its common role as a building block of proteins, proline is indeed also involved in the cellular response to osmotic and oxidative stress conditions. Genome analysis of Bacillus subtilis identifies the presence of four genes (ProH, ProI, ProG, and ComER) that, based on bioinformatic and phylogenic studies, were defined as respectively coding a putative P5C reductase. Here we describe the cloning, heterologous expression, functional analysis and small-angle X-ray scattering studies of the four affinity-purified proteins. Results showed that two of them, namely ProI and ComER, lost their catalytic efficiency or underwent subfunctionalization. In the case of ComER, this could be likely explained by the loss of the ability to form a dimer, which has been previously shown to be an essential structural feature of the catalytically active P5C reductase. The properties of the two active enzymes are consistent with a constitutive role for ProG, and suggest that ProH expression may be beneficial to satisfy an increased need for proline.

  18. The aerosols' fate in a putative ammonia ocean on Titan

    Science.gov (United States)

    Ramírez, S. I.; Coll, P.; Buch, A.; Brassé, C.; Poch, O.; Raulin, F.

    2010-04-01

    A laboratory study on the chemical transformation of Titan's aerosol analogues placed under putative surface conditions of the satellite was performed. The surface of Titan was one of the targets of the Cassini-Huygens mission and of several of the Cassini orbiter instruments, especially ISS, VIMS and Radar. The first images revealed an interesting solid surface with features that suggest aeolian, tectonic, fluvial processes and even an impact structure[1]. Since then, more detailed descriptions of dunes, channels, lakes, impact craters and cryovolcanic structures have been documented[2]. The existence of an internal liquid water ocean, containing a few percent ammonia has been proposed[2, 3]. It has also been proposed that ammonia-water mixtures can erupt from the putative subsurface ocean leading to cryovolcanism[4]. The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar (SAR) images during 2004 and 2005 that revealed a highly complex geology occurring at Titan's surface[5], among which cryovolcanic features play a central role. The composition of the cryomagma is mainly proposed to be a mixture of water ice and ammonia[6, 7, 8], although ammonia has not been directly detected on Titan, but suggested by recent Cassini-VIMS observations[9]. In order to understand the role that ammonia may play on the chemical transformation of atmospheric aerosols once they reach the surface, we designed the following protocol: laboratory analogues of Titan's aerosols were synthesized from a N2:CH4 (98:2) mixture irradiated under a continuous flow regime of 845 sccm inside which, a cold plasma of 180 W was established. The synthesized analogues were recovered and partitioned in several 10.0 mg samples that were placed in 4.0 mL-volume of aqueous ammonia solutions (25.00, 12.50, 6.25 and 3.125%) at different temperatures (298, 277, 253 and 93 K) for 10 weeks. After a derivatization process performed to the aerosols' refractory phase with N

  19. Molecular diagnosis of putative Stargardt disease probands by exome sequencing

    Directory of Open Access Journals (Sweden)

    Strom Samuel P

    2012-08-01

    Full Text Available Abstract Background The commonest genetic form of juvenile or early adult onset macular degeneration is Stargardt Disease (STGD caused by recessive mutations in the gene ABCA4. However, high phenotypic and allelic heterogeneity and a small but non-trivial amount of locus heterogeneity currently impede conclusive molecular diagnosis in a significant proportion of cases. Methods We performed whole exome sequencing (WES of nine putative Stargardt Disease probands and searched for potentially disease-causing genetic variants in previously identified retinal or macular dystrophy genes. Follow-up dideoxy sequencing was performed for confirmation and to screen for mutations in an additional set of affected individuals lacking a definitive molecular diagnosis. Results Whole exome sequencing revealed seven likely disease-causing variants across four genes, providing a confident genetic diagnosis in six previously uncharacterized participants. We identified four previously missed mutations in ABCA4 across three individuals. Likely disease-causing mutations in RDS/PRPH2, ELOVL, and CRB1 were also identified. Conclusions Our findings highlight the enormous potential of whole exome sequencing in Stargardt Disease molecular diagnosis and research. WES adequately assayed all coding sequences and canonical splice sites of ABCA4 in this study. Additionally, WES enables the identification of disease-related alleles in other genes. This work highlights the importance of collecting parental genetic material for WES testing as the current knowledge of human genome variation limits the determination of causality between identified variants and disease. While larger sample sizes are required to establish the precision and accuracy of this type of testing, this study supports WES for inherited early onset macular degeneration disorders as an alternative to standard mutation screening techniques.

  20. A putatively novel form of spontaneous coordination in neural activity.

    Science.gov (United States)

    Hermer-Vazquez, Raymond; Hermer-Vazquez, Linda; Srinivasan, Sridhar

    2009-04-06

    We simultaneously recorded local field potentials from three sites along the olfactory-entorhinal axis in rats lightly anesthetized with isoflurane, as part of another experiment. While analyzing the initial data from that experiment with spectrograms, we discovered a potentially novel form of correlated neural activity, with near-simultaneous occurrence across the three widely separated brain sites. After validating their existence further, we named these events Synchronous Frequency Bursts (SFBs). Here we report our initial investigations into their properties and their potential functional significance. In Experiment 1, we found that SFBs have highly regular properties, consisting of brief (approximately 250 ms), high amplitude bursts of LFP energy spanning frequency ranges from the delta band (1-4 Hz) to at least the low gamma band (30-50 Hz). SFBs occurred almost simultaneously across recording sites, usually with onsets sites. While the SFBs had fairly typical, exponentially decaying power spectral density plots, their coherence structure was unusual, with high peaks in several narrow frequency ranges and little coherence in other bands. In Experiment 2, we found that SFBs occurred far more often under light anesthesia than deeper anesthetic states, and were especially prevalent as the animals regained consciousness. Finally, in Experiment 3 we showed that SFBs occur simultaneously at a significant rate across brain sites from putatively different functional subsystems--olfactory versus motor pathways. We suggest that SFBs do not carry information per se, but rather, play a role in coordinating activity in different frequency bands, potentially brain-wide, as animals progress from sleep or anesthesia toward full consciousness.

  1. A putative viral defence mechanism in archaeal cells

    Directory of Open Access Journals (Sweden)

    Reidun Lillestøl

    2006-01-01

    Full Text Available Clusters of regularly spaced direct repeats, separated by unconserved spacer sequences, are ubiquitous in archaeal chromosomes and occur in some plasmids. Some clusters constitute around 1% of chromosomal DNA. Similarly structured clusters, generally smaller, also occur in some bacterial chromosomes. Although early studies implicated these clusters in segregation/partition functions, recent evidence suggests that the spacer sequences derive from extrachromosomal elements, and, primarily, viruses. This has led to the proposal that the clusters provide a defence against viral propagation in cells, and that both the mode of inhibition of viral propagation and the mechanism of adding spacer-repeat units to clusters, are dependent on RNAs transcribed from the clusters. Moreover, the putative inhibitory apparatus (piRNA-based may be evolutionarily related to the interference RNA systems (siRNA and miRNA, which are common in eukarya. Here, we analyze all the current data on archaeal repeat clusters and provide some new insights into their diverse structures, transcriptional properties and mode of structural development. The results are consistent with larger cluster transcripts being processed at the centers of the repeat sequences and being further trimmed by exonucleases to yield a dominant, intracellular RNA species, which corresponds approximately to the size of a spacer. Furthermore, analysis of the extensive clusters of Sulfolobus solfataricus strains P1 and P2B provides support for the presence of a flanking sequence adjoining a cluster being a prerequisite for the incorporation of new spacer-repeat units, which occurs between the flanking sequence and the cluster. An archaeal database summarizing the data will be maintained at http://dac.molbio.ku.dk/dbs/SRSR/.

  2. Kinetic Measurements for Enzyme Immobilization.

    Science.gov (United States)

    Cooney, Michael J

    2017-01-01

    Enzyme kinetics is the study of the chemical reactions that are catalyzed by enzymes, with a focus on their reaction rates. The study of an enzyme's kinetics considers the various stages of activity, reveals the catalytic mechanism of this enzyme, correlates its value to assay conditions, and describes how a drug or a poison might inhibit the enzyme. Victor Henri initially reported that enzyme reactions were initiated by a bond between the enzyme and the substrate. By 1910, Michaelis and Menten were advancing their work by studying the kinetics of an enzyme saccharase which catalyzes the hydrolysis of sucrose into glucose and fructose. They published their analysis and ever since the Michaelis-Menten equation has been used as the standard to describe the kinetics of many enzymes. Unfortunately, soluble enzymes must generally be immobilized to be reused for long times in industrial reactors. In addition, other critical enzyme properties have to be improved like stability, activity, inhibition by reaction products, and selectivity towards nonnatural substrates. Immobilization is by far the chosen process to achieve these goals.Although the Michaelis-Menten approach has been regularly adapted to the analysis of immobilized enzyme activity, its applicability to the immobilized state is limited by the barriers the immobilization matrix places upon the measurement of compounds that are used to model enzyme kinetics. That being said, the estimated value of the Michaelis-Menten coefficients (e.g., V max, K M) can be used to evaluate effects of immobilization on enzyme activity in the immobilized state when applied in a controlled manner. In this review enzyme activity and kinetics are discussed in the context of the immobilized state, and a few novel protocols are presented that address some of the unique constraints imposed by the immobilization barrier.

  3. Putative Risk Factors in Developmental Dyslexia: A Case-Control Study of Italian Children

    Science.gov (United States)

    Mascheretti, Sara; Marino, Cecilia; Simone, Daniela; Quadrelli, Ermanno; Riva, Valentina; Cellino, Maria Rosaria; Maziade, Michel; Brombin, Chiara; Battaglia, Marco

    2015-01-01

    Although dyslexia runs in families, several putative risk factors that cannot be immediately identified as genetic predict reading disability. Published studies analyzed one or a few risk factors at a time, with relatively inconsistent results. To assess the contribution of several putative risk factors to the development of dyslexia, we conducted…

  4. Putative Risk Factors in Developmental Dyslexia: A Case-Control Study of Italian Children

    Science.gov (United States)

    Mascheretti, Sara; Marino, Cecilia; Simone, Daniela; Quadrelli, Ermanno; Riva, Valentina; Cellino, Maria Rosaria; Maziade, Michel; Brombin, Chiara; Battaglia, Marco

    2015-01-01

    Although dyslexia runs in families, several putative risk factors that cannot be immediately identified as genetic predict reading disability. Published studies analyzed one or a few risk factors at a time, with relatively inconsistent results. To assess the contribution of several putative risk factors to the development of dyslexia, we conducted…

  5. A new versatile microarray-based method for high throughput screening of carbohydrate-active enzymes.

    Science.gov (United States)

    Vidal-Melgosa, Silvia; Pedersen, Henriette L; Schückel, Julia; Arnal, Grégory; Dumon, Claire; Amby, Daniel B; Monrad, Rune Nygaard; Westereng, Bjørge; Willats, William G T

    2015-04-03

    Carbohydrate-active enzymes have multiple biological roles and industrial applications. Advances in genome and transcriptome sequencing together with associated bioinformatics tools have identified vast numbers of putative carbohydrate-degrading and -modifying enzymes including glycoside hydrolases and lytic polysaccharide monooxygenases. However, there is a paucity of methods for rapidly screening the activities of these enzymes. By combining the multiplexing capacity of carbohydrate microarrays with the specificity of molecular probes, we have developed a sensitive, high throughput, and versatile semiquantitative enzyme screening technique that requires low amounts of enzyme and substrate. The method can be used to assess the activities of single enzymes, enzyme mixtures, and crude culture broths against single substrates, substrate mixtures, and biomass samples. Moreover, we show that the technique can be used to analyze both endo-acting and exo-acting glycoside hydrolases, polysaccharide lyases, carbohydrate esterases, and lytic polysaccharide monooxygenases. We demonstrate the potential of the technique by identifying the substrate specificities of purified uncharacterized enzymes and by screening enzyme activities from fungal culture broths.

  6. Identification of biotransformation enzymes in the antennae of codling moth Cydia pomonella.

    Science.gov (United States)

    Huang, Xinglong; Liu, Lu; Su, Xiaoji; Feng, Jinian

    2016-04-10

    Biotransformation enzymes are found in insect antennae and play a critical role in degrading xenobiotics and odorants. In Cydia pomonella, we identified 26 biotransformation enzymes. Among these enzymes, twelve carboxylesterases (CXEs), two aldehyde oxidases (AOXs) and six alcohol dehydrogenases (ADs) were predominantly expressed in antennae. Each of the CpomCXEs presents a conserved catalytic triad "Ser-His-Glu", which is the structural characteristic of known insect CXEs. CpomAOXs present two redox centers, a FAD-binding domain and a molybdenum cofactor/substrate-binding domain. The antennal CpomADs are from two protein families, short-chain dehydrogenases/reducetases (SDRs) and medium-chain dehydrogenases/reducetases (MDRs). Putative catalytic active domain and cofactor binding domain were found in these CpomADs. Potential functions of these enzymes were determined by phylogenetic analysis. The results showed that these enzymes share close relationship with odorant degrading enzymes (ODEs) and resistance-associated enzymes of other insect species. Because of commonly observed roles of insect antennal biotransformation enzymes, we suggest antennal biotransformation enzymes presented here are candidate that involved in degradation of odorants and xenobiotics within antennae of C. pomonella.

