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Sample records for catalytically active trp

  1. Spectroscopic evidence for an engineered, catalytically active Trp radical that creates the unique reactivity of lignin peroxidase.

    Science.gov (United States)

    Smith, Andrew T; Doyle, Wendy A; Dorlet, Pierre; Ivancich, Anabella

    2009-09-22

    The surface oxidation site (Trp-171) in lignin peroxidase (LiP) required for the reaction with veratryl alcohol a high-redox-potential (1.4 V) substrate, was engineered into Coprinus cinereus peroxidase (CiP) by introducing a Trp residue into a heme peroxidase that has similar protein fold but lacks this activity. To create the catalytic activity toward veratryl alcohol in CiP, it was necessary to reproduce the Trp site and its negatively charged microenvironment by means of a triple mutation. The resulting D179W+R258E+R272D variant was characterized by multifrequency EPR spectroscopy. The spectra unequivocally showed that a new Trp radical [g values of g(x) = 2.0035(5), g(y) = 2.0027(5), and g(z) = 2.0022(1)] was formed after the [Fe(IV)=O Por(*+)] intermediate, as a result of intramolecular electron transfer between Trp-179 and the porphyrin. Also, the EPR characterization crucially showed that [Fe(IV)=O Trp-179(*)] was the reactive intermediate with veratryl alcohol. Accordingly, our work shows that it is necessary to take into account the physicochemical properties of the radical, fine-tuned by the microenvironment, as well as those of the preceding [Fe(IV)=O Por(*+)] intermediate to engineer a catalytically competent Trp site for a given substrate. Manipulation of the microenvironment of the Trp-171 site in LiP allowed the detection by EPR spectroscopy of the Trp-171(*), for which direct evidence has been missing so far. Our work also highlights the role of Trp residues as tunable redox-active cofactors for enzyme catalysis in the context of peroxidases with a unique reactivity toward recalcitrant substrates that require oxidation potentials not realized at the heme site.

  2. Synthetic modulators of TRP channel activity.

    Science.gov (United States)

    Harteneck, Christian; Klose, Chihab; Krautwurst, Dietmar

    2011-01-01

    In humans, 27 TRP channels from 6 related families contribute to a broad spectrum of cellular functions, such as thermo-, pressure-, volume-, pain- and chemosensation. Pain and inflammation-inducing compounds represent potent plant and animal defense mechanisms explaining the great variety of the naturally occurring, TRPV1-, TRPM8-, and TRPA1-activating ligands. The discovery of the first vanilloid receptor (TRPV1) and its involvement in nociception triggered the euphoria and the hope in novel therapeutic strategies treating pain, and this clear-cut indication inspired the development of TRPV1-selective ligands. On the other hand the nescience in the physiological role and putative clinical indication hampered the development of a selective drug in the case of the other TRP channels. Therefore, currently only a handful of mostly un-selective blocker is available to target TRP channels. Nevertheless, there is an ongoing quest for new, natural or synthetic ligands and modulators. In this chapter, we will give an overview on available broad-range blocker, as well as first TRP channel-selective compounds. PMID:21290290

  3. Role of Non-Active-Site Residue Trp-93 in the Function and Stability of New Delhi Metallo-β-Lactamase 1

    Science.gov (United States)

    Rehman, M. Tabish

    2015-01-01

    New Delhi metallo-β-lactamase-1 (NDM-1) is expressed by various members of Enterobacteriaceae as a defense mechanism to hydrolyze β-lactam antibiotics. Despite various studies showing the significance of active-site residues in the catalytic mechanism, there is a paucity of reports addressing the role of non-active-site residues in the structure and function of NDM-1. In this study, we investigated the significance of non-active-site residue Trp-93 in the structure and function of NDM-1. We cloned blaNDM-1 from an Enterobacter cloacae clinical strain (EC-15) and introduced the mutation of Trp-93 to Ala (yielding the Trp93Ala mutant) by PCR-based site-directed mutagenesis. Proteins were expressed and purified to homogeneity by affinity chromatography. The MICs of the Trp93Ala mutant were reduced 4- to 8-fold for ampicillin, cefotaxime, ceftazidime, cefoxitin, imipenem, and meropenem. The poor hydrolytic activity of the Trp93Ala mutant was also reflected by its reduced catalytic efficiency. The overall catalytic efficiency of the Trp93Ala mutant was reduced by 40 to 55% (the Km was reduced, while the kcat was similar to that of wild-type NDM-1 [wtNDM-1]). Heat-induced denaturation showed that the ΔGDo and Tm of Trp93Ala mutant were reduced by 1.8 kcal/mol and 4.8°C, respectively. Far-UV circular dichroism (CD) analysis showed that the α-helical content of the Trp93Ala mutant was reduced by 2.9%. The decrease in stability and catalytic efficiency of the Trp93Ala mutant was due to the loss of two hydrogen bonds with Ser-63 and Val-73 and hydrophobic interactions with Leu-65, Val-73, Gln-123, and Asp-124. The study provided insight into the role of non-active-site amino acid residues in the hydrolytic mechanism of NDM-1. PMID:26525789

  4. Physiological effects of anti-TRAP protein activity and tRNA(Trp) charging on trp operon expression in Bacillus subtilis.

    Science.gov (United States)

    Cruz-Vera, Luis R; Gong, Ming; Yanofsky, Charles

    2008-03-01

    The Bacillus subtilis anti-TRAP protein regulates the ability of the tryptophan-activated TRAP protein to bind to trp operon leader RNA and promote transcription termination. AT synthesis is regulated both transcriptionally and translationally by uncharged tRNA(Trp). In this study, we examined the roles of AT synthesis and tRNA(Trp) charging in mediating physiological responses to tryptophan starvation. Adding excess phenylalanine to wild-type cultures reduced the charged tRNA(Trp) level from 80% to 40%; the charged level decreased further, to 25%, in an AT-deficient mutant. Adding tryptophan with phenylalanine increased the charged tRNA(Trp) level, implying that phenylalanine, when added alone, reduces the availability of tryptophan for tRNA(Trp) charging. Changes in the charged tRNA(Trp) level observed during growth with added phenylalanine were associated with increased transcription of the genes of tryptophan metabolism. Nutritional shift experiments, from a medium containing tryptophan to a medium with phenylalanine and tyrosine, showed that wild-type cultures gradually reduced their charged tRNA(Trp) level. When this shift was performed with an AT-deficient mutant, the charged tRNA(Trp) level decreased even further. Growth rates for wild-type and mutant strains deficient in AT or TRAP or that overproduce AT were compared in various media. A lack of TRAP or overproduction of AT resulted in phenylalanine being required for growth. These findings reveal the importance of AT in maintaining a balance between the synthesis of tryptophan versus the synthesis of phenylalanine, with the level of charged tRNA(Trp) acting as the crucial signal regulating AT production. PMID:18178730

  5. C. elegans TRP channels.

    Science.gov (United States)

    Xiao, Rui; Xu, X Z Shawn

    2011-01-01

    Transient receptor potential (TRP) channels represent a superfamily of cation channels found in all eukaryotes. The C. elegans genome encodes seventeen TRP channels covering all of the seven TRP subfamilies. Genetic analyses in C. elegans have implicated TRP channels in a wide spectrum of behavioral and physiological processes, ranging from sensory transduction (e.g. chemosensation, touch sensation, proprioception and osmosensation) to fertilization, drug dependence, organelle biogenesis, apoptosis, gene expression, and neurotransmitter/hormone release. Many C. elegans TRP channels share similar activation and regulatory mechanisms with their vertebrate counterparts. Studies in C. elegans have also revealed some previously unrecognized functions and regulatory mechanisms of TRP channels. C. elegans represents an excellent genetic model organism for the study of function and regulation of TRP channels in vivo. PMID:21290304

  6. Catalytic activity of Au nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Janssens, Ton V.W.; Clausen, Bjerne;

    2007-01-01

    Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change with par......Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change...... with particle size. We find that the fraction of low-coordinated Au atoms scales approximately with the catalytic activity, suggesting that atoms on the corners and edges of Au nanoparticles are the active sites. This effect is explained using density functional calculations....

  7. TRP channel mediated neuronal activation and ablation in freely behaving zebrafish

    OpenAIRE

    Chen, Shijia; Chiu, Cindy N.; McArthur, Kimberly L.; Fetcho, Joseph R.; Prober, David A.

    2015-01-01

    The zebrafish (Danio rerio) is a useful vertebrate model system in which to study neural circuits and behavior, but tools to modulate neurons in freely behaving animals are limited. As poikilotherms that live in water, zebrafish are amenable to thermal and pharmacological perturbations. We exploit these properties by using transient receptor potential (TRP) channels to activate or ablate specific neuronal populations using the chemical and thermal agonists of heterologously expressed TRPV1, T...

  8. TRP channel mediated neuronal activation and ablation in freely behaving zebrafish.

    Science.gov (United States)

    Chen, Shijia; Chiu, Cindy N; McArthur, Kimberly L; Fetcho, Joseph R; Prober, David A

    2016-02-01

    The zebrafish (Danio rerio) is a useful vertebrate model system in which to study neural circuits and behavior, but tools to modulate neurons in freely behaving animals are limited. As poikilotherms that live in water, zebrafish are amenable to thermal and pharmacological perturbations. We exploit these properties by using transient receptor potential (TRP) channels to activate or ablate specific neuronal populations using the chemical and thermal agonists of heterologously expressed TRPV1, TRPM8 and TRPA1. PMID:26657556

  9. Position-Dependent Influence of the Three Trp Residues on the Membrane Activity of the Antimicrobial Peptide, Tritrpticin

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    Mauricio Arias

    2014-11-01

    Full Text Available Antimicrobial peptides (AMPs constitute promising candidates for the development of new antibiotics. Among the ever-expanding family of AMPs, tritrpticin has strong antimicrobial activity against a broad range of pathogens. This 13-residue peptide has an unusual amino acid sequence that is almost symmetrical and features three central Trp residues with two Arg residues near each end of the peptide. In this work, the role of the three sequential Trp residues in tritrpticin was studied in a systematic fashion by making a series of synthetic peptides with single-, double- and triple-Trp substitutions to Tyr or Ala. 1H NMR and fluorescence spectroscopy demonstrated the ability of all of the tritrpticin-analog peptides to interact with negatively-charged membranes. Consequently, most tritrpticin analogs exhibited the ability to permeabilize synthetic ePC:ePG (egg-yolk phosphatidylcholine (ePC, egg-yolk phosphatidylglycerol (ePG vesicles and live Escherichia coli bacteria. The membrane perturbation characteristics were highly dependent on the location of the Trp residue substitution, with Trp6 being the most important residue and Trp8 the least. The membrane permeabilization activity of the peptides in synthetic and biological membranes was directly correlated with the antimicrobial potency of the peptides against E. coli. These results contribute to the understanding of the role of each of the three Trp residues to the antimicrobial activity of tritrpticin.

  10. Thermodynamics of tryptophan-mediated activation of the trp RNA-binding attenuation protein.

    Science.gov (United States)

    McElroy, Craig A; Manfredo, Amanda; Gollnick, Paul; Foster, Mark P

    2006-06-27

    The trp RNA-binding attenuation protein (TRAP) functions in many bacilli to control the expression of the tryptophan biosynthesis genes. Transcription of the trp operon is controlled by TRAP through an attenuation mechanism, in which competition between two alternative secondary-structural elements in the 5' leader sequence of the nascent mRNA is influenced by tryptophan-dependent binding of TRAP to the RNA. Previously, NMR studies of the undecamer (11-mer) suggested that tryptophan-dependent control of RNA binding by TRAP is accomplished through ligand-induced changes in protein dynamics. We now present further insights into this ligand-coupled event from hydrogen/deuterium (H/D) exchange analysis, differential scanning calorimetry (DSC), and isothermal titration calorimetry (ITC). Scanning calorimetry showed tryptophan dissociation to be independent of global protein unfolding, while analysis of the temperature dependence of the binding enthalpy by ITC revealed a negative heat capacity change larger than expected from surface burial, a hallmark of binding-coupled processes. Analysis of this excess heat capacity change using parameters derived from protein folding studies corresponds to the ordering of 17-24 residues per monomer of TRAP upon tryptophan binding. This result is in agreement with qualitative analysis of residue-specific broadening observed in TROSY NMR spectra of the 91 kDa oligomer. Implications for the mechanism of ligand-mediated TRAP activation through a shift in a preexisting conformational equilibrium and an induced-fit conformational change are discussed. PMID:16784236

  11. Computational Introduction of Catalytic Activity into Proteins.

    Science.gov (United States)

    Bertolani, Steve J; Carlin, Dylan Alexander; Siegel, Justin B

    2016-01-01

    Recently, there have been several successful cases of introducing catalytic activity into proteins. One method that has been used successfully to achieve this is the theozyme placement and enzyme design algorithms implemented in Rosetta Molecular Modeling Suite. Here, we illustrate how to use this software to recapitulate the placement of catalytic residues and ligand into a protein using a theozyme, protein scaffold, and catalytic constraints as input. PMID:27094294

  12. Alphavirus replicon particles expressing TRP-2 provide potent therapeutic effect on melanoma through activation of humoral and cellular immunity.

    Directory of Open Access Journals (Sweden)

    Francesca Avogadri

    Full Text Available BACKGROUND: Malignant melanoma is the deadliest form of skin cancer and is refractory to conventional chemotherapy and radiotherapy. Therefore alternative approaches to treat this disease, such as immunotherapy, are needed. Melanoma vaccine design has mainly focused on targeting CD8+ T cells. Activation of effector CD8+ T cells has been achieved in patients, but provided limited clinical benefit, due to immune-escape mechanisms established by advanced tumors. We have previously shown that alphavirus-based virus-like replicon particles (VRP simultaneously activate strong cellular and humoral immunity against the weakly immunogenic melanoma differentiation antigen (MDA tyrosinase. Here we further investigate the antitumor effect and the immune mechanisms of VRP encoding different MDAs. METHODOLOGY/PRINCIPAL FINDINGS: VRP encoding different MDAs were screened for their ability to prevent the growth of the B16 mouse transplantable melanoma. The immunologic mechanisms of efficacy were investigated for the most effective vaccine identified, focusing on CD8+ T cells and humoral responses. To this end, ex vivo immune assays and transgenic mice lacking specific immune effector functions were used. The studies identified a potent therapeutic VRP vaccine, encoding tyrosinase related protein 2 (TRP-2, which provided a durable anti-tumor effect. The efficacy of VRP-TRP2 relies on a novel immune mechanism of action requiring the activation of both IgG and CD8+ T cell effector responses, and depends on signaling through activating Fcγ receptors. CONCLUSIONS/SIGNIFICANCE: This study identifies a VRP-based vaccine able to elicit humoral immunity against TRP-2, which plays a role in melanoma immunotherapy and synergizes with tumor-specific CD8+ T cell responses. These findings will aid in the rational design of future immunotherapy clinical trials.

  13. Phytochemicals from Ruta graveolens Activate TAS2R Bitter Taste Receptors and TRP Channels Involved in Gustation and Nociception.

    Science.gov (United States)

    Mancuso, Giuseppe; Borgonovo, Gigliola; Scaglioni, Leonardo; Bassoli, Angela

    2015-01-01

    Ruta graveolens (rue) is a spontaneous plant in the Mediterranean area with a strong aroma and a very intense bitter taste, used in gastronomy and in folk medicine. From the leaves, stems and fruits of rue, we isolated rutin, rutamarin, three furanocoumarins, two quinolinic alkaloids, a dicoumarin and two long chain ketones. Bitter taste and chemesthetic properties have been evaluated by in vitro assays with twenty receptors of the TAS2R family and four TRP ion channels involved in gustation and nociception. Among the alkaloids, skimmianine was active as a specific agonist of T2R14, whereas kokusaginin did not activate any of the tested receptors. The furanocoumarins activates TAS2R10, 14, and 49 with different degrees of selectivity, as well as the TRPA1 somatosensory ion channel. Rutamarin is an agonist of TRPM5 and TRPV1 and a strong antagonist of TRPM8 ion channels. PMID:26501253

  14. Phytochemicals from Ruta graveolens Activate TAS2R Bitter Taste Receptors and TRP Channels Involved in Gustation and Nociception.

    Science.gov (United States)

    Mancuso, Giuseppe; Borgonovo, Gigliola; Scaglioni, Leonardo; Bassoli, Angela

    2015-10-16

    Ruta graveolens (rue) is a spontaneous plant in the Mediterranean area with a strong aroma and a very intense bitter taste, used in gastronomy and in folk medicine. From the leaves, stems and fruits of rue, we isolated rutin, rutamarin, three furanocoumarins, two quinolinic alkaloids, a dicoumarin and two long chain ketones. Bitter taste and chemesthetic properties have been evaluated by in vitro assays with twenty receptors of the TAS2R family and four TRP ion channels involved in gustation and nociception. Among the alkaloids, skimmianine was active as a specific agonist of T2R14, whereas kokusaginin did not activate any of the tested receptors. The furanocoumarins activates TAS2R10, 14, and 49 with different degrees of selectivity, as well as the TRPA1 somatosensory ion channel. Rutamarin is an agonist of TRPM5 and TRPV1 and a strong antagonist of TRPM8 ion channels.

  15. Phytochemicals from Ruta graveolens Activate TAS2R Bitter Taste Receptors and TRP Channels Involved in Gustation and Nociception

    Directory of Open Access Journals (Sweden)

    Giuseppe Mancuso

    2015-10-01

    Full Text Available Ruta graveolens (rue is a spontaneous plant in the Mediterranean area with a strong aroma and a very intense bitter taste, used in gastronomy and in folk medicine. From the leaves, stems and fruits of rue, we isolated rutin, rutamarin, three furanocoumarins, two quinolinic alkaloids, a dicoumarin and two long chain ketones. Bitter taste and chemesthetic properties have been evaluated by in vitro assays with twenty receptors of the TAS2R family and four TRP ion channels involved in gustation and nociception. Among the alkaloids, skimmianine was active as a specific agonist of T2R14, whereas kokusaginin did not activate any of the tested receptors. The furanocoumarins activates TAS2R10, 14, and 49 with different degrees of selectivity, as well as the TRPA1 somatosensory ion channel. Rutamarin is an agonist of TRPM5 and TRPV1 and a strong antagonist of TRPM8 ion channels.

  16. Heparin enhances the catalytic activity of des-ETW-thrombin.

    Science.gov (United States)

    Goodwin, C A; Deadman, J J; Le Bonniec, B F; Elgendy, S; Kakkar, V V; Scully, M F

    1996-04-01

    The thrombin mutant, des-ETW-thrombin, lacking Glu(146), Thr(147), and Trp(148) within a unique insertion loop located at the extreme end of the primary specificity pocket, has been shown previously to exhibit reduced catalytic activity with respect to macromolecular and synthetic thrombin substrates and reduced or enhanced susceptibility to inhibition. Investigation of the hydrolysis of peptidyl p-nitroanilide substrates by des-ETW-thrombin showed increased activity in the presence of heparin and other sulphated glycosaminoglycans. No effect was observed upon the activity of wild-type thrombin. Heparin was found to decrease the K(m) for cleavage of four thrombin-specific substrates by des-ETW-thrombin by 3-4-fold. Similarly, pentosan polysulphate (PPS) decreased the K(m) with these substrates by 8-10-fold. Heparin also increased the rate of inhibition of des-ETW-thrombin by antithrombin III and D-phenylalanyl-prolyl-arginylchloromethane (PPACK). The inhibition of des-ETW-thrombin by a number of thrombin-specific peptide boronic acids also showed significant reduction in the final K(i) in the presence of heparin, due to reduction in the off-rate. A peptide analogue of a sequence of hirudin which binds thrombin tightly to exosite I (fibrinogen recognition site) potentiated the activity of des-ETW-thrombin against peptide p-nitroanilide substrates in a manner similar to heparin. The K(i) for the inhibition of des-ETW-thrombin by p-aminobenzamidine was decreased by these ligands from 9.7 mM to 7.5 mM, 5.1 mM, and 2.5 mM in the presence of heparin, hirudin peptide and PPS respectively, suggesting the increased catalytic activity is due to enhanced access to the primary specificity pocket. The positive influence of these ligands on des-ETW-thrombin was reversed in the presence of ATP or ADP; the latter has previously been shown to inhibit thrombin activity by blocking initial interaction with fibrinogen at exosite 1. Because the effect of heparin and PPS is similar to

  17. Preparation and Catalytic Oxidation Activity on 2-mercaptoethanol of a Novel Catalytic Cellulose Fibres

    Institute of Scientific and Technical Information of China (English)

    YAO Yu-yuan; LI Ying-jie; CHEN Wen-xing; Lü Wang-yang; Lü Su-fang; XU Min-hong; LIU Fan

    2007-01-01

    Cobalt tetra(N-carbonylacylic) aminophthalocyanine was supported on cellulose fibres by graft reaction to obtain a novel polymer catalyst, catalytic cellulose fibres (CCF),and the optimal supporting conditions were pH = 6, 80℃,t = 120 min. The catalytic oxidation activity of CCF towards oxidation of 2-mereaptoethanol (MEA) in aqueous solution was investigated. The experimental results demonstrated that CCF had good catalytic oxidation activity on MEA at room temperature, causing no secondary pollution and remaining efficient for the repetitive tests with no obvious decrease of catalytic activity.

  18. Reforming of methane in tubes with a catalytic active wall

    International Nuclear Information System (INIS)

    The heterogeneous steam reforming process in tubes with catalytic active inner surface is studied. The purpose of this ivestigation is to find a method of predicting the reaction rate of the catalytic conversion of methane by steam. The dependency of the reaction rate upon the temperature, pressure, gas composition, Reynolds number, geometrical sizes of tubes and catalytic behaviour of the catalytic active inner wall of these tubes has been examined. It was found that the reaction rate mainly depends on the temperature. The reaction rate is limited by the catalytic behaviour and the heat resisting properties of the materials used. (author)

  19. A temperature-sensitive trpS mutation interferes with trp RNA-binding attenuation protein (TRAP) regulation of trp gene expression in Bacillus subtilis.

    OpenAIRE

    Lee, A I; Sarsero, J P; Yanofsky, C

    1996-01-01

    In Bacillus subtilis, the tryptophan-activated trp RNA-binding attenuation protein (TRAP) regulates expression of the seven tryptophan biosynthetic genes by binding to specific repeat sequences in the transcripts of the trp operon and of the folate operon, the operon containing trpG. Steinberg observed that strains containing a temperature-sensitive mutant form of tryptophanyl-tRNA synthetase, encoded by the trpS1 allele, produced elevated levels of the tryptophan pathway enzymes, when grown ...

  20. Impaired 8-Hydroxyguanine Repair Activity of MUTYH Variant p.Arg109Trp Found in a Japanese Patient with Early-Onset Colorectal Cancer

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    Kazuya Shinmura

    2014-01-01

    Full Text Available Purpose. The biallelic inactivation of the 8-hydroxyguanine repair gene MUTYH leads to MUTYH-associated polyposis (MAP, which is characterized by colorectal multiple polyps and carcinoma(s. However, only limited information regarding MAP in the Japanese population is presently available. Since early-onset colorectal cancer (CRC is a characteristic of MAP and might be caused by the inactivation of another 8-hydroxyguanine repair gene, OGG1, we investigated whether germline MUTYH and OGG1 mutations are involved in early-onset CRC in Japanese patients. Methods. Thirty-four Japanese patients with early-onset CRC were examined for germline MUTYH and OGG1 mutations using sequencing. Results. Biallelic pathogenic mutations were not found in any of the patients; however, a heterozygous p.Arg19*  MUTYH variant and a heterozygous p.Arg109Trp MUTYH variant were detected in one patient each. The p.Arg19* and p.Arg109Trp corresponded to p.Arg5* and p.Arg81Trp, respectively, in the type 2 nuclear-form protein. The defective DNA repair activity of p.Arg5* is apparent, while that of p.Arg81Trp has been demonstrated using DNA cleavage and supF forward mutation assays. Conclusion. These results suggest that biallelic MUTYH or OGG1 pathogenic mutations are rare in Japanese patients with early-onset CRC; however, the p.Arg19* and p.Arg109Trp MUTYH variants are associated with functional impairments.

  1. REPLACEMENT OF TRYPTOPHAN RESIDUES IN HALOALKANE DEHALOGENASE REDUCES HALIDE BINDING AND CATALYTIC ACTIVITY

    NARCIS (Netherlands)

    KENNES, C; PRIES, F; KROOSHOF, GH; BOKMA, E; Kingma, Jacob; JANSSEN, DB

    1995-01-01

    Haloalkane dehalogenase catalyzes the hydrolytic cleavage of carbon-halogen bonds in short-chain haloalkanes. Two tryptophan residues of the enzyme (Trp125 and Trp175) form a halide-binding site in the active-site cavity, and were proposed to play a role in catalysis. The function of these residues

  2. Evolution of Thermal Response Properties in a Cold-Activated TRP Channel

    OpenAIRE

    Myers, Benjamin R.; Sigal, Yaron M.; David Julius

    2009-01-01

    Animals sense changes in ambient temperature irrespective of whether core body temperature is internally maintained (homeotherms) or subject to environmental variation (poikilotherms). Here we show that a cold-sensitive ion channel, TRPM8, displays dramatically different thermal activation ranges in frogs versus mammals or birds, consistent with variations in these species' cutaneous and core body temperatures. Thus, somatosensory receptors are not static through evolution, but show functiona...

  3. Evolution of thermal response properties in a cold-activated TRP channel.

    Science.gov (United States)

    Myers, Benjamin R; Sigal, Yaron M; Julius, David

    2009-01-01

    Animals sense changes in ambient temperature irrespective of whether core body temperature is internally maintained (homeotherms) or subject to environmental variation (poikilotherms). Here we show that a cold-sensitive ion channel, TRPM8, displays dramatically different thermal activation ranges in frogs versus mammals or birds, consistent with variations in these species' cutaneous and core body temperatures. Thus, somatosensory receptors are not static through evolution, but show functional diversity reflecting the characteristics of an organism's ecological niche. PMID:19492038

  4. Evolution of thermal response properties in a cold-activated TRP channel.

    Directory of Open Access Journals (Sweden)

    Benjamin R Myers

    Full Text Available Animals sense changes in ambient temperature irrespective of whether core body temperature is internally maintained (homeotherms or subject to environmental variation (poikilotherms. Here we show that a cold-sensitive ion channel, TRPM8, displays dramatically different thermal activation ranges in frogs versus mammals or birds, consistent with variations in these species' cutaneous and core body temperatures. Thus, somatosensory receptors are not static through evolution, but show functional diversity reflecting the characteristics of an organism's ecological niche.

  5. Akt activation synergizes with Trp53 loss in oral epithelium to produce a novel mouse model for head and neck squamous cell carcinoma

    OpenAIRE

    Moral, Marta; Segrelles, Carmen; Lara, M. Fernanda; Martinez-Cruz, Ana Belen; Lorz, Corina; Santos, Mirentxu; Garcia-Escudero, Ramon; Lu, Jerry; Kiguchi, Kaoru; Buitrago, Agueda; Costa, Clotilde; Saiz, Cristina; Rodriguez-Peralto, Jose L; Martinez-Tello, Francisco J; Rodriguez-Pinilla, Maria

    2009-01-01

    Head and neck squamous cell carcinoma is a common human neoplasia with poor prognosis and survival that frequently display Akt overactivation. Here we show that mice displaying constitutive Akt activity (myrAkt) in combination with Trp53 loss in stratified epithelia develop oral cavity tumors that phenocopy human HNSCC. The myrAkt mice develop oral lesions making it a possible model of human oral dysplasia. The malignant conversion of these lesions, which is hampered due to the induction of p...

  6. Synthesis and Catalytic Activity of Two New Cyclic Tetraaza Ligands

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    Burkhard König

    2003-05-01

    Full Text Available Two new chiral cyclic tetraaza ligands were synthesized and characterized. Their catalytic activity was tested in the asymmetric addition of diethylzinc to benzaldehyde. The expected secondary alcohol was obtained in moderate yields, but with very low enantioselectivity.

  7. Insights on TRP Channels from In Vivo Studies in Drosophila

    Science.gov (United States)

    Minke, Baruch; Parnas, Moshe

    2007-01-01

    Transient receptor potential (TRP) channels mediate responses in a large variety of signaling mechanisms. Most studies on mammalian TRP channels rely on heterologous expression, but their relevance to in vivo tissues is not entirely clear. In contrast, Drosophila TRP and TRP-like (TRPL) channels allow direct analyses of in vivo function. In Drosophila photoreceptors, activation of TRP and TRPL is mediated via the phosphoinositide cascade, with both Ca2+ and diacylglycerol (DAG) essential for generating the light response. In tissue culture cells, TRPL channels are constitutively active, and lipid second messengers greatly facilitate this activity. Inhibition of phospholipase C (PLC) completely blocks lipid activation of TRPL, suggesting that lipid activation is mediated via PLC. In vivo studies in mutant Drosophila also reveal an acute requirement for lipid-producing enzyme, which may regulate PLC activity. Thus, PLC and its downstream second messengers, Ca2+ and DAG, constitute critical mediators of TRP/TRPL gating in vivo. PMID:16460287

  8. Catalytic activities of zeolite compounds for decomposing aqueous ozone.

    Science.gov (United States)

    Kusuda, Ai; Kitayama, Mikito; Ohta, Yoshio

    2013-12-01

    The advanced oxidation process (AOP), chemical oxidation using aqueous ozone in the presence of appropriate catalysts to generate highly reactive oxygen species, offers an attractive option for removing poorly biodegradable pollutants. Using the commercial zeolite powders with various Si/Al ratios and crystal structures, their catalytic activities for decomposing aqueous ozone were evaluated by continuously flowing ozone to water containing the zeolite powders. The hydrophilic zeolites (low Si/Al ratio) with alkali cations in the crystal structures were found to possess high catalytic activity for decomposing aqueous ozone. The hydrophobic zeolite compounds (high Si/Al ratio) were found to absorb ozone very well, but to have no catalytic activity for decomposing aqueous ozone. Their catalytic activities were also evaluated by using the fixed bed column method. When alkali cations were removed by acid rinsing or substituted by alkali-earth cations, the catalytic activities was significantly deteriorated. These results suggest that the metal cations on the crystal surface of the hydrophilic zeolite would play a key role for catalytic activity for decomposing aqueous ozone.

  9. TRP channels in disease.

    Science.gov (United States)

    Jordt, S E; Ehrlich, B E

    2007-01-01

    The transient receptor potential (TRP) channels are a large family of proteins with six main subfamilies termed the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin) groups. The sheer number of different TRPs with distinct functions supports the statement that these channels are involved in a wide range of processes ranging from sensing of thermal and chemical signals to reloading intracellular stores after responding to an extracellular stimulus. Mutations in TRPs are linked to pathophysiology and specific diseases. An understanding of the role of TRPs in normal physiology is just beginning; the progression from mutations in TRPs to pathophysiology and disease will follow. In this review, we focus on two distinct aspects of TRP channel physiology, the role of TRP channels in intracellular Ca2+ homeostasis, and their role in the transduction of painful stimuli in sensory neurons. PMID:18193640

  10. Augmented activity of the pelvic nerve afferent mediated by TRP channels in dextran sulfate sodium (DSS)-induced colitis of rats.

    Science.gov (United States)

    Makimura, Yukitoshi; Ito, Koichi; Kuwahara, Masayoshi; Tsubone, Hirokazu

    2012-08-01

    Enteritis has been recognized as a major symptom in domestic animals and human patients suffering from feed and food poisonings. The aim of the present study was to clarify the excitatory mechanism of the pelvic nerve afferent which may influence the occurrence of enteritis in response to nociceptive chemical stimuli of the colon in normal and abnormal rats with colitis induced by dextran sulfate sodium (DSS). The pelvic nerve afferent activity was markedly increased by colonic instillation of solution (0.5 ml) of acetic acid (5-25%) and capsaicin (100 μg/ml). The nerve activity was augmented by colonic instillation of capsaicin to a greater extent in rats with DSS-induced colitis than in normal control rats. This augmented activity by capsaicin was more prominent at one day (DSS-1) than at 8 day (DSS-8) after the administration of DSS. The increased nerve activity caused by capsaicin in DSS-1 and DSS-8 was significantly inhibited by pretreatment with ruthenium red, which is a nonselective inhibitor of TRP channels of unmyelinated C-fibers (nociceptors). In conclusion, it was elucidated that the nociceptive function of the pelvic nerve was largely elevated at one day after DSS-induced colitis and such increased function was mostly mediated by TRP channels.

  11. Psychiatric Disorders and TRP Channels: Focus on Psychotropic Drugs

    OpenAIRE

    Nazıroğlu, Mustafa; Demirdaş, Arif

    2015-01-01

    Psychiatric and neurological disorders are mostly associated with the changes in neural calcium ion signaling pathways required for activity-triggered cellular events. One calcium channel family is the TRP cation channel family, which contains seven subfamilies. Results of recent papers have discovered that calcium ion influx through TRP channels is important. We discuss the latest advances in calcium ion influx through TRP channels in the etiology of psychiatric disorders. Activation of TRPC...