  7. Crystallization and X-ray diffraction analysis of a putative bacterial class I labdane-related diterpene synthase.

    Science.gov (United States)

    Serrano-Posada, Hugo; Centeno-Leija, Sara; Rojas-Trejo, Sonia; Stojanoff, Vivian; Rodríguez-Sanoja, Romina; Rudiño-Piñera, Enrique; Sánchez, Sergio

    2015-09-01

    Labdane-related diterpenoids are natural products with potential pharmaceutical applications that are rarely found in bacteria. Here, a putative class I labdane-related diterpene synthase (LrdC) identified by genome mining in a streptomycete was successfully crystallized using the microbatch method. Crystals of the LrdC enzyme were obtained in a holo form with its natural cofactor Mg(2+) (LrdC-Mg(2+)) and in complex with inorganic pyrophosphate (PPi) (LrdC-Mg(2+)-PPi). Crystals of native LrdC-Mg(2+) diffracted to 2.50 Å resolution and belonged to the trigonal space group P3221, with unit-cell parameters a = b = 107.1, c = 89.2 Å. Crystals of the LrdC-Mg(2+)-PPi complex grown in the same conditions as the native enzyme with PEG 8000 diffracted to 2.36 Å resolution and also belonged to the trigonal space group P3221. Crystals of the LrdC-Mg(2+)-PPi complex grown in a second crystallization condition with PEG 3350 diffracted to 2.57 Å resolution and belonged to the monoclinic space group P21, with unit-cell parameters a = 49.9, b = 104.1, c = 66.5 Å, β = 111.4°. The structure was determined by the single-wavelength anomalous dispersion (SAD) technique using the osmium signal from a potassium hexachloroosmate (IV) derivative.

  8. Identification of interleukin-8 converting enzyme as cathepsin L.

    Science.gov (United States)

    Ohashi, Kensaku; Naruto, Masanobu; Nakaki, Toshio; Sano, Emiko

    2003-06-26

    IL-8 is produced by various cells, and the NH(2)-terminal amino acid sequence of IL-8 displays heterogeneity among cell types. The mature form of IL-8 has 72 amino acids (72IL-8), while a precursor form (77IL-8) of IL-8 has five additional amino acids to the 72IL-8 NH(2)-terminal. However, it has been unclear how IL-8 is processed to yield the mature form. In this study, converting enzyme was purified as a single 31-kDa band on silver-stained polyacrylamide gel from 160 l of cultured fibroblast supernatant by sequential chromatography. NH(2)-terminal amino acid sequence analysis revealed a sequence, EAPRSVDWRE, which was identified as a partial sequence of cathepsin L. Polyclonal antibodies raised against cathepsin L recognized the purified converting enzyme on Western blot. Moreover, human hepatic cathepsin L cleaved 77IL-8 between Arg(5) and Ser(6), which is the same cleavage site as the putative converting enzyme, resulting in 72IL-8 formation. These data indicate that the converting enzyme of the partially purified fraction of the human fibroblast culture supernatant was cathepsin L. Furthermore, 72IL-8 was sevenfold more potent than 77IL-8 in a neutrophil chemotaxis assay. These results show that cathepsin L is secreted from human fibroblasts in response to external stimuli and plays an important role in IL-8 processing in inflammatory sites.

  9. Gene transcript accumulation and in situ mRNA hybridization of two putative glutamate dehydrogenase genes in etiolated Glycine max seedlings.

    Science.gov (United States)

    Dimou, M; Tsaniklidis, G; Aivalakis, G; Katinakis, P

    2015-01-01

    Glutamate dehydrogenase (EC 1.4.1.2) is a multimeric enzyme that catalyzes the reversible amination of α-ketoglutarate to form glutamate. We characterized cDNA clones of two Glycine max sequences, GmGDH1 and GmGDH2, that code for putative α- and β-subunits, respectively, of the NADH dependent enzyme. Temporal and spatial gene transcript accumulation studies using semiquantitative RT-PCR and in situ hybridization have shown an overlapping gene transcript accumulation pattern with differences in relative gene transcript accumulation in the organs examined. Detection of NADH-dependent glutamate dehydrogenase activity in situ using a histochemical method showed concordance with the spatial gene transcript accumulation patterns. Our findings suggest that although the two gene transcripts are co-localized in roots of etiolated soybean seedlings, the ratio of the two subunits of the active holoenzyme may vary among tissues.

  10. Structure of a putative acetyltransferase (PA1377) from Pseudomonas aeruginosa

    Energy Technology Data Exchange (ETDEWEB)

    Davies, Anna M.; Tata, Renée; Chauviac, François-Xavier; Sutton, Brian J.; Brown, Paul R., E-mail: paul.brown@kcl.ac.uk [Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London Bridge, London SE1 1UL (United Kingdom)

    2008-05-01

    The crystal structure of an acetyltransferase encoded by the gene PA1377 from Pseudomonas aeruginosa has been determined at 2.25 Å resolution. Comparison with a related acetyltransferase revealed a structural difference in the active site that was taken to reflect a difference in substrate binding and/or specificity between the two enzymes. Gene PA1377 from Pseudomonas aeruginosa encodes a 177-amino-acid conserved hypothetical protein of unknown function. The structure of this protein (termed pitax) has been solved in space group I222 to 2.25 Å resolution. Pitax belongs to the GCN5-related N-acetyltransferase family and contains all four sequence motifs conserved among family members. The β-strand structure in one of these motifs (motif A) is disrupted, which is believed to affect binding of the substrate that accepts the acetyl group from acetyl-CoA.

  11. Clinical utility of diagnostic guidelines and putative biomarkers in lymphangioleiomyomatosis

    Directory of Open Access Journals (Sweden)

    Chang William YC

    2012-04-01

    Full Text Available Abstract Background Lymphangioleiomyomatosis is a rare disease occurring almost exclusively in women. Diagnosis often requires surgical biopsy and the clinical course varies between patients with no predictors of progression. We evaluated recent diagnostic guidelines, clinical features and serum biomarkers as diagnostic and prognostic tools. Methods Serum vascular endothelial growth factor-D (VEGF-D, angiotensin converting enzyme (ACE, matrix metalloproteinases (MMP -2 and -9, clinical phenotype, thoracic and abdominal computerised tomography, lung function and quality of life were examined in a cohort of 58 patients. 32 healthy female controls had serum biomarkers measured. Results Serum VEGF-D, ACE and total MMP-2 levels were elevated in patients. VEGF-D was the strongest discriminator between patients and controls (median = 1174 vs. 332 pg/ml p  Conclusions Combining ERS criteria and serum VEGF-D reduces the need for lung biopsy in LAM. VEGF-D was associated with lymphatic disease but not lung function.

  12. Characterization of salt-adapted secreted lignocellulolytic enzymes from the mangrove fungus Pestalotiopsis sp

    OpenAIRE

    Chevret, Didier; Henrissat, Bernard; Berrin, Jean-Guy; Levasseur, Anthony; Record, Eric

    2013-01-01

    Fungi are important for biomass degradation processes in mangrove forests. Given the presence of sea water in these ecosystems, mangrove fungi are adapted to high salinity. Here we isolate Pestalotiopsis sp. NCi6, a halotolerant and lignocellulolytic mangrove fungus of the order Xylariales. We study its lignocellulolytic enzymes and analyse the effects of salinity on its secretomes. De novo transcriptome sequencing and assembly indicate that this fungus possesses of over 400 putative lignocel...

  13. Putative functions of extracellular matrix glycoproteins in secondary palate morphogenesis

    Science.gov (United States)

    d'Amaro, Rocca; Scheidegger, Rolf; Blumer, Susan; Pazera, Pawel; Katsaros, Christos; Graf, Daniel; Chiquet, Matthias

    2012-01-01

    Cleft palate is a common birth defect in humans. Elevation and fusion of paired palatal shelves are coordinated by growth and transcription factors, and mutations in these can cause malformations. Among the effector genes for growth factor signaling are extracellular matrix (ECM) glycoproteins. These provide substrates for cell adhesion (e.g., fibronectin, tenascins), but also regulate growth factor availability (e.g., fibrillins). Cleft palate in Bmp7 null mouse embryos is caused by a delay in palatal shelf elevation. In contrast, palatal shelves of Tgf-β3 knockout mice elevate normally, but a cleft develops due to their failure to fuse. However, nothing is known about a possible functional interaction between specific ECM proteins and Tgf-β/Bmp family members in palatogenesis. To start addressing this question, we studied the mRNA and protein distribution of relevant ECM components during secondary palate development, and compared it to growth factor expression in wildtypewild type and mutant mice. We found that fibrillin-2 (but not fibrillin-1) mRNA appeared in the mesenchyme of elevated palatal shelves adjacent to the midline epithelial cells, which were positive for Tgf-β3 mRNA. Moreover, midline epithelial cells started expressing fibronectin upon contact of the two palatal shelves. These findings support the hypothesis that fibrillin-2 and fibronectin are involved in regulating the activity of Tgf-β3 at the fusing midline. In addition, we observed that tenascin-W (but not tenascin-C) was misexpressed in palatal shelves of Bmp7-deficient mouse embryos. In contrast to tenascin-C, tenascin-W secretion was strongly induced by Bmp7 in embryonic cranial fibroblasts in vitro. These results are consistent with a putative function for tenascin-W as a target of Bmp7 signaling during palate elevation. Our results indicate that distinct ECM proteins are important for morphogenesis of the secondary palate, both as downstream effectors and as regulators of Tgf

  14. Selection of enzymes for terminal restriction fragment length polymorphism analysis of fungal internally transcribed spacer sequences.

    Science.gov (United States)

    Alvarado, Pablo; Manjón, Jose L

    2009-07-01

    Terminal restriction fragment length polymorphism (TRFLP) profiling of the internally transcribed spacer (ITS) ribosomal DNA of unknown fungal communities is currently unsupported by a broad-range enzyme-choosing rationale. An in silico study of terminal fragment size distribution was therefore performed following virtual digestion (by use of a set of commercially available 135 type IIP restriction endonucleases) of all published fungal ITS sequences putatively annealing to primers ITS1 and ITS4. Different diversity measurements were used to rank primer-enzyme pairs according to the richness and evenness that they showed. Top-performing pairs were hierarchically clustered to test for data dependency. The enzyme set composed of MaeII, BfaI, and BstNI returned much better results than randomly chosen enzyme sets in computer simulations and is therefore recommended for in vitro TRFLP profiling of fungal ITSs.

  15. Measuring the Enzyme Activity of Arabidopsis Deubiquitylating Enzymes.

    Science.gov (United States)

    Kalinowska, Kamila; Nagel, Marie-Kristin; Isono, Erika

    2016-01-01

    Deubiquitylating enzymes, or DUBs, are important regulators of ubiquitin homeostasis and substrate stability, though the molecular mechanisms of most of the DUBs in plants are not yet understood. As different ubiquitin chain types are implicated in different biological pathways, it is important to analyze the enzyme characteristic for studying a DUB. Quantitative analysis of DUB activity is also important to determine enzyme kinetics and the influence of DUB binding proteins on the enzyme activity. Here, we show methods to analyze DUB activity using immunodetection, Coomassie Brilliant Blue staining, and fluorescence measurement that can be useful for understanding the basic characteristic of DUBs.

  16. Prioritization of putative metabolite identifications in LC-MS/MS experiments using a computational pipeline.

    Science.gov (United States)

    Zhou, Bin; Xiao, Jun Feng; Ressom, Habtom W

    2013-01-01

    One of the major bottle-necks in current LC-MS-based metabolomic investigations is metabolite identification. An often-used approach is to first look up metabolites from databases through peak mass, followed by verification of the obtained putative identifications using MS/MS data. However, the mass-based search may provide inappropriate putative identifications when the observed peak is from isotopes, fragments, or adducts. In addition, a large fraction of peaks is often left with multiple putative identifications. To differentiate these putative identifications, manual verification of metabolites through comparison between biological samples and authentic compounds is necessary. However, such experiments are laborious, especially when multiple putative identifications are encountered. It is desirable to use computational approaches to obtain more reliable putative identifications and prioritize them before performing experimental verification of the metabolites. In this article, a computational pipeline is proposed to assist metabolite identification with improved metabolome coverage and prioritization capability. Multiple publicly available software tools and databases, along with in-house developed algorithms, are utilized to fully exploit the information acquired from LC-MS/MS experiments. The pipeline is successfully applied to identify metabolites on the basis of LC-MS as well as MS/MS data. Using accurate masses, retention time values, MS/MS spectra, and metabolic pathways/networks, more appropriate putative identifications are retrieved and prioritized to guide subsequent metabolite verification experiments.