  12. Anti-tumor Immunity Elicited by Adenovirus Encoding AdhTrp2 or AdmTrp2 without Vitiligo

    Institute of Scientific and Technical Information of China (English)

    Hongju LIU; Xianzhi XIONG; Zuoya LI; Jianbao XIN; Xiaonan TAO; Yu HU

    2008-01-01

    To compare the difference in tumor immunity and autoimmunity elicited by adenovirus (Ad) encoding human or murine tyrosinase-related protein 2 (AdhTRP2 or AdmTRP2), and to find the most effective way to induce immunity by AdhTRP2 or AdmTRP2, C57BL/6 mice were im-munized with AdhTRP2 or AdmTRP2 intramuscularly at different doses of 105, 106, 107 and 108 separately (10 mice for each dose). Two weeks after the immunization, in vivo CTL assay and in- tracellular staining (ICS) of IFN-γ were carried out to analyze the dose-effect relationship. Tumor growth and vitiligo (as an sign of autoimmunity) were observed until 3 months after challenge with 105 B I6F10 tumor cells. The results showed that Ad encoding AdmTrp2 induced weak tumor im- mune response. Similar immunization with AdhTrp-2 elicited stronger protective immunity. CTL activity and IFN-γ-produced CD8+T cells were directly proportional to dose of AdhTrp2 or AdmTrp2. Moreover, AdhTrp2 group showed tumor rejection in 100% of challenged mice till the end of 3rd month while 60% of mice immunized with AdmTrp2 were protected against tumor. In the whole process of this experiment, no vitiligo was observed in mice immunized either with AdhTrp2 or AdmTrp2. It is concluded that anti-melanoma responses induced by genetic vaccina- tion expressing xenoantigens breaks immune tolerance effectively and is able to elicit strong anti-gen-specific cytotoxic T cell response without vitiligo.

  13. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....

  14. Size-dependent catalytic activity of supported metal clusters

    Science.gov (United States)

    Xu, Z.; Xiao, F.-S.; Purnell, S. K.; Alexeev, O.; Kawi, S.; Deutsch, S. E.; Gates, B. C.

    1994-11-01

    BECAUSE catalysis by metals is a surface phenomenon, many technological catalysts contain small (typically nanometre-sized) supported metal particles with a large fraction of the atoms exposed1. Many reactions, such as hydrocarbon hydrogenations, are structure-insensitive, proceeding at approximately the same rate on metal particles of various sizes provided that they are larger than about 1 nm and show bulk-like metallic behaviour1. But it is not known whether the catalytic properties of metal particles become size-dependent as the particles become so small that they are no longer metallic in character. Here we investigate the catalytic behaviour of precisely defined clusters of just four and six iridium atoms on solid supports. We find that the Ir4 and Ir6 clusters differ in catalytic activity both from each other and from metallic Ir particles. This raises the possibility of tailoring the catalytic behaviour of metal clusters by controlling the cluster size.

  15. Targeting TRP channels for novel migraine therapeutics.

    Science.gov (United States)

    Dussor, Gregory; Yan, J; Xie, Jennifer Y; Ossipov, Michael H; Dodick, David W; Porreca, Frank

    2014-11-19

    Migraine is increasingly understood to be a disorder of the brain. In susceptible individuals, a variety of "triggers" may influence altered central excitability, resulting in the activation and sensitization of trigeminal nociceptive afferents surrounding blood vessels (i.e., the trigeminovascular system), leading to migraine pain. Transient receptor potential (TRP) channels are expressed in a subset of dural afferents, including those containing calcitonin gene related peptide (CGRP). Activation of TRP channels promotes excitation of nociceptive afferent fibers and potentially lead to pain. In addition to pain, allodynia to mechanical and cold stimuli can result from sensitization of both peripheral afferents and of central pain pathways. TRP channels respond to a variety of endogenous conditions including chemical mediators and low pH. These channels can be activated by exogenous stimuli including a wide range of chemical and environmental irritants, some of which have been demonstrated to trigger migraine in humans. Activation of TRP channels can elicit CGRP release, and blocking the effects of CGRP through receptor antagonism or antibody strategies has been demonstrated to be effective in the treatment of migraine. Identification of approaches that can prevent activation of TRP channels provides an additional novel strategy for discovery of migraine therapeutics.

  16. Trends in the Catalytic CO Oxidation Activity of Nanoparticles

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Falsig, Hanne; Larsen, Britt Hvolbæk;

    2008-01-01

    Going for gold: Density functional calculations show how gold nanoparticles are more active catalysts for CO oxidation than other metal nanoparticles. The high catalytic activity of nanosized gold clusters at low temperature is found to be related to the ability of low-coordinate metal atoms...

  17. Post-Translational Modifications of TRP Channels

    Directory of Open Access Journals (Sweden)

    Olaf Voolstra

    2014-04-01

    Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

  18. Preparation of Pt-Ru hydrophobic catalysts and catalytic activities for liquid phase catalytic exchange reaction

    International Nuclear Information System (INIS)

    Pt/C and Pt-Ru/C catalysts with different ratios of Pt to Ru were synthesized, using ethylene glycol as both the dispersant and reducing agent at 1-2 MPa by microwave-assisted method. The catalysts were characterized by XRD, TEM and XPS. The mean particle sizes of the Pt/C and Pt-Ru/C catalysts were 1.9-2.0 nm. Pt and Ru existed as Pt(0), Pt(II), Pt(IV), Ru(0) and Ru(IV) for Pt-Ru/C catalysts, respectively. The face-centered cubic structure of the active mental particles would be changed upon the addition of Ru gradually. Then polytetrafluoroethylene and carbon-supported Pt and Pt-Ru catalysts were supported on foamed nickel to obtain hydrophobic catalysts. The catalytic activity was increased for liquid phase catalytic exchange (LPCE) when uniform Pt based hydrophobic catalysts was mixed into appropriate Ru. Hydrogen isotope exchange reaction occurs between hydration layer(H2O)nH+(ads)(n≥2) and D atoms due to intact water molecules being on Pt surface for LPCE. Water molecules have a tendency to dissociate to OH(ads) and H(ads) on metal Ru surface, and there is the other reaction path for Pt-Ru binary catalysts, which is probably the main reason of the increase of the catalytic activity of the hydrophobic Pt-Ru catalyst. (authors)

  19. Synthesis, characterization and catalytic activity of chromium substituted cobalt ferrospinels

    International Nuclear Information System (INIS)

    Chromium substituted cobalt ferrospinels were prepared by soft citrate gel method. The synthesized material was characterized by various physico-chemical methods. All the samples showed a single-phase cubic structure. Lattice constant varies from 8.389 to 8.323 A. Transmission electron microscopic study indicated the nanostructure of the catalysts while homogenous grain distribution was presented by scanning electron microscopic studies. The catalytic activity of the samples was investigated towards acetylation of phenols. The presence of active centers on the surface of the material was confirmed through pyridine adsorption studies. The surface acidity of the catalyst is responsible for better catalytic performance. The material was found to serve as a promising catalyst for acylation and benzoylation of phenols under solvent free condition. These catalysts are ∼100% selective towards o-acylation of phenols, a promising reaction for perfumery intermediates. The catalysts were seen to be reusable without any further treatment. Catalytic activities of cobalt, chromium and iron oxides were also investigated for comparison. The cobalt ferrospinel was found to have better catalytic activity as compared to the Cr-substituted ferrospinels and the pure oxides. Cobalt ferrite catalyst offers high yields in a short reaction time under solvent-free conditions.

  20. Synthesis, characterization and catalytic activity of chromium substituted cobalt ferrospinels

    Energy Technology Data Exchange (ETDEWEB)

    Hankare, P.P., E-mail: p_hankarep@rediffmail.com [Department of Chemistry, Shivaji University, Kolhapur, Maharashtra, 416 004 (India); Sankpal, U.B., E-mail: sankpalumesh@gmail.com [Department of Chemistry, Shivaji University, Kolhapur, Maharashtra, 416 004 (India); Patil, R.P. [Department of Chemistry, Shivaji University, Kolhapur, Maharashtra, 416 004 (India); Lokhande, P.D. [Department of Chemistry, University of Pune, Pune, Maharashtra, 411 007 (India); Sasikala, R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2011-02-15

    Chromium substituted cobalt ferrospinels were prepared by soft citrate gel method. The synthesized material was characterized by various physico-chemical methods. All the samples showed a single-phase cubic structure. Lattice constant varies from 8.389 to 8.323 A. Transmission electron microscopic study indicated the nanostructure of the catalysts while homogenous grain distribution was presented by scanning electron microscopic studies. The catalytic activity of the samples was investigated towards acetylation of phenols. The presence of active centers on the surface of the material was confirmed through pyridine adsorption studies. The surface acidity of the catalyst is responsible for better catalytic performance. The material was found to serve as a promising catalyst for acylation and benzoylation of phenols under solvent free condition. These catalysts are {approx}100% selective towards o-acylation of phenols, a promising reaction for perfumery intermediates. The catalysts were seen to be reusable without any further treatment. Catalytic activities of cobalt, chromium and iron oxides were also investigated for comparison. The cobalt ferrospinel was found to have better catalytic activity as compared to the Cr-substituted ferrospinels and the pure oxides. Cobalt ferrite catalyst offers high yields in a short reaction time under solvent-free conditions.

  1. Design parameters for measurements of local catalytic activity on surfaces

    DEFF Research Database (Denmark)

    Johansson, Martin; Johannessen, Tue; Jørgensen, Jan Hoffmann;

    2006-01-01

    Computational fluid dynamics in combination with experiments is used to characterize a gas sampling device for measurements of the local catalytic activity on surfaces. The device basically consists of a quartz capillary mounted concentrically inside an aluminum tube. Reactant gas is blown toward...

  2. Pair interaction of catalytically active colloids: from assembly to escape

    Science.gov (United States)

    Sharifi-Mood, Nima; Mozaffari, Ali; Córdova-Figueroa, Ubaldo M.

    2016-07-01

    The dynamics and pair trajectory of two self-propelled colloids are reported. The autonomous motions of the colloids are due to a catalytic chemical reaction taking place asymmetrically on their surfaces that generates a concentration gradient of interactive solutes around the particles and actuate particle propulsion. We consider two spherical particles with symmetric catalytic caps extending over the local polar angles $\\theta^1_{cap}$ and $\\theta^2_{cap}$ from the centers of active sectors in an otherwise quiescent fluid. A combined analytical-numerical technique was developed to solve the coupled mass transfer equation and the hydrodynamics in the Stokes flow regime. The ensuing pair trajectory of the colloids is controlled by the reacting coverages $\\theta^j_{cap}$ and their initial relative orientation with respect to each other. Our analysis indicates two possible scenarios for pair trajectories of catalytic self-propelled particles: either the particles approach, come into contact and assemble or they interact and move away from each other (escape). For arbitrary motions of the colloids, it is found that the direction of particle rotations is the key factor in determining the escape or assembly scenario. Based on the analysis, a phase diagram is sketched for the pair trajectory of the catalytically active particles as a function of active coverages and their initial relative orientations. We believe this study has important implications in elucidation of collective behaviors of auotophoretically self-propelled colloids.

  3. Trp aporepressor production is controlled by autogenous regulation and inefficient translation.

    OpenAIRE

    Kelley, R.L.; Yanofsky, C

    1982-01-01

    We constructed a trpR-lacZ gene fusion that specifies a hybrid protein that has full beta-galactosidase activity. The gene fusion was associated with the unaltered trpR transcription and translation control region; thus, hybrid beta-galactosidase production was an indicator of expression of the trp aporepressor (trpR) operon. To facilitate in vivo expression studies, a DNA segment containing the trpR-lacZ gene fusion and the trpR controlling region was transferred to bacteriophage lambda and ...

  4. Thrombomodulin Binding Selects the Catalytically Active Form of Thrombin.

    Science.gov (United States)

    Handley, Lindsey D; Treuheit, Nicholas A; Venkatesh, Varun J; Komives, Elizabeth A

    2015-11-01

    Human α-thrombin is a serine protease with dual functions. Thrombin acts as a procoagulant, cleaving fibrinogen to make the fibrin clot, but when bound to thrombomodulin (TM), it acts as an anticoagulant, cleaving protein C. A minimal TM fragment consisting of the fourth, fifth, and most of the sixth EGF-like domain (TM456m) that has been prepared has much improved solubility, thrombin binding capacity, and anticoagulant activity versus those of previous TM456 constructs. In this work, we compare backbone amide exchange of human α-thrombin in three states: apo, D-Phe-Pro-Arg-chloromethylketone (PPACK)-bound, and TM456m-bound. Beyond causing a decreased level of amide exchange at their binding sites, TM and PPACK both cause a decreased level of amide exchange in other regions including the γ-loop and the adjacent N-terminus of the heavy chain. The decreased level of amide exchange in the N-terminus of the heavy chain is consistent with the historic model of activation of serine proteases, which involves insertion of this region into the β-barrel promoting the correct conformation of the catalytic residues. Contrary to crystal structures of thrombin, hydrogen-deuterium exchange mass spectrometry results suggest that the conformation of apo-thrombin does not yet have the N-terminus of the heavy chain properly inserted for optimal catalytic activity, and that binding of TM allosterically promotes the catalytically active conformation. PMID:26468766

  5. TRP channels in skin: from physiological implications to clinical significances.

    Science.gov (United States)

    Ho, Ji-Chen; Lee, Chih-Hung

    2015-01-01

    TRP channels are expressed in various cells in skin. As an organ system to border the host and environment, many nonneuronal cells, including epidermal keratinocytes and melanocytes, express several TRP channels functionally distinct from sensory processing. TRPV1 and TRPV3 in keratinocytes of the epidermis and hair apparatus inhibit proliferation, induce terminal differentiation, induce apoptosis, and promote inflammation. Activation of TRPV4, 6, and TRPA1 promotes regeneration of the severed skin barriers. TRPA1 also enhances responses in contact hypersensitivity. TRPCs in keratinocytes regulate epidermal differentiation. In human diseases with pertubered epidermal differentiation, the expression of TRPCs are altered. TRPMs, which contribute to melanin production in melanocytes, serve as significant prognosis markers in patients with metastatic melanoma. In summary, not only act in sensory processing, TRP channels also contribute to epidermal differentiation, proliferation, barrier integration, skin regeneration, and immune responses. In diseases with aberrant TRP channels, TRP channels might be good therapeutic targets. PMID:27493510

  6. Guiding catalytically active particles with chemically patterned surfaces

    CERN Document Server

    Uspal, W E; Dietrich, S; Tasinkevych, M

    2016-01-01

    Catalytically active Janus particles suspended in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate "point-particle" approach, that by chemically patterning a planar substrate one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either "dock" at the chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governi...

  7. The trp RNA-binding attenuation protein of Bacillus subtilis regulates translation of the tryptophan transport gene trpP (yhaG) by blocking ribosome binding.

    Science.gov (United States)

    Yakhnin, Helen; Zhang, Hong; Yakhnin, Alexander V; Babitzke, Paul

    2004-01-01

    Expression of the Bacillus subtilis tryptophan biosynthetic genes (trpEDCFBA and pabA [trpG]) is regulated in response to tryptophan by TRAP, the trp RNA-binding attenuation protein. TRAP-mediated regulation of the tryptophan biosynthetic genes includes a transcription attenuation and two distinct translation control mechanisms. TRAP also regulates translation of trpP (yhaG), a single-gene operon that encodes a putative tryptophan transporter. Its translation initiation region contains triplet repeats typical of TRAP-regulated mRNAs. We found that regulation of trpP and pabA is unaltered in a rho mutant strain. Results from filter binding and gel mobility shift assays demonstrated that TRAP binds specifically to a segment of the trpP transcript that includes the untranslated leader and translation initiation region. While the affinities of TRAP for the trpP and pabA transcripts are similar, TRAP-mediated translation control of trpP is much more extensive than for pabA. RNA footprinting revealed that the trpP TRAP binding site consists of nine triplet repeats (five GAG, three UAG, and one AAG) that surround and overlap the trpP Shine-Dalgarno (S-D) sequence and translation start codon. Results from toeprint and RNA-directed cell-free translation experiments indicated that tryptophan-activated TRAP inhibits TrpP synthesis by preventing binding of a 30S ribosomal subunit. Taken together, our results establish that TRAP regulates translation of trpP by blocking ribosome binding. Thus, TRAP coordinately regulates tryptophan synthesis and transport by three distinct mechanisms: attenuation transcription of the trpEDCFBA operon, promoting formation of the trpE S-D blocking hairpin, and blocking ribosome binding to the pabA and trpP transcripts. PMID:14702295

  8. Highly Selective Synthesis of Catalytically Active Monodisperse Rhodium Nanocubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Grass, M.E.; Kuhn, J.N.; Tao, F.; Habas, S.E.; Huang, W.; Yang, P.; Somorjai, G.A.

    2009-02-21

    Synthesis of monodisperse and shape-controlled colloidal inorganic nanocrystals (NCs) is of increasing scientific interest and technological significance. Recently, shape control of Pt, Pd, Ag, Au, and Rh NCs has been obtained by tuning growth kinetics in various solution-phase approaches, including modified polyol methods, seeded growth by polyol reduction, thermolysis of organometallics, and micelle techniques. Control of reduction kinetics of the noble metal precursors and regulation of the relative growth rates of low-index planes (i.e. {l_brace}100{r_brace} and {l_brace}111{r_brace}) via selective adsorption of selected chemical species are two keys for achieving shape modification of noble metal NCs. One application for noble metal NCs of well-defined shape is in understanding how NC faceting (determines which crystallographic planes are exposed) affects catalytic performance. Rh NCs are used in many catalytic reactions, including hydrogenation, hydroformylation, hydrocarbonylation, and combustion reactions. Shape manipulation of Rh NCs may be important in understanding how faceting on the nanoscale affects catalytic properties, but such control is challenging and there are fewer reports on the shape control of Rh NCs compared to other noble metals. Xia and coworkers obtained Rh multipods exhibiting interesting surface plasmonic properties by a polyol approach. The Somorjai and Tilley groups synthesized crystalline Rh multipods, cubes, horns and cuboctahedra, via polyol seeded growth. Son and colleagues prepared catalytically active monodisperse oleylamine-capped tetrahedral Rh NCs for the hydrogenation of arenes via an organometallic route. More recently, the Somorjai group synthesized sizetunable monodisperse Rh NCs using a one-step polyol technique. In this Communication, we report the highly selective synthesis of catalytically active, monodisperse Rh nanocubes of < 10 nm by a seedless polyol method. In this approach, Br{sup -} ions from trimethyl

  9. Catalytically active single-atom niobium in graphitic layers.

    Science.gov (United States)

    Zhang, Xuefeng; Guo, Junjie; Guan, Pengfei; Liu, Chunjing; Huang, Hao; Xue, Fanghong; Dong, Xinglong; Pennycook, Stephen J; Chisholm, Matthew F

    2013-01-01

    Carbides of groups IV through VI (Ti, V and Cr groups) have long been proposed as substitutes for noble metal-based electrocatalysts in polymer electrolyte fuel cells. However, their catalytic activity has been extremely limited because of the low density and stability of catalytically active sites. Here we report the excellent performance of a niobium-carbon structure for catalysing the cathodic oxygen reduction reaction. A large number of single niobium atoms and ultra small clusters trapped in graphitic layers are directly identified using state-of-the-art aberration-corrected scanning transmission electron microscopy. This structure not only enhances the overall conductivity for accelerating the exchange of ions and electrons, but it suppresses the chemical/thermal coarsening of the active particles. Experimental results coupled with theory calculations reveal that the single niobium atoms incorporated within the graphitic layers produce a redistribution of d-band electrons and become surprisingly active for O2 adsorption and dissociation, and also exhibit high stability. PMID:23715283

  10. Catalytically and biologically active silver nanoparticles synthesized using essential oil

    Science.gov (United States)

    Vilas, Vidya; Philip, Daizy; Mathew, Joseph

    2014-11-01

    There are numerous reports on phytosynthesis of silver nanoparticles and various phytochemicals are involved in the reduction and stabilization. Pure explicit phytosynthetic protocol for catalytically and biologically active silver nanoparticles is of importance as it is an environmentally benign green method. This paper reports the use of essential oil of Myristica fragrans enriched in terpenes and phenyl propenes in the reduction and stabilization. FTIR spectra of the essential oil and the synthesized biogenic silver nanoparticles are in accordance with the GC-MS spectral analysis reports. Nanosilver is initially characterized by an intense SPR band around 420 nm, followed by XRD and TEM analysis revealing the formation of 12-26 nm sized, highly pure, crystalline silver nanoparticles. Excellent catalytic and bioactive potential of the silver nanoparticles is due to the surface modification. The chemocatalytic potential of nanosilver is exhibited by the rapid reduction of the organic pollutant, para nitro phenol and by the degradation of the thiazine dye, methylene blue. Significant antibacterial activity of the silver colloid against Gram positive, Staphylococcus aureus (inhibition zone - 12 mm) and Gram negative, Escherichia coli (inhibition zone - 14 mm) is demonstrated by Agar-well diffusion method. Strong antioxidant activity of the biogenic silver nanoparticles is depicted through NO scavenging, hydrogen peroxide scavenging, reducing power, DPPH and total antioxidant activity assays.

  11. Hydrophobic catalysts for liquid phase catalytic exchange: a review of preparation methods and influencing factors of catalytic activities

    International Nuclear Information System (INIS)

    Liquid phase catalytic exchange (LPCE) between liquid water and gaseous hydro- gen has been developed for various applications, such as tritium recovery, water upgrade and heavy-water production. Good wetproofing properties of the hydrophobic catalysts can make the reaction to proceed smoothly. In this article, the preparation methods of the hydrophobic catalysts and the factors affecting the catalytic activities are reviewed. In particular, progress on the hydrophobic Pt/C/inert carrier catalysts is introduced, including the selection of inert carrier and active metal carrier, and the preparation methods of carbon- supported Pt based catalysts. Basic research activities on controllable fabrication of hydro- phobic catalysts are discussed, including the LPCE reaction mechanism, and the relation between the microstructure of active metal and the catalytic activity, etc. Finally, questions remaining to be answered and future directions in the field of hydrophobic catalysts are discussed. (authors)

  12. Protein composition of catalytically active human telomerase from immortal cells

    DEFF Research Database (Denmark)

    Cohen, Scott B; Graham, Mark E; Lovrecz, George O;

    2007-01-01

    Telomerase is a ribonucleoprotein enzyme complex that adds 5'-TTAGGG-3' repeats onto the ends of human chromosomes, providing a telomere maintenance mechanism for approximately 90% of human cancers. We have purified human telomerase approximately 10(8)-fold, with the final elution dependent on the...... enzyme's ability to catalyze nucleotide addition onto a DNA oligonucleotide of telomeric sequence, thereby providing specificity for catalytically active telomerase. Mass spectrometric sequencing of the protein components and molecular size determination indicated an enzyme composition of two molecules...... each of telomerase reverse transcriptase, telomerase RNA, and dyskerin....

  13. Catalytic activity trends of CO oxidation – A DFT study

    DEFF Research Database (Denmark)

    Jiang, Tao

    There are two goals of this thesis, the first one is to understand the reactivity of noble metal nanoparticles for CO oxidation reaction. The second goal is to gain understanding to the second derivative (Hessian matrix) of the potential energy surfaces (PES) of adsorption systems, especially its...... eigenmodes and eigenvalues, and improving algorithms for geometry optimization in electronic structure calculations. The catalytic activity of gold nanoparticles has received wide attention since the discovery of their activity on CO oxidation by Professor Haruta in 1987. By using density functional theory...... oxidation by molecular O2 occurs via a different reaction pathway, which instead involves a meta-stable intermediate CO-O2. However, although the two oxidizing agents used proceeded via different reaction pathways on different active sites, the apparent overall activation barriers obtained from both theory...

  14. TRP channel-associated factors are a novel protein family that regulates TRPM8 trafficking and activity.

    NARCIS (Netherlands)

    Gkika, D.; Lemonnier, L.; Shapovalov, G.; Gordienko, D.; Poux, C.; Bernardini, M.; Bokhobza, A.; Bidaux, G.; Degerny, C.; Verreman, K.; Guarmit, B.; Benahmed, M.; Launoit, Y. de; Bindels, R.J.M.; Fiorio Pla, A.; Prevarskaya, N.

    2015-01-01

    TRPM8 is a cold sensor that is highly expressed in the prostate as well as in other non-temperature-sensing organs, and is regulated by downstream receptor-activated signaling pathways. However, little is known about the intracellular proteins necessary for channel function. Here, we identify two pr

  15. Calmodulin modulates the delay period between release of calcium from internal stores and activation of calcium influx via endogenous TRP1 channels.

    Science.gov (United States)

    Vaca, Luis; Sampieri, Alicia

    2002-11-01

    In the present study we have explored the role of calmodulin (CaM) and inositol 1,4,5-trisphosphate receptor (IP(3)R) in the communication process activated after the release of calcium from the endoplasmic reticulum (ER) and the activation of calcium influx via endogenous TRP1 channels from Chinese hamster ovary cells. Experiments using combined rapid confocal calcium and electrophysiology measurements uncovered a consistent delay of around 900 ms between the first detectable calcium released from the ER and the activation of the calcium current. This delay was evident with two different methods used to release calcium from the ER: either the blockade of the microsomal calcium ATPase with thapsigargin or activation of bradykinin receptors linked to the IP(3) cascade. Direct application of IP(3) or a peptide from the NH(2)-terminal region of the IP(3)R activated store operated calcium, reducing the delay period. Introduction of CaM into the cell via the patch pipette increased the delay period from 900 +/- 100 ms to 10 +/- 2.1 s (n = 18). Furthermore, the use of selective CaM antagonists W7 and trifluoperazine maleate resulted in a substantial reduction of the delay period to 200 +/- 100 ms with 5 microm trifluoperazine maleate (n = 16) and 150 +/- 50 ms with 500 nm W7 (n = 22). CaM reduced also the current density activated by thapsigargin or brandykinin to about 60% from control. The CaM antagonists did not affect significantly the current density. The results presented here are consistent with an antagonistic effect of IP(3)R and CaM for the activation of store operated calcium after depletion of the ER. The functional competition between the activating effect of IP(3)R and the inhibiting effect of CaM may modulate the delay period between the release of calcium from the ER and the activation of calcium influx observed in different cells, as well as the amount of current activated after depletion of the ER.

  16. Size Effect of Gold Sol/γ-Alumina on the Catalytic Activities of CO Oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-Hua; GAO Geng-Yu

    2006-01-01

    The relationship between particle size and catalytic activity of gold nanoparticle catalysts with γ-Al2O3 as support has been investigated. The catalysts were prepared via the gold sol with different particle sizes by micelle method, and their structures were characterized by HRTEM and XRD, respectively. Furthermore, the catalytic activities were tested by CO oxidation. Experimental results showed that the catalytic activity became much weaker when gold particles were increased from 3.2 to 6.6 nm. Additionally, the particle size was also a key factor to govern catalytic activity with regard to gold supported on TiO2 prepared by the methods of deposition-precipitation.

  17. Study of Single Catalytic Events at Copper-in-Charcoal: Localization of Click Activity Through Subdiffraction Observation of Single Catalytic Events.

    Science.gov (United States)

    Decan, Matthew R; Scaiano, Juan C

    2015-10-15

    Single molecule fluorescence microscopy reveals that copper-in-charcoal--a high performance click catalyst- has remarkably few catalytic sites, with 90% of the charcoal particles being inactive, and for the catalytic ones the active sites represent a minute fraction (∼0.003%) of the surface. The intermittent nature of the catalytic events enables subdiffraction resolution and mapping of the catalytic sites. PMID:26722775

  18. Orthogonal gene knock out and activation with a catalytically active Cas9 nuclease

    OpenAIRE

    Dahlman, James E.; Abudayyeh, Omar O.; Joung, Julia; Gootenberg, Jonathan S.; Zhang, Feng; Konermann, Silvana

    2015-01-01

    We have developed a CRISPR-based method that uses catalytically active Cas9 and distinct sgRNA constructs to knock out and activate different genes in the same cell. These sgRNAs, with 14 15 bp target sequences and MS2 binding loops, can activate gene expression using an active Cas9 nuclease, without inducing DSBs. We use these ‘dead RNAs’ to perform orthogonal gene knockout and transcriptional activation in human cells.

  19. Synthesis, characterization and catalytic activity of CdO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Singh, G., E-mail: gsingh4us@yahoo.com [Department of Chemistry, D.D.U. Gorakhpur University, Gorakhpur 273009 (India); Kapoor, I.P.S.; Dubey, Reena; Srivastava, Pratibha [Department of Chemistry, D.D.U. Gorakhpur University, Gorakhpur 273009 (India)

    2011-02-15

    In this paper, we report the synthesis of nanocrystalline cadmium oxide (CdO) and its characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Its catalytic activity was investigated on the thermal decomposition of 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), ammonium perchlorate (AP), hydroxyl terminated polybutadiene (HTPB) and composite solid propellants (CSPs) using thermogravimetric analysis (TG), simultaneous thermogravimerty and differential scanning calorimetry (TG-DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + CdO has also been investigated using model free (isoconversional) and model-fitting approaches which have been applied to data for isothermal TG decomposition. All these studies show enhancement in the rate of decomposition of AP, HTPB and CSPs but no effect on HMX. The burning rate of CSPs has also been found to be increased with CdO nanocrystals.

  20. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    International Nuclear Information System (INIS)

    Graphical abstract: NiWO4 nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: ► NiWO4 spherical nanoparticles were synthesized via direct precipitation method. ► Taguchi robust design was used for optimization of synthesis reaction parameters. ► Composition and structural properties of NiWO4 nanoparticles were characterized. ► EDAX, XRD, SEM, FT-IR, UV–vis and photoluminescence techniques were employed. ► Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV–vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

  1. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pourmortazavi, Seied Mahdi, E-mail: pourmortazavi@yahoo.com [Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Rahimi-Nasrabadi, Mehdi, E-mail: rahiminasrabadi@gmail.com [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Khalilian-Shalamzari, Morteza [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh [Islamic Azad University, Varamin Pishva Branch, Varamin (Iran, Islamic Republic of); Omrani, Ismail [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of)

    2012-12-15

    Graphical abstract: NiWO{sub 4} nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: Black-Right-Pointing-Pointer NiWO{sub 4} spherical nanoparticles were synthesized via direct precipitation method. Black-Right-Pointing-Pointer Taguchi robust design was used for optimization of synthesis reaction parameters. Black-Right-Pointing-Pointer Composition and structural properties of NiWO{sub 4} nanoparticles were characterized. Black-Right-Pointing-Pointer EDAX, XRD, SEM, FT-IR, UV-vis and photoluminescence techniques were employed. Black-Right-Pointing-Pointer Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO{sub 4} nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO{sub 4} particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO{sub 4} were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV

  2. Development of novel catalytically active polymer-metal-nanocomposites based on activated foams and textile fibers

    Science.gov (United States)

    Domènech, Berta; Ziegler, Kharla K.; Carrillo, Fernando; Muñoz, Maria; Muraviev, Dimitri N.; Macanás, Jorge

    2013-05-01

    In this paper, we report the intermatrix synthesis of Ag nanoparticles in different polymeric matrices such as polyurethane foams and polyacrylonitrile or polyamide fibers. To apply this technique, the polymer must bear functional groups able to bind and retain the nanoparticle ion precursors while ions should diffuse through the matrix. Taking into account the nature of some of the chosen matrices, it was essential to try to activate the support material to obtain an acceptable value of ion exchange capacity. To evaluate the catalytic activity of the developed nanocomposites, a model catalytic reaction was carried out in batch experiments: the reduction of p-nitrophenol by sodium borohydride.

  3. Bacillus pumilus Cyanide Dihydratase Mutants with Higher Catalytic Activity.

    Science.gov (United States)

    Crum, Mary A; Sewell, B Trevor; Benedik, Michael J

    2016-01-01

    Cyanide degrading nitrilases are noted for their potential to detoxify industrial wastewater contaminated with cyanide. However, such application would benefit from an improvement to characteristics such as their catalytic activity and stability. Following error-prone PCR for random mutagenesis, several cyanide dihydratase mutants from Bacillus pumilus were isolated based on improved catalysis. Four point mutations, K93R, D172N, A202T, and E327K were characterized and their effects on kinetics, thermostability and pH tolerance were studied. K93R and D172N increased the enzyme's thermostability whereas E327K mutation had a less pronounced effect on stability. The D172N mutation also increased the affinity of the enzyme for its substrate at pH 7.7 but lowered its k cat. However, the A202T mutation, located in the dimerization or the A surface, destabilized the protein and abolished its activity. No significant effect on activity at alkaline pH was observed for any of the purified mutants. These mutations help confirm the model of CynD and are discussed in the context of the protein-protein interfaces leading to the protein quaternary structure. PMID:27570524

  4. Catalytic activities of platinum nanotubes: a density functional study

    Science.gov (United States)

    Mukherjee, Prajna; Gupta, Bikash C.; Jena, Puru

    2015-10-01

    In this work we investigate the catalytic properties of platinum nanotubes using density functional theory based calculations. In particular, we study the dissociation of hydrogen and oxygen molecules as well as oxidation of CO molecules. The results indicate that platinum nanotubes have good catalytic properties and can be effectively used in converting CO molecule to CO2.

  5. Isolation of an Active Catalytic Core of Streptococcus downei MFe28 GTF-I Glucosyltransferase

    OpenAIRE

    Monchois, Vincent; Arguello-Morales, Martha; Russell, Roy R. B.

    1999-01-01

    Truncated variants of GTF-I from Streptococcus downei MFe28 were purified by means of a histidine tag. Sequential deletions showed that the C-terminal domain was not directly involved in the catalytic process but was required for primer activation. A fully active catalytic core of only 100 kDa was isolated.

  6. Catalytically active cobalt and copper complexes in polyelectrolyte multilayer films

    International Nuclear Information System (INIS)

    In this work an approach to obtain effective and easy reusable heterogeneous catalyst, LbL deposition of polyelectrolytes followed by covalently binding with cobalt (II) and copper (II) ions were described. Immobilization of metal complexes via covalent attachment to insoluble template is an attractive method to facilitate catalyst recovery, recycling. The reaction in the heterogeneous catalysis goes in the interface of catalyst and reaction solution and it is important to create a catalyst with large surface area. We have used polycations as polyethyleneimine (BPEI), quaternized poly(4- vynilpyridine) (QPVP) and polyanions as poly(acrylic acid) (PAA), poly(styrene sulphonate) sodium salt (PSS) and the electrostatic layer-by-layer assembly technique to make uniform thin film coating on SiO2 nanoparticles and glass slides with controllable thickness, roughness and mechanically durability. The stability of metals within multilayers in reaction condition were tested. We compared the amount of metal in PEMs of different polyelectrolytes. The stability constants of complex forming processes of the polymer-metal complexes in water and in alcohol were calculated by modified method of Bjerrum. Catalytic activity of immobilized catalysts was investigated for oxidation of toluene by molecular oxygen. Catalysts were separated from reaction mixture easily and had been used for this reaction five times without significant loss of activity. Key words: catalysis, layer-by-layer (LbL), polymer-metal complexes, oxidation, cobalt and copper immobilization

  7. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sherly, K. B.; Rakesh, K. [Mahatma Gandhi University Regional Research Center in Chemistry, Department of Chemistry, Mar Athanasius College, Kothamangalam-686666, Kerala (India)

    2014-01-28

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl{sub 2}⋅8H{sub 2}O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  8. Kinetics of catalytically activated duplication in aggregation growth

    Institute of Scientific and Technical Information of China (English)

    Wang Hai-Feng; Lin Zhen-Quan; Gao Yan; Xu Chao

    2009-01-01

    We propose a catalytically activated duplication model to mimic the coagulation and duplication of the DNA polymer system under the catalysis of the primer RNA.In the model,two aggregates of the same species can coagulate themselves and a DNA aggregate of any size can yield a new monomer or double itself with the help of RNA aggregates.By employing the mean-field rate equation approach we analytically investigate the evolution behaviour of the system.For the system with catalysis-driven monomer duplications,the aggregate size distribution of DNA polymers ak(t) always follows a power law in size in the long-time limit,and it decreases with time or approaches a time-independent steady-state form in the case of the duplication rate independent of the size of the mother aggregates,while it increases with time increasing in the case of the duplication rate proportional to the size of the mother aggregates.For the system with complete catalysis-driven duplications,the aggregate size distribution ak(t) approaches a generalized or modified scaling form.

  9. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    Science.gov (United States)

    Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

    2012-12-01

    Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV-vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

  10. The different roles of tryptophan transfer RNA in regulating trp operon expression in E. coli versus B. subtilis.

    Science.gov (United States)

    Yanofsky, Charles

    2004-08-01

    Escherichia coli and Bacillus subtilis use different mechanisms of sensing and responding to tryptophan and uncharged tRNA(Trp) as regulatory signals. In E. coli, tryptophan activates a repressor that binds to the trp promoter- operator, inhibiting transcription initiation. In B. subtilis, tryptophan activates an RNA-binding protein, TRAP, which binds to the trp operon leader RNA, causing transcription termination. In E. coli uncharged tRNA(Trp) accumulation stalls the ribosome attempting translation of tandem Trp codons in the leader-peptide coding region of the operon. This stalling permits the formation of an RNA antiterminator structure, preventing transcription termination. In B. subtilis uncharged tRNA(Trp) accumulation activates transcription and translation of the at operon. AT protein inhibits tryptophan-activated TRAP, thereby preventing TRAP-mediated transcription termination. These differences might reflect the unique organizational features of the respective trp operons and their ancestry. PMID:15262409

  11. [Role of thermo TRP channels in cutaneous neurogenic inflammation and itch].

    Science.gov (United States)

    XIE, Zhi-qiang

    2009-07-01

    The temperature-sensitive transient receptor potential (TRP) channels, is also called thermo TRP, including TRPV1, TRPV2, TRPV3, TRPV4, TRPM8 and TRPA1, which are expressed in sensory neurons and non-neuronal cells (e.g.keratinocyte, mast cell) of the skin. Thermo TRP channels are activated/sensitized by physical and chemical mediators, which participate in thermosensation and thermoregulation, so that they are key players in pruritus or pain pathogenesis. Thermo TRP channels are also involved in cutaneous neurogenic inflammation, thus they are regarded as molecular targets for future therapy in skin inflammation, pruritus and pain. In addition, following a basic syntax and molecular substrate of nociception and pruriception established by TRP channels-centered concept, the sensory categories can be distinguished and re-defined. Thermo TRP channels should be taken into account when analyzing the pathogenesis and management of itch or pruritic dermatosis.

  12. STUDIES ON THE CATALYTIC REACTION OF NITROGEN OXIDE ON METAL MODIFIED ACTIVATED CARBON FIBERS

    Institute of Scientific and Technical Information of China (English)

    FU Ruowen; DU Xiuying; LIN Yuansheng; XU Hao; HU Yiongjun

    2003-01-01

    The catalytic reaction of NO with CO and decomposition of NO over metal modified ACFs were investigated and compared with other carriers supported catalysts. It is demonstrated that Pd/ACF and Pd/Cu/ACF have high catalytic activity for the reaction of NO/CO, while Pt/ACF.Pt/Cu/ACF and Co/Cu/ACF have very Iow catalytic activity in similar circumstance. Pd-modified ACF possesses high catalytic decomposition of NO at 300 ℃. Pd/CB and Pd/GAC present good catalytic decomposition ability for NO only at low flowrate. Pd/G, Pd/ZMS and Pd/A however, do not show any catalytic activity for NO decomposition even at 400 ℃. Catalytic temperature, NO flowrate and loading of metal components affect the decomposition rate of NO. The coexistence of Cu with Pd on Cu/Pd/ACF leads to crystalline of palladium to more unperfected so as to that increase the catalytic activity.

  13. Nanoscale mapping of catalytic activity using tip-enhanced Raman spectroscopy.

    Science.gov (United States)

    Kumar, N; Stephanidis, B; Zenobi, R; Wain, A J; Roy, D

    2015-04-28

    Chemical mapping of a photocatalytic reaction with nanoscale spatial resolution is demonstrated for the first time using tip-enhanced Raman spectroscopy (TERS). An ultrathin alumina film applied to the Ag-coated TERS tip blocks catalytic interference whilst maintaining near-field electromagnetic enhancement, thus enabling spectroscopic imaging of catalytic activity on nanostructured Ag surfaces.

  14. A novel strategy to analyze L-tryptophan through allosteric Trp repressor based on rolling circle amplification.

    Science.gov (United States)

    Zhao, Guojie; Hu, Tianyu; Li, Jun; Wei, Hua; Shang, Hong; Guan, Yifu

    2015-09-15

    Rolling circle amplification (RCA) has been considered as a powerful tool for nucleic acids detection. Here, a novel repressor-RCA-based method for L-tryptophan (L-Trp) detection was developed. This method utilizes the specific interaction between the RCA circular template and the Trp repressor protein (TrpR) involved in trp operon of Escherichia coli (E. coli). In the absence of L-Trp, the TrpR protein could not bind to the RCA template, and the RCA process can be continued. When L-Trp is present, the activated TrpR will bind to the operon sequence on the RCA template and inhibit the RCA reaction. Thus, the concentration of L-Trp is correlated directly with the fluorescent RCA signals. We succeeded in detecting L-Trp in a single step in simple homogeneous reaction system. The detection limit was estimated to be 0.77 μM (S/N=3) with good linearity. The method can unambiguously distinguish L-Trp from other 19 standard amino acids and L-Trp analogs. This strategy is also promising for detecting many small molecules such as other amino acids and carbohydrates.

  15. A novel strategy to analyze L-tryptophan through allosteric Trp repressor based on rolling circle amplification.

    Science.gov (United States)

    Zhao, Guojie; Hu, Tianyu; Li, Jun; Wei, Hua; Shang, Hong; Guan, Yifu

    2015-09-15

    Rolling circle amplification (RCA) has been considered as a powerful tool for nucleic acids detection. Here, a novel repressor-RCA-based method for L-tryptophan (L-Trp) detection was developed. This method utilizes the specific interaction between the RCA circular template and the Trp repressor protein (TrpR) involved in trp operon of Escherichia coli (E. coli). In the absence of L-Trp, the TrpR protein could not bind to the RCA template, and the RCA process can be continued. When L-Trp is present, the activated TrpR will bind to the operon sequence on the RCA template and inhibit the RCA reaction. Thus, the concentration of L-Trp is correlated directly with the fluorescent RCA signals. We succeeded in detecting L-Trp in a single step in simple homogeneous reaction system. The detection limit was estimated to be 0.77 μM (S/N=3) with good linearity. The method can unambiguously distinguish L-Trp from other 19 standard amino acids and L-Trp analogs. This strategy is also promising for detecting many small molecules such as other amino acids and carbohydrates. PMID:25889351

  16. Synthesis and characterization of vanadium nanoparticles on activated carbon and their catalytic activity in thiophene hydrodesulphurization

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, Susana [Centro de Catalisis, Petroleo y Petroquimica, Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, AP, Caracas 40679 (Venezuela); Centro de Quimica Organometalica y Macromolecular, Facultad de Ciencias, Universidad Central de Venezuela, AP, Caracas 47778 (Venezuela); D' Ornelas, Lindora [Centro de Quimica Organometalica y Macromolecular, Facultad de Ciencias, Universidad Central de Venezuela, AP, Caracas 47778 (Venezuela); Betancourt, Paulino [Centro de Catalisis, Petroleo y Petroquimica, Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, AP, Caracas 40679 (Venezuela)], E-mail: pbetanco@strix.ciens.ucv.ve

    2008-06-30

    Vanadium nanoparticles ({approx}7 nm) stabilized on activated carbon were synthesized by the reduction of VCl{sub 3}.3THF with K[BEt{sub 3}H]. This material was characterized by inductive coupled plasma-atomic emission spectroscopy (ICP-AES), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses. The catalytic performance of the carbon-supported vanadium was studied using thiophene hydrodesulfurization (HDS) as model reaction at 300 deg. C and P = 1 atm. The catalytic activity of the vanadium carbide phase on the activated carbon carrier was more significant than that of the reference catalysts, alumina supported NiMoS. The method proposed for the synthesis of such a catalyst led to an excellent performance of the HDS process.

  17. Synthesis and characterization of vanadium nanoparticles on activated carbon and their catalytic activity in thiophene hydrodesulphurization

    Science.gov (United States)

    Pinto, Susana; D'Ornelas, Lindora; Betancourt, Paulino

    2008-06-01

    Vanadium nanoparticles (˜7 nm) stabilized on activated carbon were synthesized by the reduction of VCl 3·3THF with K[BEt 3H]. This material was characterized by inductive coupled plasma-atomic emission spectroscopy (ICP-AES), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses. The catalytic performance of the carbon-supported vanadium was studied using thiophene hydrodesulfurization (HDS) as model reaction at 300 °C and P = 1 atm. The catalytic activity of the vanadium carbide phase on the activated carbon carrier was more significant than that of the reference catalysts, alumina supported NiMoS. The method proposed for the synthesis of such a catalyst led to an excellent performance of the HDS process.

  18. Quantitative study of catalytic activity and catalytic deactivation of Fe–Co/Al2O3 catalysts for multi-walled carbon nanotube synthesis by the CCVD process

    OpenAIRE

    Pirard, Sophie; Heyen, Georges; Pirard, Jean-Paul

    2010-01-01

    The catalytic deactivation during multi-walled carbon nanotube (MWNT) synthesis by the CCVD process and the influence of hydrogen on it were quantified. Initial specific reaction rate, relative specific productivity and catalytic deactivation were studied. Carbon source was ethylene, and a bimetallic iron–cobalt catalyst supported on alumina was used. The catalytic deactivation was modeled by a decreasing hyperbolic law, reflecting the progressive accumulation of amorphous carbon on active si...

  19. Optical activity of catalytic elements of hetero-metallic nanostructures

    Science.gov (United States)

    Antosiewicz, Tomasz J.; Apell, S. Peter; Wadell, Carl; Langhammer, Christoph

    2015-05-01

    Interaction of light with metals in the form of surface plasmons is used in a wide range of applications in which the scattering decay channel is important. The absorption channel is usually thought of as unwanted and detrimental to the efficiency of the device. This is true in many applications, however, recent studies have shown that maximization of the decay channel of surface plasmons has potentially significant uses. One of these is the creation of electron-hole pairs or hot electrons which can be used for e.g. catalysis. Here, we study the optical properties of hetero-metallic nanostructures that enhance light interaction with the catalytic elements of the nanostructures. A hybridized LSPR that matches the spectral characteristic of the light source is excited. This LSPR through coupling between the plasmonic elements maximizes light absorption in the catalytic part of the nanostructure. Numerically calculated visible light absorption in the catalytic nanoparticles is enhanced 12-fold for large catalytic disks and by more 30 for small nanoparticles on the order of 5 nm. In experiments we measure a sizable increase in the absorption cross section when small palladium nanoparticles are coupled to a large silver resonator. These observations suggest that heterometallic nanostructures can enhance catalytic reaction rates.

  20. Evolutionary conservation and changes in insect TRP channels

    Directory of Open Access Journals (Sweden)

    Tominaga Makoto

    2009-09-01

    Full Text Available Abstract Background TRP (Transient Receptor Potential channels respond to diverse stimuli and thus function as the primary integrators of varied sensory information. They are also activated by various compounds and secondary messengers to mediate cell-cell interactions as well as to detect changes in the local environment. Their physiological roles have been primarily characterized only in mice and fruit flies, and evolutionary studies are limited. To understand the evolution of insect TRP channels and the mechanisms of integrating sensory inputs in insects, we have identified and compared TRP channel genes in Drosophila melanogaster, Bombyx mori, Tribolium castaneum, Apis mellifera, Nasonia vitripennis, and Pediculus humanus genomes as part of genome sequencing efforts. Results All the insects examined have 2 TRPV, 1 TRPN, 1 TRPM, 3 TRPC, and 1 TRPML subfamily members, demonstrating that these channels have the ancient origins in insects. The common pattern also suggests that the mechanisms for detecting mechanical and visual stimuli and maintaining lysosomal functions may be evolutionarily well conserved in insects. However, a TRPP channel, the most ancient TRP channel, is missing in B. mori, A. mellifera, and N. vitripennis. Although P. humanus and D. melanogaster contain 4 TRPA subfamily members, the other insects have 5 TRPA subfamily members. T. castaneum, A. mellifera, and N. vitripennis contain TRPA5 channels, which have been specifically retained or gained in Coleoptera and Hymenoptera. Furthermore, TRPA1, which functions for thermotaxis in Drosophila, is missing in A. mellifera and N. vitripennis; however, they have other Hymenoptera-specific TRPA channels (AmHsTRPA and NvHsTRPA. NvHsTRPA expressed in HEK293 cells is activated by temperature increase, demonstrating that HsTRPAs function as novel thermal sensors in Hymenoptera. Conclusion The total number of insect TRP family members is 13-14, approximately half that of mammalian TRP

  1. DEVELOPMENT OF HIGH ACTIVITY, CATALYTIC SYSTEMS FOR NOx REDUCTION

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2001-12-01

    This project was directed at an investigation of catalytic NO{sub x} reduction on carbonaceous supports at low temperatures. The experimental work was conducted primarily in a packed bed reactor/gas flow system that was constructed for this work. The analytical techniques employed were mass spectrometry, NO{sub x} chemiluminescence, and gas chromatography. The experimental plan was focused on steady-state reactivity experiments, followed by temperature programmed desorption (TPD) of surface intermediates, and also selected temperature-programmed reaction (TPR) experiments. Both uncatalyzed and catalyzed (potassium-promoted) phenolic resin char, were investigated as well as the catalytic effect of additional CO in the gas phase.

  2. Size-dependent peroxidase-like catalytic activity of Fe3O4 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Fang Fang Peng; Yu Zhang; Ning Gu

    2008-01-01

    Peroxidase-like catalytic properties of Fe3O4 nanoparticles (NPs) with three different sizes, synthesized by chemical coprecipitation and sol-gel methods, were investigated by UV-vis spectrum analysis. By comparing Fe3O4 NPs with average diameters of 11,20, and 150 nm, we found that the catalytic activity increases with the reduced nanoparticle size. The electrochemical method to characterize the catalytic activity of Fe3O4 NPs using the response currents of the reaction product and substrate was also developed.

  3. Integrating nanotubes into microsystems with electron beam lithography and in situ catalytically activated growth

    DEFF Research Database (Denmark)

    Gjerde, Kjetil; Fornés-Mora, Marc; Kjelstrup-Hansen, Jakob;

    2006-01-01

    Integration of freestanding wire-like structures such as multi walled carbon nanotubes (MWCNT) into microsystems has many potential applications. Devices such as AFM tips or improved electrodes for conductivity measurements are obvious candidates. Catalytically activated growth opens up...

  4. Microbially supported synthesis of catalytically active bimetallic Pd-Au nanoparticles

    DEFF Research Database (Denmark)

    Hosseinkhani, Baharak; Søbjerg, Lina Sveidal; Rotaru, Amelia-Elena;

    2012-01-01

    Bimetallic nanoparticles are considered the next generation of nanocatalysts with increased stability and catalytic activity. Bio-supported synthesis of monometallic nanoparticles has been proposed as an environmentally friendly alternative to the conventional chemical and physical protocols. In ...

  5. Degradation of paracetamol by catalytic wet air oxidation and sequential adsorption - Catalytic wet air oxidation on activated carbons

    Energy Technology Data Exchange (ETDEWEB)

    Quesada-Penate, I. [Universite de Toulouse, INPT, UPS, Laboratoire de Genie Chimique, 4, Allee Emile Monso, F-31432 Toulouse (France); CNRS, Laboratoire de Genie Chimique, F-31432 Toulouse (France); Julcour-Lebigue, C., E-mail: carine.julcour@ensiacet.fr [Universite de Toulouse, INPT, UPS, Laboratoire de Genie Chimique, 4, Allee Emile Monso, F-31432 Toulouse (France); CNRS, Laboratoire de Genie Chimique, F-31432 Toulouse (France); Jauregui-Haza, U.J. [Instituto Superior de Tecnologias y Ciencias Aplicadas, Ave. Salvador Allende y Luaces, Habana (Cuba); Wilhelm, A.M.; Delmas, H. [Universite de Toulouse, INPT, UPS, Laboratoire de Genie Chimique, 4, Allee Emile Monso, F-31432 Toulouse (France); CNRS, Laboratoire de Genie Chimique, F-31432 Toulouse (France)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer Three activated carbons (AC) compared as adsorbents and oxidation catalysts. Black-Right-Pointing-Pointer Similar evolution for catalytic and adsorptive properties of AC over reuses. Black-Right-Pointing-Pointer Acidic and mesoporous AC to be preferred, despite lower initial efficiency. Black-Right-Pointing-Pointer Oxidative degradation of paracetamol improves biodegradability. Black-Right-Pointing-Pointer Convenient hybrid adsorption-regenerative oxidation process for continuous treatment. - Abstract: The concern about the fate of pharmaceutical products has raised owing to the increasing contamination of rivers, lakes and groundwater. The aim of this paper is to evaluate two different processes for paracetamol removal. The catalytic wet air oxidation (CWAO) of paracetamol on activated carbon was investigated both as a water treatment technique using an autoclave reactor and as a regenerative treatment of the carbon after adsorption in a sequential fixed bed process. Three activated carbons (ACs) from different source materials were used as catalysts: two microporous basic ACs (S23 and C1) and a meso- and micro-porous acidic one (L27). During the first CWAO experiment the adsorption capacity and catalytic performance of fresh S23 and C1 were higher than those of fresh L27 despite its higher surface area. This situation changed after AC reuse, as finally L27 gave the best results after five CWAO cycles. Respirometry tests with activated sludge revealed that in the studied conditions the use of CWAO enhanced the aerobic biodegradability of the effluent. In the ADOX process L27 also showed better oxidation performances and regeneration efficiency. This different ageing was examined through AC physico-chemical properties.

  6. Suppression of the SOS-inducing activity of Trp-P-1 and aflatoxin B1 by meso-dihydroguaiaretic acid from Machilus thunbergii in the Salmonella typhimurium TA1535/pSK1002 umu test.

    Science.gov (United States)

    Miyazawa, M; Okuno, Y; Oshiro, K; Kasahara, H; Shimamura, H; Nakamura, S; Kameoka, H

    1998-07-01

    The methanol extract from Machilus thunbergii showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), which requires liver metabolizing enzymes. The methanol extract from M. thunbergii was successively re-extracted with chloroform, butanol and water. A suppressive compound in the chloroform extract fraction was isolated by SiO2 column chromatography and identified as meso-dihydroguaiaretic acid by GC-MS, and 1H- and 13C-NMR spectroscopy. Meso-dihydroguaiaretic acid inhibited of the SOS-inducing activity of Trp-P-1 in the umu test. Gene expression was suppressed by 62% at less than 0.18 mumol/ml, the ID50 value being 0.08 mumol/ml. Compound 1 was also assayed with aflatoxin B1 (AfB1) and showed a suppressive effect. PMID:9720227

  7. Functional interaction between TRP4 and CFTR in mouse aorta endothelial cells

    Directory of Open Access Journals (Sweden)

    Droogmans Guy

    2001-05-01

    Full Text Available Abstract Background This study describes the functional interaction between the putative Ca2+ channel TRP4 and the cystic fibrosis transmembrane conductance regulator, CFTR, in mouse aorta endothelium (MAEC. Results MAEC cells express CFTR transcripts as shown by RT-PCR analysis. Application of a phosphorylating cocktail activated a Cl- current with characteristics similar to those of CFTR mediated currents in other cells types (slow activation by cAMP, absence of rectification, block by glibenclamide. The current is present in trp4 +/+ MAEC, but not in trp4 -/- cells, although the expression of CFTR seems unchanged in the trp4 deficient cells as judged from RT-PCR analysis. Conclusions It is concluded that TRP4 is necessary for CFTR activation in endothelium, possibly by providing a scaffold for the formation of functional CFTR channels.

  8. Transient receptor potential (TRP gene superfamily encoding cation channels

    Directory of Open Access Journals (Sweden)

    Pan Zan

    2011-01-01

    Full Text Available Abstract Transient receptor potential (TRP non-selective cation channels constitute a superfamily, which contains 28 different genes. In mammals, this superfamily is divided into six subfamilies based on differences in amino acid sequence homology between the different gene products. Proteins within a subfamily aggregate to form heteromeric or homomeric tetrameric configurations. These different groupings have very variable permeability ratios for calcium versus sodium ions. TRP expression is widely distributed in neuronal tissues, as well as a host of other tissues, including epithelial and endothelial cells. They are activated by environmental stresses that include tissue injury, changes in temperature, pH and osmolarity, as well as volatile chemicals, cytokines and plant compounds. Their activation induces, via intracellular calcium signalling, a host of responses, including stimulation of cell proliferation, migration, regulatory volume behaviour and the release of a host of cytokines. Their activation is greatly potentiated by phospholipase C (PLC activation mediated by coupled GTP-binding proteins and tyrosine receptors. In addition to their importance in maintaining tissue homeostasis, some of these responses may involve various underlying diseases. Given the wealth of literature describing the multiple roles of TRP in physiology in a very wide range of different mammalian tissues, this review limits itself to the literature describing the multiple roles of TRP channels in different ocular tissues. Accordingly, their importance to the corneal, trabecular meshwork, lens, ciliary muscle, retinal, microglial and retinal pigment epithelial physiology and pathology is reviewed.

  9. Solubility of cerium in LaCoO3-influence on catalytic activity.

    Science.gov (United States)

    French, S A; Catlow, C R A; Oldman, R J; Rogers, S C; Axon, S A

    2002-11-21

    The recent interest in the catalytic properties of lanthanum perovskites for methane combustion and three way catalysis has led to considerable debate as to their structure and defect chemistry. We have investigated the doping of LaCoO3 with the tetravalent cerium cation using atomistic simulation techniques. We have compared three routes for cerium insertion and identified the favoured doping mechanism, which explain experimental observations relating to the effect of cerium on catalytic activity.

  10. Catalytic activities of a cocaine hydrolase engineered from human butyrylcholinesterase against (+)- and (−)-cocaine

    OpenAIRE

    Xue, Liu; Hou, Shurong; Wenchao YANG; Fang, Lei; Zheng, Fang; Zhan, Chang-Guo

    2012-01-01

    It can be argued that an ideal anti-cocaine medication would be one that accelerates cocaine metabolism producing biologically inactive metabolites via a route similar to the primary cocaine-metabolizing pathway, i.e. hydrolysis catalyzed by butyrylcholinesterase (BChE) in plasma. However, wild-type BChE has a low catalytic efficiency against naturally occurring (−)cocaine. Interestingly, wild-type BChE has a much higher catalytic activity against unnatural (+)cocaine. According to available ...

  11. Some aspects of catalytic activity of pyrolyzed coals

    Energy Technology Data Exchange (ETDEWEB)

    Zubkova, Valentina [Institute of Chemistry, Jan Kochanowski University, Swietokrzyska Str.15G, 25-406 Kielce (Poland); Grigoreva, Evgenija [Institute of High Temperature, The Russian Academy of Science, 13/19 Izhorskaja Street, Moscow (Russian Federation); Strojwas, Andrzej, E-mail: andrzej.strojwas@wp.pl [Institute of Chemistry, Jan Kochanowski University, Swietokrzyska Str.15G, 25-406 Kielce (Poland); Czaplicka, Marianna [Institute of Non-Ferrous Metals, J. Sowińskiego Str. 5, 44-100 Gliwice (Poland); Prezhdo, Victor; Pruszkowska, Jolanta [Institute of Chemistry, Jan Kochanowski University, Swietokrzyska Str.15G, 25-406 Kielce (Poland)

    2013-10-10

    Graphical abstract: - Highlights: • The pyrolysates of coal were investigated using XRD, SEM, FT–IR and GC–MS. • The pyrolyzed coal in the m.s.g. increases the destruction rate constant by 16.7 times. • In the m.s.g. some substances have catalytic influence on breakage of ether bonding. - Abstract: The influence of additives of initial coal and selected pyrolysates of this coal on the reaction rate constant was investigated during the test reaction of breakage of ether bonding. It was stated that pyrolyzed coal at the stage of maximally swollen grains increases the destruction rate constant by 16.7 times. The pyrolysates were investigated using X-ray diffraction, electron scanning microscopy (SEM), and FT–IR spectroscopy. The resistivity values were measured for the coal and its pyrolysates. Dichloromethane extracts of the pyrolyzed coals were analyzed by gas chromatography. It was proved that the composition and structure of substances in the layer of maximally swollen grains differ substantially from those of substances in the nearby layers. The authors suggest that in the maximally swollen grains some substances can be formed which have catalytic influence on the reaction of breakage of ether bonding.

  12. Structural models of vanadate-dependent haloperoxidases, their reactivity, immobilization on polymer support and catalytic activities

    Indian Academy of Sciences (India)

    Mannar R Maurya

    2011-03-01

    The design of structural and functional models of enzymes vanadate-dependent haloperoxidases (VHPO) and the isolation and/or generation of species having {VO(H2O)}, {VO2}, {VO(OH)} and {VO(O2)} cores, proposed as intermediate(s) during catalytic action, in solution have been studied. Catalytic potential of these complexes have been tested for oxo-transfer as well as oxidative bromination and sulfide oxidation reactions. Some of the oxidovanadium(IV) and dioxidovanadium(V) complexes have been immobilized on polymer support in order to improve their recycle ability during catalytic activities and turn over number. The formulations of the polymer-anchored complexes are based on the respective neat complexes and conclusions drawn from the various characterization studies. These catalysts have successfully been used for all catalytic reactions mentioned above. These catalysts are stable and recyclable.

  13. High activity in catalytic cracking of large molecules over micro-mesoporous silicoaluminophosphate with controlled morphology

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel micro-mesoporous silicoaluminophosphate(MUS-5) with controlled morphology has been first synthesized in a two-step route.The physical properties of the silicoaluminophosphate were characterized using XRD,SEM,TEM,nitrogen adsorption-desorption and NH3-TPD techniques.When the pH value of the solution system was varied in the range from 2.0 to 5.0,three different morphologies of silicoaluminophosphate including chain-like,flower-like and barrel-like morphology were obtained.Catalytic tests showed that the silicoaluminophosphate exhibited higher catalytic activity compared with the conventional microporous SAPO-5 under the same conditions for catalytic cracking of 1,3,5-triisopropylbenzene heavy aromatics.The remarkable catalytic reactivity was mainly attributed to the presence of the hierarchical porosity in the silicoaluminophosphate catalyst.

  14. Removal performance and mechanism of ibuprofen from water by catalytic ozonation using sludge-corncob activated carbon as catalyst.

    Science.gov (United States)

    Wang, Hongjuan; Zhang, Liqiu; Qi, Fei; Wang, Xue; Li, Lu; Feng, Li

    2014-09-01

    To discover the catalytic activity of sludge-corncob activated carbon in catalytic ozonation of Ibuprofen, the performance of sludge-corncob activated carbon and three selected commercial activated carbons as catalysts in catalytic ozonation was investigated. The observation indicates the degradation rate of Ibuprofen increases significantly in the presence of sludge-corncob activated carbon and the catalytic activity of sludge-corncob activated carbon is much higher than that of the other three commercial activated carbons. Ibuprofen's removal rate follows pseudo-first order kinetics model well. It is also found that the adsorption removal of Ibuprofen by sludge-corncob activated carbon is less than 30% after 40 min. And the removal efficiency of Ibuprofen in the hybrid ozone/sludge-corncob activated carbon system is higher than the sum of sludge-corncob activated carbon adsorption and ozonation alone, which is a supportive evidence for catalytic reaction. In addition, the results of radical scavenger experiments demonstrate that catalytic ozonation of Ibuprofen by sludge-corncob activated carbon follows a hydroxyl radical reaction pathway. During ozonation of Ibuprofen in the presence of activated carbon, ozone could be catalytically decomposed to form hydrogen peroxide, which can promote the formation of hydroxyl radical. The maximum amount of hydrogen peroxide occurs in the presence of sludge-corncob activated carbon, which can explain why sludge-corncob activated carbon has the best catalytic activity among four different activated carbons.

  15. Catalytic activity of cerium-doped Ru/Al2O3 during ozonation of dimethyl phthalate

    Institute of Scientific and Technical Information of China (English)

    Yunrui ZHOU; Wanpeng ZHU; Xun CHEN

    2008-01-01

    In this paper, factors influencing the mineraliza-tion of dimethyl phthalate (DMP) during catalytic ozona-tion with a cerium-doped Ru/Al2O3 catalyst were studied. The catalytic contribution was calculated through the results of a companrison experiment. It showed that doping cerium significantly enhanced catalytic activity. The total organic carbon (TOC) removal over the doped catalyst at 100 rain reached 75.1%, 61.3% using Ru/Al2O3 catalyst and only 14.0% using ozone alone. Catalytic activity reached the maximum when 0.2% of ruthenium and 1.0% of cerium'were simultaneously loaded onto Al2O3 support. Results of experiments on oxidation by ozone alone, adsorption of the catalyst, Ce ion's and heterogeneous catalytic ozonation confirmed that the contribution of het-erogeneous catalytic ozonation was about 50%, which showed the obvious effect of Ru-Ce/Al2O3 on catalytic activity.

  16. [Catalytic ozonation of nitrobenzene in water by acidification-activated red mud].

    Science.gov (United States)

    Kang, Ya-ning; Li, Hua-nan; Xu, Bing-bing; Qi, Fei; Zhao, Lun

    2013-05-01

    Red mud as one kind of aluminum industrial wastes was used as raw material for catalyst preparation. It was activated by acidification in order to enhance its catalytic activity in the system of catalytic ozonation. Furthermore, removal performance and reaction mechanism in degradation of organic pollutants were discussed. Results showed that acid modified red mud had more significant catalytic activity than the raw red mud. The removal efficiency of nitrobenzene by catalytic ozonation with acidified red mud (RM6.0) increased with the increasing ozone concentration. When the ozone concentration was increased from 0.4 mg x L(-1) to 1.7 mg x L(-1), the removal efficiency of nitrobenzene increased from 45% to 92%. There was a consistent effect of water pH on the removal efficiency and the ozone concentration variation. The variation of the removal efficiency depended on the initial water pH. This was because the concentration of OH(-) led to ozone decomposition to generate hydroxyl radicals. The higher water pH value led to the quenching of hydroxyl radicals, resulting in the reduction of catalytic activity of RM6.0. The experimental results of aqueous ozone concentration variation in the presence of RM6.0 and inhibition by hydroxyl radicals indicated that the main reaction mechanism was catalytic ozonation of NB. Firstly, aqueous ozone was absorbed onto the surface of RM6.0, and then the concentrated ozone oxidized NB in water which was with a combination of direct and indirect oxidation. In catalytic reaction, hydroxyl radicals were present, which were generated during the oxidation of NB on the surface of RM6.0.