  17. In silico Prediction, in vitro Antibacterial Spectrum, and Physicochemical Properties of a Putative Bacteriocin Produced by Lactobacillus rhamnosus Strain L156.4.

    Science.gov (United States)

    Oliveira, Letícia de C; Silveira, Aline M M; Monteiro, Andréa de S; Dos Santos, Vera L; Nicoli, Jacques R; Azevedo, Vasco A de C; Soares, Siomar de C; Dias-Souza, Marcus V; Nardi, Regina M D

    2017-01-01

    A bacteriocinogenic Lactobacillus rhamnosus L156.4 strain isolated from the feces of NIH mice was identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. The entire genome was sequenced using Illumina, annotated in the PGAAP, and RAST servers, and deposited. Conserved genes associated with bacteriocin synthesis were predicted using BAGEL3, leading to the identification of an open reading frame (ORF) that shows homology with the L. rhamnosus GG (ATCC 53103) prebacteriocin gene. The encoded protein contains a conserved protein motif associated a structural gene of the Enterocin A superfamily. We found ORFs related to the prebacteriocin, immunity protein, ABC transporter proteins, and regulatory genes with 100% identity to those of L. rhamnosus HN001. In this study, we provide evidence of a putative bacteriocin produced by L. rhamnosus L156.4 that was further confirmed by in vitro assays. The antibacterial activity of the substances produced by this strain was evaluated using the deferred agar-spot and spot-on-the lawn assays, and a wide antimicrobial activity spectrum against human and foodborne pathogens was observed. The physicochemical characterization of the putative bacteriocin indicated that it was sensitive to proteolytic enzymes, heat stable and maintained its antibacterial activity in a pH ranging from 3 to 9. The activity against Lactobacillus fermentum, which was used as an indicator strain, was detected during bacterial logarithmic growth phase, and a positive correlation was confirmed between bacterial growth and production of the putative bacteriocin. After a partial purification from cell-free supernatant by salt precipitation, the putative bacteriocin migrated as a diffuse band of approximately 1.0-3.0 kDa by SDS-PAGE. Additional studies are being conducted to explore its use in the food industry for controlling bacterial growth and for probiotic applications.

  18. In silico Prediction, in vitro Antibacterial Spectrum, and Physicochemical Properties of a Putative Bacteriocin Produced by Lactobacillus rhamnosus Strain L156.4

    Directory of Open Access Journals (Sweden)

    Letícia de C. Oliveira

    2017-05-01

    Full Text Available A bacteriocinogenic Lactobacillus rhamnosus L156.4 strain isolated from the feces of NIH mice was identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. The entire genome was sequenced using Illumina, annotated in the PGAAP, and RAST servers, and deposited. Conserved genes associated with bacteriocin synthesis were predicted using BAGEL3, leading to the identification of an open reading frame (ORF that shows homology with the L. rhamnosus GG (ATCC 53103 prebacteriocin gene. The encoded protein contains a conserved protein motif associated a structural gene of the Enterocin A superfamily. We found ORFs related to the prebacteriocin, immunity protein, ABC transporter proteins, and regulatory genes with 100% identity to those of L. rhamnosus HN001. In this study, we provide evidence of a putative bacteriocin produced by L. rhamnosus L156.4 that was further confirmed by in vitro assays. The antibacterial activity of the substances produced by this strain was evaluated using the deferred agar-spot and spot-on-the lawn assays, and a wide antimicrobial activity spectrum against human and foodborne pathogens was observed. The physicochemical characterization of the putative bacteriocin indicated that it was sensitive to proteolytic enzymes, heat stable and maintained its antibacterial activity in a pH ranging from 3 to 9. The activity against Lactobacillus fermentum, which was used as an indicator strain, was detected during bacterial logarithmic growth phase, and a positive correlation was confirmed between bacterial growth and production of the putative bacteriocin. After a partial purification from cell-free supernatant by salt precipitation, the putative bacteriocin migrated as a diffuse band of approximately 1.0–3.0 kDa by SDS-PAGE. Additional studies are being conducted to explore its use in the food industry for controlling bacterial growth and for probiotic applications.

  19. Enzyme molecules in solitary confinement.

    Science.gov (United States)

    Liebherr, Raphaela B; Gorris, Hans H

    2014-09-12

    Large arrays of homogeneous microwells each defining a femtoliter volume are a versatile platform for monitoring the substrate turnover of many individual enzyme molecules in parallel. The high degree of parallelization enables the analysis of a statistically representative enzyme population. Enclosing individual enzyme molecules in microwells does not require any surface immobilization step and enables the kinetic investigation of enzymes free in solution. This review describes various microwell array formats and explores their applications for the detection and investigation of single enzyme molecules. The development of new fabrication techniques and sensitive detection methods drives the field of single molecule enzymology. Here, we introduce recent progress in single enzyme molecule analysis in microwell arrays and discuss the challenges and opportunities.

  20. Enzyme Molecules in Solitary Confinement

    Directory of Open Access Journals (Sweden)

    Raphaela B. Liebherr

    2014-09-01

    Full Text Available Large arrays of homogeneous microwells each defining a femtoliter volume are a versatile platform for monitoring the substrate turnover of many individual enzyme molecules in parallel. The high degree of parallelization enables the analysis of a statistically representative enzyme population. Enclosing individual enzyme molecules in microwells does not require any surface immobilization step and enables the kinetic investigation of enzymes free in solution. This review describes various microwell array formats and explores their applications for the detection and investigation of single enzyme molecules. The development of new fabrication techniques and sensitive detection methods drives the field of single molecule enzymology. Here, we introduce recent progress in single enzyme molecule analysis in microwell arrays and discuss the challenges and opportunities.

  1. Antioxidant enzyme levels in cancer

    OpenAIRE

    Oberley, T. D.; Oberley, L W

    1997-01-01

    Normal cells are protected by antioxidant enzymes from the toxic effects of high concentrations of reactive oxygen species generated during cellular metabolism. Even though cancer cells generate reactive oxygen species, it has been demonstrated biochemically that antioxidant enzyme levels are low in most animal and human cancers. However, a few cancer types have been found to have elevated levels of antioxidant enzymes, particularly manganese superoxide dismuta...

  2. Heat Stable Enzymes from Thermophiles

    Science.gov (United States)

    1998-02-01

    ultrafiltration and microfiltration that might be suitable. These utilize hollow fiber membranes manufactured in such a manner that they are free of...words) Alkaline phosphatase is widely used in the military and civilian sectors . Commercially available enzyme from calf intestine is the weak link in...widely used enzymes with numerous uses in both the military and civilian sectors . The commercially available enzyme from calf intestine breaks down

  3. Allosteric activation of protein phosphatase 2C by D-chiro-inositol-galactosamine, a putative mediator mimetic of insulin action.

    Science.gov (United States)

    Brautigan, D L; Brown, M; Grindrod, S; Chinigo, G; Kruszewski, A; Lukasik, S M; Bushweller, J H; Horal, M; Keller, S; Tamura, S; Heimark, D B; Price, J; Larner, A N; Larner, J

    2005-08-23

    Insulin-stimulated glucose disposal in skeletal muscle proceeds predominantly through a nonoxidative pathway with glycogen synthase as a rate-limiting enzyme, yet the mechanisms for insulin activation of glycogen synthase are not understood despite years of investigation. Isolation of putative insulin second messengers from beef liver yielded a pseudo-disaccharide consisting of pinitol (3-O-methyl-d-chiro-inositol) beta-1,4 linked to galactosamine chelated with Mn(2+) (called INS2). Here we show that chemically synthesized INS2 has biological activity that significantly enhances insulin reduction of hyperglycemia in streptozotocin diabetic rats. We used computer modeling to dock INS2 onto the known three-dimensional crystal structure of protein phosphatase 2C (PP2C). Modeling and FlexX/CScore energy minimization predicted a unique favorable site on PP2C for INS2 in a surface cleft adjacent to the catalytic center. Binding of INS2 is predicted to involve formation of multiple H-bonds, including one with residue Asp163. Wild-type PP2C activity assayed with a phosphopeptide substrate was potently stimulated in a dose-dependent manner by INS2. In contrast, the D163A mutant of PP2C was not activated by INS2. The D163A mutant and wild-type PP2C in the absence of INS2 had the same Mn(2+)-dependent phosphatase activity with p-nitrophenyl phosphate as a substrate, showing that this mutation did not disrupt the catalytic site. We propose that INS2 allosterically activates PP2C, fulfilling the role of a putative mediator mimetic of insulin signaling to promote protein dephosphorylation and metabolic responses.

  4. Multi-enzyme Process Modeling

    DEFF Research Database (Denmark)

    Andrade Santacoloma, Paloma de Gracia

    The subject of this thesis is to develop a methodological framework that can systematically guide mathematical model building for better understanding of multi-enzyme processes. In this way, opportunities for process improvements can be identified by analyzing simulations of either existing...... are affected (in a positive or negative way) by the presence of the other enzymes and compounds in the media. In this thesis the concept of multi-enzyme in-pot term is adopted for processes that are carried out by the combination of enzymes in a single reactor and implemented at pilot or industrial scale...

  5. Enzyme therapeutics for systemic detoxification.

    Science.gov (United States)

    Liu, Yang; Li, Jie; Lu, Yunfeng

    2015-08-01

    Life relies on numerous biochemical processes working synergistically and correctly. Certain substances disrupt these processes, inducing living organism into an abnormal state termed intoxication. Managing intoxication usually requires interventions, which is referred as detoxification. Decades of development on detoxification reveals the potential of enzymes as ideal therapeutics and antidotes, because their high substrate specificity and catalytic efficiency are essential for clearing intoxicating substances without adverse effects. However, intrinsic shortcomings of enzymes including low stability and high immunogenicity are major hurdles, which could be overcome by delivering enzymes with specially designed nanocarriers. Extensive investigations on protein delivery indicate three types of enzyme-nanocarrier architectures that show more promise than others for systemic detoxification, including liposome-wrapped enzymes, polymer-enzyme conjugates, and polymer-encapsulated enzymes. This review highlights recent advances in these nano-architectures and discusses their applications in systemic detoxifications. Therapeutic potential of various enzymes as well as associated challenges in achieving effective delivery of therapeutic enzymes will also be discussed.

  6. Digestive Enzyme Replacement Therapy: Pancreatic Enzymes and Lactase.

    Science.gov (United States)

    Felicilda-Reynaldo, Rhea Faye D; Kenneally, Maria

    2016-01-01

    Maldigestion occurs when digestive enzymes are lacking to help break complex food components into absorbable nutrients within the gastrointestinal tract. Education is needed to help patients manage the intricacies of digestive enzyme replacement therapies and ensure their effectiveness in reducing symptoms of maldigestion.

  7. Enzymic synthesis of isoflavones.

    Science.gov (United States)

    Kochs, G; Grisebach, H

    1986-03-03

    The NADPH and oxygen-dependent conversion of (2S)-naringenin to genistein catalyzed by a microsomal preparation from elicitor-treated soybean cell suspension cultures has been resolved into two steps. In the first step (2S)-naringenin is converted to a product (P-2) which yields genistein in a second step. The chemical behaviour of P-2 and its ultraviolet and mass spectral data are consistent with a 2-hydroxyisoflavanone structure. The conversion of (2S)-naringenin to P-2 requires NADPH, oxygen and cytochrome P-450. The participation of cytochrome P-450 was demonstrated by CO inhibition of the reaction and its partial reversal by light, and by inhibition with typical cytochrome P-450 inhibitors. On a Percoll gradient the membrane fraction which catalyzes P-2 formation coincides with marker enzymes for the endoplasmic reticulum and with the position of cytochrome P-450. Enzymatic activity for conversion of P-2 to genistein is mainly present in the supernatant of the 160 000 X g fraction. This reaction, formally a dehydration, does not require NADPH or oxygen.

  8. Deubiquitylating enzymes and disease

    Directory of Open Access Journals (Sweden)

    Baker Rohan T

    2008-10-01

    Full Text Available Abstract Deubiquitylating enzymes (DUBs can hydrolyze a peptide, amide, ester or thiolester bond at the C-terminus of UBIQ (ubiquitin, including the post-translationally formed branched peptide bonds in mono- or multi-ubiquitylated conjugates. DUBs thus have the potential to regulate any UBIQ-mediated cellular process, the two best characterized being proteolysis and protein trafficking. Mammals contain some 80–90 DUBs in five different subfamilies, only a handful of which have been characterized with respect to the proteins that they interact with and deubiquitylate. Several other DUBs have been implicated in various disease processes in which they are changed by mutation, have altered expression levels, and/or form part of regulatory complexes. Specific examples of DUB involvement in various diseases are presented. While no specific drugs targeting DUBs have yet been described, sufficient functional and structural information has accumulated in some cases to allow their rapid development. Publication history Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com.

  9. [The rise of enzyme engineering in China].

    Science.gov (United States)

    Li, Gaoxiang

    2015-06-01

    Enzyme engineering is an important part of the modern biotechnology. Industrial biocatalysis is considered the third wave of biotechnology following pharmaceutical and agricultural waves. In 25 years, China has made a mighty advances in enzyme engineering research. This review focuses on enzyme genomics, enzyme proteomics, biosynthesis, microbial conversion and biosensors in the Chinese enzyme engineering symposiums and advances in enzyme preparation industry in China.

  10. Computational enzyme design: transitioning from catalytic proteins to enzymes.

    Science.gov (United States)

    Mak, Wai Shun; Siegel, Justin B

    2014-08-01

    The widespread interest in enzymes stem from their ability to catalyze chemical reactions under mild and ecologically friendly conditions with unparalleled catalytic proficiencies. While thousands of naturally occurring enzymes have been identified and characterized, there are still numerous important applications for which there are no biological catalysts capable of performing the desired chemical transformation. In order to engineer enzymes for which there is no natural starting point, efforts using a combination of quantum chemistry and force-field based protein molecular modeling have led to the design of novel proteins capable of catalyzing chemical reactions not catalyzed by naturally occurring enzymes. Here we discuss the current status and potential avenues to pursue as the field of computational enzyme design moves forward.

  11. Stability of Enzymes in Granular Enzyme Products for Laundry Detergents

    DEFF Research Database (Denmark)

    Biran, Suzan; Bach, Poul; Simonsen, Ole

    . However, incorporating enzymes in detergent formulations gives rise to numerous practical problems due to their incompatibility with and stability against various detergent components. In powdered detergent formulations, these issues can be partly overcome by physically isolating the enzymes in separate...... of this study. The inactivation kinetics of technical grade enzyme powder was determined in a newly developed experimental setup, which was simple and effective and provided a better control over test conditions and fast sample generation. The method was based on the generation of hydrogen peroxide vapor...... the moisture is believed to play an important role in the stability of proteins, the monolayer hydration level of Savinase® was experimentally determined and theoretically calculated. Adsorbed moisture was found to have 3 a negative effect on enzyme activity. Below monolayer hydration level, the enzyme...

  12. Putative role of prostaglandin receptor in intracerebral hemorrhage

    Directory of Open Access Journals (Sweden)

    Shekher eMohan

    2012-10-01

    Full Text Available Each year, approximately 795,000 people experience a new or recurrent stroke. Of all strokes, 84% are ischemic, 13% are intracerebral hemorrhage (ICH strokes and 3% are subarachnoid hemorrhage (SAH strokes. Despite the decreased incidence of ischemic stroke, there has been no change in the incidence of hemorrhagic stroke in the last decade. ICH is a devastating disease 37-38% of patients between the ages of 45-64 die within 30 days. In an effort to prevent ischemic and hemorrhagic strokes we and others have been studying the role of prostaglandins and their receptors. Prostaglandins are bioactive lipids derived from the metabolism of arachidonic acid. They sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response. Most prostaglandins are produced from specific enzymes and act upon cells via distinct G-protein coupled receptors. The presence of multiple prostaglandin receptor’s cross-reactivity and coupling to different signal transduction pathways allow differentiated cells to respond to prostaglandins in a unique manner. Due to the number of prostaglandin receptors, prostaglandin-dependent signaling can function either to promote neuronal survival or injury following acute excitotoxicity, hypoxia, and stress induced by ICH. To better understand the mechanisms of neuronal survival and neurotoxicity mediated by prostaglandin receptors, it is essential to understand downstream signaling. Several groups including ours have discovered unique roles for prostaglandin receptors in rodent models of ischemic stroke, excitotoxicity, and Alzheimer disease, highlighting the emerging role of prostaglandin receptor signaling in hemorrhagic stroke with a focus on cyclic-adenosine monophosphate (cAMP and calcium (Ca2+ signaling. We review current ICH data and discuss future directions notably on prostaglandin receptors, which may lead to the development of unique therapeutic targets against hemorrhagic stroke and

  13. Role of pectinolytic enzymes identified in Clostridium thermocellum cellulosome.

    Science.gov (United States)

    Chakraborty, Soumyadeep; Fernandes, Vania O; Dias, Fernando M V; Prates, Jose A M; Ferreira, Luis M A; Fontes, Carlos M G A; Goyal, Arun; Centeno, Maria S J

    2015-01-01

    The cloning, expression and characterization of three cellulosomal pectinolytic enzymes viz., two variants of PL1 (PL1A and PL1B) and PL9 from Clostridium thermocellum was carried out. The comparison of the primary sequences of PL1A, PL1B and PL9 revealed that these proteins displayed considerable sequence similarities with family 1 and 9 polysaccharide lyases, respectively. PL1A, PL1B and PL9 are the putative catalytic domains of protein sequence ABN54148.1 and ABN53381.1 respectively. These two protein sequences also contain putative carbohydrate binding module (CBM) and type-I dockerin. The associated putative CBM of PL1A showed strong homology with family 6 CBMs while those of PL1B and PL9 showed homology with family 35 CBMs. Recombinant derivatives of these three enzymes showed molecular masses of approximately 34 kDa, 40 kDa and 32 kDa for PL1A, PL1B and PL9, respectively. PL1A, PL1B and PL9 displayed high activity toward polygalacturonic acid and pectin (up to 55% methyl-esterified) from citrus fruits. However, PL1B showed relatively higher activity towards 55% and 85% methyl-esterified pectin (citrus). PL1A and PL9 showed higher activity on rhamnogalacturonan than PL1B. Both PL1A and PL9 displayed maximum activity at pH 8.5 with optimum temperature of 50°C and 60°C respectively. PL1B achieved highest activity at pH 9.8, under an optimum temperature of 50°C. PL1A, PL1B and PL9 all produced two or more unsaturated galacturonates from pectic substrates as displayed by TLC analysis confirming that they are endo-pectate lyase belonging to family 1 and 9, respectively. This report reveals that pectinolytic activity displayed by Clostridium thermocellum cellulosome is coordinated by a sub-set of at least three multi-modular enzymes.

  14. Role of pectinolytic enzymes identified in Clostridium thermocellum cellulosome.

    Directory of Open Access Journals (Sweden)

    Soumyadeep Chakraborty

    Full Text Available The cloning, expression and characterization of three cellulosomal pectinolytic enzymes viz., two variants of PL1 (PL1A and PL1B and PL9 from Clostridium thermocellum was carried out. The comparison of the primary sequences of PL1A, PL1B and PL9 revealed that these proteins displayed considerable sequence similarities with family 1 and 9 polysaccharide lyases, respectively. PL1A, PL1B and PL9 are the putative catalytic domains of protein sequence ABN54148.1 and ABN53381.1 respectively. These two protein sequences also contain putative carbohydrate binding module (CBM and type-I dockerin. The associated putative CBM of PL1A showed strong homology with family 6 CBMs while those of PL1B and PL9 showed homology with family 35 CBMs. Recombinant derivatives of these three enzymes showed molecular masses of approximately 34 kDa, 40 kDa and 32 kDa for PL1A, PL1B and PL9, respectively. PL1A, PL1B and PL9 displayed high activity toward polygalacturonic acid and pectin (up to 55% methyl-esterified from citrus fruits. However, PL1B showed relatively higher activity towards 55% and 85% methyl-esterified pectin (citrus. PL1A and PL9 showed higher activity on rhamnogalacturonan than PL1B. Both PL1A and PL9 displayed maximum activity at pH 8.5 with optimum temperature of 50°C and 60°C respectively. PL1B achieved highest activity at pH 9.8, under an optimum temperature of 50°C. PL1A, PL1B and PL9 all produced two or more unsaturated galacturonates from pectic substrates as displayed by TLC analysis confirming that they are endo-pectate lyase belonging to family 1 and 9, respectively. This report reveals that pectinolytic activity displayed by Clostridium thermocellum cellulosome is coordinated by a sub-set of at least three multi-modular enzymes.

  15. Enzymic hydrolysis of chlorella cells

    Energy Technology Data Exchange (ETDEWEB)

    Khraptsova, G.I.; Tsaplina, I.A.; Burdenko, L.G.; Khoreva, S.L.; Loginova, L.G.

    1981-01-01

    Treatment of C. ellipsoidea, C. pyrenoidosa, and C. vulgaris with cellulolytic enzymes (from Aspergillus terreus) and pectofoetidin p10x (from A. foetidus) resulted in the degradation and lysis of the algae cells. The cells were more sensitive to cellulase than to pectinase. The combination of both enzymes produced a synergistic effect on cell lysis.

  16. An enzyme with rhamnogalacturonase activity.

    NARCIS (Netherlands)

    Kovod, L.V.; Dalboge, H.; Andersen, L.N.; Kauppinen, M.; Christgan, S.; Heldt-Hansen, H.P.; Christophersen, C.; Nielsen, P.M.; Voragen, A.G.J.; Schols, H.A.

    1994-01-01

    An enzyme exhibiting rhamnogalacturonase activity, which enzyme: a) is encoded by the DNA sequence shown in SEQ ID No. 1 or a sequence homologous thereto encoding a polypeptide with RGase activity, b) has the amino acid sequence shown in SEQ ID No. 2 or an analogue thereof, c) is reactive with an

  17. Phage lytic enzymes: a history

    Institute of Scientific and Technical Information of China (English)

    David; Trudil

    2015-01-01

    There are many recent studies regarding the efficacy of bacteriophage-related lytic enzymes: the enzymes of ‘bacteria-eaters’ or viruses that infect bacteria. By degrading the cell wall of the targeted bacteria, these lytic enzymes have been shown to efficiently lyse Gram-positive bacteria without affecting normal flora and non-related bacteria. Recent studies have suggested approaches for lysing Gram-negative bacteria as well(Briersa Y, et al., 2014). These enzymes include: phage-lysozyme, endolysin, lysozyme, lysin, phage lysin, phage lytic enzymes, phageassociated enzymes, enzybiotics, muralysin, muramidase, virolysin and designations such as Ply, PAE and others. Bacteriophages are viruses that kill bacteria, do not contribute to antimicrobial resistance, are easy to develop, inexpensive to manufacture and safe for humans, animals and the environment. The current focus on lytic enzymes has been on their use as anti-infectives in humans and more recently in agricultural research models. The initial translational application of lytic enzymes, however, was not associated with treating or preventing a specifi c disease but rather as an extraction method to be incorporated in a rapid bacterial detection assay(Bernstein D, 1997).The current review traces the translational history of phage lytic enzymes–from their initial discovery in 1986 for the rapid detection of group A streptococcus in clinical specimens to evolving applications in the detection and prevention of disease in humans and in agriculture.

  18. Tropomyosin-1, A Putative Tumor-Suppressor and a Biomarker of Human Breast Cancer

    Science.gov (United States)

    2004-10-01

    cDNA. Lobular carcinoma - 2 A polyclonal pan-TM antibody that recognizes multiple TM Phyllodes tumor - 1 Not determined from the initial pathology...AD Award Number: DAMD17-98-1-8162 TITLE: Tropomyosin-1, A Putative Tumor -Suppressor and a Biomarker of Human Breast Cancer PRINCIPAL INVESTIGATOR...4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Tropomyosin-l, A Putative Tumor -Suppressor and a Biomarker DAMD17-98-1-8162 of Human Breast Cancer 6. A UTHOR

  19. Fluoroquinolone-Resistant Haemophilus parasuis Isolates Exhibit More Putative Virulence Factors than Their Susceptible Counterparts

    OpenAIRE

    Zhang, Qiang; Liu, Jiantao; Yan, Shuxian; Yang, Yujie; Zhang, Anding; Jin, Meilin

    2013-01-01

    The prevalence of 23 putative virulence factors among fluoroquinolone-susceptible and -resistant Haemophilus parasuis isolates was analyzed. Putative hemolysin precursor, fimbrial assembly chaperone, and type I site-specific restriction modification system R subunit genes were more prevalent among fluoroquinolone-resistant H. parasuis isolates than among fluoroquinolone-susceptible H. parasuis isolates. Fluoroquinolone resistance may be associated with an increase in the presence of some viru...