  17. Effects of Particle Size on the Gas Sensitivity and Catalytic Activity of In2O3

    Science.gov (United States)

    Zhang, Xiaoshui; Gu, Ruiqin; Zhao, Jinling; Jin, Guixin; Zhao, Mengke; Xue, Yongliang

    2015-10-01

    Nanosized In2O3 powders with different particle sizes were prepared by the microemulsion synthetic method. The effects of particle size on the gas-sensing and catalytic properties of the as-prepared In2O3 were investigated. Reductions in particle size to nanometer levels improved the sensitivity and catalytic activity of In2O3 to i-C4H10 and C2H5OH. The sensitivity of nanosized In2O3 (<42 nm) sensors to i-C4H10, H2 and C2H5OH was 2-4 times higher than that of chemically precipitated In2O3 (130 nm) sensor. A nearly linear relationship was observed between the catalytic activity and specific surface area of In2O3 for the oxidation of i-C4H10 and C2H5OH at 275 °C. The relationship between gas sensitivity and catalytic activity was further discussed. The results of this work reveal that catalytic activity plays a key role in enhancing the sensitivity of gas-sensing materials.

  18. Effect of BaO on Catalytic Activity of Pt-Rh TWC

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of BaO doping on the three-way catalytic activity of Pt-Rh catalyst and on water-gas shift were investigated. The results show that the light-off temperatures of hydrocarbon and carbon monoxide and nitrogen oxides of the fresh catalysts slightly differ from those of the aged catalysts, and the catalysts containing CeO2-ZrO2-BaO have lower lightoff temperature and better catalytic activity than these containing BaO and CeO2-ZrO2 after hydrothermal aging for 5 h at 1000 C. The catalysts were characterized by means of the temperature-programmed reduction (TPR) in hydrogen and the temperature-programmed desorption (TPD) in oxygen. It is confirmed that the suggested route of CeO2-ZrO2-BaO by coprecipitation can improve the catalytic activity of catalysts.

  19. cDNA cloning of human DNA topoisomerase I. Catalytic activity of a 67.7-kDa carboxyl-terminal fragment

    International Nuclear Information System (INIS)

    cDNA clones encoding human topoisomerase I were isolated from an expression vector library (λgt11) screened with autoimmune anti-topoisomerase I serum. One of these clones has been expressed as a fusion protein comprised of a 32-kDa fragment of the bacterial TrpE protein linked to 67.7 kDa of protein encoded by the cDNA. Three lines of evidence indicate that the cloned cDNA encodes topoisomerase I. (i) Proteolysis maps of the fusion protein and human nuclear topoisomerase I are essentially identical. (ii) The fusion protein relaxes supercoiled DNA, an activity that can be immunoprecipitated by anti-topoisomerase I serum. (iii) Sequence analysis has revealed that the longest cDNA clone (3645 base pairs) encodes a protein of 765 amino acids that shares 42% identity with Saccharomyces cerevisiae topoisomerase I. The sequence data also show that the catalytically active 67.7-kDa fragment is comprised of the carboxyl terminus

  20. Fluorescence kinetics of Trp-Trp dipeptide and its derivatives in water via ultrafast fluorescence spectroscopy.

    Science.gov (United States)

    Jia, Menghui; Yi, Hua; Chang, Mengfang; Cao, Xiaodan; Li, Lei; Zhou, Zhongneng; Pan, Haifeng; Chen, Yan; Zhang, Sanjun; Xu, Jianhua

    2015-08-01

    Ultrafast fluorescence dynamics of Tryptophan-Tryptophan (Trp-Trp/Trp2) dipeptide and its derivatives in water have been investigated using a picosecond resolved time correlated single photon counting (TCSPC) apparatus together with a femtosecond resolved upconversion spectrophotofluorometer. The fluorescence decay profiles at multiple wavelengths were fitted by a global analysis technique. Nanosecond fluorescence kinetics of Trp2, N-tert-butyl carbonyl oxygen-N'-aldehyde group-l-tryptophan-l-tryptophan (NBTrp2), l-tryptophan-l-tryptophan methyl ester (Trp2Me), and N-acetyl-l-tryptophan-l-tryptophan methyl ester (NATrp2Me) exhibit multi-exponential decays with the average lifetimes of 1.99, 3.04, 0.72 and 1.22ns, respectively. Due to the intramolecular interaction between two Trp residues, the "water relaxation" lifetime was observed around 4ps, and it is noticed that Trp2 and its derivatives also exhibit a new decay with a lifetime of ∼100ps, while single-Trp fluorescence decay in dipeptides/proteins shows 20-30ps. The intramolecular interaction lifetime constants of Trp2, NBTrp2, Trp2Me and NATrp2Me were then calculated to be 3.64, 0.93, 11.52 and 2.40ns, respectively. Candidate mechanisms (including heterogeneity, solvent relaxation, quasi static self-quenching or ET/PT quenching) have been discussed.

  1. A Model of Irregular Impurity at the Surface of Nanoparticle and Catalytic Activity

    Institute of Scientific and Technical Information of China (English)

    I.V.Blinova; V.V.Gusarov; I.Yu.Popov

    2012-01-01

    A problem of nanocatalyst improvement is considered. The existence of irregularities at the surface of nanoparticle leads to the increasing of the surface/volume ratio and, correspondingly, to the improvement of the catalytic activity. But this impurity gives one an additional effect due to the change of the electronic density at the surface. We suggest simple model for the description of this effect. The model allows one to find the discrete spectrum of the Schrdinger operator for nanoparticle. Due to this impurity induced bound states the electron density increases near the surface. It leads to the increase of the catalytic activity of nanoparticles with surface impurities.

  2. Influence of Al content on textural properties and catalytic activity of hierarchical porous aluminosilicate materials

    Indian Academy of Sciences (India)

    Ling Xu; Limei Duan; Zongrui Liu; Jingqi Guan; Qiubin Kan

    2013-12-01

    A series of hierarchical porous aluminosilicate materials were prepared using hydrothermal treatment of the composite formed by polystyrene colloidal spheres and aluminosilicate gel. Influence of Al content on the textural properties, acidic properties and catalytic activity of the hierarchical porous aluminosilicate materials was studied. The results showed that textural and acidic properties of the hierarchical porous aluminosilicate materials were strongly related to Al content. As Al content is increased (Si/Al = 25), the hierarchical porous catalysts exhibited higher catalytic activity and major product selectivity for alkylation of phenol with tert-butanol than the catalysts with a lower Al content (Si/Al = 50).

  3. Catalytic decomposition of low level ozone with gold nanoparticles supported on activated carbon

    Institute of Scientific and Technical Information of China (English)

    Pengyi ZHANG; Bo ZHANG; Rui SHI

    2009-01-01

    Highly dispersed gold nanoparticles were supported on coal-based activated carbon (AC) by a sol immobilization method and were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature. Nitrogen adsorption-desorption,scanning electron microscope (SEM), and X-ray photo-electron spectroscopy (XPS) were used to characterize the catalysts before and after ozone decomposition. The results showed that the supported gold nanoparticles prepared with microwave heating were much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating, exhibiting higher catalytic activity for ozone decomposition. The pH values of gold precursor solution significantly influenced the catalytic activity of supported gold for ozone decomposition, and the best pH value was 8. In the case of space velocity of 120000 h-1, inlet ozone concentration of 50mg/m3, and relative humidity of 45%, the Au/AC catalyst maintained the ozone removal ratio at 90.7% after 2500 min. After being used for ozone decomposition, the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly, while its specific surface area and pore volume only decreased a little.Ozone was mainly catalytically decomposed by the gold nanoparticles supported on the activated carbon.

  4. The Impact of Enzyme Orientation and Electrode Topology on the Catalytic Activity of Adsorbed Redox Enzymes

    Science.gov (United States)

    McMillan, Duncan G. G.; Marritt, Sophie J.; Kemp, Gemma L.; Gordon-Brown, Piers; Butt, Julea N.; Jeuken, Lars J. C.

    2014-01-01

    It is well established that the structural details of electrodes and their interaction with adsorbed enzyme influences the interfacial electron transfer rate. However, for nanostructured electrodes, it is likely that the structure also impacts on substrate flux near the adsorbed enzymes and thus catalytic activity. Furthermore, for enzymes converting macro-molecular substrates it is possible that the enzyme orientation determines the nature of interactions between the adsorbed enzyme and substrate and therefore catalytic rates. In essence the electrode may impede substrate access to the active site of the enzyme. We have tested these possibilities through studies of the catalytic performance of two enzymes adsorbed on topologically distinct electrode materials. Escherichia coli NrfA, a nitrite reductase, was adsorbed on mesoporous, nanocrystalline SnO2 electrodes. CymA from Shewanella oneidensis MR-1 reduces menaquinone-7 within 200 nm sized liposomes and this reaction was studied with the enzyme adsorbed on SAM modified ultra-flat gold electrodes. PMID:24634538

  5. The Impact of Enzyme Orientation and Electrode Topology on the Catalytic Activity of Adsorbed Redox Enzymes.

    Science.gov (United States)

    McMillan, Duncan G G; Marritt, Sophie J; Kemp, Gemma L; Gordon-Brown, Piers; Butt, Julea N; Jeuken, Lars J C

    2013-11-01

    It is well established that the structural details of electrodes and their interaction with adsorbed enzyme influences the interfacial electron transfer rate. However, for nanostructured electrodes, it is likely that the structure also impacts on substrate flux near the adsorbed enzymes and thus catalytic activity. Furthermore, for enzymes converting macro-molecular substrates it is possible that the enzyme orientation determines the nature of interactions between the adsorbed enzyme and substrate and therefore catalytic rates. In essence the electrode may impede substrate access to the active site of the enzyme. We have tested these possibilities through studies of the catalytic performance of two enzymes adsorbed on topologically distinct electrode materials. Escherichia coli NrfA, a nitrite reductase, was adsorbed on mesoporous, nanocrystalline SnO2 electrodes. CymA from Shewanella oneidensis MR-1 reduces menaquinone-7 within 200 nm sized liposomes and this reaction was studied with the enzyme adsorbed on SAM modified ultra-flat gold electrodes.

  6. Study on the Carbon-Methanation and Catalytic Activity of Ru/AC for Ammonia Synthesis

    Institute of Scientific and Technical Information of China (English)

    祝一锋; 李小年; 季德春; 刘化章

    2004-01-01

    The effects of promoters K, Ba, Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon (Ru/AC) for ammonia synthesis have been studied by means of TG-DTG (thermalgravity-differential thermalgravity), temperature-programmed desorption, and activity test. Promoters Ba,K, and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly. Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters. Indeed, the triply promoted catalyst showed the highest activity, coupled to a surprisingly high resistance to methanation. The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen. The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen, which results in the decrease of catalytic activity.

  7. Sulphate-activated phosphorylase b: the pH-dependence of catalytic activity.

    Science.gov (United States)

    Zographos, S E; Oikonomakos, N G; Dixon, H B; Griffin, W G; Johnson, L N; Leonidas, D D

    1995-09-01

    The pH-dependence of sulphate-activated phosphorylase b has been studied in the direction of glycogen synthesis. The bell-shaped curve of the pH-dependence of the catalytic constant for the AMP-activated enzyme showed pK values of 6.1 and 7.3, but the curve for the enzyme activated by 0.9 M ammonium sulphate showed a drop of activity on the acid side at much higher pH values. Its bell was centred at pH 7.8 but it was too narrow to be characterized by only two pK values. The narrowness of the curve could be explained by positive co-operativity, but not its unusually steep acid side. We suggest that the fall on the acid side is due to more than one hydronation (addition of H+). The points can be fitted by a curve with two de-activating hydronations and a de-activating dehydronation having identical titration pK values of 7.5, and hence molecular values of 7.0, 7.5 and 8.0. If both 0.9 M ammonium sulphate and 5 mM AMP are added, the bell is as broad as with AMP alone, but is somewhat raised in pH optimum. The results are discussed in the light of new structural data from crystallographic studies on binary complexes of the enzyme. PMID:7654195

  8. Role of Phe-99 and Trp-196 of sepiapterin reductase from Chlorobium tepidum in the production of L-threo-tetrahydrobiopterin

    Institute of Scientific and Technical Information of China (English)

    Supangat; Sun Ok Park; Kyung Hye Seo; Sang Yeol Lee; Young Shik Park; Kon Ho Lee

    2008-01-01

    Sepiapterin reductase from Chlorobium tepidum (cSR) catalyzes the synthesis of a distinct tetrahydrobiopterin (BH4), L-threo-BH4, different from the mammalian enzyme product. The 3-D crystal structure of cSR has revealed that the product configuration is determined solely by the substrate binding mode within the well-conserved catalytic triads. In cSR, the sepiapterin is stacked between two aromatic side chains of Phe-99 and Trp-196 and rotated approximately 180o around the active site from the position in mouse sepiapterin reductase. To confirm their roles in substrate binding, we mutated Phe-99 and/or Trp-196 to alanine (F99A, W196A) by site-directed mutagenesis and comparatively examined substrate binding of the purified proteins by kinetics analysis and differential scanning calorimetry. These mutants had higher Km values than the wild type. Remarkably, the W196A mutation resulted in a higher Km increase compared with the F99A mutation. Consistent with the results, the melting temperature (Tm) in the presence of sepiapterin was lower in the mutant proteins and the worst was W196A. These findings indicate that the two residues are indispensable for substrate binding in cSR, and Trp-196 is more important than Phe-99 for different stereoisomer production.

  9. Catalytic deactivation of methane steam reforming catalysts. I. Activation

    Energy Technology Data Exchange (ETDEWEB)

    Agnelli, M.E.; Demicheli, M.C.; Ponzi, E.N.

    1987-08-01

    An alumina-supported catalyst was studied both in its original state and after activation and sintering. Chemical composition and textural properties were determined, and crystalline compounds were identified. Active-phase and support transformations occurring during activation were determined by differential thermoanalysis (DTA), temperature-programmed reduction (TPR), and X-ray diffraction. The catalyst activated by means of various procedures was characterized by measuring crystallite size.

  10. Effects of in vitro fertilization and embryo culture on TRP53 and Bax expression in B6 mouse embryos

    Directory of Open Access Journals (Sweden)

    Chami Omar

    2006-11-01

    Full Text Available Abstract In the mouse, embryo culture results in a characteristic phenotype of retarded embryo preimplantation development and reduced numbers of cells within embryos. The expression of TRP53 is central to the regulation of the cell's capacity to proliferate and survive. In this study we found that Trp53 mRNA is expressed throughout the preimplantation stage of development. Levels of TRP53 protein expression were low during the cleavage stages and increased at the morula and blastocyst stages in B6 embryos collected from the reproductive tract. Embryos collected at the zygote stage and cultured for 96 h also showed low levels of TRP53 expression at precompaction stages. There were higher levels of TRP53 in cultured morula and the level in cultured blastocysts was clearly increased above blastocysts collected directly from the uterus. Immunolocalization of TRP53 showed that its increased expression in cultured blastocysts corresponded with a marked accumulation of TRP53 within the nuclei of embryonic cells. This pattern of expression was enhanced in embryos produced by in vitro fertilization and subjected to culture. The TRP53 was transcriptionally active since culture also induced increased expression of Bax, yet this did not occur in embryos lacking Trp53 (Trp53-/-. The rate of development of Trp53-/- zygotes to the blastocyst stage was not different to wildtype controls when embryos were cultured in groups of ten but was significantly faster when cultured individually. The results show that zygote culture resulted in the accumulation of transcription activity of TRP53 in the resulting blastocysts. This accounts for the adverse effects of culture of embryos individually, but does not appear to be the sole cause of the retarded preimplantation stage growth phenotype associated with culture in vitro.

  11. Studies relevant to the catalytic activation of carbon monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Ford, P.C.

    1992-06-04

    Research activity during the 1991--1992 funding period has been concerned with the following topics relevant to carbon monoxide activation. (1) Exploratory studies of water gas shift catalysts heterogenized on polystyrene based polymers. (2) Mechanistic investigation of the nucleophilic activation of CO in metal carbonyl clusters. (3) Application of fast reaction techniques to prepare and to investigate reactive organometallic intermediates relevant to the activation of hydrocarbons toward carbonylation and to the formation of carbon-carbon bonds via the migratory insertion of CO into metal alkyl bonds.

  12. CATALYTIC ACTIVITIES OF RARE-EARTH CALIXARENE COMPLEXES IN POLYMER SYNTHESES

    Institute of Scientific and Technical Information of China (English)

    Zhi-quan Shen

    2005-01-01

    The studies of our group on the catalytic activities of rare earth calixarene complexes in polymer syntheses are reviewed. Rare earth calixarene complexes are effect catalysts for the polymerizations of butadiene, isoprene, ethylene,styrene, propylene oxide, styrene oxide, trimethylene carbonate and 2,2-dimethyl-trimethylene carbonate.

  13. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  14. Synthesis of concave gold nanocuboids with high-index facets and their enhanced catalytic activity.

    Science.gov (United States)

    Li, Lidong; Peng, Yi; Yue, Yonghai; Hu, Ye; Liang, Xiu; Yin, Penggang; Guo, Lin

    2015-07-25

    Novel concave gold nanocuboids bounded by 24 high-index {611} facets are synthesized using the seed-mediated growth method via an overgrowth mechanism. The as-synthesized products demonstrated greatly enhanced catalytic activity for the electro-oxidation of glucose and the reduction of 4-nitrothiophenol (4-NTP) under a laser. PMID:26097908

  15. Synthesis and catalytic activity of histidine-based NHC ruthenium complexes

    OpenAIRE

    Monney, Angèle; Venkatachalam, Galmari; Albrecht, Martin

    2011-01-01

    Main-chain C,N-protected histidine has been successfully alkylated at both side-chain nitrogens. The corresponding histidinium salt was metallated with ruthenium(II) by a transmetalation procedure, thus providing histidine-derived NHC ruthenium complexes. These bio-inspired comsxsxsplexes show appreciable activity in the catalytic transfer hydrogenation of ketones. peer-reviewed

  16. p53 regulation by TRP2 is not pervasive in melanoma.

    Directory of Open Access Journals (Sweden)

    Roland Houben

    Full Text Available p53 is a central tumor suppressor protein and its inhibition is believed to be a prerequisite for cancer development. In approximately 50% of all malignancies this is achieved by inactivating mutations in the p53 gene. However, in several cancer entities, including melanoma, p53 mutations are rare. It has been recently proposed that tyrosinase related protein 2 (TRP2, a protein involved in melanin synthesis, may act as suppressor of the p53 pathway in melanoma. To scrutinize this notion we analyzed p53 and TRP2 expression by immunohistochemistry in 172 melanoma tissues and did not find any correlation. Furthermore, we applied three different TRP2 shRNAs to five melanoma cell lines and could not observe a target specific effect of the TRP2 knockdown on either p53 expression nor p53 reporter gene activity. Likewise, ectopic expression of TRP2 in a TRP2 negative melanoma cell line had no impact on p53 expression. In conclusion our data suggest that p53 repression critically controlled by TRP2 is not a general event in melanoma.

  17. Activity prediction of substrates in NADH-dependent carbonyl reductase by docking requires catalytic constraints and charge parameterization of catalytic zinc environment.

    Science.gov (United States)

    Dhoke, Gaurao V; Loderer, Christoph; Davari, Mehdi D; Ansorge-Schumacher, Marion; Schwaneberg, Ulrich; Bocola, Marco

    2015-11-01

    Molecular docking of substrates is more challenging compared to inhibitors as the reaction mechanism has to be considered. This becomes more pronounced for zinc-dependent enzymes since the coordination state of the catalytic zinc ion is of greater importance. In order to develop a predictive substrate docking protocol, we have performed molecular docking studies of diketone substrates using the catalytic state of carbonyl reductase 2 from Candida parapsilosis (CPCR2). Different docking protocols using two docking methods (AutoDock Vina and AutoDock4.2) with two different sets of atomic charges (AM1-BCC and HF-RESP) for catalytic zinc environment and substrates as well as two sets of vdW parameters for zinc ion were examined. We have selected the catalytic binding pose of each substrate by applying mechanism based distance criteria. To compare the performance of the docking protocols, the correlation plots for the binding energies of these catalytic poses were obtained against experimental Vmax values of the 11 diketone substrates for CPCR2. The best correlation of 0.73 was achieved with AutoDock4.2 while treating catalytic zinc ion in optimized non-bonded (NBopt) state with +1.01 charge on the zinc ion, compared to 0.36 in non-bonded (+2.00 charge on the zinc ion) state. These results indicate the importance of catalytic constraints and charge parameterization of catalytic zinc environment for the prediction of substrate activity in zinc-dependent enzymes by molecular docking. The developed predictive docking protocol described here is in principle generally applicable for the efficient in silico substrate spectra characterization of zinc-dependent ADH.

  18. Synthesis and antibacterial activity of cyclo(L-Trp-L-Pro) derivatives%环(L-色-L-脯)衍生物的合成及其抑菌活性研究

    Institute of Scientific and Technical Information of China (English)

    吴昊; 马养民; 冯婷婷

    2014-01-01

    Four cyclo(L-Trp-L-Pro)derivatives were synthesized starting with methyl L-tryptophanate hydrochloride,aromatic alde-hydes and N-Fmoc-L-proline through Pictet-Spengler reaction,Schotten-Baumann reaction,NBS ring-opening and base catalyzed an-nelation. The structures were characterized by m. p. tests,NMR spectrum and elemental analysis. All compounds were shown good activity against bacteria according to the antimicrobial activities test.%以L-色氨酸甲酯盐酸盐、芳香醛和N-Fmoc-L-脯氨酸为原料,经过Pictet-Spengler反应、Schotten-Baumann反应、NBS开环反应、碱催化增环反应,得到4个环( L-色-L-脯)的衍生物,其结构均经过熔点测定、NMR、元素分析表征。在抑菌活性测试中发现,该类化合物对细菌有较好的抑制活性。

  19. Comparison of three microbial hosts for the expression of an active catalytic scFv.

    Science.gov (United States)

    Robin, Sylvain; Petrov, Kliment; Dintinger, Thierry; Kujumdzieva, Anna; Tellier, Charles; Dion, Michel

    2003-01-01

    Antibodies represent an interesting protein framework on which catalytic functions can be grafted. In previous studies, we have reported the characterization of the catalytic antibody 4B2 obtained on the basis of the "bait and switch" strategy which catalyzes two different chemical reactions: the allylic isomerization of beta,gamma-unsaturated ketones and the Kemp elimination. We have cloned the antibody 4B2 and expressed it as a single-chain Fv (scFv) fragment in different expression systems, Escherichia coli and two yeasts species, in order to elicit the most suitable system to study its catalytic activity. The scFv4B2 was secreted as an active form in the culture medium of Pichia pastoris and Kluyveromyces lactis, which led respectively to 4 and 1.3mg/l after purification. In E. coli, different strategies were investigated to increase the cytoplasmic soluble fraction, which resulted, in all cases, in the expression of a low amount of functional antibodies. By contrast, substantial amount of scFv4B2 could be purified when it was expressed as inclusion bodies (12mg/l) and submitted to an in vitro refolding process. Its catalytic activity was measured and proved to be comparable to that of the whole IgG. However, the instability of the scFv4B2 in solution prevented from an exhaustive characterization of its activity and stabilization of this protein appears to be essential before designing strategies to improve its catalytic activity. PMID:12531284

  20. Positions of Trp codons in the leader peptide-coding region of the at operon influence anti-trap synthesis and trp operon expression in Bacillus licheniformis.

    Science.gov (United States)

    Levitin, Anastasia; Yanofsky, Charles

    2010-03-01

    Tryptophan, phenylalanine, tyrosine, and several other metabolites are all synthesized from a common precursor, chorismic acid. Since tryptophan is a product of an energetically expensive biosynthetic pathway, bacteria have developed sensing mechanisms to downregulate synthesis of the enzymes of tryptophan formation when synthesis of the amino acid is not needed. In Bacillus subtilis and some other Gram-positive bacteria, trp operon expression is regulated by two proteins, TRAP (the tryptophan-activated RNA binding protein) and AT (the anti-TRAP protein). TRAP is activated by bound tryptophan, and AT synthesis is increased upon accumulation of uncharged tRNA(Trp). Tryptophan-activated TRAP binds to trp operon leader RNA, generating a terminator structure that promotes transcription termination. AT binds to tryptophan-activated TRAP, inhibiting its RNA binding ability. In B. subtilis, AT synthesis is upregulated both transcriptionally and translationally in response to the accumulation of uncharged tRNA(Trp). In this paper, we focus on explaining the differences in organization and regulatory functions of the at operon's leader peptide-coding region, rtpLP, of B. subtilis and Bacillus licheniformis. Our objective was to correlate the greater growth sensitivity of B. licheniformis to tryptophan starvation with the spacing of the three Trp codons in its at operon leader peptide-coding region. Our findings suggest that the Trp codon location in rtpLP of B. licheniformis is designed to allow a mild charged-tRNA(Trp) deficiency to expose the Shine-Dalgarno sequence and start codon for the AT protein, leading to increased AT synthesis. PMID:20061467

  1. Different expression patterns of TRP genes in murine B and T lymphocytes

    International Nuclear Information System (INIS)

    A prolonged increase in the intracellular calcium concentration ([Ca2+]i) is essential for lymphocyte activation that includes cell proliferation and differentiation. This increase in [Ca2+]i results from Ca2+ release from the intracellular store and the subsequent Ca2+ influx from the extracellular environment via calcium channels located on the plasma membrane. Although transient receptor potential (TRP) channels have been reported to play important roles in the [Ca2+]i increase in lymphocytes, the function of these channels in lymphocyte activation remains unknown. Here, we report the comprehensive expression profile of TRP channel gene families including TRPC, TRPV, and TRPM in the murine immune system. RT-PCR analysis revealed different expression patterns of the TRP channel genes in B and T lymphocytes isolated from the spleen. Therefore, our results provide an appropriate reference of TRP gene expression in murine lymphocytes

  2. Anacardic acid inhibits the catalytic activity of matrix metalloproteinase-2 and matrix metalloproteinase-9.

    Science.gov (United States)

    Omanakuttan, Athira; Nambiar, Jyotsna; Harris, Rodney M; Bose, Chinchu; Pandurangan, Nanjan; Varghese, Rebu K; Kumar, Geetha B; Tainer, John A; Banerji, Asoke; Perry, J Jefferson P; Nair, Bipin G

    2012-10-01

    Cashew nut shell liquid (CNSL) has been used in traditional medicine for the treatment of a wide variety of pathophysiological conditions. To further define the mechanism of CNSL action, we investigated the effect of cashew nut shell extract (CNSE) on two matrix metalloproteinases, MMP-2/gelatinase A and MMP-9/gelatinase B, which are known to have critical roles in several disease states. We observed that the major constituent of CNSE, anacardic acid, markedly inhibited the gelatinase activity of 3T3-L1 cells. Our gelatin zymography studies on these two secreted gelatinases, present in the conditioned media from 3T3-L1 cells, established that anacardic acid directly inhibited the catalytic activities of both MMP-2 and MMP-9. Our docking studies suggested that anacardic acid binds into the MMP-2/9 active site, with the carboxylate group of anacardic acid chelating the catalytic zinc ion and forming a hydrogen bond to a key catalytic glutamate side chain and the C15 aliphatic group being accommodated within the relatively large S1' pocket of these gelatinases. In agreement with the docking results, our fluorescence-based studies on the recombinant MMP-2 catalytic core domain demonstrated that anacardic acid directly inhibits substrate peptide cleavage in a dose-dependent manner, with an IC₅₀ of 11.11 μM. In addition, our gelatinase zymography and fluorescence data confirmed that the cardol-cardanol mixture, salicylic acid, and aspirin, all of which lack key functional groups present in anacardic acid, are much weaker MMP-2/MMP-9 inhibitors. Our results provide the first evidence for inhibition of gelatinase catalytic activity by anacardic acid, providing a novel template for drug discovery and a molecular mechanism potentially involved in CNSL therapeutic action. PMID:22745359

  3. Synthesis, Characterization and Catalytic Activity of Cu/Cu2O Nanoparticles Prepared in Aqueous Medium

    Directory of Open Access Journals (Sweden)

    Sayed M. Badawy

    2015-07-01

    Full Text Available Copper/Copper oxide (Cu/Cu2O nanoparticles were synthesized by modified chemical reduction method in an aqueous medium using hydrazine as reducing agent and copper sulfate pentahydrate as precursor. The Cu/Cu2O nanoparticles were characterized by X-ray Diffraction (XRD, Energy Dispersive X-ray Fluorescence (EDXRF, Scanning Electron Microscope (SEM, and Transmission Electron Microscope (TEM. The analysis revealed the pattern of face-centered cubic (fcc crystal structure of copper Cu metal and cubic cuprites structure for Cu2O. The SEM result showed monodispersed and agglomerated particles with two micron sizes of about 180 nm and 800 nm, respectively. The TEM result showed few single crystal particles of face-centered cubic structures with average particle size about 11-14 nm. The catalytic activity of Cu/Cu2O nanoparticles for the decomposition of hydrogen peroxide was investigated and compared with manganese oxide MnO2. The results showed that the second-order equation provides the best correlation for the catalytic decomposition of H2O2 on Cu/Cu2O. The catalytic activity of hydrogen peroxide by Cu/Cu2O is less than the catalytic activity of MnO2 due to the presence of copper metal Cu with cuprous oxide Cu2O. © 2015 BCREC UNDIP. All rights reservedReceived: 6th January 2015; Revised: 14th March 2015; Accepted: 15th March 2015How to Cite: Badawy, S.M., El-Khashab, R.A., Nayl, A.A. (2015. Synthesis, Characterization and Catalytic Activity of Cu/Cu2O Nanoparticles Prepared in Aqueous Medium. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (2: 169-174. (doi:10.9767/bcrec.10.2.7984.169-174 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.7984.169-174  

  4. Engineering a hyper-catalytic enzyme by photo-activated conformation modulation

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Pratul K [ORNL

    2012-01-01

    Enzyme engineering for improved catalysis has wide implications. We describe a novel chemical modification of Candida antarctica lipase B that allows modulation of the enzyme conformation to promote catalysis. Computational modeling was used to identify dynamical enzyme regions that impact the catalytic mechanism. Surface loop regions located distal to active site but showing dynamical coupling to the reaction were connected by a chemical bridge between Lys136 and Pro192, containing a derivative of azobenzene. The conformational modulation of the enzyme was achieved using two sources of light that alternated the azobenzene moiety in cis and trans conformations. Computational model predicted that mechanical energy from the conformational fluctuations facilitate the reaction in the active-site. The results were consistent with predictions as the activity of the engineered enzyme was found to be enhanced with photoactivation. Preliminary estimations indicate that the engineered enzyme achieved 8-52 fold better catalytic activity than the unmodulated enzyme.

  5. Gold Sulfinyl Mesoionic Carbenes: Synthesis, Structure, and Catalytic Activity.

    Science.gov (United States)

    Frutos, María; Avello, Marta G; Viso, Alma; Fernández de la Pradilla, Roberto; de la Torre, María C; Sierra, Miguel A; Gornitzka, Heinz; Hemmert, Catherine

    2016-08-01

    Gold mesoionic carbenes having a chiral sulfoxide group attached to the C4 position of the five membered ring have been prepared and tested as catalysts in the cycloisomerization of enynes. These new catalysts are very efficient, with the sulfoxide moiety playing a key role in their activity and the N1-substituent in control of the regioselectivity of these processes. PMID:27403763

  6. Role of renal TRP channels in physiology and pathology.

    Science.gov (United States)

    Tomilin, Viktor; Mamenko, Mykola; Zaika, Oleg; Pochynyuk, Oleh

    2016-05-01

    Kidneys critically contribute to the maintenance of whole-body homeostasis by governing water and electrolyte balance, controlling extracellular fluid volume, plasma osmolality, and blood pressure. Renal function is regulated by numerous systemic endocrine and local mechanical stimuli. Kidneys possess a complex network of membrane receptors, transporters, and ion channels which allows responding to this wide array of signaling inputs in an integrative manner. Transient receptor potential (TRP) channel family members with diverse modes of activation, varied permeation properties, and capability to integrate multiple downstream signals are pivotal molecular determinants of renal function all along the nephron. This review summarizes experimental data on the role of TRP channels in a healthy mammalian kidney and discusses their involvement in renal pathologies. PMID:26385481

  7. New insights into TRP channels: Interaction with pattern recognition receptors.

    Science.gov (United States)

    Han, Huirong; Yi, Fan

    2014-01-01

    An increasing number of studies have implicated that the activation of innate immune system and inflammatory mechanisms are of importance in the pathogenesis of numerous diseases. The innate immune system is present in almost all multicellular organisms in response to pathogens or tissue injury, which is performed via germ-line encoded pattern-recognition receptors (PRRs) to recognize pathogen-associated molecular patterns (PAMPs) or dangers-associated molecular patterns (DAMPs). Intracellular pathways linking immune and inflammatory response to ion channel expression and function have been recently identified. Among ion channels, transient receptor potential (TRP) channels are a major family of non-selective cation-permeable channels that function as polymodal cellular sensors involved in many physiological and pathological processes. In this review, we summarize current knowledge about classifications, functions, and interactions of TRP channels and PRRs, which may provide new insights into their roles in the pathogenesis of inflammatory diseases.

  8. Study on the active sites of Cu-ZSM-5 in trichloroethylene catalytic combustion with air

    Institute of Scientific and Technical Information of China (English)

    Cheng Hua Xu; Chuan Qi Liu; Yan Zhong; Xiu Zhou Yang; Jian Ying Liu; Ying Chun Yang; Zhi Xiang Ye

    2008-01-01

    The catalytic activity of Cu-ZSM-5 in trichloroethylene (TCE) combustion increases with the increasing skeletal Cu amount and however decreases with the increase of surface amorphous CuO,which is detected by infrared spectroscopy (IR) and diffuse reflectance ultraviolet-visible spectroscopy (DRS-UV-vis),therefore the skeletal Cu species are concluded to be the active sites for the TCE combustion.