  20. Statistical Mechanics of Allosteric Enzymes.

    Science.gov (United States)

    Einav, Tal; Mazutis, Linas; Phillips, Rob

    2016-07-07

    The concept of allostery in which macromolecules switch between two different conformations is a central theme in biological processes ranging from gene regulation to cell signaling to enzymology. Allosteric enzymes pervade metabolic processes, yet a simple and unified treatment of the effects of allostery in enzymes has been lacking. In this work, we take a step toward this goal by modeling allosteric enzymes and their interaction with two key molecular players-allosteric regulators and competitive inhibitors. We then apply this model to characterize existing data on enzyme activity, comment on how enzyme parameters (such as substrate binding affinity) can be experimentally tuned, and make novel predictions on how to control phenomena such as substrate inhibition.

  1. Prevalence and characteristics of Streptococcus pneumoniae "putative serotype 6E" isolates from Asian countries.

    Science.gov (United States)

    Baek, Jin Yang; Park, In Ho; So, Thomas Man-kit; Lalitha, M K; Shimono, Nobuyuki; Yasin, Rohani Md; Carlos, Celia C; Perera, Jennifer; Thamlikitkul, Visanu; Hsueh, Po-Ren; Van, Pham Hung; Shibl, Atef M; Song, Jae-Hoon; Ko, Kwan Soo

    2014-12-01

    The prevalence, antimicrobial susceptibility, and genotypes of Streptococcus pneumoniae “putative serotype 6E” isolates from Asian countries were investigated. A total of 244 S. pneumoniae serogroup 6 isolates obtained from 11 Asian countries were included in this study. Of the 244 serogroup 6 isolates, 101 (41.4%) were typed as "putative serotype 6E," followed by serotypes 6A, 6B, 6C, and 6D (27.0, 20.1, 5.7, and 5.7%, respectively). Multilocus sequence typing revealed that clonal complex (CC) 90, including ST90 and its variants, was the most prevalent clonal group of "putative serotype 6E" isolates (n = 63; 62.4%). CC146 and CC315 were also found frequently in some of the countries. Most of the "putative serotype 6E" isolates showed very high resistance rates against cefuroxime, erythromycin, azithromycin, clarithromycin, clindamycin, and trimethoprim/sulfamethoxazole, probably due to their highly resistant to antimicrobials clone, CC90. Our results indicate that “putative serotype 6E” is prevalent in Asian countries. The clonal dissemination of "putative serotype 6E" isolates was also identified.

  2. Identification of putative candidate genes for juvenile wood density in Pinus radiata.

    Science.gov (United States)

    Li, Xinguo; Wu, Harry X; Southerton, Simon G

    2012-08-01

    Wood formation is a complex developmental process driven by the annual activity of the vascular cambium. Conifers usually produce juvenile wood at young ages followed by mature wood for the rest of their lifetime. Juvenile wood exhibits poorer wood quality (i.e., lower density) compared with mature wood and can account for up to 50% of short-rotation harvested logs, thus representing a major challenge for commercial forestry globally. Wood density is an important quality trait for many timber-related products. Understanding the molecular mechanisms involved in the regulation of juvenile wood density is critical for the improvement of juvenile wood quality via marker-aided selection. A previous study has identified several candidate genes affecting mature wood density in Picea sitchensis (Bong.) Carr.; however, genes associated with juvenile wood density in conifers remain poorly characterized. Here, cDNA microarrays containing 3320 xylem unigenes were used to investigate genes differentially transcribed in juvenile wood with high (HD) and low density (LD) in Pinus radiata D.Don. In total, 814 xylem unigenes with differential transcription were identified in at least one of two microarray experiments and 73 genes (45 for HD, 28 for LD) were identified in both experiments, thus representing putative candidate genes for juvenile wood density. Interestingly, cellulose synthases (PrCesA3, PrCesA11) and sucrose synthase (SuSy), which are involved in secondary cell wall formation, had stronger transcription in juvenile wood with HD, while genes functioning in primary wall formation (pectin synthesis, cell expansion and other modifications) were more transcribed in LD wood. Cell wall genes encoding monolignol biosynthesis enzymes, arabinogalactan proteins, actins and tubulins were differentially transcribed in either HD or LD juvenile wood; however, the latter had exclusively greater transcription of genes involved in monolignol polymerization (laccase and peroxidase). The

  3. Recent advances in azo dye degrading enzyme research.

    Science.gov (United States)

    Chen, Huizhong

    2006-04-01

    Azo dyes, which are characterized by one or more azo bonds, are a predominant class of colorants used in tattooing, cosmetics, foods, and consumer products. These dyes are mainly metabolized by bacteria to colorless aromatic amines, some of which are carcinogenic, by azoreductases that catalyze a NAD(P)H-dependent reduction. The resulting amines are further degraded aerobically by bacteria. Some bacteria have the ability to degrade azo dyes both aerobically and anaerobically. Plant-degrading white rot fungi can break down azo dyes by utilizing a number of oxidases and peroxidases as well. In yeast, a ferric reductase system participates in the extracellular reduction of azo dyes. Recently, two types of azoreductases have been discovered in bacteria. The first class of azoreductases is monomeric flavin-free enzymes containing a putative NAD(P)H binding motif at their N-termini; the second class is polymeric flavin dependent enzymes which are studied more extensively. Azoreductases from bacteria represent novel families of enzymes with little similarity to other reductases. Dissociation and reconstitution of the flavin dependent azoreductases demonstrate that the non-covalent bound flavin prosthetic group is required for the enzymatic functions. In this review, structures and carcinogenicity of azo colorants, protein structure, enzymatic function, and substrate specificity, as well as application of the azo dyes and azoreductases will be discussed.

  4. Characterization of recombinant human nicotinamide mononucleotide adenylyl transferase (NMNAT), a nuclear enzyme essential for NAD synthesis.

    Science.gov (United States)

    Schweiger, M; Hennig, K; Lerner, F; Niere, M; Hirsch-Kauffmann, M; Specht, T; Weise, C; Oei, S L; Ziegler, M

    2001-03-09

    Nicotinamide mononucleotide adenylyl transferase (NMNAT) is an essential enzyme in all organisms, because it catalyzes a key step of NAD synthesis. However, little is known about the structure and regulation of this enzyme. In this study we established the primary structure of human NMNAT. The human sequence represents the first report of the primary structure of this enzyme for an organism higher than yeast. The enzyme was purified from human placenta and internal peptide sequences determined. Analysis of human DNA sequence data then permitted the cloning of a cDNA encoding this enzyme. Recombinant NMNAT exhibited catalytic properties similar to the originally purified enzyme. Human NMNAT (molecular weight 31932) consists of 279 amino acids and exhibits substantial structural differences to the enzymes from lower organisms. A putative nuclear localization signal was confirmed by immunofluorescence studies. NMNAT strongly inhibited recombinant human poly(ADP-ribose) polymerase 1, however, NMNAT was not modified by poly(ADP-ribose). NMNAT appears to be a substrate of nuclear kinases and contains at least three potential phosphorylation sites. Endogenous and recombinant NMNAT were phosphorylated in nuclear extracts in the presence of [gamma-(32)P]ATP. We propose that NMNAT's activity or interaction with nuclear proteins are likely to be modulated by phosphorylation.

  5. Integrative computational approach for genome-based study of microbial lipid-degrading enzymes.

    Science.gov (United States)

    Vorapreeda, Tayvich; Thammarongtham, Chinae; Laoteng, Kobkul

    2016-07-01

    Lipid-degrading or lipolytic enzymes have gained enormous attention in academic and industrial sectors. Several efforts are underway to discover new lipase enzymes from a variety of microorganisms with particular catalytic properties to be used for extensive applications. In addition, various tools and strategies have been implemented to unravel the functional relevance of the versatile lipid-degrading enzymes for special purposes. This review highlights the study of microbial lipid-degrading enzymes through an integrative computational approach. The identification of putative lipase genes from microbial genomes and metagenomic libraries using homology-based mining is discussed, with an emphasis on sequence analysis of conserved motifs and enzyme topology. Molecular modelling of three-dimensional structure on the basis of sequence similarity is shown to be a potential approach for exploring the structural and functional relationships of candidate lipase enzymes. The perspectives on a discriminative framework of cutting-edge tools and technologies, including bioinformatics, computational biology, functional genomics and functional proteomics, intended to facilitate rapid progress in understanding lipolysis mechanism and to discover novel lipid-degrading enzymes of microorganisms are discussed.

  6. dEMBF: A Comprehensive Database of Enzymes of Microalgal Biofuel Feedstock.

    Science.gov (United States)

    Misra, Namrata; Panda, Prasanna Kumar; Parida, Bikram Kumar; Mishra, Barada Kanta

    2016-01-01

    Microalgae have attracted wide attention as one of the most versatile renewable feedstocks for production of biofuel. To develop genetically engineered high lipid yielding algal strains, a thorough understanding of the lipid biosynthetic pathway and the underpinning enzymes is essential. In this work, we have systematically mined the genomes of fifteen diverse algal species belonging to Chlorophyta, Heterokontophyta, Rhodophyta, and Haptophyta, to identify and annotate the putative enzymes of lipid metabolic pathway. Consequently, we have also developed a database, dEMBF (Database of Enzymes of Microalgal Biofuel Feedstock), which catalogues the complete list of identified enzymes along with their computed annotation details including length, hydrophobicity, amino acid composition, subcellular location, gene ontology, KEGG pathway, orthologous group, Pfam domain, intron-exon organization, transmembrane topology, and secondary/tertiary structural data. Furthermore, to facilitate functional and evolutionary study of these enzymes, a collection of built-in applications for BLAST search, motif identification, sequence and phylogenetic analysis have been seamlessly integrated into the database. dEMBF is the first database that brings together all enzymes responsible for lipid synthesis from available algal genomes, and provides an integrative platform for enzyme inquiry and analysis. This database will be extremely useful for algal biofuel research. It can be accessed at http://bbprof.immt.res.in/embf.

  7. Stability of Enzymes in Granular Enzyme Products for Laundry Detergents

    OpenAIRE

    Biran, Suzan; Jensen, Anker Degn; Kiil, Søren; Bach, Poul; Simonsen, Ole

    2010-01-01

    Enzymes have long been of interest to the detergent industry due to their ability to improve the cleaning efficiency of synthetic detergents, contribute to shortening washing times, and reduce energy and water consumption, provision of environmentally friendlier wash water effluents and fabric care. However, incorporating enzymes in detergent formulations gives rise to numerous practical problems due to their incompatibility with and stability against various detergent components. In powdered...

  8. Functions of genes and enzymes involved in phenalinolactone biosynthesis.

    Science.gov (United States)

    Daum, Martina; Schnell, Hans-Jörg; Herrmann, Simone; Günther, Andreas; Murillo, Renato; Müller, Rolf; Bisel, Philippe; Müller, Michael; Bechthold, Andreas

    2010-07-05

    Phenalinolactones are novel terpene glycoside antibiotics produced by Streptomyces sp. Tü6071. Inactivation of three oxygenase genes (plaO2, plaO3 and plaO5), two dehydrogenase genes (plaU, plaZ) and one putative acetyltransferase gene (plaV) led to the production of novel phenalinolactone derivatives (PL HS6, PL HS7, PL HS2 and PL X1). Furthermore, the exact biosynthetic functions of two enzymes were determined, and their in vitro activities were demonstrated. PlaO1, an Fe(II)/alpha-ketoglutarate-dependent dioxygenase, is responsible for the key step in gamma-butyrolactone formation, whereas PlaO5, a cytochrome P450-dependent monooxygenase, catalyses the 1-C-hydroxylation of phenalinolactone D. In addition, stable isotope feeding experiments with biosynthetic precursors shed light on the origin of the carbons in the gamma-butyrolactone moiety.