  9. Chelating ruthenium phenolate complexes: synthesis, general catalytic activity, and applications in olefin metathesis polymerization.

    Science.gov (United States)

    Kozłowska, Anna; Dranka, Maciej; Zachara, Janusz; Pump, Eva; Slugovc, Christian; Skowerski, Krzysztof; Grela, Karol

    2014-10-20

    Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer.

  10. Chelating ruthenium phenolate complexes: synthesis, general catalytic activity, and applications in olefin metathesis polymerization.

    Science.gov (United States)

    Kozłowska, Anna; Dranka, Maciej; Zachara, Janusz; Pump, Eva; Slugovc, Christian; Skowerski, Krzysztof; Grela, Karol

    2014-10-20

    Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer. PMID:25204738

  11. Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

    Science.gov (United States)

    Shim, Wang Geun; Nahm, Seung Won; Park, Hyuk Ryeol; Yun, Hyung Sun; Seo, Seong Gyu; Kim, Sang Chai

    2011-02-01

    To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

  12. Spectroscopic properties and the catalytic activity of new organo-lead supramolecular coordination polymer containing quinoxaline

    Science.gov (United States)

    Etaiw, Safaa El-din H.; Abdou, Safaa N.

    2015-01-01

    The 3D-supramolecular coordination polymer (SCP) 3∞[ Cu2(CN)3(Me3Pb)(qox)], 1, as the first example of the CuCN SCP containing the (Me3Pb) fragment, was explored to investigate its catalytic and photo-catalytic activities. The structure of 1 contains two chemically identical but crystallographically different [Cu2(CN)3ṡMe3Pbṡqox]2 units with four Cu(I) sites assuming distorted TP-3 geometry. Two non-linear chains of equal abundance are formed producing corrugated parallel chains which are connected laterally by quinoxaline creating 2D-layers which are arranged parallel in an (AB⋯AB⋯AB)n fashion forming 3D-network. IR, mass, electronic absorption and fluorescence spectra are also investigated. The SCP 1 is diamagnetic and exhibits good catalytic and photo-catalytic activities for the degradation of methylene blue (MB). The reaction is first order with respect to MB dye. The irradiation of the reaction with UV-light enhanced the rate of MB mineralization. The efficiency of recycled the 1 and the mechanism of degradation of MB dye were investigated.

  13. Trends in Catalytic Activity for SOFC Anode materials

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Bessler, W. G.

    2008-01-01

    Quantum mechanical calculations on the level of density-functional theory are used to calculate the stability of surface-adsorbed hydrogen atoms, oxygen atoms, and hydroxyl radicals for a variety of metals (Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Pt, Au) that may be used as electrode materials...... for solid oxide fuel cell (SOFC) anodes. The reaction energies along the hydrogen oxidation pathway were quantified for both, oxygen spillover and hydrogen spillover mechanisms at the three-phase boundary. The ab initio results are compared to previously-obtained experimental anode activities measured...... that oxygen spillover, where adsorbed oxygen is a key intermediate, is the dominant reaction pathway under the conditions used in the experiments. In this way the activity is linked directly to the microscopic binding affinities of reaction intermediates, providing a new understanding of the anode reaction...

  14. Stability and phase transfer of catalytically active platinum nanoparticle suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Sriram, Indira; Curtin, Alexandra E.; Chiaramonti, Ann N.; Cuchiaro, J. Hunter; Weidner, Andrew R.; Tingley, Tegan M.; Greenlee, Lauren F.; Jeerage, Kavita M., E-mail: jeerage@boulder.nist.gov [National Instrument of Standards and Technology, Applied Chemicals and Materials Division (United States)

    2015-05-15

    In this work, we present a robust synthesis protocol for platinum nanoparticles that yields a monomodal dispersion of particles that are approximately 100 nm in diameter. We determine that these particles are actually agglomerates of much smaller particles, creating a “raspberry” morphology. We demonstrate that these agglomerates are stable at room temperature for at least 8 weeks by dynamic light scattering. Furthermore, we demonstrate consistent electrocatalytic activity for methanol oxidation. Finally, we quantitatively explore the relationship between dispersion solvent and particle agglomeration; specifically, particles are found to agglomerate abruptly as solvent polarity decreases.

  15. Structural properties of cyanase. Denaturation, renaturation, and role of sulfhydryls and oligomeric structure in catalytic activity.

    Science.gov (United States)

    Little, R M; Anderson, P M

    1987-07-25

    Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to give ammonia and bicarbonate. The enzyme is composed of 8-10 identical subunits (Mr = 17,008). The objective of this study was to clarify some of the structural properties of cyanase for the purpose of understanding the relationship between oligomeric structure and catalytic activity. Circular dichroism studies showed that cyanase has a significant amount of alpha-helix and beta-sheet structure. The one sulfhydryl group per subunit does not react with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) unless cyanase is denatured. Denaturation is apparently complete in 10 M urea or 6 M guanidine hydrochloride, but is significantly reduced in 10 M urea by the presence of azide (analog of cyanate) and is incomplete in 8 M urea. Denatured cyanase could be renatured and reactivated (greater than 85%) by removal of denaturants. Reactivation was greatly facilitated by the presence of certain anions, particularly bicarbonate, and by high ionic strength and protein concentration. The catalytic activity of renatured cyanase was associated only with oligomer. Cyanase that had been denatured in the presence of DTNB to give a cyanase-DTNB derivative could also be renatured at 26 degrees C to give active cyanase-DTNB oligomer. The active oligomeric form of the cyanase-DTNB derivative could be converted reversibly to inactive dimer by lowering the temperature to 4 degrees C or by reduction of the ionic strength and removal of monoanions. These results provide evidence that free sulfhydryl groups are not required for catalytic activity and that catalytic activity may be dependent upon oligomeric structure.

  16. Comprehensive Characterization of AMP-Activated Protein Kinase Catalytic Domain by Top-Down Mass Spectrometry

    Science.gov (United States)

    Yu, Deyang; Peng, Ying; Ayaz-Guner, Serife; Gregorich, Zachery R.; Ge, Ying

    2016-02-01

    AMP-activated protein kinase (AMPK) is a serine/threonine protein kinase that is essential in regulating energy metabolism in all eukaryotic cells. It is a heterotrimeric protein complex composed of a catalytic subunit (α) and two regulatory subunits (β and γ). C-terminal truncation of AMPKα at residue 312 yielded a protein that is active upon phosphorylation of Thr172 in the absence of β and γ subunits, which is refered to as the AMPK catalytic domain and commonly used to substitute for the AMPK heterotrimeric complex in in vitro kinase assays. However, a comprehensive characterization of the AMPK catalytic domain is lacking. Herein, we expressed a His-tagged human AMPK catalytic domin (denoted as AMPKΔ) in E. coli, comprehensively characterized AMPKΔ in its basal state and after in vitro phosphorylation using top-down mass spectrometry (MS), and assessed how phosphorylation of AMPKΔ affects its activity. Unexpectedly, we found that bacterially-expressed AMPKΔ was basally phosphorylated and localized the phosphorylation site to the His-tag. We found that AMPKΔ had noticeable basal activity and was capable of phosphorylating itself and its substrates without activating phosphorylation at Thr172. Moreover, our data suggested that Thr172 is the only site phosphorylated by its upstream kinase, liver kinase B1, and that this phosphorylation dramatically increases the kinase activity of AMPKΔ. Importantly, we demonstrated that top-down MS in conjunction with in vitro phosphorylation assay is a powerful approach for monitoring phosphorylation reaction and determining sequential order of phosphorylation events in kinase-substrate systems.

  17. Expression of the benign HEXA mutations, Arg247Trp and Arg249Trp, associated with beta-hexosaminidase A pseudodeficiency

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Z.; Petroulakis, E.; Salo, T. [Univ. of Manitoba (Canada)] [and others

    1994-09-01

    {beta}-Hexosaminidase (Hex A) is a heterodimer of {alpha} and {beta} subunits encoded by the HEXA and HEXB genes, respectively. Mutations in the HEXA gene typically cause Tay-Sachs disease or less severe forms of G{sub M2} gangliosidosis. However, two benign mutations (Arg247Trp and Arg249Trp) in the {alpha}-subunit of Hex A account for Hex A deficiency in {approximately}36% of non-Jewish enzyme-defined Tay-Sachs disease carriers. These mutations do not result in any apparent clinical phenotype in individuals who are genetic compounds with a second disease-causing mutation. We expressed the {alpha}-subunit harboring each of the benign mutations separately to study activity toward the synthetic substrate, 4-MUGS, for comparison to activity from enzymes containing mutations associated with other forms of G{sub M2} gangliosidosis. The C739T (Arg247Trp;benign), C745T (Arg 249Trp; benign), G805A (Gly269Ser; adult-onset), G749A (Gly250Asp; juvenile), and C508T (Arg170Trp; infantile) mutations were introduced into the {alpha}-subunit cDNA. These were transfected alone, or with the {beta}-subunit cDNA, to generate Hex S ({alpha}{alpha}) or Hex A ({alpha}{beta}), respectively. The activities were monitored using 4-MUGS, and the levels of {alpha}-subunit protein were assessed by Western blotting. Repeated experiments show that the benign mutations produce approximately 35% of normal Hex S and 40% of normal Hex A activity. This level is much higher than that of Hex A harbouring the Gly169Ser adult-onset mutation (12%). A sequential decrease in expressed Hex A activity is observed as mutations associated with more severe phenotypes are expressed. The benign mutations also result in lower levels of mature {alpha}-subunit protein compared to normal, and slightly reduced levels of {alpha}-subunit precursor protein. The Hex A deficiency resulting from benign mutations is not as great as that associated with disease-causing mutations.

  18. Catalytic activity of pyrite for coal liquefaction reaction; Tennen pyrite no shokubai seino ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, K.; Kozu, M.; Okada, T.; Kobayashi, M. [Nippon Coal Oil Co. Ltd., Tokyo (Japan)

    1996-10-28

    Since natural pyrite is easy to obtain and cheap as coal liquefaction catalyst, it is to be used for the 150 t/d scale NEDOL process bituminous coal liquefaction pilot plant. NEDO and NCOL have investigated the improvement of catalytic activity of pulverized natural pyrite for enhancing performance and economy of the NEDOL process. In this study, coal liquefaction tests were conducted using natural pyrite catalyst pulverized by dry-type bowl mill under nitrogen atmosphere. Mechanism of catalytic reaction of the natural pyrite was discussed from relations between properties of the catalyst and liquefaction product. The natural pyrite provided an activity to transfer gaseous hydrogen into the liquefaction product. It was considered that pulverized pyrite promotes the hydrogenation reaction of asphaltene because pulverization increases its contact rate with reactant and the amount of active points on its surface. It was inferred that catalytic activity of pyrite is affected greatly by the chemical state of Fe and S on its surface. 3 refs., 4 figs., 1 tab.

  19. A substrate-driven allosteric switch that enhances PDI catalytic activity

    Science.gov (United States)

    Bekendam, Roelof H.; Bendapudi, Pavan K.; Lin, Lin; Nag, Partha P.; Pu, Jun; Kennedy, Daniel R.; Feldenzer, Alexandra; Chiu, Joyce; Cook, Kristina M.; Furie, Bruce; Huang, Mingdong; Hogg, Philip J.; Flaumenhaft, Robert

    2016-01-01

    Protein disulfide isomerase (PDI) is an oxidoreductase essential for folding proteins in the endoplasmic reticulum. The domain structure of PDI is a–b–b′–x–a′, wherein the thioredoxin-like a and a′ domains mediate disulfide bond shuffling and b and b′ domains are substrate binding. The b′ and a′ domains are connected via the x-linker, a 19-amino-acid flexible peptide. Here we identify a class of compounds, termed bepristats, that target the substrate-binding pocket of b′. Bepristats reversibly block substrate binding and inhibit platelet aggregation and thrombus formation in vivo. Ligation of the substrate-binding pocket by bepristats paradoxically enhances catalytic activity of a and a′ by displacing the x-linker, which acts as an allosteric switch to augment reductase activity in the catalytic domains. This substrate-driven allosteric switch is also activated by peptides and proteins and is present in other thiol isomerases. Our results demonstrate a mechanism whereby binding of a substrate to thiol isomerases enhances catalytic activity of remote domains. PMID:27573496

  20. Chaperones are necessary for the expression of catalytically active potato apyrases in prokaryotic cells.

    Science.gov (United States)

    Porowińska, Dorota; Czarnecka, Joanna; Komoszyński, Michał

    2014-07-01

    NTPDases (nucleoside triphosphate diphosphohydrolases) (also called in plants apyrases) hydrolyze nucleoside 5'-tri- and/or diphosphate bonds producing nucleosides di or monophosphate and inorganic phosphate. For years, studies have been carried out to use both plant and animal enzymes for medicine. Therefore, there is a need to develop an efficient method for the quick production of large amounts of homogeneous proteins with high catalytic activity. Expression of proteins in prokaryotic cells is the most common way for the protein production. The aim of our study was to develop a method of expression of potato apyrase (StAPY4, 5, and 6) genes in bacterial cells under conditions that allowed the production of catalytically active form of these enzymes. Apyrase 4 and 6 were overexpressed in BL21-CodonPlus (DE3) bacteria strain but they were accumulated in inclusion bodies, regardless of the culture conditions and induction method. Co-expression of potato apyrases with molecular chaperones allowed the expression of catalytically active apyrase 5. However, its high nucleotidase activity could be toxic for bacteria and is therefore synthesized in small amounts in cells. Our studies show that each protein requires other conditions for maturation and even small differences in amino acid sequence can essentially affect protein folding regardless of presence of chaperones.

  1. An improved d-band model of the catalytic activity of magnetic transition metal surfaces

    CERN Document Server

    Bhattacharjee, Satadeep; Lee, S C

    2016-01-01

    The d-band center model of Hammer and N{\\o}rskov is widely used in understanding and predicting catalytic activity on transition metal (TM) surfaces. Here, we demonstrate that this model is inadequate for capturing the complete catalytic activity of the magnetically polarized TM surfaces and propose its generalization. We validate the generalized model through comparison of adsorption energies of the NH$_3$ molecule on the surfaces of 3d TMs (V, Cr, Mn, Fe, Co, Ni, Cu and Zn) determined with spin-polarized density functional theory (DFT)-based methods with the predictions of our model. Compared to the conventional d-band model, where the nature of the metal-adsorbate interaction is entirely determined through the energy and the occupation of the d-band center, we emphasize that for the surfaces with high spin polarization, the metal-adsorbate system can be stabilized through a competition of the spin-dependent metal-adsorbate interactions.

  2. Catalytic activity of platinum on ruthenium electrodes with modified (electro)chemical states.

    Science.gov (United States)

    Park, Kyung-Won; Sung, Yung-Eun

    2005-07-21

    Using Pt on Ru thin-film electrodes with various (electro)chemical states designed by the sputtering method, the effect of Ru states on the catalytic activity of Pt was investigated. The chemical and electrochemical properties of Pt/Ru thin-film samples were confirmed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In addition, Pt nanoparticles on Ru metal or oxide for an actual fuel cell system showed an effect of Ru states on the catalytic activity of Pt in methanol electrooxidation. Finally, it was concluded that such an enhancement of methanol electrooxidation on the Pt is responsible for Ru metallic and/or oxidation sites compared to pure Pt without any Ru state. PMID:16852701

  3. Gold Incorporated Mesoporous Silica Thin Film Model Surface as a Robust SERS and Catalytically Active Substrate

    Directory of Open Access Journals (Sweden)

    Anandakumari Chandrasekharan Sunil Sekhar

    2016-05-01

    Full Text Available Ultra-small gold nanoparticles incorporated in mesoporous silica thin films with accessible pore channels perpendicular to the substrate are prepared by a modified sol-gel method. The simple and easy spin coating technique is applied here to make homogeneous thin films. The surface characterization using FESEM shows crack-free films with a perpendicular pore arrangement. The applicability of these thin films as catalysts as well as a robust SERS active substrate for model catalysis study is tested. Compared to bare silica film our gold incorporated silica, GSM-23F gave an enhancement factor of 103 for RhB with a laser source 633 nm. The reduction reaction of p-nitrophenol with sodium borohydride from our thin films shows a decrease in peak intensity corresponding to –NO2 group as time proceeds, confirming the catalytic activity. Such model surfaces can potentially bridge the material gap between a real catalytic system and surface science studies.

  4. ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Biener, M M; Biener, J; Wichmann, A; Wittstock, A; Baumann, T F; Baeumer, M; Hamza, A V

    2011-03-24

    Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications.

  5. Catalytic Activity of Iridium Dioxide With Different Morphologies for Oxygen Reduction Reaction

    Institute of Scientific and Technical Information of China (English)

    WANG Guangjin; HUANG Fei; XU Tian; YU Yi; CHENG Feng; ZHANG Yue; PAN Mu

    2015-01-01

    Iridium dioxide with different morphologies (nanorod and nanogranular) is successfully prepared by a modiifed sol-gel and Adams methods. The catalytic activity of both samples for oxygen reduction reaction is investigated in an alkaline solution. The electrochemical results show that the catalytic activity of the nanogranular IrO2 sample is superior to that of the nanorod sample due to its higher onset potential for oxygen reduction reaction and higher electrode current density in low potential region. The results of Koutecky-Levich analysis indicate that the oxygen reduction reaction catalyzed by both samples is a mixture transfer pathway. It is dominated by four electron transfer pathway for both samples in high overpotential area, while it is controlled by two electron transfer process for both samples in low overpotential area.

  6. Peroxidase-like catalytic activity of Ag3PO4 nanocrystals prepared by a colloidal route.

    Directory of Open Access Journals (Sweden)

    Yuanjun Liu

    Full Text Available Nearly monodispersed Ag3PO4 nanocrystals with size of 10 nm were prepared through a colloidal chemical route. It was proven that the synthesized Ag3PO4 nanoparticles have intrinsic peroxidase-like catalytic activity. They can quickly catalyze oxidation of the peroxidase substrate 3, 3, 5, 5-tetramethylbenzidine (TMB in the presence of H2O2, producing a blue color. The catalysis reaction follows Michaelis-Menten kinetics. The calculated kinetic parameters indicate a high catalytic activity and the strong affinity of Ag3PO4 nanocrystals to the substrate (TMB. These results suggest the potential applications of Ag3PO4 nanocrystals in fields such as biotechnology, environmental chemistry, and medicine.

  7. Twinning in fcc lattice creates low-coordinated catalytically active sites in porous gold.

    Science.gov (United States)

    Krajčí, Marian; Kameoka, Satoshi; Tsai, An-Pang

    2016-08-28

    We describe a new mechanism for creation of catalytically active sites in porous gold. Samples of porous gold prepared by de-alloying Al2Au exhibit a clear correlation between the catalytic reactivity towards CO oxidation and structural defects in the fcc lattice of Au. We have found that on the stepped {211} surfaces quite common twin boundary defects in the bulk structure of porous gold can form long close-packed rows of atoms with the coordination number CN = 6. DFT calculations confirm that on these low-coordinated Au sites dioxygen chemisorbs and CO oxidation can proceed via the Langmuir-Hinshelwood mechanism with the activation energy of 37 kJ/mol or via the CO-OO intermediate with the energy barrier of 19 kJ/mol. The existence of the twins in porous gold is stabilized by the surface energy.

  8. Analysis list: Trp53 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Trp53 Embryo,Embryonic fibroblast + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Trp53....1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Trp53.5.tsv http://dbarchive.bi...osciencedbc.jp/kyushu-u/mm9/target/Trp53.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Trp53.Em...bryo.tsv,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Trp53.Embryonic_fibr

  9. Orange II removal by catalytic wet peroxide oxidation using activated carbon xerogels

    OpenAIRE

    Pinho, Maria; Silva, Adrián; Fathy, Nady; Attia, Amina; Gomes, Helder; Faria, Joaquim

    2013-01-01

    Orange II is a synthetic dye widely employed in the textile industry and responsible for serious environrnentaI cancerns. Dyes like this urge the development af new technologies for the treatment af wastewaters generated in this industrial activity. Those include catalytic wet peroxide oxidation (CWPO), which is an advanced oxidation process (AOP) based on the generation of hydroxyl radicais (I-lO·) from hydrogen peroxide with tlle aid ofa suitable catalysl [I].

  10. Synthesis and catalytic activities of porphyrin-based PCP pincer complexes.

    OpenAIRE

    Fujimoto, Keisuke; Yoneda, Tomoki; Yorimitsu, Hideki; Osuka, Atsuhiro

    2013-01-01

    2,18-Bis(diphenylphosphino)porphyrins undergo peripheral cyclometalation with group 10 transition-metal salts to afford the corresponding porphyrin-based PCP pincer complexes. The porphyrinic plane and the PCP-pincer unit are apparently coplanar, with small strain. The catalytic activities of the porphyrin-based pincer complexes at the periphery were investigated in the allylation of benzaldehyde with allylstannane and in the 1,4-reduction of chalcone to discover the electronic interplay betw...

  11. Catalytic layer for oxygen activation on ionic solid electrolytes at high temperature

    OpenAIRE

    Serra Alfaro, José Manuel; Vert Belenguer, Vicente Bernard; Escolástico Rozalén, Sonia

    2008-01-01

    The present invention relates to a catalytic porous layer for oxygen activation which may be utilised in solid oxide fuel cells (SOFCs) and in dense ceramic membranes for oxygen separation at high temperature. Said porous layer is principally formed by a mixed electron and oxygen ion conductive material possessing a structure selected from among structures of the simple perovskite or double perovskite type or structures related to perovskite, that is to say: structures of the Ruddlesden-Poppe...

  12. A simple red-ox titrimetric method for the evaluation of photo-catalytic activity of titania based catalysts

    Indian Academy of Sciences (India)

    Y S Satpute; S A Borkar; S R Dharwadkar

    2003-12-01

    A simple red-ox titrimetry method has been developed for rapid evaluation of the photo catalytic activity of TiO2 based photo-catalysts. The analytical procedure employs monitoring the kinetics of a simple one electron transfer reduction reaction of conversion of Ce4+ to Ce3+ in dilute aqueous solution in presence of sunlight. The photo-catalytic activity of TiO2 synthesized by two different routes was evaluated by the above technique. The effect of surface area, crystallite size and polymorphic contents on the photo-catalytic activity of TiO2 was also studied employing this method.

  13. A microreactor array for spatially resolved measurement of catalytic activity for high-throughput catalysis science

    Energy Technology Data Exchange (ETDEWEB)

    Kondratyuk, Petro; Gumuslu, Gamze; Shukla, Shantanu; Miller, James B; Morreale, Bryan D; Gellman, Andrew J

    2013-04-01

    We describe a 100 channel microreactor array capable of spatially resolved measurement of catalytic activity across the surface of a flat substrate. When used in conjunction with a composition spread alloy film (CSAF, e.g. Pd{sub x}Cu{sub y}Au{sub 1-x-y}) across which component concentrations vary smoothly, such measurements permit high-throughput analysis of catalytic activity and selectivity as a function of catalyst composition. In the reported implementation, the system achieves spatial resolution of 1 mm{sup 2} over a 10×10 mm{sup 2} area. During operation, the reactant gases are delivered at constant flow rate to 100 points of differing composition on the CSAF surface by means of a 100-channel microfluidic device. After coming into contact with the CSAF catalyst surface, the product gas mixture from each of the 100 points is withdrawn separately through a set of 100 isolated channels for analysis using a mass spectrometer. We demonstrate the operation of the device on a Pd{sub x}Cu{sub y}Au{sub 1-x-y} CSAF catalyzing the H{sub 2}-D{sub 2} exchange reaction at 333 K. In essentially a single experiment, we measured the catalytic activity over a broad swathe of concentrations from the ternary composition space of the Pd{sub x}Cu{sub y}Au{sub 1-x-y} alloy.

  14. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface.

    Science.gov (United States)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, Lindsay R; Lammich, Lutz; Besenbacher, Flemming; Mavrikakis, Manos; Wendt, Stefan

    2015-08-25

    Within the area of surface science, one of the "holy grails" is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFT+U calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  15. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface

    Energy Technology Data Exchange (ETDEWEB)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, L. R.; Lammich, Lutz; Besenbacher, Fleming; Mavrikakis, Manos; Wendt, Stefen

    2015-08-25

    Within the area of surface science, one of the “holy grails” is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFTþU calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  16. Isolated metal active site concentration and stability control catalytic CO2 reduction selectivity.

    Science.gov (United States)

    Matsubu, John C; Yang, Vanessa N; Christopher, Phillip

    2015-03-01

    CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability. PMID:25671686

  17. Supercritical CO{sub 2} mediated synthesis and catalytic activity of graphene/Pd nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Lulu [School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeoungbuk 712-749 (Korea, Republic of); Nguyen, Van Hoa [School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeoungbuk 712-749 (Korea, Republic of); Department of Chemistry, Nha Trang University, 2 Nguyen Dinh Chieu, Nha Trang (Viet Nam); Shim, Jae-Jin, E-mail: jjshim@yu.ac.kr [School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeoungbuk 712-749 (Korea, Republic of)

    2015-11-15

    Highlights: • RGO/Pd composite was efficiently prepared via a facile method in supercritical CO{sub 2}. • Graphene sheets were coated uniformly with Pd nanoparticles with a size of ∼8 nm. • Composites exhibited excellent catalytic activity in the Suzuki reaction even after 10 cycles. - Abstract: Graphene sheets were decorated with palladium nanoparticles using a facile and efficient method in supercritical CO{sub 2}. The nanoparticles were formed on the graphene sheets by the simple hydrogen reduction of palladium(II) hexafluoroacetylacetonate precursor in supercritical CO{sub 2}. The product was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Highly dispersed nanoparticles with various sizes and shapes adhered well to the graphene sheets. The composites showed high catalytic activities for the Suzuki reaction under aqueous and aerobic conditions within 5 min. The effects of the different Pd precursor loadings on the catalytic activities of the composites were also examined.

  18. The influence of copper in dealloyed binary platinum–copper electrocatalysts on methanol electroxidation catalytic activities

    International Nuclear Information System (INIS)

    In this study, we prepared and characterized carbon paper-supported dealloyed binary Pt–Cu core–shell electrocatalysts (denoted as PtxCu(100−x)/CP) by cyclic co-electrodeposition and selective copper dealloying in an acidic medium, and we investigated the effect of the copper content in the samples on the catalytic activities toward methanol electroxidation reaction (MOR). X-ray photo-emission spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) indicated that the structure of dealloyed binary Pt–Cu catalysts possessed a Pt-rich shell and a Cu rich core. X-ray absorption near edge spectroscopy (XANES) displayed that the oxidation states of Pt and Cu were zero and one, respectively, implying the formation of metallic Pt and Cu2O, respectively. X-ray diffraction spectroscopy (XRD) confirmed that Cu was inserted into a face-centered cubic Pt structure forming Pt–Cu alloys. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) displayed a cubic shape of Pt/CP and a spherical shape of PtxCu(100−x)/CP with several hundred nanometer sizes of agglomeration that depended on the Cu content. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to confirm that the sample of Pt70Cu30/CP exhibited the best catalytic activities in terms of the specific current, current density, catalytic poisoning tolerance, and stability. - Graphical abstract: Display Omitted - Highlights: • Binary electrocatalysts of PtxCu(100−x)/CP were prepared by cyclic co-electrodeposition and selective copper dealloying. • The structures of PtxCu(100−x)/CP were a Pt rich shell and a Cu rich core. • The Pt70Cu30/CP was the excellent catalytic activity towards methanol electrooxidation and COads tolerance

  19. Restoration of a translational stop-start overlap reinstates translational coupling in a mutant trpB'-trpA gene pair of the Escherichia coli tryptophan operon.

    OpenAIRE

    Das, A.; Yanofsky, C

    1989-01-01

    The trpB and trpA coding regions of the polycistronic trp mRNA of Escherichia coli are separated by overlapping translation stop and start codons. Efficient translation of the trpA coding region is subject to translational coupling, i.e., maximal trpA expression is dependent on prior translation of the trpB coding region. Previous studies demonstrated that the trpA Shine-Dalgarno sequence (within trpB) and/or the location of the trpB stop codon influenced trpA expression. To examine the effec...

  20. The non-catalytic domains of Drosophila katanin regulate its abundance and microtubule-disassembly activity.

    Directory of Open Access Journals (Sweden)

    Kyle D Grode

    Full Text Available Microtubule severing is a biochemical reaction that generates an internal break in a microtubule and regulation of microtubule severing is critical for cellular processes such as ciliogenesis, morphogenesis, and meiosis and mitosis. Katanin is a conserved heterodimeric ATPase that severs and disassembles microtubules, but the molecular determinants for regulation of microtubule severing by katanin remain poorly defined. Here we show that the non-catalytic domains of Drosophila katanin regulate its abundance and activity in living cells. Our data indicate that the microtubule-interacting and trafficking (MIT domain and adjacent linker region of the Drosophila katanin catalytic subunit Kat60 cooperate to regulate microtubule severing in two distinct ways. First, the MIT domain and linker region of Kat60 decrease its abundance by enhancing its proteasome-dependent degradation. The Drosophila katanin regulatory subunit Kat80, which is required to stabilize Kat60 in cells, conversely reduces the proteasome-dependent degradation of Kat60. Second, the MIT domain and linker region of Kat60 augment its microtubule-disassembly activity by enhancing its association with microtubules. On the basis of our data, we propose that the non-catalytic domains of Drosophila katanin serve as the principal sites of integration of regulatory inputs, thereby controlling its ability to sever and disassemble microtubules.

  1. Block copolymer hollow fiber membranes with catalytic activity and pH-response

    KAUST Repository

    Hilke, Roland

    2013-08-14

    We fabricated block copolymer hollow fiber membranes with self-assembled, shell-side, uniform pore structures. The fibers in these membranes combined pores able to respond to pH and acting as chemical gates that opened above pH 4, and catalytic activity, achieved by the incorporation of gold nanoparticles. We used a dry/wet spinning process to produce the asymmetric hollow fibers and determined the conditions under which the hollow fibers were optimized to create the desired pore morphology and the necessary mechanical stability. To induce ordered micelle assembly in the doped solution, we identified an ideal solvent mixture as confirmed by small-angle X-ray scattering. We then reduced p-nitrophenol with a gold-loaded fiber to confirm the catalytic performance of the membranes. © 2013 American Chemical Society.

  2. Probing substrate interactions in the active tunnel of a catalytically deficient cellobiohydrolase (Cel7)

    DEFF Research Database (Denmark)

    Westh, Peter; Colussi, Francieli; Sørensen, Trine Holst;

    2015-01-01

    Cellobiohydrolases (CBHs) break down cellulose sequentially by sliding along the crystal surface with a single cellulose strand threaded through the catalytic tunnel of the enzyme. This so-called processive mechanism relies on a complex pattern of enzyme-substrate interactions, which need to be...... sites in the catalytic tunnel, and using COS ligands with a degree of polymerization (DP) from 2 to 8, different regions of the tunnel could be probed. For COS ligands with DP of 2-3 the binding constants were around 105 M-1, and for longer ligands (DP 5-8) this value was about 107 M-1. Within each of......) decreased monotonously with both temperature and DP. Combined interpretation of these thermodynamic results and previously published structural data allowed assessment of an affinity profile along the length axis of the active tunnel...

  3. Layered Double Hydroxide Nanoclusters: Aqueous, Concentrated, Stable, and Catalytically Active Colloids toward Green Chemistry.

    Science.gov (United States)

    Tokudome, Yasuaki; Morimoto, Tsuyoshi; Tarutani, Naoki; Vaz, Pedro D; Nunes, Carla D; Prevot, Vanessa; Stenning, Gavin B G; Takahashi, Masahide

    2016-05-24

    Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems.

  4. Nickel-doped ceria nanoparticles for promoting catalytic activity of Pt/C for ethanol electrooxidation

    Science.gov (United States)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2014-10-01

    This paper reports the facile synthesis of monodispersed nickel-doped ceria nanoparticles by a thermal decomposition method, which is used to promote catalytic properties of Pt/C. The Pt/Ni-doped CeO2/C catalyst obtained exhibits remarkably high activity and stability towards the ethanol electrooxidation in acidic media. This is attributed to higher oxygen releasing capacity and stronger interaction of Ni-doped CeO2 with Pt than pure CeO2 nanoparticles that contribute positively to the removal of poisoning intermediates. We believe that the design concept and synthetic strategy of metal doped oxides used for fuel cell catalysts can be potentially extended to other catalytic fields.

  5. Layered Double Hydroxide Nanoclusters: Aqueous, Concentrated, Stable, and Catalytically Active Colloids toward Green Chemistry.

    Science.gov (United States)

    Tokudome, Yasuaki; Morimoto, Tsuyoshi; Tarutani, Naoki; Vaz, Pedro D; Nunes, Carla D; Prevot, Vanessa; Stenning, Gavin B G; Takahashi, Masahide

    2016-05-24

    Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems. PMID:27124717

  6. Catalytic Activity and Photophysical Properties of Biomolecules Immobilized on Mesoporous Silica

    DEFF Research Database (Denmark)

    Ikemoto, Hideki

    Michaelis constant (KM) and maximum rate (Vmax) were determined. Both thermal stability and the stability toward the denaturing agents guanidinium chloride and urea, of free and immobilized enzymes were compared next. The thermal stability of the immobilized enzyme is significantly improved in comparison...... with free HRP. The catalytic kinetics is slowed down notably, but Vmax is much more robust to heat than for the free enzyme. The stability resistance of the enzyme toward the denaturing agents depends on the chemical nature of the denaturing agentsand interactions between enzyme and silica nanopore walls....... Guanidinium chloride showed similar attenuation of the catalytic activity of immobilized and free enzyme. In contrast, immobilized HRP was much more resistant to urea than the free enzyme. The different behavior of free and immobilized enzyme is most likely due to different hydrogen bonding of water...

  7. Green synthesis of silver nanoparticles, decorated on graphene oxide nanosheets and their catalytic activity

    Science.gov (United States)

    Sreekanth, T. V. M.; Jung, Min-Ji; Eom, In-Yong

    2016-01-01

    In this study, we develop an inexpensive and green route for the synthesis of silver nanoparticles (AgNPs) using Picrasma quassioides bark aqueous extract as reducing and capping agent and also eco-friendly decorate graphene oxide (GO) nanosheets with AgNPs (GO-AgNPs). Green synthesized AgNPs and GO-AgNPs composites were characterized by UV-Visible spectroscopy, SEM-EDX, and TEM-SAED techniques. The resulting GO-AgNPs contained about 41.35% of Ag and the AgNPs size ranges 17.5-66.5 nm, and GO-AgNPs size ranges 10-49.5 nm. Moreover, the GO-AgNPs exhibited excellent catalytic activity towards the methylene blue (MB) in the presence of sodium borohydride (NaBH4) at room temperature. This catalytic reaction completed within 15 min.

  8. Green synthesis, characterization and catalytic activity of palladium nanoparticles by xanthan gum

    Science.gov (United States)

    Santoshi kumari, Amrutham; Venkatesham, Maragoni; Ayodhya, Dasari; Veerabhadram, Guttena

    2015-03-01

    Here, we report the synthesis, characterization and catalytic evaluation of palladium nanoparticles (PdNPs) using xanthan gum, acting as both reducing and stabilizing agent without using any synthetic reagent. The uniqueness of our method lies in its fast synthesis rates using hydrothermal method in autoclave at a pressure of 15 psi and at 120 °C temperature by 10 min time. The formation and size of the PdNPs were characterized by UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The catalytic activity of PdNPs was evaluated on the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride using spectrophotometry.

  9. The Trp53 delta proline (Trp53ΔP) mouse exhibits increased genome instability and susceptibility to radiation-induced, but not spontaneous, tumor development.

    Science.gov (United States)

    Adams, Cassandra J; Yu, Jennifer S; Mao, Jian-Hua; Jen, Kuang-Yu; Costes, Sylvain V; Wade, Mark; Shoemake, Jocelyn; Aina, Olulanu H; Del Rosario, Reyno; Menchavez, Phuong Thuy; Cardiff, Robert D; Wahl, Geoffrey M; Balmain, Allan

    2016-09-01

    The tumor suppressor TP53 can initiate a plethora of anti-proliferative effects to maintain genomic integrity under conditions of genotoxic stress. The N-terminal proline-rich domain (PRD) of TP53 is important in the regulation of TP53 activity and stability. A common polymorphism at codon 72 in this region has been associated with altered cancer risk in humans. The Trp53ΔP mouse, which carries a germline homozygous deletion of a region of the PRD, does not develop spontaneous tumors in a mixed 129/Sv and C57BL/6 genetic background, but is highly susceptible to a broad range of tumor types following total body exposure to 4 Gy gamma (γ) radiation. This contrasts with the tumor spectrum in Trp53 null (-/-) mice, which mainly develop thymic lymphomas and osteosarcomas. Analysis of genomic instability in tissues and cells from Trp53ΔP mice demonstrated elevated basal levels of aneuploidy, but this is not sufficient to drive spontaneous tumorigenesis, which requires an additional DNA damage stimulus. Levels of genomic instability did not increase significantly in Trp53ΔP mice following irradiation exposure, suggesting that other radiation effects including tissue inflammation, altered metabolism or autophagy, may play an important role. The Trp53ΔP mouse is a novel model to dissect the mechanisms of tumor development induced by radiation exposure. © 2015 Wiley Periodicals, Inc. PMID:26310697

  10. Synthesis, characterization and catalytic activity toward methanol oxidation of electrocatalyst Pt4+-NH2-MCM-41

    International Nuclear Information System (INIS)

    Highlights: ► It was first confirmed that the Pt4+ exhibited a good electro-catalytic property for methanol oxidation. ► The Pt4+ perfectly distributed on a mesoporous molecular sieve matrix synthesis by a facile method. ► The good performance of catalyst resistance to poisoning because of a homogeneous distribution of Pt4+ and large specific surface area. - Abstract: Mesoporous material with functional group (Pt4+-NH2-MCM-41) was prepared by grafting aminopropyl group and adsorbing platinum ions on the surface of the commercial molecular sieve (MCM-41). The characterization carried out by X-ray photoelectron spectroscopy, X-ray diffraction, and N2 adsorption–desorption measurement pointed out that Pt was adsorbed on the NH2-MCM-41 surface as the oxidation state (Pt4+) and the surface area of Pt4+-NH2-MCM-41 was up to 564 m2/g. Transmission electron microscopy and elemental mapping indicated a homogeneous distribution of Pt4+ throughout all surface of the mesoporous materials. Electro-catalytic properties of methanol oxidation on the Pt4+-NH2-MCM-41 electrode were investigated with electrochemical methods. The results showed that the Pt4+-NH2-MCM-41 electrode exhibited catalytic activity in the methanol electro-oxidation with the apparent activation energy being 49.29 kJ/mol, and the control step of methanol electro-oxidation was the mass transfer process. It is first proved that platinum ions had good electro-catalytic property for methanol oxidation and provided a new idea for developing electrode materials in future.

  11. Electrosynthesis and catalytic activity of polymer-nickel particles composite electrode materials

    Energy Technology Data Exchange (ETDEWEB)

    Melki, Tahar; Zouaoui, Ahmed; Bendemagh, Barkahoum [Universite Ferhat Abbas, Setif (Algeria). Faculte des Sciences de l' Ingenieur. Dept. du Tronc Commun; Oliveira, Ione M.F. de; Oliveira, Gilver F. de [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Quimica; Lepretre, Jean-Claude [UMR-5631 CNRS-INPG-UJF, St. Martin d' Heres Cedex (France). Lab. d' Electrochimie et de Physicochimie des Materiaux et Interfaces; Bucher, Christophe; Mou tet, Jean-Claude [Universite Joseph Fourier Grenoble 1 (France). Dept. de Chimie Moleculaire], e-mail: Jean-Claude.Moutet@ujf-grenoble.fr

    2009-07-01

    Nickel-polymer composite electrode materials have been synthesized using various strategies, all comprising the electrochemical reduction of nickel(II) cations or complexes, incorporated by either ion-exchange or complexation into various poly(pyrrole-carboxylate) thin films coated by oxidative electropolymerization onto carbon electrodes. The electrocatalytic activity and the stability of the different composites have been then evaluated in the course of the electrocatalytic hydrogenation of ketones and enones in aqueous electrolytes. The best results were obtained using nickel-polymer composites synthesized by electroreduction of nickel(II) ions complexed into polycarboxylate films, which are characterized by a high catalytic activity and a good operational stability. (author)

  12. Importance of the oxygen bond strength for catalytic activity in soot oxidation

    DEFF Research Database (Denmark)

    Christensen, Jakob M.; Grunwaldt, Jan-Dierk; Jensen, Anker D.

    2016-01-01

    (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation...... oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe2O3 and α-Cr2O3. Guided by an interpolation principle FeaCrbOx binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr2Ox binary oxide...

  13. ThermoTRP channels as modular proteins with allosteric gating.

    Science.gov (United States)

    Latorre, Ramon; Brauchi, Sebastian; Orta, Gerardo; Zaelzer, Cristián; Vargas, Guillermo

    2007-01-01

    Ion channels activate by sensing stimuli such as membrane voltage, ligand binding or temperature and transduce this information into conformational changes that open the channel pore. Thus, a key question in understanding ion channel function is how do the protein domains involved in sensing stimuli (sensors) and opening the pore (gates) communicate. In this regard, transient receptor potential (TRP) channels that confer thermosensation [A. Dhaka, V. Viswanath, A. Patapoutian, TRP ion channels and temperature sensation, Annu. Rev. Neurosci. 29 (2006) 135-161; I.S. Ramsey, M. Delling, D.E. Clapham, An introduction to TRP channels, Annu. Rev. Physiol. 68 (2006) 619-647] (thermoTRP; Q(10)>10) are unique to the extent that they integrate a variety of physical and chemical stimuli. In some cases such as, for example, the vanilloid receptor TRPV1 [M.J. Caterina, M.A. Schumacher, M. Tominaga, T.A. Rosen, J.D. Levine, D. Julius, The capsaicin receptor: a heat-activated ion channel in the pain pathway, Nature 389 (1997) 816-824] and TRPA1 [G.M. Story, A.M. Peier, A.J. Reeve, S.R. Eid, J. Mosbacher, T.R. Hricik, T.J. Earley, A.C. Hergarden, D.A. Andersson, S.W. Hwang, P. McIntyre, T. Jegla, S. Bevan, A. Patapoutian, ANKTM1, a TRP-like channel expressed in nociceptive neurons, is activated by cold temperatures, Cell 112 (2003) 819-829; S. Jordt, D. Julius, Molecular basis for species-specific sensitivity to "hot" chilli peppers, Cell 108 (2002) 421-430] the integration of these stimuli elicit pain [M. Tominaga, M.J. Caterina, A.B. Malmberg, T.A. Rosen, H. Gilbert, K. Skinner, B.E. Raumann, A.I. Basbaum, D. Julius, The cloned capsaicin receptor integrates multiple pain-producing stimuli, Neuron 21 (1998) 531-543; M. Bandell, A. Dubin, M. Petrus, A. Orth, J. Mathur, S. Hwang, A. Patapoutian, High-throughput random mutagenesis screen reveals TRPM8 residues specifically required for activation by menthol, Nat. Neurosci. 9 (2006) 466-468; S. Zurborg, B. Yurgionas, JA. Jira, O

  14. Influence of hydrophobic mismatch on the catalytic activity of Escherichia coli GlpG rhomboid protease.

    Science.gov (United States)

    Foo, Alexander C Y; Harvey, Brandon G R; Metz, Jeff J; Goto, Natalie K

    2015-04-01

    Rhomboids comprise a broad family of intramembrane serine proteases that are found in a wide range of organisms and participate in a diverse array of biological processes. High-resolution structures of the catalytic transmembrane domain of the Escherichia coli GlpG rhomboid have provided numerous insights that help explain how hydrolytic cleavage can be achieved below the membrane surface. Key to this are observations that GlpG hydrophobic domain dimensions may not be sufficient to completely span the native lipid bilayer. This formed the basis for a model where hydrophobic mismatch Induces thinning of the local membrane environment to promote access to transmembrane substrates. However, hydrophobic mismatch also has the potential to alter the functional properties of the rhomboid, a possibility we explore in the current work. For this purpose, we purified the catalytic transmembrane domain of GlpG into phosphocholine or maltoside detergent micelles of varying alkyl chain lengths, and assessed proteolytic function with a model water-soluble substrate. Catalytic turnover numbers were found to depend on detergent alkyl chain length, with saturated chains containing 10-12 carbon atoms supporting maximal activity. Similar results were obtained in phospholipid bicelles, with no proteolytic activity being detected in longer-chain lipids. Although differences in thermal stability and GlpG oligomerization could not explain these activity differences, circular dichroism spectra suggest that mismatch gives rise to a small change in structure. Overall, these results demonstrate that hydrophobic mismatch can exert an inhibitory effect on rhomboid activity, with the potential for changes in local membrane environment to regulate activity in vivo.

  15. Identification and characterization of TRP14, a thioredoxin-related protein of 14 kDa from orange-spotted grouper, Epinephelus coioides.

    Science.gov (United States)

    Wei, Jingguang; Ji, Huasong; Guo, Minglan; Yan, Yang; Qin, Qiwei

    2013-11-01

    Thioredoxin (abbreviated as Trx) is an important ubiquitous disulfide reductase, which can protect organisms against various oxidative stresses. In the present study, a thioredoxin-related protein of 14 kDa (named as Ec-TRP14) was identified from the marine fish grouper, Epinephelus coioides by RACE PCR. The full-length cDNA of Ec-TRP14 was comprised of 1066 bp with a 372 bp open reading frame that encodes a putative protein of 123 amino acids. Similar to most TRP14s, Ec-TRP14 contained the conserved motif C-P-D-C. Ec-TRP14 mRNA is predominately expressed in liver, brain and muscle. The expression of Ec-TRP14 was up-regulated in the liver of grouper challenged with SGIV. Ec-TRP14 was recombined and expressed in Escherichia coli BL21 (DE3), and the rEc-Ec-TRP14 fusion protein was demonstrated to possess the antioxidant activity. The grouper spleen (GS) cells were treated with a high concentration of rEc-TRP14 (8.3 μg/ml), which significantly enhanced cells viability under damage caused by viral infection. These results together indicated that Ec-TRP14 could function as an important antioxidant in a physiological context, and might be involved in the responses to viral challenge.

  16. Species-specific identity elements of tRNA Trp

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Through the comparisons among 91 tRNA Trp sequences from prokaryotes, archea and eukaryotes, the potential species-specific identity elements of tRNA Trp are found to be located within acceptor stem, dihydrouridine (D) stem, anticodon(AC) stem and discriminator base. Mutagenesis of B. subtilis tRNA Trp to the eukaryotic consensus se quence, in vitro transcription and enzymatic assay of tRNA Trp toward different tryptophanyl-tRNA synthetases (TrpRS) were employed to shed light on these species-specific identity elements and demonstrate the accurate recognition and the coevolution between tRNA and TrpRS. B. subtilis tRNA Trp with its acceptor stem and discriminator base transplanted by eukaryotic counterparts exhibited diminished reactivity toward B. subtilis enzyme but could be efficiently aminoacylated by rat liver crude enzyme. In contrast, B. subtilis tRNA Trp analog with the eukaryotic anticodon stem and D stem retains its recognition by B. subtilis enzyme. The results provide a strong evidence that the species-specific identity elements of tRNA Trp are orientated within the acceptor stem and discriminator base of tRNA Trp, and the anticodon stem and D stem are of little importance to the interaction between tRNA Trp and its cognate synthetase (TrpRS).

  17. Brevicompanine C, cyclo-(D-Ile-L-Trp), and cyclo-(D-Leu-L-Trp), plant growth regulators from Penicillium brevi-compactum.

    Science.gov (United States)

    Kimura, Yasuo; Sawada, Aya; Kuramata, Masato; Kusano, Miyako; Fujioka, Shozo; Kawano, Tsuyoshi; Shimada, Atsumi

    2005-02-01

    New plant growth regulators, named brevicompanine C (1), cyclo-(D-Ile-L-Trp) (2), and cyclo-(D-Leu-L-Trp) (3), have been isolated from Penicillium brevi-compactum Dierckx, and their structures have been established by spectroscopic methods including 2D NMR and chiral TLC analysis. Plant growth activities of 1, 2, and 3 have been examined using lettuce seedling bioassay methods. All compounds accelerated the root growth of the seedlings in proportion to their concentration from 1 to 100 mg/L.

  18. Catalytic oxidation of pulping effluent by activated carbon-supported heterogeneous catalysts.

    Science.gov (United States)

    Yadav, Bholu Ram; Garg, Anurag

    2016-01-01

    The present study deals with the non-catalytic and catalytic wet oxidation (CWO) for the removal of persistent organic compounds from the pulping effluent. Two activated carbon-supported heterogeneous catalysts (Cu/Ce/AC and Cu/Mn/AC) were used for CWO after characterization by the following techniques: temperature-programmed reduction, Fourier transform infrared spectroscopy and thermo-gravimetric analysis. The oxidation reaction was performed in a batch high-pressure reactor (capacity = 0.7  L) at moderate oxidation conditions (temperature = 190°C and oxygen pressure = 0.9 MPa). With Cu/Ce/AC catalyst, the maximum chemical oxygen demand (COD), total organic carbon (TOC) and lignin removals of 79%, 77% and 88% were achieved compared to only 50% removal during the non-catalytic process. The 5-day biochemical oxygen demand (BOD5) to COD ratio (a measure for biodegradability) of the pulping effluent was improved to 0.52 from an initial value of 0.16. The mass balance calculations for solid recovered after CWO reaction showed 8% and 10% deduction in catalyst mass primarily attributed to the loss of carbon and metal leaching. After the CWO process, carbon deposition was also observed on the recovered catalyst which was responsible for around 3-4% TOC reduction. PMID:26508075

  19. Catalytically active and hierarchically porous SAPO-11 zeolite synthesized in the presence of polyhexamethylene biguanidine

    KAUST Repository

    Liu, Yan

    2014-03-01

    Hierarchically porous SAPO-11 zeolite (H-SAPO-11) is rationally synthesized from a starting silicoaluminophosphate gel in the presence of polyhexamethylene biguanidine as a mesoscale template. The sample is well characterized by XRD, N2 sorption, SEM, TEM, NMR, XPS, NH3-TPD, and TG techniques. The results show that the sample obtained has good crystallinity, hierarchical porosity (mesopores at ca. 10nm and macropores at ca. 50-200nm), high BET surface area (226m2/g), large pore volume (0.25cm3/g), and abundant medium and strong acidic sites (0.36mmol/g). After loading Pt (0.5wt.%) on H-SAPO-11 by using wet impregnation method, catalytic hydroisomerization tests of n-dodecane show that the hierarchical Pt/SAPO-11 zeolite exhibits high conversion of n-dodecane and enhanced selectivity for branched products as well as reduced selectivity for cracking products, compared with conventional Pt/SAPO-11 zeolite. This phenomenon is reasonably attributed to the presence of hierarchical porosity, which is favorable for access of reactants on catalytically active sites. The improvement in catalytic performance in long-chain paraffin hydroisomerization over Pt/SAPO-11-based catalyst is of great importance for its industrial applications in the future. © 2013 Elsevier Inc.

  20. Effects of Colloidal Silica Binder on Catalytic Activity and Adhesion of HZSM-5 Coatings for Structured Reactors

    Institute of Scientific and Technical Information of China (English)

    Guozhu Liu; Jinhua Guo; Fanxu Meng; Xiangwen Zhang; Li Wang

    2014-01-01

    HZSM-5 coating using three colloidal silica binders, acidic col oidal silica (ACS), neutral colloidal silica (NCS) and basic col oidal silica (BCS), was prepared to study the effect of binders on their adhesion and catalytic activity. Scanning electron microscopy characterization indicated that the zeolite coating using BCS shows the smoothest surface with higher homogeneity and adherence strength. The specific surface area, relative crystallization and acid site strength of zeolites are also dependent on the binder used. Catalytic cracking of supercritical n-dodecane over the series of zeolite coating with various binders indicated that HZSM-5 coating with BCS exhibits the highest and the most stable catalytic activity compared with other kinds of binders, and also exhibits a stable catalytic activity ascribed to its proper acid property and microstructure.

  1. Physics-based enzyme design: predicting binding affinity and catalytic activity.

    Science.gov (United States)

    Sirin, Sarah; Pearlman, David A; Sherman, Woody

    2014-12-01

    Computational enzyme design is an emerging field that has yielded promising success stories, but where numerous challenges remain. Accurate methods to rapidly evaluate possible enzyme design variants could provide significant value when combined with experimental efforts by reducing the number of variants needed to be synthesized and speeding the time to reach the desired endpoint of the design. To that end, extending our computational methods to model the fundamental physical-chemical principles that regulate activity in a protocol that is automated and accessible to a broad population of enzyme design researchers is essential. Here, we apply a physics-based implicit solvent MM-GBSA scoring approach to enzyme design and benchmark the computational predictions against experimentally determined activities. Specifically, we evaluate the ability of MM-GBSA to predict changes in affinity for a steroid binder protein, catalytic turnover for a Kemp eliminase, and catalytic activity for α-Gliadin peptidase variants. Using the enzyme design framework developed here, we accurately rank the most experimentally active enzyme variants, suggesting that this approach could provide enrichment of active variants in real-world enzyme design applications.

  2. Modulating TRAP-mediated transcription termination by AT during transcription of the leader region of the Bacillus subtilis trp operon

    OpenAIRE

    Sharma, Shraddha; Gollnick, Paul

    2014-01-01

    An 11-subunit protein called trp RNA binding Attenuation Protein (TRAP) controls attenuation of the tryptophan biosynthetic (trpEDCFBA) operon in Bacillus subtilis. Tryptophan-activated TRAP binds to 11 (G/U)AG repeats in the 5′ leader region of trp mRNAs, and downregulates expression of the operon by promoting transcription termination prior to the structural genes. Anti-TRAP (AT) is an antagonist that binds to tryptophan-activated TRAP and prevents TRAP from binding to RNA, thereby upregula...

  3. Characterization of a soluble, catalytically active form of Escherichia coli leader peptidase: requirement of detergent or phospholipid for optimal activity.

    Science.gov (United States)

    Tschantz, W R; Paetzel, M; Cao, G; Suciu, D; Inouye, M; Dalbey, R E

    1995-03-28

    Leader peptidase is a novel serine protease in Escherichia coli, which functions to cleave leader sequences from exported proteins. Its catalytic domain extends into the periplasmic space and is anchored to the membrane by two transmembrane segments located at the N-terminal end of the protein. At present, there is no information on the structure of the catalytic domain. Here, we report on the properties of a soluble form of leader peptidase (delta 2-75), and we compare its properties to those of the wild-type enzyme. We find that the truncated leader peptidase has a kcat of 3.0 S-1 and a Km of 32 microM with a pro-OmpA nuclease A substrate. In contrast to the wild-type enzyme (pI of 6.8), delta 2-75 is water-soluble and has an acidic isoelectric point of 5.6. We also show with delta 2-75 that the replacement of serine 90 and lysine 145 with alanine residues results in a 500-fold reduction in activity, providing further evidence that leader peptidase employs a catalytic serine/lysine dyad. Finally, we find that the catalysis of delta 2-75 is accelerated by the presence of the detergent Triton X-100, regardless if the substrate is pro-OmpA nuclease A or a peptide substrate. Triton X-100 is required for optimal activity of delta 2-75 at a level far below the critical micelle concentration. Moreover, we find that E. coli phospholipids stimulate the activity of delta 2-75, suggesting that phospholipids may play an important physiological role in the catalytic mechanism of leader peptidase. PMID:7696258

  4. A Redox 2-Cys Mechanism Regulates the Catalytic Activity of Divergent Cyclophilins1[W

    Science.gov (United States)

    Campos, Bruna Medéia; Sforça, Mauricio Luis; Ambrosio, Andre Luis Berteli; Domingues, Mariane Noronha; Brasil de Souza, Tatiana de Arruda Campos; Barbosa, João Alexandre Ribeiro Gonçalvez; Leme, Adriana Franco Paes; Perez, Carlos Alberto; Whittaker, Sara Britt-Marie; Murakami, Mario Tyago; Zeri, Ana Carolina de Matos; Benedetti, Celso Eduardo

    2013-01-01

    The citrus (Citrus sinensis) cyclophilin CsCyp is a target of the Xanthomonas citri transcription activator-like effector PthA, required to elicit cankers on citrus. CsCyp binds the citrus thioredoxin CsTdx and the carboxyl-terminal domain of RNA polymerase II and is a divergent cyclophilin that carries the additional loop KSGKPLH, invariable cysteine (Cys) residues Cys-40 and Cys-168, and the conserved glutamate (Glu) Glu-83. Despite the suggested roles in ATP and metal binding, the functions of these unique structural elements remain unknown. Here, we show that the conserved Cys residues form a disulfide bond that inactivates the enzyme, whereas Glu-83, which belongs to the catalytic loop and is also critical for enzyme activity, is anchored to the divergent loop to maintain the active site open. In addition, we demonstrate that Cys-40 and Cys-168 are required for the interaction with CsTdx and that CsCyp binds the citrus carboxyl-terminal domain of RNA polymerase II YSPSAP repeat. Our data support a model where formation of the Cys-40-Cys-168 disulfide bond induces a conformational change that disrupts the interaction of the divergent and catalytic loops, via Glu-83, causing the active site to close. This suggests a new type of allosteric regulation in divergent cyclophilins, involving disulfide bond formation and a loop-displacement mechanism. PMID:23709667

  5. Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals.

    Science.gov (United States)

    Vats, T; Dutt, S; Kumar, R; Siril, P F

    2016-01-01

    Amazing conductivity, perfect honeycomb sp(2) arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity. PMID:27619321

  6. Electro-catalytic activity of Ni–Co-based catalysts for oxygen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Hua [School of Urban Rail Transportation, Soochow University, Suzhou 215006 (China); Li, Zhihu [College of Physics, Optoelectronics and Energy, Soochow University, Moye Rd. 688, Suzhou 215006 (China); Xu, Yanhui, E-mail: xuyanhui@suda.edu.cn [College of Physics, Optoelectronics and Energy, Soochow University, Moye Rd. 688, Suzhou 215006 (China)

    2015-04-15

    Graphical abstract: The electro-catalytic activity of different electro-catalysts with a porous electrode structure was compared considering the real electrode area that was evaluated by cyclic measurement. - Highlights: • Ni–Co-based electro-catalysts for OER have been studied and compared. • The real electrode area is calculated and used for assessing the electro-catalysts. • Exchange current and reaction rate constant are estimated. • Ni is more useful for OER reaction than Co. - Abstract: In the present work, Ni–Co-based electrocatalysts (Ni/Co = 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0) have been studied for oxygen evolution reaction. The phase structure has been analyzed by X-ray diffraction technique. Based on the XRD and SEM results, it is believed that the synthesized products are poorly crystallized. To exclude the disturbance of electrode preparation technology on the evaluation of electro-catalytic activity, the real electrode surface area is calculated based on the cyclic voltammetry data, assumed that the specific surface capacitance is 60 μF cm{sup −2} for metal oxide electrode. The real electrode area data are used to calculate the current density. The reaction rate constant of OER at different electrodes is also estimated based on basic reaction kinetic equations. It is found that the exchange current is 0.05–0.47 mA cm{sup −2} (the real surface area), and the reaction rate constant has an order of magnitude of 10{sup −7}–10{sup −6} cm s{sup −1}. The influence of the electrode potential on OER rate has been also studied by electrochemical impedance spectroscopy (EIS) technique. Our investigation has shown that the nickel element has more contribution than the cobalt; the nickel oxide has the best electro-catalytic activity toward OER.

  7. Electro-catalytic activity of Ni–Co-based catalysts for oxygen evolution reaction

    International Nuclear Information System (INIS)

    Graphical abstract: The electro-catalytic activity of different electro-catalysts with a porous electrode structure was compared considering the real electrode area that was evaluated by cyclic measurement. - Highlights: • Ni–Co-based electro-catalysts for OER have been studied and compared. • The real electrode area is calculated and used for assessing the electro-catalysts. • Exchange current and reaction rate constant are estimated. • Ni is more useful for OER reaction than Co. - Abstract: In the present work, Ni–Co-based electrocatalysts (Ni/Co = 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0) have been studied for oxygen evolution reaction. The phase structure has been analyzed by X-ray diffraction technique. Based on the XRD and SEM results, it is believed that the synthesized products are poorly crystallized. To exclude the disturbance of electrode preparation technology on the evaluation of electro-catalytic activity, the real electrode surface area is calculated based on the cyclic voltammetry data, assumed that the specific surface capacitance is 60 μF cm−2 for metal oxide electrode. The real electrode area data are used to calculate the current density. The reaction rate constant of OER at different electrodes is also estimated based on basic reaction kinetic equations. It is found that the exchange current is 0.05–0.47 mA cm−2 (the real surface area), and the reaction rate constant has an order of magnitude of 10−7–10−6 cm s−1. The influence of the electrode potential on OER rate has been also studied by electrochemical impedance spectroscopy (EIS) technique. Our investigation has shown that the nickel element has more contribution than the cobalt; the nickel oxide has the best electro-catalytic activity toward OER

  8. Structure of the catalytic domain of Plasmodium falciparum ARF GTPase-activating protein (ARFGAP)

    Energy Technology Data Exchange (ETDEWEB)

    Cook, William J.; Senkovich, Olga; Chattopadhyay, Debasish (UAB)

    2012-03-26

    The crystal structure of the catalytic domain of the ADP ribosylation factor GTPase-activating protein (ARFGAP) from Plasmodium falciparum has been determined and refined to 2.4 {angstrom} resolution. Multiwavelength anomalous diffraction (MAD) data were collected utilizing the Zn{sup 2+} ion bound at the zinc-finger domain and were used to solve the structure. The overall structure of the domain is similar to those of mammalian ARFGAPs. However, several amino-acid residues in the area where GAP interacts with ARF1 differ in P. falciparum ARFGAP. Moreover, a number of residues that form the dimer interface in the crystal structure are unique in P. falciparum ARFGAP.

  9. Facile synthesis and excellent catalytic activity of gold nanoparticles on graphene oxide

    Institute of Scientific and Technical Information of China (English)

    Yong Qiang He; Na Na Zhang; Yu Liu; Jian Ping Gao; Mao Cong Yi; Qiao Juan Gong; Hai Xia Qiu

    2012-01-01

    For the first time,Au nanoparticles on graphene oxide (GO-AuNPs) were successfully fabricated without applying any additional reductants,just by the redox reaction between AuCl4-1 and GO.Their structure was characterized by transmission electron microscopy and X-ray powder diffraction.The results show that flower-like AuNPs were successfully dispersed on GO surface.Importantly,they showed a high catalytic activity for the Suzuki-Miyaura coupling reaction in an aqueous medium.

  10. Polyvinylpyrrolidone adsorption effects on the morphologies of synthesized platinum particles and its catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ooi, Mahayatun Dayana Johan [Nano - Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia); Aziz, Azlan Abdul [Nano - Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia); Nanobiotechnology Research and Innovation (NanoBRI), INFORMM, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia)

    2015-04-24

    Flower-like Platinum micro-structures were synthesized from different concentration of the PVP using solvothermal method. At 5.0×10{sup −3} mmol of PVP, well-defined flower-like pattern consists of triangular petals radiating from the centre were produced whereas larger flower network developed at higher PVP concentration. High degree of crystallinity was obtained upon each increment of PVP. The well defined flower like pattern synthesized using 5.0×10{sup −3} mmol PVP exhibit the highest catalytic activity and stability towards electro-oxidation of formic acid.

  11. Polyvinylpyrrolidone adsorption effects on the morphologies of synthesized platinum particles and its catalytic activity

    Science.gov (United States)

    Ooi, Mahayatun Dayana Johan; Aziz, Azlan Abdul

    2015-04-01

    Flower-like Platinum micro-structures were synthesized from different concentration of the PVP using solvothermal method. At 5.0×10-3 mmol of PVP, well-defined flower-like pattern consists of triangular petals radiating from the centre were produced whereas larger flower network developed at higher PVP concentration. High degree of crystallinity was obtained upon each increment of PVP. The well defined flower like pattern synthesized using 5.0×10-3 mmol PVP exhibit the highest catalytic activity and stability towards electro-oxidation of formic acid.

  12. Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

    OpenAIRE

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

    2015-01-01

    Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetram...

  13. Enhanced catalytic activity over MIL-100(Fe) loaded ceria catalysts for the selective catalytic reduction of NOx with NH₃ at low temperature.

    Science.gov (United States)

    Wang, Peng; Sun, Hong; Quan, Xie; Chen, Shuo

    2016-01-15

    The development of catalysts for selective catalytic reduction (SCR) reactions that are highly active at low temperatures and show good resistance to SO2 and H2O is still a challenge. In this study, we have designed and developed a high-performance SCR catalyst based on nano-sized ceria encapsulated inside the pores of MIL-100(Fe) that combines excellent catalytic power with a metal organic framework architecture synthesized by the impregnation method (IM). Transmission electron microscopy (TEM) revealed the encapsulation of ceria in the cavities of MIL-100(Fe). The prepared IM-CeO2/MIL-100(Fe) catalyst shows improved catalytic activity both at low temperatures and throughout a wide temperature window. The temperature window for 90% NOx conversion ranges from 196 to 300°C. X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) analysis indicated that the nano-sized ceria encapsulated inside MIL-100(Fe) promotes the production of chemisorbed oxygen on the catalyst surface, which greatly enhances the formation of the NO2 species responsible for fast SCR reactions. PMID:26414927

  14. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion.

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W; Liu, Yan; Walter, Nils G; Yan, Hao

    2016-02-10

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  15. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-02-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  16. Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

    Science.gov (United States)

    Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

    2015-08-18

    nanoparticles on oxide supports and Pt-CdSe-Pt nanodumbbells. We show that the accumulation or depletion of hot electrons on metal nanoparticles, in turn, can also influence catalytic reactions. Mechanisms suggested for hot-electron-induced chemical reactions on a photoexcited plasmonic metal are discussed. We propose that the manipulation of the flow of hot electrons by changing the electrical characteristics of metal-oxide and metal-semiconductor interfaces can give rise to the intriguing capability of tuning the catalytic activity of hybrid nanocatalysts. PMID:26181684

  17. The Botrytis cinerea xylanase Xyn11A contributes to virulence with its necrotizing activity, not with its catalytic activity

    Directory of Open Access Journals (Sweden)

    González Celedonio

    2010-02-01

    Full Text Available Abstract Background The Botrytis cinerea xylanase Xyn11A has been previously shown to be required for full virulence of this organism despite its poor contribution to the secreted xylanase activity and the low xylan content of B. cinerea hosts. Intriguingly, xylanases from other fungi have been shown to have the property, independent of the xylan degrading activity, to induce necrosis when applied to plant tissues, so we decided to test the hypothesis that secreted Xyn11A contributes to virulence by promoting the necrosis of the plant tissue surrounding the infection, therefore facilitating the growth of this necrotroph. Results We show here that Xyn11A has necrotizing activity on plants and that this capacity is conserved in site-directed mutants of the protein lacking the catalytic activity. Besides, Xyn11A contributes to the infection process with the necrotizing and not with the xylan hydrolyzing activity, as the catalytically-impaired Xyn11A variants were able to complement the lower virulence of the xyn11A mutant. The necrotizing activity was mapped to a 30-amino acids peptide in the protein surface, and this region was also shown to mediate binding to tobacco spheroplasts by itself. Conclusions The main contribution of the xylanase Xyn11A to the infection process of B. cinerea is to induce necrosis of the infected plant tissue. A conserved 30-amino acids region on the enzyme surface, away from the xylanase active site, is responsible for this effect and mediates binding to plant cells.