  9. A mitochondrial-like targeting signal on the hydrogenosomal malic enzyme from the anaerobic fungus Neocallimastix frontalis : Support for the hypothesis that hydrogenosomes are modified mitochondria

    NARCIS (Netherlands)

    vanderGiezen, M; Rechinger, KB; Svendsen, [No Value; Durand, R; Hirt, RP; Fevre, M; Embley, TM; Prins, RA

    1997-01-01

    The hydrogenosomal malic enzyme (ME) was purified from the anaerobic fungus Neocallimastix frontalis. Using reverse genetics, the corresponding cDNA was isolated and characterized. The deduced amino acid sequence of the ME showed high similarity to ME from metazoa, plants and protists. Putative func

  10. X-ray structure of putative acyl-ACP desaturase DesA2 from Mycobacterium tuberculosis H37Rv

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, David H.; Lyle, Karen S.; Rayment, Ivan; Fox, Brian G. (UW)

    2010-07-13

    Genome sequencing showed that two proteins in Mycobacterium tuberculosis H37Rv contain the metal binding motif (D/E)X{sub 2}HX{sub {approx}100}(D/E)X{sub 2}H characteristic of the soluble diiron enzyme superfamily. These putative acyl-ACP desaturase genes desA1 and desA2 were cloned from genomic DNA and expressed in Escherichia coli BL21(DE3). DesA1 was found to be insoluble, but in contrast, DesA2 was a soluble protein amenable to biophysical characterization. Here, we report the 2.0 {angstrom} resolution X-ray structure of DesA2 determined by multiple anomalous dispersion (MAD) phasing from a Se-met derivative and refinement against diffraction data obtained on the native protein. The X-ray structure shows that DesA2 is a homodimeric protein with a four-helix bundle core flanked by five additional helices that overlay with 192 structurally equivalent amino acids in the structure of stearoyl-ACP {Delta}9 desaturase from castor plant with an rms difference 1.42 {angstrom}. In the DesA2 crystals, one metal (likely Mn from the crystallization buffer) was bound in high occupancy at the B-site of the conserved metal binding motif, while the A-site was not occupied by a metal ion. Instead, the amino group of Lys-76 occupied this position. The relationships between DesA2 and known diiron enzymes are discussed.

  11. Correlating capacity loss of stoichiometric and nonstoichiometric lithium manganese oxide spinel electrodes with their structural integrity

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Vincent, C.A.; Bruce, P.G.

    1999-10-01

    It is known that stoichiometric spinel, LiMn{sub 2}O{sub 4}, was used as a lithium-ion battery cathode, exhibits significant capacity fade on cycling at room temperature, whereas by making the spinel slightly nonstoichiometric the capacity retention on cycling is improved to a great extent. To help understand this difference in performance, X-ray diffraction (XRD) was used to investigate the spinel structure during lithium extraction and reinsertion. The stoichiometric spinel shows degradation during the first lithium extraction which becomes more severe at high rates. The XRD pattern measured at the end of 50 cycles showed significant low of structural integrity, with several prominent peaks that were not present prior to cycling. In contrast, the nonstoichiometric spinel showed no evidence of degradation up to at least 300 cycles, even at high rates. It is suggested that in the case of stoichiometric spinel, {lambda}-MnO{sub 2}, which forms upon extraction of lithium, accumulates during cycling and, becomes disconnected from the active electrode, capacity fade is significant.

  12. Coprecipitation and redox reactions of manganese oxides with copper and nickel

    Science.gov (United States)

    Hem, J.D.; Lind, Carol J.; Roberson, C.E.

    1989-01-01

    Open-system, continuous-titration experiments have been done in which a slow flux of ???0.02 molar solution of Mn2+ chloride, nitrate, or perchlorate with Cu2+ or Ni2+ in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu2Mn3O8 in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, ??MnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO2 where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included ??MnOOH, Ni(OH)2, and the same two forms of MnO2. The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu2+ and Ni2+ generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems. ?? 1989.

  13. Permanganic acid: a novel precursor for the preparation of manganese oxide catalysts

    NARCIS (Netherlands)

    C. Kappenstein; T. Wahdan; D. Duprez; M.I. Zaki; D. Brands; E. Poels; A. Bliek

    1994-01-01

    Unsupported and ψ-alumina supported MnOx catalysts (1-10 wt-% Mn) were preparedfrom aqueous solutions of HMnO4 and compared with nitrate based samples. They were characterized by XRD, XPS, BET area, oxygen storage capacity and by their catalytic behaviour versus ammonia DeNOx reaction. The unsupport

  14. Abiotic protein fragmentation by manganese oxide: implications for a mechanism to supply soil biota with oligopeptides

    Energy Technology Data Exchange (ETDEWEB)

    Reardon, Patrick N.; Chacon, Stephany S.; Walter, Eric D.; Bowden, Mark E.; Washton, Nancy M.; Kleber, Markus W.

    2016-03-14

    Proteins facilitate a wide range of chemical transformations important in soil as well as being a major reservoir of soil nitrogen themselves. The interactions and reactions of proteins with soils and minerals are of key importance to our understanding of their functional persistence in the environment. We combined NMR and EPR spectroscopies to distinguish the reaction of a model protein with a redox active mineral surface (Birnessite, MnO2) from its response to a redox neutral phyllosilicate (Kaolinite). Our data demonstrate that birnessite fragments the model protein while kaolinite has little impact on the protein structure. NMR and EPR spectroscopies are shown to be valuable tools to observe these reactions and capture the extent of protein transformation together with the extent of mineral response. These data suggest that mineral surfaces can have both promoting and retarding roles in terrestrial nitrogen cycling, with redox active minerals acting as accelerators by catalyzing the breakdown of proteins and proteinaceous materials while phyllosilicates are more likely to act as preservative media.

  15. Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece

    Science.gov (United States)

    Hein, J.R.; Stamatakis, G.; Dowling, J.S.

    2000-01-01

    The Cape Vani Mn oxide and barite deposit on Milos Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Milos Island is part of the active Aegean volcanic arc. A 1 km long basin located between two dacitic domes in northwest Milos is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly δ-MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. The Mn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water that penetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustained by heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and filling dilatational fractures along with barite.

  16. Multifunctional nanosheets based on folic acid modified manganese oxide for tumor-targeting theranostic application

    Science.gov (United States)

    Hao, Yongwei; Wang, Lei; Zhang, Bingxiang; Zhao, Hongjuan; Niu, Mengya; Hu, Yujie; Zheng, Cuixia; Zhang, Hongling; Chang, Junbiao; Zhang, Zhenzhong; Zhang, Yun

    2016-01-01

    It is highly desirable to develop smart nanocarriers with stimuli-responsive drug-releasing and diagnostic-imaging functions for cancer theranostics. Herein, we develop a reduction and pH dual-responsive tumor theranostic platform based on degradable manganese dioxide (MnO2) nanosheets. The MnO2 nanosheets with a size of 20-60 nm were first synthesized and modified with (3-Aminopropyl) trimethoxysilane (APTMS) to get amine-functionalized MnO2, and then functionalized by NH2-PEG2000-COOH (PEG). The tumor-targeting group, folic acid (FA), was finally conjugated with the PEGylated MnO2 nanosheets. Then, doxorubicin (DOX), a chemotherapeutic agent, was loaded onto the modified nanosheets through a physical adsorption, which was designated as MnO2-PEG-FA/DOX. The prepared MnO2-PEG-FA/DOX nanosheets with good biocompatibility can not only efficiently deliver DOX to tumor cells in vitro and in vivo, leading to enhanced anti-tumor efficiency, but can also respond to a slightly acidic environment and high concentration of reduced glutathione (GSH), which caused degradation of MnO2 into manganese ions enabling magnetic resonance imaging (MRI). The longitudinal relaxation rate r 1 was 2.26 mM-1 s-1 at pH 5.0 containing 2 mM GSH. These reduction and pH dual-responsive biodegradable nanosheets combining efficient MRI and chemotherapy provide a novel and promising platform for tumor-targeting theranostic application.

  17. Manganese-oxidizing and -reducing microorganisms isolated from biofilms in chlorinated drinking water systems.

    Science.gov (United States)

    Cerrato, José M; Falkinham, Joseph O; Dietrich, Andrea M; Knocke, William R; McKinney, Chad W; Pruden, Amy

    2010-07-01

    The interaction of chemical, physical and biological factors that affect the fate, transport and redox cycling of manganese in engineered drinking water systems is not clearly understood. This research investigated the presence of Mn-oxidizing and -reducing bacteria in conventional water treatment plants exposed to different levels of chlorine. Mn(II)-oxidizing and Mn(IV)-reducing bacteria, principally Bacillus spp., were isolated from biofilm samples recovered from four separate drinking water systems. Rates of Mn-oxidation and -reduction for selected individual isolates were represented by pseudo-first-order kinetics. Pseudo-first-order rate constants were obtained for Mn-oxidation (range: 0.106-0.659 days(-1)), aerobic Mn-reduction (range: 0.036-0.152 days(-1)), and anaerobic Mn-reduction (range: 0.024-0.052 days(-1)). The results indicate that microbial-catalyzed Mn-oxidation and -reduction (aerobic and anaerobic) can take place simultaneously in aqueous environments exposed to considerable oxygen and chlorine levels and thus affect Mn-release and -deposition in drinking water systems. This has important implications for Mn-management strategies, which typically assume Mn-reduction is not possible in the presence of chlorine and oxidizing conditions. Copyright 2010 Elsevier Ltd. All rights reserved.

  18. Impact of Mn(II)-Manganese Oxide Reactions on Ni and Zn Speciation.

    Science.gov (United States)

    Hinkle, Margaret A G; Dye, Katherine G; Catalano, Jeffrey G

    2017-03-01

    Layered Mn oxide minerals (phyllomanganates) often control trace metal fate in natural systems. The strong uptake of metals such as Ni and Zn by phyllomanganates results from adsorption on or incorporation into vacancy sites. Mn(II) also binds to vacancies and subsequent comproportionation with structural Mn(IV) may alter sheet structures by forming larger and distorted Mn(III)O6 octahedra. Such Mn(II)-phyllomanganate reactions may thus alter metal uptake by blocking key reactive sites. Here we investigate the effect of Mn(II) on Ni and Zn binding to phyllomanganates of varying initial vacancy content (δ-MnO2, hexagonal birnessite, and triclinic birnessite) at pH 4 and 7 under anaerobic conditions. Dissolved Mn(II) decreases macroscopic Ni and Zn uptake at pH 4 but not pH 7. Extended X-ray absorption fine structure spectroscopy demonstrates that decreased uptake at pH 4 corresponds with altered Ni and Zn adsorption mechanisms. These metals transition from binding in the interlayer to sheet edges, with Zn increasing its tetrahedrally coordinated fraction. These effects on metal uptake and binding correlate with Mn(II)-induced structural changes, which are more substantial at pH 4 than 7. Through these structural effects and the pH-dependence of Mn(II)-metal competitive adsorption, system pH largely controls metal binding to phyllomanganates in the presence of dissolved Mn(II).

  19. Mesoporous iron–manganese oxides for sulphur mustard and soman degradation

    Energy Technology Data Exchange (ETDEWEB)

    Štengl, Václav, E-mail: stengl@iic.cas.cz [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 Řež (Czech Republic); J.E. Purkyně University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Grygar, Tomáš Matys [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 Řež (Czech Republic); J.E. Purkyně University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Bludská, Jana [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 Řež (Czech Republic); Opluštil, František; Němec, Tomáš [Military Technical Institute of Protection Brno, Veslařská 230, 628 00 Brno (Czech Republic)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► New nanodispersive materials based on Fe and Mn oxides for degradations of warfare agents. ► The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min). ► One pot synthesis with friendly transformed to industrial conditions. -- Abstract: Substituted iron(III)–manganese(III, IV) oxides, ammonio-jarosite and birnessite, were prepared by a homogeneous hydrolysis of potassium permanganate and iron(III) sulphate with 2-chloroacetamide and urea, respectively. Synthesised oxides were characterised using Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy and scanning electron microscopy (SEM). The oxides were taken for an experimental evaluation of their reactivity against sulphur mustard (HD) and soman (GD). When ammonio-jarosite formation is suppressed by adding urea to the reaction mixture, the reaction products are mixtures of goethite, schwertmannite and ferrihydrite, and their degradation activity against soman considerably increases. The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min) were observed for FeMn{sub 7}5 with 32.6 wt.% Fe (36.8 wt.% Mn) and FeMn{sub 3}7U with 60.8 wt.% Fe (10.1 wt.% Mn) samples, respectively.

  20. NMR investigation of field-induced magnetic order in barium manganese oxide

    Science.gov (United States)

    Suh, Steve

    As early as 1956, Matsubara and Matsuda found an exact correspondence between a lattice gas model and a quantum antiferromagnet model[1]. They paved the way for the language of integer spin boson particles to be used interchangeably with quantum magnetic insulator systems in a general manner. For example, an analogy of density of bosons is found in magnetization, and analogy of chemical potential is found in external field. Just as there exist corresponding parameters between these two seemingly unrelated systems, quantum magnets can also exhibit consequences of Boson particle systems. In particular, spin-ordering transition in quantum magnets can be interpreted as Bose-Einstein condensate (BEC) transition in Boson particle framework. Direct observation of BEC in Boson particles has been realized in 4He's superfluid transition and in dilute atomic gas clouds cooled to very low temperatures[2]. In this thesis, we try to realize and analyze BEC transition through field-induced spin-ordering transition in the S = 1 antiferromagnetic dimer system, Ba3Mn2O8. We perform NMR measurements with 135,137Ba nucleus as a local probe. Although S = 1 spin properties of Ba 3Mn2O8 come from electronic spins on Mn atoms, hyperfine coupling between Mn electronic spins and Ba nuclear spins allow us to infer Mn electrons' spin information. Since there are 2 inequivalent Ba sites, Ba(1) and Ba(2), in Ba3Mn2O8, we essentially have two probes that provide a detailed picture of structure and nature of magnetism in this material. There are many antiferromagnetic BEC candidates, but there is a significant advantage of studying Ba3Mn 2O8. Unlike the other popular antiferromagnetic BEC candidates such as TlCuCl3[3] or BaCuSi2O6[4], we find no evidence of lattice deformation in Ba3Mn2O8 . This allows us an unprecedented clean look at magnetic properties. Aside from the aforementioned simple technical advantage, there are new physics that we can learn from Ba3Mn2O 8. The geometric frustration of the triangular Mn5+ magnetic lattice of Ba3Mn2O8 coupled with interdimer interaction is predicted to result in incommensurate spin structure when the symmetry axis of Ba3Mn2O8 is aligned parallel to the field. Because of single ion anisotropy of the system, Ba3Mn 2O8 has phase diagram that depends on its alignment with respect to the external field[5]. This means that the microscopic spin structure is different depending on whether the material's symmetry axis is aligned parallel or perpendicular to the field. Also, since we are dealing with S = 1, we have potential to investigate spin-gap closure due to singlet and triplet states as well as triplet and quintet states if we are able to access high enough fields (15T to 30T). Measurements at National High Magnetic Field Laboratory (NHMFL), gives us a superficial taste of what it is like to be in the phase created by triplet and quintet gap closure. The temperature range allowed by the Oxford dilution refrigerator system at Brown Lab, UCLA is from 1K down to 30mK. The magnetic field range allowed by the superconducting magnet at Brown Lab, UCLA is from 0T up to 12T. This combination of temperature and field range allows us to investigate the first quantum critical point (Hc1) in detail with various NMR measurements. Normal state frequency shift as a function of temperature near Hc1 reveals behavior consistent with dilute hardcore bose gas. Analysis of the lineshapes of NMR spectra going into spin order BEC phase as a function of field, we directly observe incommensurate nature of spin order and deduce development of order parameter consistent with mean-field theory. Finally, we verify that the language of dilute 3D Bosons also applies to Ba3Mn2O8 through T1 measurements. From critical behavior inferred in T1 measurements, we complete phase boundary diagram at low temperatures and apply general concept of softening in Goldstone mode near Hc1 to describe our T 1 dependence as a function of temperature.

  1. The origin of ferro-manganese oxide coated pumice from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Pearce, N.J.G.; Parthiban, G.; Smith, V.C.; Mudholkar, A.V.; Rao, N.R.

    ). HDT samples have relatively low SiO 2 and Na2 O while the remaining oxides (TiO 2, Al2 O3, Fe2 O3, MgO and K2 O) are all enriched compared to CIOB coated pumice. Similarly analyses from the MTT, and OTT fiamme and welded tuff are also different from... of plagioclase but with low content of An of 45 ± 5 and 30 ± 5 and other sample has more of albite than anorthite with An content of 40 ± 5 and 25 ± 5. Spinel in partially coated pumice is of magnetite (FeO-83.1%, TiO 2-10.6%) where as, fully coated pumice have...

  2. Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo; Aykol, Muratahan; Luo, Langli; Wu, Jinsong; Myers, Benjamin D.; Iddir, Hakim; Russell, John T.; Saldana, Spencer J.; Kumar, Rajan; Thackeray, Michael M.; Curtiss, Larry A.; Dravid, Vinayak P.; Wolverton, Christopher M.; Hersam, Mark C.

    2015-06-24

    Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.

  3. Thin, Flexible Supercapacitors Made from Carbon Nanofiber Electrodes Decorated at Room Temperature with Manganese Oxide Nanosheets

    Directory of Open Access Journals (Sweden)

    S. K. Nataraj

    2013-01-01

    Full Text Available We report the fabrication and electrochemical performance of a flexible thin film supercapacitor with a novel nanostructured composite electrode. The electrode was prepared by in situ coprecipitation of two-dimensional (2D MnO2 nanosheets at room temperature in the presence of carbon nanofibers (CNFs. The highest specific capacitance of 142 F/g was achieved for CNFs-MnO2 electrodes in sandwiched assembly with PVA-H4SiW12O40·nH2O polyelectrolyte separator.

  4. Improved capacity retention in rechargeable 4 V lithium/lithium manganese oxide (spinel) cells.

    CSIR Research Space (South Africa)

    Gummow, RJ

    1994-04-01

    Full Text Available , it is probable that they will nat be used as the initial elec- trodes in rechargeable lithium cells. R.J. Gummow et al. /SolidState Ionics 69 (1994) 59-67 ?no8 600 - B 4 400- ZOO- II 10 20 30 40 50 50 70 80 T...

  5. Seebeck Coefficient of Manganese Oxide Nanoparticles as a Function of Ohmic Resistance

    Science.gov (United States)

    Francis, Nicholas; Hedden, Morgan; Constantin, Costel

    2013-03-01

    Due to the ever increasing energy demand and growing global concern over the environmental impact of CO2 emissions, there is an urging need to seek solutions to transit from fossil fuels to sustainable energy. Thermoelectric (TE) materials show great promise for converting waste heat energy into electricity. TE systems have many unique advantages such as silent operationality, time reliability, and dimensional scalability. Most recently, researchers Song et al. found that MnO2 nanoparticles show a giant Seebeck coefficient of S = 20 mV/K, which is100 times higher than bismuth telluride, one of the best TE materials. Song et al. concluded the paper claiming that the giant S is related to the surface density of the electronic states (DOS). However, they provided very little information about the S as a function of Ohmic resistance [R] for different nano particle sizes which can give information about the DOS. Our preliminary results show that there is a sudden increase of S from 0.33-0.63 mV/K as R increases from 80-110 Ohms. This transition has never been seen before and it can give clues as to the existence of the Giant S observed in this material. This work was supported in part by U.S. Department of Energy Grant #DE-EE0003100..

  6. Intertwined nanocarbon and manganese oxide hybrid foam for high-energy supercapacitors.

    Science.gov (United States)

    Wang, Wei; Guo, Shirui; Bozhilov, Krassimir N; Yan, Dong; Ozkan, Mihrimah; Ozkan, Cengiz S

    2013-11-11

    Rapid charging and discharging supercapacitors are promising alternative energy storage systems for applications such as portable electronics and electric vehicles. Integration of pseudocapacitive metal oxides with single-structured materials has received a lot of attention recently due to their superior electrochemical performance. In order to realize high energy-density supercapacitors, a simple and scalable method is developed to fabricate a graphene/MWNT/MnO2 nanowire (GMM) hybrid nanostructured foam, via a two-step process. The 3D few-layer graphene/MWNT (GM) architecture is grown on foamed metal foils (nickel foam) via ambient pressure chemical vapor deposition. Hydrothermally synthesized α-MnO2 nanowires are conformally coated onto the GM foam by a simple bath deposition. The as-prepared hierarchical GMM foam yields a monographical graphene foam conformally covered with an intertwined, densely packed CNT/MnO2 nanowire nanocomposite network. Symmetrical electrochemical capacitors (ECs) based on GMM foam electrodes show an extended operational voltage window of 1.6 V in aqueous electrolyte. A superior energy density of 391.7 Wh kg(-1) is obtained for the supercapacitor based on the GMM foam, which is much higher than ECs based on GM foam only (39.72 Wh kg(-1) ). A high specific capacitance (1108.79 F g(-1) ) and power density (799.84 kW kg(-1) ) are also achieved. Moreover, the great capacitance retention (97.94%) after 13 000 charge-discharge cycles and high current handability demonstrate the high stability of the electrodes of the supercapacitor. These excellent performances enable the innovative 3D hierarchical GMM foam to serve as EC electrodes, resulting in energy-storage devices with high stability and power density in neutral aqueous electrolyte.

  7. Ferroelectricity of Europium Manganese Oxide EuMn2O5 with Helimagnetic Ordering

    OpenAIRE

    Nakamura, H.; Ishikawa, M; Kohn, K.

    1997-01-01

    From the measurements of pyroelectricity, dielectric constant, magnetic susceptibility and specific heat, we conclude that EuMn2O5 is ferroelectric below the Curie temperature TC of 38.6 K. This temperature coincides with the Néel temperature of the helimagnetic ordering of Mn3+ and Mn4+ moments within the accuracy of the measurements. The spontaneous polarization is along the b-direction.

  8. Manganese Oxide-Surface Modified Titanium(IV Dioxide as Environmental Catalyst

    Directory of Open Access Journals (Sweden)

    Hiroaki Tada

    2013-04-01

    Full Text Available The purpose of this study is to present an “environmental catalyst” possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnOx clusters are highly dispersed on the surface of TiO2 (anatase/rutile = 4/1 w/w, P-25, Degussa by the chemisorption-calcination cycle technique using Mn(acac3 complex as a precursor (MnOx/TiO2. The thermo- and photo-catalytic activities of MnOx/TiO2 were studied for the degradation of 2-naphthol used as a model water pollutant. In contrast to the FeOx/TiO2 system, MnOx/TiO2 exhibits high thermocatalytic activity exceeding those of bulk β-β-MnO2 and Mn2O3. Also, visible-light activity is induced by the surface modification of TiO2 with MnOx clusters, whereas its UV-light activity decreases.

  9. Spontaneous and continuous anti-virus disinfection from nonstoichiometric perovskite-type lanthanum manganese oxide

    Institute of Scientific and Technical Information of China (English)

    Ding Weng; Chao Lei; Ting-Ting Wu; Ren Sun; Meiqing Shen; Yunfeng Lu

    2015-01-01

    Viral pathogens have threatened human being's health for a long time, from periodically breakout flu epidemics to recent rising Ebola virus disease. Herein, we report a new application of nonstoichiometric Perovskite-type LaxMnO3 (x ¼ 1, 0.95, and 0.9) compounds in spontaneous and continuous disinfection of viruses. Perovskite-type LaxMnO3 (x ¼ 1, 0.95, and 0.9) is well-known for their catalytic properties involving oxidization reactions, which are usually utilized as electrodes in fuel cells. By utilizing superb oxidative ability of LaxMnO3 (x ¼ 1, 0.95, and 0.9), amino acid residues in viral envelope proteins are oxidized, thus envelope proteins are denatured and infectivity of the virus is neutralized. It is of great importance that this process does not require external energy sources like light or heat. The A/PR/8/34H1N1 influenza A virus (PR8) was employed as the sample virus in our demonstration, and high-throughput disinfections were observed. The efficiency of disinfection was correlated to oxidative ability of LaxMnO3 (x ¼ 1, 0.95, and 0.9) by EPR and H2-TPR results that La0.9MnO3 had the highest oxidative ability and correspondingly gave out the best disinfecting results within three nonstoichiometric compounds. Moreover, denaturation of hemagglutinin and neuraminidase, the two key envelope proteins of influenza A viruses, was demonstrated by HA unit assay with chicken red blood cells and NA fluorescence assay, respectively. This unique disinfecting application of La0.9MnO3 is considered as a great make up to current sterilizing methods especially to photocatalyst based disinfectants and can be widely applied to cut-off spread routes of viruses, either viral aerosol or contaminated fluid, and help in controlling the possibly upcoming epidemics like flus and hemorrhagic fever.

  10. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    Science.gov (United States)

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

    2017-01-01

    Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles. PMID:28287183

  11. Manganese oxide thin films deposited by SILAR method for supercapacitor application

    Science.gov (United States)

    Jadhav, P. R.; Shinde, V. V.; Navathe, G. J.; Karanjkar, M. M.; Patil, P. S.

    2013-06-01

    The amorphous MnO2 thin films were prepared by simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The prepared thin films were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrochemical study was carried out by cyclic voltammetry in 1 M Na2SO4 electrolyte. The films showed the maximum specific capacitance of 243 F.g-1 at the scan rate of 10 mV.s-1. It is observed that two distinct peaks occurs in cyclic voltammogram during charging and discharging which correspond to the electrochemical oxidation and reduction reaction and different oxidation states of the Mn as Mn2+ and Mn3+. Further, the increase in specific capacitance is observed with the increase in the precursor concentration.

  12. [Removal Kinetics and Mechanism of Aniline by Manganese-oxide-modified Diatomite].