  18. Relation between the structure and catalytic activity for automotive emissions. Use of x-ray anomalous dispersion effect

    CERN Document Server

    Mizuki, J; Tanaka, H

    2003-01-01

    The employment of the X-ray anomalous dispersion effect allows us to detect the change in structure of catalytic converters with the environment exposed. Here we show that palladium atoms in a perovskite crystal move into and out of the crystal by anomalous X-ray diffraction and absorption techniques. This movement of the precious metal plays an important role to keep the catalytic activity long-lived. (author)

  19. Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx

    International Nuclear Information System (INIS)

    Nanocrystalline zeolites with discrete crystal sizes of less than 100 nm have different properties relative to zeolites with larger crystal sizes. Nanocrystalline zeolites have improved mass transfer properties and very large internal and external surface areas that can be exploited for many different applications. The additional external surface active sites and the improved mass transfer properties of nanocrystalline zeolites offer significant advantages for selective catalytic reduction (SCR) catalysis with ammonia as a reductant in coal-fired power plants relative to current zeolite based SCR catalysts. Nanocrystalline NaY was synthesized with a crystal size of 15-20 nm and was thoroughly characterized using x-ray diffraction, electron paramagnetic resonance spectroscopy, nitrogen adsorption isotherms and Fourier Transform Infrared (FT-IR) spectroscopy. Copper ions were exchanged into nanocrystalline NaY to increase the catalytic activity. The reactions of nitrogen dioxides (NOx) and ammonia (NH3) on nanocrystalline NaY and CuY were investigated using FT-IR spectroscopy. Significant conversion of NO2 was observed at room temperature in the presence of NH3 as monitored by FT-IR spectroscopy. Copper-exchanged nanocrystalline NaY was more active for NO2 reduction with NH3 relative to nanocrystalline NaY

  20. CO oxidation over ruthenium: identification of the catalytically active phases at near-atmospheric pressures

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Goodman, Wayne D.

    2012-05-21

    CO oxidation was carried out over Ru(0001) and RuO2(110) thin film grown on Ru(0001) at various O2/CO ratios near atmospheric pressures. Reaction kinetics, coupled with in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and post-reaction Auger electron spectroscopy (AES) measurements were used to identify the catalytically relevant phases at different reaction conditions. Under stoichiometric and reducing conditions at all reaction temperatures, as well as net-oxidizing reaction conditions below {approx}475 K, a reduced metallic phase with chemisorbed oxygen is the thermodynamically stable and catalytically active phase. On this surface CO oxidation occurs at surface defect sites, for example step edges. Only at net-oxidizing reaction conditions and above {approx}475 K is the RuO2 thin film grown on metallic Ru stable and active. However, RuO2 is not active itself without the existence of the metal substrate, suggesting the importance of a strong metal-substrate interaction (SMSI).

  1. Parkin mitochondrial translocation is achieved through a novel catalytic activity coupled mechanism

    Institute of Scientific and Technical Information of China (English)

    Xinde Zheng; Tony Hunter

    2013-01-01

    Pink1,a mitochondrial kinase,and Parkin,an E3 ubiquitin ligase,function in mitochondrial maintenance.Pink1 accumulates on depolarized mitochondria,where it recruits Parkin to mainly induce K63-1inked chain ubiquitination of outer membrane proteins and eventually mitophagy.Parkin belongs to the RBR E3 iigase family.Recently,it has been proposed that the RBR domain transfers ubiquitin to targets via a cysteine-ubiquitin enzyme intermediate,in a manner similar to HECT domain E3 ligases.However,direct evidence for a ubiquitin transfer mechanism and its importance for Parkin's in vivo function is still missing.Here,we report that Parkin E3 activity relies on cysteinemediated ubiquitin transfer during mitophagy.Mutating the putative catalytic cysteine to serine (Parkin C431S)traps ubiquitin,and surprisingly,also abrogates Parkin mitochondrial translocation,indicating that E3 activity is essential for Parkin translocation.We found that Parkin can bind to K63-1inked ubiquitin chains,and that targeting K63-mimicking ubiquitin chains to mitochondria restores Parkin C431S localization.We propose that Parkin translocation is achieved through a novel catalytic activity coupled mechanism.

  2. Parkin mitochondrial translocation is achieved through a novel catalytic activity coupled mechanism

    Science.gov (United States)

    Zheng, Xinde; Hunter, Tony

    2013-01-01

    Pink1, a mitochondrial kinase, and Parkin, an E3 ubiquitin ligase, function in mitochondrial maintenance. Pink1 accumulates on depolarized mitochondria, where it recruits Parkin to mainly induce K63-linked chain ubiquitination of outer membrane proteins and eventually mitophagy. Parkin belongs to the RBR E3 ligase family. Recently, it has been proposed that the RBR domain transfers ubiquitin to targets via a cysteine∼ubiquitin enzyme intermediate, in a manner similar to HECT domain E3 ligases. However, direct evidence for a ubiquitin transfer mechanism and its importance for Parkin's in vivo function is still missing. Here, we report that Parkin E3 activity relies on cysteine-mediated ubiquitin transfer during mitophagy. Mutating the putative catalytic cysteine to serine (Parkin C431S) traps ubiquitin, and surprisingly, also abrogates Parkin mitochondrial translocation, indicating that E3 activity is essential for Parkin translocation. We found that Parkin can bind to K63-linked ubiquitin chains, and that targeting K63-mimicking ubiquitin chains to mitochondria restores Parkin C431S localization. We propose that Parkin translocation is achieved through a novel catalytic activity coupled mechanism. PMID:23670163

  3. BAX and tumor suppressor TRP53 are important in regulating mutagenesis in spermatogenic cells in mice.

    Science.gov (United States)

    Xu, Guogang; Vogel, Kristine S; McMahan, C Alex; Herbert, Damon C; Walter, Christi A

    2010-12-01

    During the first wave of spermatogenesis, and in response to ionizing radiation, elevated mutant frequencies are reduced to a low level by unidentified mechanisms. Apoptosis is occurring in the same time frame that the mutant frequency declines. We examined the role of apoptosis in regulating mutant frequency during spermatogenesis. Apoptosis and mutant frequencies were determined in spermatogenic cells obtained from Bax-null or Trp53-null mice. The results showed that spermatogenic lineage apoptosis was markedly decreased in Bax-null mice and was accompanied by a significantly increased spontaneous mutant frequency in seminiferous tubule cells compared to that of wild-type mice. Apoptosis profiles in the seminiferous tubules for Trp53-null were similar to control mice. Spontaneous mutant frequencies in pachytene spermatocytes and in round spermatids from Trp53-null mice were not significantly different from those of wild-type mice. However, epididymal spermatozoa from Trp53-null mice displayed a greater spontaneous mutant frequency compared to that from wild-type mice. A greater proportion of spontaneous transversions and a greater proportion of insertions/deletions 15 days after ionizing radiation were observed in Trp53-null mice compared to wild-type mice. Base excision repair activity in mixed germ cell nuclear extracts prepared from Trp53-null mice was significantly lower than that for wild-type controls. These data indicate that BAX-mediated apoptosis plays a significant role in regulating spontaneous mutagenesis in seminiferous tubule cells obtained from neonatal mice, whereas tumor suppressor TRP53 plays a significant role in regulating spontaneous mutagenesis between postmeiotic round spermatid and epididymal spermatozoon stages of spermiogenesis. PMID:20739667

  4. The influence of copper in dealloyed binary platinum–copper electrocatalysts on methanol electroxidation catalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Poochai, Chatwarin [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Veerasai, Waret, E-mail: waret.vee@mahidol.ac.th [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Somsook, Ekasith [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Dangtip, Somsak [Department of Physics, and NANOTEC COE at Mahidol University, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand)

    2015-08-01

    In this study, we prepared and characterized carbon paper-supported dealloyed binary Pt–Cu core–shell electrocatalysts (denoted as Pt{sub x}Cu{sub (100−x)/}CP) by cyclic co-electrodeposition and selective copper dealloying in an acidic medium, and we investigated the effect of the copper content in the samples on the catalytic activities toward methanol electroxidation reaction (MOR). X-ray photo-emission spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) indicated that the structure of dealloyed binary Pt–Cu catalysts possessed a Pt-rich shell and a Cu rich core. X-ray absorption near edge spectroscopy (XANES) displayed that the oxidation states of Pt and Cu were zero and one, respectively, implying the formation of metallic Pt and Cu{sub 2}O, respectively. X-ray diffraction spectroscopy (XRD) confirmed that Cu was inserted into a face-centered cubic Pt structure forming Pt–Cu alloys. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) displayed a cubic shape of Pt/CP and a spherical shape of Pt{sub x}Cu{sub (100−x)/}CP with several hundred nanometer sizes of agglomeration that depended on the Cu content. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to confirm that the sample of Pt{sub 70}Cu{sub 30}/CP exhibited the best catalytic activities in terms of the specific current, current density, catalytic poisoning tolerance, and stability. - Graphical abstract: Display Omitted - Highlights: • Binary electrocatalysts of Pt{sub x}Cu{sub (100−x)}/CP were prepared by cyclic co-electrodeposition and selective copper dealloying. • The structures of Pt{sub x}Cu{sub (100−x)}/CP were a Pt rich shell and a Cu rich core. • The Pt{sub 70}Cu{sub 30}/CP was the excellent catalytic activity towards methanol electrooxidation and CO{sub ads} tolerance.

  5. Precursor type affecting surface properties and catalytic activity of sulfated zirconia

    Directory of Open Access Journals (Sweden)

    Zarubica Aleksandra R.

    2007-01-01

    Full Text Available Zirconium-hydroxide precursor samples are synthesized from Zr-hydroxide, Zr-nitrate, and Zr-alkoxide, by precipitation/impregnation, as well as by a modified sol-gel method. Precursor samples are further sulphated for the intended SO4 2- content of 4 wt.%, and calcined at 500-700oC. Differences in precursors’ origin and calcination temperature induce the incorporation of SO4 2- groups into ZrO2 matrices by various mechanisms. As a result, different amounts of residual sulphates are coupled with other structural, as well as surface properties, resulting in various catalytic activities of sulphated zirconia samples. Catalyst activity and selectivity are a complex synergistic function of tetragonal phase fraction, sulphates contents, textural and surface characteristics. Superior activity of SZ of alkoxide origin can be explained by a beneficial effect of meso-pores owing to a better accommodation of coke deposits.

  6. Effect of citrate on Aspergillus niger phytase adsorption and catalytic activity in soil

    Science.gov (United States)

    Mezeli, Malika; Menezes-Blackburn, Daniel; Zhang, Hao; Giles, Courtney; George, Timothy; Shand, Charlie; Lumsdon, David; Cooper, Patricia; Wendler, Renate; Brown, Lawrie; Stutter, Marc; Blackwell, Martin; Darch, Tegan; Wearing, Catherine; Haygarth, Philip

    2015-04-01

    Current developments in cropping systems that promote mobilisation of phytate in agricultural soils, by exploiting plant-root exudation of phytase and organic acids, offer potential for developments in sustainable phosphorus use. However, phytase adsorption to soil particles and phytate complexion has been shown to inhibit phytate dephosphorylation, thereby inhibiting plant P uptake, increasing the risk of this pool contributing to diffuse pollution and reducing the potential benefits of biotechnologies and management strategies aimed to utilise this abundant reserve of 'legacy' phosphorus. Citrate has been seen to increase phytase catalytic efficiency towards complexed forms of phytate, but the mechanisms by which citrate promotes phytase remains poorly understood. In this study, we evaluated phytase (from Aspergillus niger) inactivation, and change in catalytic properties upon addition to soil and the effect citrate had on adsorption of phytase and hydrolysis towards free, precipitated and adsorbed phytate. A Langmuir model was fitted to phytase adsorption isotherms showing a maximum adsorption of 0.23 nKat g-1 (19 mg protein g-1) and affinity constant of 435 nKat gˉ1 (8.5 mg protein g-1 ), demonstrating that phytase from A.niger showed a relatively low affinity for our test soil (Tayport). Phytases were partially inhibited upon adsorption and the specific activity was of 40.44 nKat mgˉ1 protein for the free enzyme and 25.35 nKat mgˉ1 protein when immobilised. The kinetics of adsorption detailed that most of the adsorption occurred within the first 20 min upon addition to soil. Citrate had no effect on the rate or total amount of phytase adsorption or loss of activity, within the studied citrate concentrations (0-4mM). Free phytases in soil solution and phytase immobilised on soil particles showed optimum activity (>80%) at pH 4.5-5.5. Immobilised phytase showed greater loss of activity at pH levels over 5.5 and lower activities at the secondary peak at pH 2

  7. Comparing ion conductance recordings of synthetic lipid bilayers with cell membranes containing TRP channels

    CERN Document Server

    Laub, Katrine R; Blicher, Andreas; Madsen, Soren B; Luckhoff, Andreas; Heimburg, Thomas

    2011-01-01

    In this article we compare electrical conductance events from single channel recordings of three TRP channel proteins (TRPA1, TRPM2 and TRPM8) expressed in human embryonic kidney cells with channel events recorded on synthetic lipid membranes close to melting transitions. Ion channels from the TRP family are involved in a variety of sensory processes including thermo- and mechano-reception. Synthetic lipid membranes close to phase transitions display channel-like events that respond to stimuli related to changes in intensive thermodynamic variables such as pressure and temperature. TRP channel activity is characterized by typical patterns of current events dependent on the type of protein expressed. Synthetic lipid bilayers show a wide spectrum of electrical phenomena that are considered typical for the activity of protein ion channels. We find unitary currents, burst behavior, flickering, multistep-conductances, and spikes behavior in both preparations. Moreover, we report conductances and lifetimes for lipi...

  8. Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

    Science.gov (United States)

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-03-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  9. Photo-catalytic activities of plant hormones on semiconductor nanoparticles by laser-activated electron tunneling and emitting.

    Science.gov (United States)

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-01-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO₂), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi₂O₃)₀.₀₇(CoO)₀.₀₃(ZnO)₀.₉ semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  10. Activities of human RRP6 and structure of the human RRP6 catalytic domain

    Energy Technology Data Exchange (ETDEWEB)

    Januszyk, Kurt; Liu, Quansheng; Lima, Christopher D. (SKI)

    2011-08-29

    The eukaryotic RNA exosome is a highly conserved multi-subunit complex that catalyzes degradation and processing of coding and noncoding RNA. A noncatalytic nine-subunit exosome core interacts with Rrp44 and Rrp6, two subunits that possess processive and distributive 3'-to-5' exoribonuclease activity, respectively. While both Rrp6 and Rrp44 are responsible for RNA processing in budding yeast, Rrp6 may play a more prominent role in processing, as it has been demonstrated to be inhibited by stable RNA secondary structure in vitro and because the null allele in budding yeast leads to the buildup of specific structured RNA substrates. Human RRP6, otherwise known as PM/SCL-100 or EXOSC10, shares sequence similarity to budding yeast Rrp6 and is proposed to catalyze 3'-to-5' exoribonuclease activity on a variety of nuclear transcripts including ribosomal RNA subunits, RNA that has been poly-adenylated by TRAMP, as well as other nuclear RNA transcripts destined for processing and/or destruction. To characterize human RRP6, we expressed the full-length enzyme as well as truncation mutants that retain catalytic activity, compared their activities to analogous constructs for Saccharomyces cerevisiae Rrp6, and determined the X-ray structure of a human construct containing the exoribonuclease and HRDC domains that retains catalytic activity. Structural data show that the human active site is more exposed when compared to the yeast structure, and biochemical data suggest that this feature may play a role in the ability of human RRP6 to productively engage and degrade structured RNA substrates more effectively than the analogous budding yeast enzyme.

  11. Molecular dynamics characterization of five pathogenic factor X mutants associated with decreased catalytic activity

    KAUST Repository

    Abdel-Azeim, Safwat

    2014-11-11

    Factor X (FX) is one of the major players in the blood coagulation cascade. Upon activation to FXa, it converts prothrombin to thrombin, which in turn converts fibrinogen into fibrin (blood clots). FXa deficiency causes hemostasis defects, such as intracranial bleeding, hemathrosis, and gastrointestinal blood loss. Herein, we have analyzed a pool of pathogenic mutations, located in the FXa catalytic domain and directly associated with defects in enzyme catalytic activity. Using chymotrypsinogen numbering, they correspond to D102N, T135M, V160A, G184S, and G197D. Molecular dynamics simulations were performed for 1.68 μs on the wild-type and mutated forms of FXa. Overall, our analysis shows that four of the five mutants considered, D102N, T135M, V160A, and G184S, have rigidities higher than those of the wild type, in terms of both overall protein motion and, specifically, subpocket S4 flexibility, while S1 is rather insensitive to the mutation. This acquired rigidity can clearly impact the substrate recognition of the mutants.

  12. Controllable preparation of CeO2 nanostructure materials and their catalytic activity

    Institute of Scientific and Technical Information of China (English)

    Shan Wenjuan; Guo Hongjuan; Liu Chang; Wang Xiaonan

    2012-01-01

    Well-crystalline CeO2 nanostructures with the morphology ofnanorods and nanocubes were synthesized by a template-free hydrothermal method.X-ray diffraction (XRD),transmission electron microscopy (TEM),Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption measurements were employed to characterize the synthesized materials.The reducibility and catalytic activity of nanostructured CeO2 were examined by hydrogen temperature-programmed reduction (H2-TPR) and CO oxidation.The results showed that CeO2 nanorods could be converted into CeO2 nanocubes with the increasing of the reaction time and the hydrothermal temperature,CeO2 nanorods became longer gradually with the increasing of the concentrations of NaOH.H2-TPR characterization demonstrated that the intense low-temperature reduction peak in the CeO2 nanorods indicated the amount of hydrogen consumed is larger than CeO2 nanocubes.Meantime the CeO2 nanorods enhanced catalytic activity for CO oxidation,the total conversion temperature was 340 ℃.The reasons were that CeO2 nanorods have much smaller crystalline sizes and higher surface areas than CeO2 nanocubes.

  13. Support-shape Dependent Catalytic Activity in Pt/alumina Systems Using USANS/SANS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Hoon; Han, Sugyeong; Ha, Heonphil; Byun, Jiyoung; Kim, Man-ho [KIST, Seoul (Korea, Republic of)

    2015-10-15

    Pt nanoparticles dispersed on ceramic powder such as alumina and ceria powder are used as catalyst materials to reduce pollution from automobile exhaust, power plant exhaust, etc. Much effort has been put to investigate the relationship between types of catalyst support materials and reactivity of the supported metallic particles. The surface shape of support materials can also be expected to control the catalysts size with the surface shape of support materials. In this presentation, we show our SANS (small angle neutron scattering) -USANS (ultra small angle neutron scattering) analysis on the structural differences of different shapes of the same γ alumina powder with different loadings of Pt nanoparticles. Then, the reactivity of the prepared catalyst materials are presented and discussed based on the investigation of the structure of the support materials by SANS. The shapes of gamma alumina, rod-like or plate-like shape, were determined from nanometer to micrometer with USANS and SANS analysis. We found that the platelet-like alumina consists of an aggregate of 2 - 3 layers, which further reduce specific surface area and catalytic activity compared to rod-like shape. Rod-like shape shows more than 100% enhancement in the catalytic activities in model three-way-catalyst (TWC) reactions of CO, NO, and C{sub 3}H{sub 6} at low temperature around 200 .deg. C.

  14. Peroxidase-like catalytic activities of ionic metalloporphyrins supported on functionalised polystyrene surface

    Indian Academy of Sciences (India)

    Mikki V Vinodu; M Padmanabhan

    2001-02-01

    Metalloderivatives of anionic tetrasulphonated tetraphenylporphyrin (MTPPS, M = Mn(III), Fe(III) and Co(III)) were synthesized and immobilized on cationically functionalised divinylbenzene(DVB)-crosslinked polystyrene(PS). These supported catalysts (PS-MTPPS) were found to exhibit peroxidase-like activity. The co-oxidation of 4-aminoantipyrine and phenol by H2O2 was attempted with these catalysts to mimic this enzyme function. The catalytic efficiency of all these immobilized MTPPS was found to be superior to the corresponding unsupported MTPPS in solution. The effect of the central metal ion of the porphyrin, H of the reaction medium and also the temperature effect are investigated. The ideal H was seen to be in the 8 0-8 5 range, with maximum effect at 8 2. The efficiency order for the various PS-MTPPS was seen to be Co>Mn>Fe, with CoTPPS showing efficiency comparable to that of horseradish peroxidase. The catalytic efficiency was found to be increasing with temperature for all the catalysts. The re-usability of these PS-MTPPS systems for peroxidase-like activity was also studied and it was found that they exhibited a very high degree of recyclability without much poisoning.

  15. The photo-catalytic activities of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO43-, HPO42-) microparticles

    Science.gov (United States)

    Zhang, Fan; Shi, Yuanji; Zhao, Zongshan; Song, Weijie; Cheng, Yang

    2014-02-01

    For the good performance of apatite-based materials in the removal of dyes and their environment-friendly advantage, five kinds of apatite microparticles of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO43-, HPO42-) were synthesized by a simple precipitation method and their photo-catalytic properties were invested. Better performance in the decolorization of methyl orange (MO) under the assistance of H2O2 than that of TiO2 were obtained for all the MPs. The photo-catalytic activity was mainly affected by surface area, energy band, impurity, crystallinity and crystal structure. The DFT calculation results demonstrated that the 2p of O and 3p of P in PO43- played the main role in the photo-catalytic process. This work would be helpful to design and synthesize low cost apatite materials with good photo-catalytic performance.

  16. Mutations in the catalytic loop HRD motif alter the activity and function of Drosophila Src64.

    Directory of Open Access Journals (Sweden)

    Taylor C Strong

    Full Text Available The catalytic loop HRD motif is found in most protein kinases and these amino acids are predicted to perform functions in catalysis, transition to, and stabilization of the active conformation of the kinase domain. We have identified mutations in a Drosophila src gene, src64, that alter the three HRD amino acids. We have analyzed the mutants for both biochemical activity and biological function during development. Mutation of the aspartate to asparagine eliminates biological function in cytoskeletal processes and severely reduces fertility, supporting the amino acid's critical role in enzymatic activity. The arginine to cysteine mutation has little to no effect on kinase activity or cytoskeletal reorganization, suggesting that the HRD arginine may not be critical for coordinating phosphotyrosine in the active conformation. The histidine to leucine mutant retains some kinase activity and biological function, suggesting that this amino acid may have a biochemical function in the active kinase that is independent of its side chain hydrogen bonding interactions in the active site. We also describe the phenotypic effects of other mutations in the SH2 and tyrosine kinase domains of src64, and we compare them to the phenotypic effects of the src64 null allele.

  17. Non-cell autonomous and non-catalytic activities of ATX in the developing brain

    Directory of Open Access Journals (Sweden)

    Raanan eGreenman

    2015-03-01

    Full Text Available The intricate formation of the cerebral cortex requires a well-coordinated series of events, which are regulated at the level of cell-autonomous and non-cell autonomous mechanisms. Whereas cell-autonomous mechanisms that regulate cortical development are well-studied, the non cell-autonomous mechanisms remain poorly understood. A non-biased screen allowed us to identify Autotaxin (ATX as a non cell-autonomous regulator of neural stem cell proliferation. ATX (also known as ENPP2 is best known to catalyze lysophosphatidic acid (LPA production. Our results demonstrate that ATX affects the localization and adhesion of neuronal progenitors in a cell autonomous and non-cell autonomous manner, and strikingly, this activity is independent from its catalytic activity in producing LPA.

  18. Synthesis, Structure and Catalytic Activity Comparison of Tris- and Tetracoordinated Lanthanide Amides

    Institute of Scientific and Technical Information of China (English)

    XIE,Mei-Hua(谢美华); LIU,Xin-Yuan(刘心元); WANG,Shao-Wu(王绍武); LIU,Li(刘莉); WU,Yong-Yong(吴勇勇); YANG,Gao-Sheng(杨高升); ZHOU,Shuang-Liu(周双六); SHENG,En-Hong(盛恩宏); HUANG,Zi-Xiang(黄子祥)

    2004-01-01

    Tetracoordinated lanthanide amides [(Me3Si)2N]3Ln (μ-Cl)Li(THF)3 (Ln=La (1), Pr (2)) were synthesized by the reaction of anhydrous lanthanide(Ⅲ) chlorides LnCl3 (Ln=La, Pr) with 3 equiv. of lithium bis(trimethylsilyl)amide (Me3Si)2NLi in THF, followed by recrystallization from toluene. Sublimation of 1 and 2 afforded the triscoordinate lanthanide amides [(Me3Si)2N]3Ln (Ln =La, Pr). The crystal structure of 2 was determined by X-ray diffraction analysis. The catalytic activity studies show that the tetracoordinate amides can be used as single-component MMA (methyl methacrylate) polymerization catalysts, while the triscoordinate amides showed poor activity on MMA polymerization under the same conditions.

  19. Catalytic enantioselective OFF ↔ ON activation processes initiated by hydrogen transfer: concepts and challenges.

    Science.gov (United States)

    Quintard, Adrien; Rodriguez, Jean

    2016-08-18

    Hydrogen transfer initiated processes are eco-compatible transformations allowing the reversible OFF ↔ ON activation of otherwise unreactive substrates. The minimization of stoichiometric waste as well as the unique activation modes provided by these transformations make them key players for a greener future for organic synthesis. Long limited to catalytic reactions that form racemic products, considerable progress on the development of strategies for controlling diastereo- and enantioselectivity has been made in the last decade. The aim of this review is to present the different strategies that enable enantioselective transformations of this type and to highlight how they can be used to construct key synthetic building blocks in fewer operations with less waste generation. PMID:27381644

  20. PiZ mouse liver accumulates polyubiquitin conjugates that associate with catalytically active 26S proteasomes.

    Directory of Open Access Journals (Sweden)

    Christopher J Haddock

    Full Text Available Accumulation of aggregation-prone human alpha 1 antitrypsin mutant Z (AT-Z protein in PiZ mouse liver stimulates features of liver injury typical of human alpha 1 antitrypsin type ZZ deficiency, an autosomal recessive genetic disorder. Ubiquitin-mediated proteolysis by the 26S proteasome counteracts AT-Z accumulation and plays other roles that, when inhibited, could exacerbate the injury. However, it is unknown how the conditions of AT-Z mediated liver injury affect the 26S proteasome. To address this question, we developed a rapid extraction strategy that preserves polyubiquitin conjugates in the presence of catalytically active 26S proteasomes and allows their separation from deposits of insoluble AT-Z. Compared to WT, PiZ extracts had about 4-fold more polyubiquitin conjugates with no apparent change in the levels of the 26S and 20S proteasomes, and unassembled subunits. The polyubiquitin conjugates had similar affinities to ubiquitin-binding domain of Psmd4 and co-purified with similar amounts of catalytically active 26S complexes. These data show that polyubiquitin conjugates were accumulating despite normal recruitment to catalytically active 26S proteasomes that were available in excess, and suggest that a defect at the 26S proteasome other than compromised binding to polyubiquitin chain or peptidase activity played a role in the accumulation. In support of this idea, PiZ extracts were characterized by high molecular weight, reduction-sensitive forms of selected subunits, including ATPase subunits that unfold substrates and regulate access to proteolytic core. Older WT mice acquired similar alterations, implying that they result from common aspects of oxidative stress. The changes were most pronounced on unassembled subunits, but some subunits were altered even in the 26S proteasomes co-purified with polyubiquitin conjugates. Thus, AT-Z protein aggregates indirectly impair degradation of polyubiquitinated proteins at the level of the 26S

  1. Catalytic activity of Mn-substituted barium hexaaluminates for methane combustion

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The catalysts of hexaaluminate (BaMnxAl12-xO19-δ , x = 1.0, 2.0, 3.0, 4.0) to be used in methane combustion have been successfully synthesized by co-precipitation method and supercritical drying. The crystalline structure and surface area of catalyst were characterized by X-ray diffraction (XRD) and nitrogen adsorption analysis of BET method. BET analysis revealed that the preparing and drying method proposed here provides stable materials with higher surface area of 51.4 m2/g in comparison to materials prepared using conventional ambient drying method for BaMnxAl12?xO19-δ calcined at 1200℃ under oxygen. XRD analysis indicated that formation of a pure single phase BaMnxAl12-xO19-δ occurred up to x = 3 in the case of Mn-substituted barium hexaaluminates. Incorporation of Mn in excess leads to BaAl2O4 phase formation. As far as the valence state of Manganese ions was concerned, the introduced Mn ions were either divalent or trivalent. The first Mn ions were introduced in the matrix essentially as Mn2+ and only for BaMn3Al9O19-δ does manganese exist exclusively as Mn3+; the higher the Mn concen- tration, the higher the proportion of Mn3+. Catalytic activity for methane combustion has been measured for Mn-substituted barium hexaaluminates, light-off temperature was observed in the 512-624℃ range. The highest activity was obtained for catalysts containing 3 Mn ions per unit cell, which reveals that the BaMnxAl12-xO19-δ catalyst was a promising methane combustion catalyst with high activity and good thermal stability. Temperature programmed reduction (TPR) under hydrogen has been used to correlate the catalytic activity with the amount of easily reducible species.

  2. Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

    Science.gov (United States)

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

    2015-01-01

    Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetramethyl-benzidine (TMB), as well as, analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes’ activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC towards oxidation of TMB is very high and shows direct two-electrons oxidation when the surface of PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent but only with appropriate drug delivery system. PMID:25886644

  3. Evaluation of the catalytic activity and cytotoxicity of palladium nanocubes: the role of oxygen.

    Science.gov (United States)

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P; Smirnov, Sergei

    2015-05-13

    Recently, it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photoexcitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,3',5,5'-tetramethylbenzidine (TMB), and analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes' activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step, followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC toward the oxidation of TMB is very high and shows direct two-electron oxidation when the surface of the PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent, but only with appropriate drug delivery system. PMID:25886644

  4. Effect of substrate (ZnO morphology on enzyme immobilization and its catalytic activity

    Directory of Open Access Journals (Sweden)

    Huang Xuelei

    2011-01-01

    Full Text Available Abstract In this study, zinc oxide (ZnO nanocrystals with different morphologies were synthesized and used as substrates for enzyme immobilization. The effects of morphology of ZnO nanocrystals on enzyme immobilization and their catalytic activities were investigated. The ZnO nanocrystals were prepared through a hydrothermal procedure using tetramethylammonium hydroxide as a mineralizing agent. The control on the morphology of ZnO nanocrystals was achieved by varying the ratio of CH3OH to H2O, which were used as solvents in the hydrothermal reaction system. The surface of as-prepared ZnO nanoparticles was functionalized with amino groups using 3-aminopropyltriethoxysilane and tetraethyl orthosilicate, and the amino groups on the surface were identified and calculated by FT-IR and the Kaiser assay. Horseradish peroxidase was immobilized on as-modified ZnO nanostructures with glutaraldehyde as a crosslinker. The results showed that three-dimensional nanomultipod is more appropriate for the immobilization of enzyme used further in catalytic reaction.

  5. Effect of substrate (ZnO) morphology on enzyme immobilization and its catalytic activity

    Science.gov (United States)

    Zhang, Yan; Wu, Haixia; Huang, Xuelei; Zhang, Jingyan; Guo, Shouwu

    2011-07-01

    In this study, zinc oxide (ZnO) nanocrystals with different morphologies were synthesized and used as substrates for enzyme immobilization. The effects of morphology of ZnO nanocrystals on enzyme immobilization and their catalytic activities were investigated. The ZnO nanocrystals were prepared through a hydrothermal procedure using tetramethylammonium hydroxide as a mineralizing agent. The control on the morphology of ZnO nanocrystals was achieved by varying the ratio of CH3OH to H2O, which were used as solvents in the hydrothermal reaction system. The surface of as-prepared ZnO nanoparticles was functionalized with amino groups using 3-aminopropyltriethoxysilane and tetraethyl orthosilicate, and the amino groups on the surface were identified and calculated by FT-IR and the Kaiser assay. Horseradish peroxidase was immobilized on as-modified ZnO nanostructures with glutaraldehyde as a crosslinker. The results showed that three-dimensional nanomultipod is more appropriate for the immobilization of enzyme used further in catalytic reaction.