    Science.gov (United States)

    Xiao, Shao-dan; Liu, Lu; Jiang, Li-ying; Chen, Jian-meng

    2015-06-01

    A novel rapid green one-step method was developed for the preparation of manganese modified diatomite (Mn-D) by treating roasted diatomite with an acidic permanganate solution. The effects of calcination temperature and mass ratio of KMnO4 and diatomite (p) on aniline removal efficiency of Mn-D were investigated. The removal kinetics and mechanism of aniline by Mn-D were also discussed. The results showed that when the optimal calcination temperature was 450 degrees C, p was 1.6, and the loading amounts of δ-MnO2 was 0.82 g x g(-1), Mn-D had a great performance for aniline removal, and more than 80% of aniline was adsorbed within 10 minutes, accompanied with the release of Mn2+. In acidic conditions, the adsorption process on Mn-D followed pseudo-second-order and was mainly controlled by intra-particle diffusion. The best fitting of the experimental adsorption data was given by the Freundlich equation. Gas chromatograph-mass spectrometer was applied to identify the reaction intermediates at different times, and azobenzene was found to be the main reaction intermediate in the degradation system. Based on the above observations, the possible degradation pathway of aniline by Mn-D was proposed.

  13. Synthesis and characterization of carbon black/manganese oxide air cathodes for zinc-air batteries

    Science.gov (United States)

    Li, Po-Chieh; Hu, Chi-Chang; Lee, Tai-Chou; Chang, Wen-Sheng; Wang, Tsin Hai

    2014-12-01

    Due to the poor electric conductivity but the excellent catalytic ability for the oxygen reduction reaction (ORR), manganese dioxide in the α phase (denoted as α-MnO2) anchored onto carbon black powders (XC72) has been synthesized by the reflux method. The specific surface area and electric conductivity of the composites are generally enhanced by increasing the XC72 content while the high XC72 content will induce the formation of MnOOH which shows a worse ORR catalytic ability than α-MnO2. The ORR activity of such air cathodes have been optimized at the XC72/α-MnO2 ratio equal to 1 determined by the thermogravimetric analysis. By using this optimized cathode under the air atmosphere, the quasi-steady-state full-cell discharge voltages are equal to 1.353 and 1.178 V at 2 and 20 mA cm-2, respectively. Due to the usage of ambient air rather than pure oxygen, this Zn-air battery shows a modestly high discharge peak power density (67.51 mW cm-2) meanwhile the power density is equal to 47.22 mW cm-2 and the specific capacity is more than 750 mAh g-1 when this cell is operated at 1 V.

  14. Manganese oxide shuttling in pre-GOE oceans - evidence from molybdenum and iron isotopes

    Science.gov (United States)

    Kurzweil, Florian; Wille, Martin; Gantert, Niklas; Beukes, Nicolas J.; Schoenberg, Ronny

    2016-10-01

    The local occurrence of oxygen-rich shallow marine water environments has been suggested to significantly predate atmospheric oxygenation, which occurred during the Great Oxidation Event (GOE) ca. 2.4 billion years ago. However, the potential influence of such 'oxygen oases' on the mobility, distribution and isotopic composition of redox sensitive elements remains poorly understood. Here, we provide new molybdenum and iron isotopic data from shallow marine carbonate and silicate iron formations of the Koegas Subgroup, South Africa, that confirm local ocean redox stratification prior to the GOE. Mn concentrations correlate negatively with both δ98 Mo and δ56 Fe values, which highlights the substantial role of particulate manganese for the cycling of Mo and Fe in the Paleoproterozoic oceans. Based on these trends we propose that pore water molybdate was recharged (1) by the diffusional transport of seawater molybdate with high δ98 Mo and (2) by the re-liberation of adsorbed molybdate with low δ98 Mo during Mn oxide dissolution within the sediment. The relative contribution of isotopically light Mo is highest close to a Mn chemocline, where the flux of Mn oxides is largest, causing the negative correlation of Mn concentrations and δ98 Mo values in the Koegas sediments. The negative correlation between δ56 Fe values and Mn concentrations is likely related to Fe isotope fractionation during Fe(II) oxidation by Mn oxides, resulting in lower δ56 Fe values in the uppermost water column close to a Mn chemocline. We argue that the preservation of these signals within Paleoproterozoic sediments implies the existence of vertically extended chemoclines with a smoother gradient, probably as a result of low atmospheric oxygen concentrations. Furthermore, we suggest that abiotic oxidation of Fe(II) by a Mn oxide particle shuttle might have promoted the deposition of the Koegas iron formations.

  15. Spontaneous and continuous anti-virus disinfection from nonstoichiometric perovskite-type lanthanum manganese oxide

    Directory of Open Access Journals (Sweden)

    Ding Weng

    2015-06-01

    Full Text Available Viral pathogens have threatened human being׳s health for a long time, from periodically breakout flu epidemics to recent rising Ebola virus disease. Herein, we report a new application of nonstoichiometric Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 compounds in spontaneous and continuous disinfection of viruses. Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 is well-known for their catalytic properties involving oxidization reactions, which are usually utilized as electrodes in fuel cells. By utilizing superb oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9, amino acid residues in viral envelope proteins are oxidized, thus envelope proteins are denatured and infectivity of the virus is neutralized. It is of great importance that this process does not require external energy sources like light or heat. The A/PR/8/34H1N1 influenza A virus (PR8 was employed as the sample virus in our demonstration, and high-throughput disinfections were observed. The efficiency of disinfection was correlated to oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9 by EPR and H2-TPR results that La0.9MnO3 had the highest oxidative ability and correspondingly gave out the best disinfecting results within three nonstoichiometric compounds. Moreover, denaturation of hemagglutinin and neuraminidase, the two key envelope proteins of influenza A viruses, was demonstrated by HA unit assay with chicken red blood cells and NA fluorescence assay, respectively. This unique disinfecting application of La0.9MnO3 is considered as a great make up to current sterilizing methods especially to photocatalyst based disinfectants and can be widely applied to cut-off spread routes of viruses, either viral aerosol or contaminated fluid, and help in controlling the possibly upcoming epidemics like flus and hemorrhagic fever.

  16. Effects of metal source in metal substitution of lithium manganese oxide spinel

    Energy Technology Data Exchange (ETDEWEB)

    Eftekhari, Ali [Laboratory of Electrochemistry, Materials and Energy Research Center, P.O. Box, 14155-4777, Tehran (Iran, Islamic Republic of)]. E-mail: eftekhari@merc.ac.ir; Moghaddam, Abdolmajid Bayandori [Laboratory of Electrochemistry, Materials and Energy Research Center, P.O. Box, 14155-4777, Tehran (Iran, Islamic Republic of); Yazdani, Bahareh [Laboratory of Electrochemistry, Materials and Energy Research Center, P.O. Box, 14155-4777, Tehran (Iran, Islamic Republic of); Moztarzadeh, Fathollah [Laboratory of Electrochemistry, Materials and Energy Research Center, P.O. Box, 14155-4777, Tehran (Iran, Islamic Republic of)

    2006-12-01

    Usefulness of W substitution for improvement of battery performance of LiMn{sub 2}O{sub 4} cathode was investigated. Small amounts of tungsten were incorporated into LiMn{sub 2}O{sub 4} spinel instead of available Mn. For this purpose, two sources of tungsten (metallic W or WO{sub 3}) were examined. W concentration and source have significant influence on both morphology and electrochemical behavior of W-substituted LiMn{sub 2}O{sub 4} spinels. W substitution of LiMn{sub 2}O{sub 4} spinel can lead to the formation of uniform spinel particles and improved battery performance. Cyclic voltammetric behaviors of the samples were examined in an aqueous solution, and Li diffusion process was investigated for different cases. The best case was the LiW{sub 0.01}Mn{sub 1.99}O{sub 4} spinel prepared from metallic W powder, as exhibits excellent rate capability, but better cycleability was observed for the LiW{sub 0.01}Mn{sub 1.99}O{sub 4} spinel prepared from WO{sub 3}. This means that because of significant influence of the dopant source, this parameter should be chosen in respect with the desire improvement.

  17. Ground Tests and In-Orbit Performance of Variable Emittance Device Based on Manganese Oxide

    Science.gov (United States)

    Tachikawa, Sumitaka; Ohnishi, Akira; Nakamura, Yasuyuki; Okamoto, Akira

    A new thermal control material named the Smart Radiation Device (SRD) has shown improvement in development. The SRD can be used as a variable emittance radiator that controls the heat radiated into deep space without assistances of any electrical instruments or mechanical parts. Its total hemispherical emittance changes from low to high as the temperature increases. This new device reduces the energy consumption of the on-board heater, and decreases the weight and the cost of the thermal control system (TCS). Space environmental simulation tests on the ground were performed, and the first generation of the SRD has been demonstrating success on the MUSES-C ‘HAYABUSA’ spacecraft that was launched in May 2003. During its cruise on the orbit, the distance from the spacecraft to the sun varied from 0.86AU to 1.70AU. As the spacecraft experienced solar intensity variation by a factor 4, it was effective to use the variable emittance radiator for decreasing the heater power. In-orbit temperature indicated that the SRD had successfully minimized component temperature variation and saved heater power, as expected. With the opportunity to validate the SRD in space, this lightweight and low cost thermal control device offers a possibility for flexible thermal control on future spacecrafts.

  18. Kinetic Modeling for Microwave-Enhanced Degradation of Methylene Blue Using Manganese Oxide

    Directory of Open Access Journals (Sweden)

    Wen-Hui Kuan

    2013-01-01

    Full Text Available This study was originally performed to compare the MnO2-based degradation of aqueous methylene blue (MB under microwave irradiation- (MW- enhanced and conventional heating- (CH- enhanced conditions. The degradation process and kinetics were investigated to elucidate the microwave effect on the reaction. The results showed that all three tested conditions, sole MnO2, MnO2/CH, and MnO2/MW, followed the third-order (second upon MB and first upon MnO2 kinetic model. However, a higher degradation rate of MB was available under the MW-enhanced process, which implies that the “athermal effect” of MW might be of more benefit for the generation of electrophilic oxygen ions (, , and to degrade MB. The results showed that the degradation percentage of MB could reach 100%, corresponding to 92% total organic carbon (TOC removal under microwave irradiation at pH 7.20 for 10 min.

  19. Effect of Structure on the Storage Characteristics of ManganeseOxide Electrode Materials

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Joon; Doeff, Marca M.

    2006-01-31

    Eleven types of manganese-containing electrode materialswere subjected to long-term storage at 55oC in 1M LiPF6 ethylenecarbonate/dimethyl carbonate (EC/DMC) solutions. The amount of manganesedissolution observed depended upon the sample surface area, the averageMn oxidation state, the structure, and substitution levels of themanganese oxide. In some cases, structural changes such as solvateformation were exacerbated by the high temperature storage, andcontributed to capacity fading upon cycling even in the absence ofsignificant Mn dissolution. The most stable materials appear to beTi-substituted tunnel structures and mixed metal layered oxides with Mnin the +4 oxidation state.

  20. Synthesis and characterization of nanostructured ternary zinc manganese oxide as novel supercapacitor material

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, Asit; Sharma, Yogesh, E-mail: yksptfpt@iitr.ernet.in

    2015-01-15

    Nanostructured ZnMn{sub 2}O{sub 4} is prepared by easy and cost effective urea combustion method, and characterized by X-ray diffraction, field-emission scanning electron microscope, transmission electron microscope and surface area analyzer. The prepared ZnMn{sub 2}O{sub 4} (ZMO) is found to be crystalline and mesoporous in nature with homogenously distributed pores. The supercapacitive properties of the synthesized materials are studied using cyclic voltammetry, galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy in 2 M KOH solution employing three-electrode system. The FESEM analysis reveals nearly spherical morphology of ZMO which is found to be beneficial for improved supercapacitive performance. Cyclic voltammetry shows unsymmetrical charge–discharge curves with the capacitance value of 160 (±5) Fg{sup −1}. The galvanostatic charge–discharge cycles exhibit good electrochemical stability of ZMO. The coulombic efficiency of ZMO is found to be almost 100% till 500 charge–discharge cycles. The electrochemical impedance spectroscopy studies confirm the structural stability and further complement the findings of cyclic voltammetry and galvanostatic cycling. The improved supercapacitive behavior of nano ZMO is ascribed to the unique morphology that consists of interlinked almost spherical nano particles. This interlinked assembly of ZMO nano particles with porous structure (homogeneous pores 10–30 nm) probably facilitates the ion kinetics at electrode-electrolyte interface. - Highlights: • Novel electrode material for supercapacitor: Mn-based Ternary metal oxide. • ZnMn{sub 2}O{sub 4} is synthesized by cost effective urea combustion technique. • Unique architecture consisting of homogeneous pores (10–30 nm) distribution. • Homogeneous pores distribution plays vital role over surface area. • Nano-ZnMn{sub 2}O{sub 4} exhibits specific capacitance of 160 Fg{sup −1}.