  6. Antibiotic Binding Drives Catalytic Activation of Aminoglycoside Kinase APH(2″)-Ia.

    Science.gov (United States)

    Caldwell, Shane J; Huang, Yue; Berghuis, Albert M

    2016-06-01

    APH(2″)-Ia is a widely disseminated resistance factor frequently found in clinical isolates of Staphylococcus aureus and pathogenic enterococci, where it is constitutively expressed. APH(2″)-Ia confers high-level resistance to gentamicin and related aminoglycosides through phosphorylation of the antibiotic using guanosine triphosphate (GTP) as phosphate donor. We have determined crystal structures of the APH(2″)-Ia in complex with GTP analogs, guanosine diphosphate, and aminoglycosides. These structures collectively demonstrate that aminoglycoside binding to the GTP-bound kinase drives conformational changes that bring distant regions of the protein into contact. These changes in turn drive a switch of the triphosphate cofactor from an inactive, stabilized conformation to a catalytically competent active conformation. This switch has not been previously reported for antibiotic kinases or for the structurally related eukaryotic protein kinases. This catalytic triphosphate switch presents a means by which the enzyme can curtail wasteful hydrolysis of GTP in the absence of aminoglycosides, providing an evolutionary advantage to this enzyme.

  7. Catalytic combustion of methane on Co/MgO. Characterisation of active cobalt sites

    Energy Technology Data Exchange (ETDEWEB)

    Ulla, M.A.; Spretz, R.; Lombardo, E. [Instituto de Investigaciones en Catalisis y Petroquimica, INCAPE (FIQ, UNL-CONICET), Santiago del Estero 2829, C.P. 3000, Santa Fe (Argentina); Daniell, W.; Knoezinger, H. [Department Chemie, Physikalische Chemie, Ludwig Maximilians Universitaet, Butenandtstr. 5-13, Haus E, D-81377 Muenchen (Germany)

    2001-02-01

    A series of Co/MgO catalysts with 3-12wt.% Co were prepared by impregnation and calcined at 1073K for 10h. The catalytic behaviour of these samples toward CH{sub 4} combustion was found to increase with cobalt loading, though a plateau was reached at ca. 9wt.% Co content. Bulk characterisation was carried out using XRD, TPR and Raman spectroscopy, and showed that the solids were made up of a CoO-MgO solid solution and a MgO phase. A detailed examination of their surfaces was achieved through FTIR spectroscopy of adsorbed CO probe molecules, which indicated that at low cobalt loadings only a small proportion of the Co going into the solid solution was present on exposed faces as either Co{sup 2+} oxo-species or pentacoordinated Co{sup 2+}. However, as the cobalt content of the samples increased, a larger amount was exposed on the surface. This effect levelled off at 9wt.% Co, after which the increase in exposed Co{sup 2+} sites was countered by the masking effect of islands of MgO. In addition, at high cobalt loadings (9 and 12wt.%) Co formed small clusters which showed bulk CoO-like behaviour. Consequently, the benefit of having surface Co{sup 2+} species was balanced by the clustering effect of these species and the presence of MgO islands, negating their contribution to the overall catalytic activity of the samples.

  8. Catalytic ozonation of pentachlorophenol in aqueous solutions using granular activated carbon

    Science.gov (United States)

    Asgari, Ghorban; Samiee, Fateme; Ahmadian, Mohammad; Poormohammadi, Ali; solimanzadeh, Bahman

    2014-11-01

    The efficiency of granular activated carbon (GAC) was investigated in this study as a catalyst for the elimination of pentachlorophenol (PCP) from contaminated streams in a laboratory-scale semi-batch reactor. The influence of important parameters including solution pH (2-10), radical scavenger (tert-butanol, 0.04 mol/L), catalyst dosage (0.416-8.33 g/L), initial PCP concentration (100-1000 mg/L) and ozone flow rate (2.3-12 mg/min) was examined on the efficiency of the catalytic ozonation process (COP) in degradation and mineralization of PCP in aqueous solution. The experimental results showed that catalytic ozonation with GAC was most effective at pH of 8 with ozone flow rate of 12 mg/min and a GAC dosage of 2 g. Compared to the sole ozonation process (SOP), the removal levels of PCP and COP were, 98, and 79 %, respectively. The degradation rate of kinetics was also investigated. The results showed that using a GAC catalyst in the ozonation of PCP produced an 8.33-fold increase in rate kinetic compared to the SOP under optimum conditions. Tert-butanol alcohol (TBA) was used as a radical scavenger. The results demonstrated that COP was affected less by TBA than by SOP. These findings suggested that GAC acts as a suitable catalyst in COP to remove refractory pollutants from aqueous solution.

  9. Improving the catalytic activity of semiconductor nanocrystals through selective domain etching.

    Science.gov (United States)

    Khon, Elena; Lambright, Kelly; Khnayzer, Rony S; Moroz, Pavel; Perera, Dimuthu; Butaeva, Evgeniia; Lambright, Scott; Castellano, Felix N; Zamkov, Mikhail

    2013-05-01

    Colloidal chemistry offers an assortment of synthetic tools for tuning the shape of semiconductor nanocrystals. While many nanocrystal architectures can be obtained directly via colloidal growth, other nanoparticle morphologies require alternative processing strategies. Here, we show that chemical etching of colloidal nanoparticles can facilitate the realization of nanocrystal shapes that are topologically inaccessible by hot-injection techniques alone. The present methodology is demonstrated by synthesizing a two-component CdSe/CdS nanoparticle dimer, constructed in a way that both CdSe and CdS semiconductor domains are exposed to the external environment. This structural morphology is highly desirable for catalytic applications as it enables both reductive and oxidative reactions to occur simultaneously on dissimilar nanoparticle surfaces. Hydrogen production tests confirmed the improved catalytic activity of CdSe/CdS dimers, which was enhanced 3-4 times upon etching treatment. We expect that the demonstrated application of etching to shaping of colloidal heteronanocrystals can become a common methodology in the synthesis of charge-separating nanocrystals, leading to advanced nanoparticles architectures for applications in areas of photocatalysis, photovoltaics, and light detection.

  10. The stability and catalytic activity of W13@Pt42 core-shell structure

    Science.gov (United States)

    Huo, Jin-Rong; Wang, Xiao-Xu; Li, Lu; Cheng, Hai-Xia; Su, Yan-Jing; Qian, Ping

    2016-01-01

    This paper reports a study of the electronic properties, structural stability and catalytic activity of the W13@Pt42 core-shell structure using the First-principles calculations. The degree of corrosion of W13@Pt42 core-shell structure is simulated in acid solutions and through molecular absorption. The absorption energy of OH for this structure is lower than that for Pt55, which inhibits the poison effect of O containing intermediate. Furthermore we present the optimal path of oxygen reduction reaction catalyzed by W13@Pt42. Corresponding to the process of O molecular decomposition, the rate-limiting step of oxygen reduction reaction catalyzed by W13@Pt42 is 0.386 eV, which is lower than that for Pt55 of 0.5 eV. In addition by alloying with W, the core-shell structure reduces the consumption of Pt and enhances the catalytic efficiency, so W13@Pt42 has a promising perspective of industrial application. PMID:27759038

  11. Synthesis and catalytic activity of metallo-organic complexes bearing 5-amino 2-ethylpyridine -2-carboximidate

    Indian Academy of Sciences (India)

    LUO MEI; XU JIA; ZHANG JING CHENG

    2016-06-01

    A series of copper, cobalt, nickel and manganese complexes were synthesized and characterized. Reaction of 5-amino-2-cyanopyridine with $ MCl_{2}$·x$H_{2}O$ (M: $Cu^{2+}$, $Co^{2+}$, $Ni^{2+}$, $Mn^{2+})$ in anhydrous ethanol resulted in the formation of four complexes $[NH_{2}EtPyCuCl_{2}(CH_{3}OH)].H_{2}O 1$, $[(NH_{2}EtPyHCl)_{3}Co]$$(Cl)_{3}.3H_{2}O 2$, $[(NH_{2}EtPy)_{2}$ 2$(H_{2}O)Ni]$ $(Cl_{2})$ 3, and $[(NH_{2}EtPy)_{2}$ 2$(H_{2}O)$ Mn]$(Cl_{2})$ 4 $[NH_{2} EtPy=5-amino-oethylpyridine-2-carboximidate], respectively. The structures of these compounds were determined by X-raydiffraction, NMR and IR spectroscopy, and elemental analysis. Each complex was then used as a catalyst in the Henry reaction, and its catalytic activity was determined by 1H NMR. Good catalytic effects were achieved (69–87%).

  12. Decreased catalytic activity and altered activation properties of PDE6C mutants associated with autosomal recessive achromatopsia

    DEFF Research Database (Denmark)

    Grau, Tanja; Artemyev, Nikolai O; Rosenberg, Thomas;

    2011-01-01

    Mutations in the gene encoding the catalytic subunit of the cone photoreceptor phosphodiesterase (PDE6C) have been recently reported in patients with autosomal recessive inherited achromatopsia (ACHM) and early-onset cone photoreceptor dysfunction. Here we present the results of a comprehensive...... characterization of six missense mutations applying the baculovirus system to express recombinant mutant and wildtype chimeric PDE6C/PDE5 proteins in Sf9 insect cells. Purified proteins were analyzed using Western blotting, phosphodiesterase (PDE) activity measurements as well as inhibition assays by zaprinast...

  13. Catalytic effect of activated carbon on bioleaching of low-grade primary copper sulfide ores

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The catalytic effect of activated carbon on the bioleaching of low-grade primary copper sulfide ores using mixture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans was investigated. The results show that the addition of activated carbon can greatly accelerate the rate and efficiency of copper dissolution from low-grade primary copper sulfide ores. The solution with the concentration of 3.0 g/L activated carbon is most beneficial to the dissolution of copper. The resting time of the mixture of activated carbon and ores has an impact on the bioleaching of low-grade primary copper sulfide ores. The 2 d resting time is most favorable to the dissolution of copper. The enhanced dissolution rate and efficiency of copper can be attributed to the galvanic interaction between activated carbon and chalcopyrite. The addition of activated carbon obviously depresses the dissolution of iron and the bacterial oxidation of ferrous ions in solution. The lower redox potentials are more favorable to the copper dissolution than the higher potentials for low-grade primary copper sulfide ores in the presence of activated carbon.

  14. Separate TRP channels mediate amplification and transduction in drosophila

    Science.gov (United States)

    Lehnert, Brendan P.; Baker, Allison E.; Wilson, Rachel I.

    2015-12-01

    Auditory receptor cells rely on mechanically-gated channels to transform sound stimuli into neural activity. Several TRP channels have been implicated in Drosophila auditory transduction, but mechanistic studies have been hampered by the inability to record subthreshold signals from receptor neurons. We developed a non-invasive method for measuring these signals by recording from a central neuron that is electrically coupled to a genetically-defined population of auditory receptors. We find that the TRPN family member NompC, which is necessary for the active amplification of motion by the auditory organ, is not required for transduction. Instead, NompC sensitizes the transduction complex to movement and precisely regulates the static forces on the complex. In contrast, the TRPV channels Nanchung and Inactive are required for responses to sound, suggesting they are components of the transduction complex. Thus, transduction and active amplification are genetically separable processes in Drosophila hearing.

  15. Optical Absorption Property and Photo-catalytic Activity of Tin Dioxide-doped Titanium Dioxides

    Institute of Scientific and Technical Information of China (English)

    LI,Huai-Xiang; XIA,Rong-Hua; JIANG,Zheng-Wei; CHEN,Shan-Shan; CHEN,De-Zhan

    2008-01-01

    SnO2-doped TiO2 films and composite oxide powders have been prepared by a sol-gel method. Ti(OC4H9)4 and SnCl4·5H2O were used as precursors and C2H5OH was used as solvent. The optical absorption measurements indicate that the composite oxide SnO2-TiO2 thin films exhibit smaller optical energy band gaps than pure TiO2 thin films and the optical energy band gap decreases as calcining temperature increases. X-ray diffraction was used to characterize the phase transition for the composite oxide powders at different calcining temperatures. Aanatase phase is the main crystal structure in both pure TiO2 and Sn0.05Ti0.95O2 samples if calcining temperature is below 500℃. The rutile phase has appeared and coexisted with the anatase crystal phase for both pure TiO2 and Sn0.05Ti0.95O2 composite oxides when calcining was at 600℃ . Transmission electron microscopy analysis shows a smaller grain size in Sn0.05Ti0.95O2 powders than TiO2 powders calcined at 600℃. When calcining temperature is 700℃ , there is only rutile phase in Sn0.05Ti0.95O2 samples, but there are still two crystal phases, anatase and rutile, coexisting in the pure TiO2 samples. Assuming the grain growth obeys the first order kinetics, Arrhenius empirical relation has been used to estimate the activation energy of 47.486 and 33.103 kJ·mol-1 for the grain growth of TiO2 and Sn0.05Ti0.95O2, respectively. The photo-catalytic activity of the powder samples has been examined by measuring the degradation of methylene blue solution under ultra-violet irradiation. Two effective factors of photo-catalytic activity namely, the content of SnO2 in the TiO2 samples and the calcining temperature, have been optimized based on the photo-catalytic degradation of methylene blue solution.

  16. TRP, TRPL and cacophony channels mediate Ca2+ influx and exocytosis in photoreceptors axons in Drosophila.

    Directory of Open Access Journals (Sweden)

    Guadalupe Astorga

    Full Text Available In Drosophila photoreceptors Ca(2+-permeable channels TRP and TRPL are the targets of phototransduction, occurring in photosensitive microvilli and mediated by a phospholipase C (PLC pathway. Using a novel Drosophila brain slice preparation, we studied the distribution and physiological properties of TRP and TRPL in the lamina of the visual system. Immunohistochemical images revealed considerable expression in photoreceptors axons at the lamina. Other phototransduction proteins are also present, mainly PLC and protein kinase C, while rhodopsin is absent. The voltage-dependent Ca(2+ channel cacophony is also present there. Measurements in the lamina with the Ca(2+ fluorescent protein G-CaMP ectopically expressed in photoreceptors, revealed depolarization-induced Ca(2+ increments mediated by cacophony. Additional Ca(2+ influx depends on TRP and TRPL, apparently functioning as store-operated channels. Single synaptic boutons resolved in the lamina by FM4-64 fluorescence revealed that vesicle exocytosis depends on cacophony, TRP and TRPL. In the PLC mutant norpA bouton labeling was also impaired, implicating an additional modulation by this enzyme. Internal Ca(2+ also contributes to exocytosis, since this process was reduced after Ca(2+-store depletion. Therefore, several Ca(2+ pathways participate in photoreceptor neurotransmitter release: one is activated by depolarization and involves cacophony; this is complemented by internal Ca(2+ release and the activation of TRP and TRPL coupled to Ca(2+ depletion of internal reservoirs. PLC may regulate the last two processes. TRP and TRPL would participate in two different functions in distant cellular regions, where they are opened by different mechanisms. This work sheds new light on the mechanism of neurotransmitter release in tonic synapses of non-spiking neurons.

  17. Size-Dependent Catalytic Activity of Palladium Nanoparticles Fabricated in Porous Organic Polymers for Alkene Hydrogenation at Room Temperature.

    Science.gov (United States)

    Mondal, John; Trinh, Quang Thang; Jana, Avijit; Ng, Wilson Kwok Hung; Borah, Parijat; Hirao, Hajime; Zhao, Yanli

    2016-06-22

    Ultrafine palladium nanoparticles (Pd NPs) with 8 and 3 nm sizes were effectively fabricated in triazine functionalized porous organic polymer (POP) TRIA that was developed by nonaqueous polymerization of 2,4,6-triallyoxy-1,3,5-triazine. The Pd NPs encapsulated POP (Pd-POP) was fully characterized using several techniques. Further studies revealed an excellent capability of Pd-POP for catalytic transfer hydrogenation of alkenes at room temperature with superior catalytic performance and high selectivity of desired products. Highly flammable H2 gas balloon at high pressure and temperature used in conventional hydrogenation reactions was not needed in the present synthetic system. Catalytic activity is strongly dependent on the size of encapsulated Pd NPs in the POP. The Pd-POP catalyst with Pd NPs of 8 nm in diameter exhibited higher catalytic activity for alkene hydrogenation as compared with the Pd-POP catalyst encapsulating 3 nm Pd NPs. Computational studies were undertaken to gain insights into different catalytic activities of these two Pd-POP catalysts. High reusability and stability as well as no Pd leaching of these Pd-POP catalysts make them highly applicable for hydrogenation reactions at room temperature. PMID:27258184

  18. Nanocasted synthesis of the mesostructured LaCoO3 perovskite and its catalytic activity in methane combustion.

    Science.gov (United States)

    Wang, Yangang; Wang, Yanqin; Liu, Xiaohui; Guo, Yun; Guo, Yanglong; Lu, Guanzhong

    2009-02-01

    Extremely high surface area, mesostructured LaCoO3 perovskite has been synthesized by nanocasting from mesoporous cubic (Ia3d) vinyl silica. Thus-prepared material was characterized by XRD, TEM, and N2-sorption, and its catalytic property was also tested in methane combustion. The catalytic results demonstrated that thus-prepared mesostructured LaCoO3 perovskite had higher activity than the conventional bulk LaCoO3 perovskite prepared by citrate method. Further analysis showed that both the high surface area and the existence of high valent cobalt ions (Co4+, XPS analysis) were contributed to the high activity.

  19. On reasons of different catalytic activity of 4B-6B subgroup metallocenedichlorides in carbon monoxide amalgam reduction

    International Nuclear Information System (INIS)

    A study was made on catalytic activity of metallocenedichlorides of 4B-6B subgroup elements (Ti, Nb, Mo, W) in carbon monoxide amalgam reduction in THP and DMFA medium. It is shown that the difference in catalytic activity of these elements is conditioned by thermodynamic factors, which dictate impossibility of amalgam reduction of catalyst-substrate complex (4th subgroup), as well as by the difference in stability of corresponding metallocenes (5B and 6B subgroups). Amalgam reduction of CO bounded in complex with metallocene proceeds under conditions of the first electron transfer opposite to potential gradient

  20. Synthesis of novel carbon/silica composites based strong acid catalyst and its catalytic activities for acetalization

    Indian Academy of Sciences (India)

    Yueqing Lu; Xuezheng Liang; Chenze Qi

    2012-06-01

    Novel solid acid based on carbon/silica composites are synthesized through one-pot hydrothermal carbonization of hydroxyethylsulfonic acid, sucrose and tetraethyl orthosilicate (TEOS). The novel solid acid owned the acidity of 2.0 mmol/g, much higher than that of the traditional solid acids such as Nafion and Amberlyst-15 (0.8 mmol/g). The catalytic activities of the solid acid are investigated through acetalization. The results showed that the novel solid acid was very efficient for the reactions. The high acidity and catalytic activities made the novel carbon/silica composites based solid acid hold great potential for the green chemical processes.

  1. Catalytic activities enhanced by abundant structural defects and balanced N distribution of N-doped graphene in oxygen reduction reaction

    Science.gov (United States)

    Bai, Xiaogong; Shi, Yantao; Guo, Jiahao; Gao, Liguo; Wang, Kai; Du, Yi; Ma, Tingli

    2016-02-01

    N-doped graphene (NG) is a promising candidate for oxygen reduction reaction (ORR) in the cathode of fuel cells. However, the catalytic activity of NG is lower than that of commercial Pt/C in alkaline and acidic media. In this study, NG samples were obtained using urea as N source. The structural defects and N distribution in the samples were adjusted by regulating the pyrolysis temperature. The new NG type exhibited remarkable catalytic activities for ORR in both alkaline and acidic media.

  2. Nickel(II) complexes containing thiosemicarbazone and triphenylphosphine: Synthesis, spectroscopy, crystallography and catalytic activity

    Science.gov (United States)

    Priyarega, S.; Kalaivani, P.; Prabhakaran, R.; Hashimoto, T.; Endo, A.; Natarajan, K.

    2011-09-01

    Four new Ni(II) complexes of the general formula [Ni(PPh 3)(L)] (L = dibasic tridentate ligand derived from 4-diethylamino-salicylaldehyde and thiosemicarbazide or 4-N-substituted thiosemicarbazide) have been reported. The new complexes have been synthesized and characterized by analytical and spectroscopic (IR, electronic, 1H NMR and 31P NMR) techniques. Molecular structure of one of the complexes has been determined by X-ray crystallography. The complex, [Ni(PPh 3)(L4)] (H 2L4 = thiosemicarbazone prepared from 4-diethylamino-salicylaldehyde and 4-phenylthiosemicarbazide) crystallized in monoclinic space group with two molecules per unit cell and has the dimensions of a = 13.232(6) Å, b = 10.181(5) Å, c = 13.574(7) Å, α = 90°, β = 98.483(2)° and γ = 90°. Catalytic activity of the complexes has been explored for aryl-aryl coupling reaction.

  3. Catalytic Pyrolyses of Rayon and the Effect on Activated Carbon Fiber

    Institute of Scientific and Technical Information of China (English)

    曾凡龙; 潘鼎

    2004-01-01

    The catalytic pyrolyses of rayon have been studied respectively by thermo-gravimetric analysis (TGA) when rayon was treated with phosphoric acid (PA), three ammonium phosphate salts and ammonium sulfate (AS). The air is favorable to the catalysis of dibasic ammonium phosphate (DAP), but not to those of ADP, PA, AP, and AS obviously. It is put forward that a peak's shape character can be described with the ratio of height to half-height-width (H/W/2) of the peak on a differential thermo-gravimetric (DTG) curve. A flat cracking peak, presenting a more moderate dehydration reaction, has a smaller ratio and could lead to higher carbonization and activation yields. The experimental results prove this view. According to expectation, the order of catalysis is: DAP≥ADP>PA>AP(>>)AS(>>) no catalyst.

  4. Catalytic activity of polymer-bound Ru(III)–EDTA complex

    Indian Academy of Sciences (India)

    Mahesh K Dalal; R N Ram

    2001-04-01

    Chloromethylated styrene–divinylbenzene copolymer was chemically modified with ethylenediaminetetraacetic acid ligand. Catalytically active polymer containing Ru(III) moieties were synthesized from this polymeric ligand. They were characterized using FTIR, UV-vis, SEM, ESR and TGA. Other physico-chemical properties such as bulk density, surface area, moisture content and swelling behaviour in different solvents were also studied. The polymer bound complex was used to study hydrogenation of 1-hexene to -hexane under mild conditions. Influence of [1-hexene], [catalyst], temperature and nature of the solvent on the rate of the reaction was investigated. A rate expression is proposed based on the observed initial rate data. Recycling efficiency of the catalyst has also been studied.

  5. Synthesis of gold nanoparticles using renewable Punica granatum juice and study of its catalytic activity

    Science.gov (United States)

    Dash, Shib Shankar; Bag, Braja Gopal

    2014-01-01

    Punica granatum juice, a delicious multivitamin drink of great medicinal significance, is rich in different types of phytochemicals, such as terpenoids, alkaloids, sterols, polyphenols, sugars, fatty acids, aromatic compounds, amino acids, tocopherols, etc. We have demonstrated the use of the juice for the synthesis of gold nanoparticles (AuNPs) at room temperature under very mild conditions. The synthesis of the AuNPs was complete in few minutes and no extra stabilizing or capping agents were necessary. The size of the nanoparticles could be controlled by varying the concentration of the fruit extract. The AuNPs were characterized by surface plasmon resonance spectroscopy, high resolution transmission electron microscopy, fourier transform infrared spectroscopy and X-ray diffraction studies. Catalytic activity of the synthesized colloidal AuNPs has also been demonstrated.

  6. Catalytic Activity of Dual Metal Cyanide Complex in Multi-component Coupling Reactions

    Institute of Scientific and Technical Information of China (English)

    Anaswara RAVINDRAN; Rajendra SRIVASTAVA

    2011-01-01

    Several dual metal cyanide catalysts were prepared from potassium ferrocyanide,metal chloride (where metal =Zn2+,Mn2+,Ni2+,Co2+ and Fe2+),t-butanol (complexing agent) and PEG-4000 (co-complexing agent).The catalysts were characterized by elemental analysis (CHN and X-ray fluorescence),X-ray diffraction,N2 adsorption-desorption,scanning electron microscopy,Fourier-transform infiared spectroscopy,and UV-Visible spectroscopy.The dual metal cyanide catalysts were used in several acid catalyzed multi-component coupling reactions for the synthesis of pharmaceutically important organic derivatives.In all these reactions,the Fe-Fe containing dual metal cyanide catalyst was the best catalyst.The catalysts can be recycled without loss in catalytic activity.The advantage of this method is the use of mild,efficient and reusable catalysts for various reactions,which makes them candidates for commercial use.

  7. Improved Acylation of Phytosterols Catalyzed by Candida Antarctica Lipase a with Superior Catalytic Activity

    DEFF Research Database (Denmark)

    Panpipat, Worawan; Xu, Xuebing; Guo, Zheng

    approach to synthesize phytosterol ( -sitosterol as a model) fatty acid esters by employing immobilized CAL A which shows a superior catalytic activity to other immobilized lipases including CAL B, Lipozyme NS-40044 TLL and Lipozyme TL IM. CAL A achieves 6-14 times faster esterification of -sitosterol...... be achieved with hexane as solvent, fatty acid (C8-C18)/-sitosterol (1:1, mol:mol), 5-10% CALA load at 40- 50°C for 24h. This work demonstrated the promising potential of CAL A in bioprocess of phytosterols for value-added application....... with myristic acid than other lipases. The effects of enzyme concentration, fatty acid types, substrate molar ratio, reaction temperature and time, and polar/non-polar organic solvents were investigated. A series of -sitosteryl fatty acid esters (C2-C18) have been successfully prepared with structural...

  8. Carbon supported trimetallic nickel-palladium-gold hollow nanoparticles with superior catalytic activity for methanol electrooxidation

    Science.gov (United States)

    Shang, Changshuai; Hong, Wei; Wang, Jin; Wang, Erkang

    2015-07-01

    In this paper, Ni nanoparticles (NPs) are prepared in an aqueous solution by using sodium borohydride as reducing agent. With Ni NPs as the sacrificial template, hollow NiPdAu NPs are successfully prepared via partly galvanic displacement reaction between suitable metal precursors and Ni NPs. The as-synthesized hollow NiPdAu NPs can well dispersed on the carbon substrate. Transmission electron microscopy, X-ray diffraction and inductively coupled plasma mass spectrometry are taken to analyze the morphology, structure and composition of the as-synthesized catalysts. The prepared catalysts show superior catalytic activity and stability for methanol electrooxidation in alkaline media compared with commercial Pd/C and Pt/C. Catalysts prepared in this work show great potential to be anode catalysts in direct methanol fuel cells.

  9. Palladium nanoparticle anchored polyphosphazene nanotubes: preparation and catalytic activity on aryl coupling reactions

    Indian Academy of Sciences (India)

    V Devi; A Ashok Kumar; S Sankar; K Dinakaran

    2015-06-01

    Highly accessible-supported palladium (Pd) nanoparticles anchored polyphosphazene (PPZ) nanotubes (NTs) having average diameter of 120 nm were synthesized rapidly at room temperature and homogeneously decorated with Pd nanoparticles. The resultant PPZ–Pd nanocomposites were morphologically and structurally characterized by means of transmission electron microscope equipped with energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. Characterization results showed that the Pd nanoparticles with good dispersibility could be well anchored onto the surfaces of the PPZ NTs. The PPZ–Pd NTs show enhanced catalytic activity for the Suzuki coupling of aryl bromides with arylboronic acid. In addition, these PPZ–Pd NTs show excellent behaviour as reusable catalysts of the Suzuki and Heck coupling reactions.

  10. Catalytic diesel particulate filters reduce the in vitro estrogenic activity of diesel exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Wenger, Daniela; Gerecke, Andreas C.; Heeb, Norbert V. [Laboratory for Analytical Chemistry, Empa, Swiss Federal Laboratories for Materials Testing and Research, Duebendorf (Switzerland); Naegeli, Hanspeter [University of Zurich-Vetsuisse, Institute of Pharmacology and Toxicology, Zurich (Switzerland); Zenobi, Renato [ETH Zurich, Department of Chemistry and Applied Biosciences, Zurich (Switzerland)

    2008-04-15

    An in vitro reporter gene assay based on human breast cancer T47D cells (ER-CALUX {sup registered}) was applied to examine the ability of diesel exhaust to induce or inhibit estrogen receptor (ER)-mediated gene expression. Exhaust from a heavy-duty diesel engine was either treated by iron- or copper/iron-catalyzed diesel particulate filters (DPFs) or studied as unfiltered exhaust. Collected samples included particle-bound and semivolatile constituents of diesel exhaust. Our findings show that all of the samples contained compounds that were able to induce ER-mediated gene expression as well as compounds that suppressed the activity of the endogenous hormone 17{beta}-estradiol (E2). Estrogenic activity prevailed over antiestrogenic activity. We found an overall ER-mediated activity of 1.63 {+-} 0.31 ng E2 CALUX equivalents (E2-CEQs) per m{sup 3} of unfiltered exhaust. In filtered exhaust, we measured 0.74 {+-} 0.07 (iron-catalyzed DPF) and 0.55 {+-} 0.09 ng E2-CEQ m{sup -3} (copper/iron-catalyzed DPF), corresponding to reductions in estrogenic activity of 55 and 66%, respectively. Our study demonstrates that both catalytic DPFs lowered the ER-mediated endocrine-disrupting potential of diesel exhaust. (orig.)

  11. Tuning the catalytic activity of graphene nanosheets for oxygen reduction reaction via size and thickness reduction.

    Science.gov (United States)

    Benson, John; Xu, Qian; Wang, Peng; Shen, Yuting; Sun, Litao; Wang, Tanyuan; Li, Meixian; Papakonstantinou, Pagona

    2014-11-26

    Currently, the fundamental factors that control the oxygen reduction reaction (ORR) activity of graphene itself, in particular, the dependence of the ORR activity on the number of exposed edge sites remain elusive, mainly due to limited synthesis routes of achieving small size graphene. In this work, the synthesis of low oxygen content (graphene nanosheets with lateral dimensions smaller than a few hundred nanometers were achieved using a combination of ionic liquid assisted grinding of high purity graphite coupled with sequential centrifugation. We show for the first time that the graphene nanosheets possessing a plethora of edges exhibited considerably higher electron transfer numbers compared to the thicker graphene nanoplatelets. This enhanced ORR activity was accomplished by successfully exploiting the plethora of edges of the nanosized graphene as well as the efficient electron communication between the active edge sites and the electrode substrate. The graphene nanosheets were characterized by an onset potential of -0.13 V vs Ag/AgCl and a current density of -3.85 mA/cm2 at -1 V, which represent the best ORR performance ever achieved from an undoped carbon based catalyst. This work demonstrates how low oxygen content nanosized graphene synthesized by a simple route can considerably impact the ORR catalytic activity and hence it is of significance in designing and optimizing advanced metal-free ORR electrocatalysts.

  12. Monoclonal Antibodies Targeting the Alpha-Exosite of Botulinum Neurotoxin Serotype/A Inhibit Catalytic Activity.

    Directory of Open Access Journals (Sweden)

    Yongfeng Fan

    Full Text Available The paralytic disease botulism is caused by botulinum neurotoxins (BoNT, multi-domain proteins containing a zinc endopeptidase that cleaves the cognate SNARE protein, thereby blocking acetylcholine neurotransmitter release. Antitoxins currently used to treat botulism neutralize circulating BoNT but cannot enter, bind to or neutralize BoNT that has already entered the neuron. The light chain endopeptidase domain (LC of BoNT serotype A (BoNT/A was targeted for generation of monoclonal antibodies (mAbs that could reverse paralysis resulting from intoxication by BoNT/A. Single-chain variable fragment (scFv libraries from immunized humans and mice were displayed on the surface of yeast, and 19 BoNT/A LC-specific mAbs were isolated by using fluorescence-activated cell sorting (FACS. Affinities of the mAbs for BoNT/A LC ranged from a KD value of 9.0×10-11 M to 3.53×10-8 M (mean KD 5.38×10-9 M and median KD 1.53×10-9 M, as determined by flow cytometry analysis. Eleven mAbs inhibited BoNT/A LC catalytic activity with IC50 values ranging from 8.3 ~73×10-9 M. The fine epitopes of selected mAbs were also mapped by alanine-scanning mutagenesis, revealing that the inhibitory mAbs bound the α-exosite region remote from the BoNT/A LC catalytic center. The results provide mAbs that could prove useful for intracellular reversal of paralysis post-intoxication and further define epitopes that could be targeted by small molecule inhibitors.

  13. Synthesis, characterization and catalytic activity of carbon-silica hybrid catalyst from rice straw

    Science.gov (United States)

    Janaun, J.; Safie, N. N.; Siambun, N. J.

    2016-07-01

    The hybrid-carbon catalyst has been studied because of its promising potential to have high porosity and surface area to be used in biodiesel production. Silica has been used as the support to produce hybrid carbon catalyst due to its mesoporous structure and high surface area properties. The chemical synthesis of silica-carbon hybrid is expensive and involves more complicated preparation steps. The presence of natural silica in rice plants especially rice husk has received much attention in research because of the potential as a source for solid acid catalyst synthesis. But study on rice straw, which is available abundantly as agricultural waste is limited. In this study, rice straw undergone pyrolysis and functionalized using fuming sulphuric acid to anchor -SO3H groups. The presence of silica and the physiochemical properties of the catalyst produced were studied before and after sulphonation. The catalytic activity of hybrid carbon silica acid catalyst, (H-CSAC) in esterification of oleic acid with methanol was also studied. The results showed the presence of silica-carbon which had amorphous structure and highly porous. The carbon surface consisted of higher silica composition, had lower S element detected as compared to the surface that had high carbon content but lower silica composition. This was likely due to the fact that Si element which was bonded to oxygen was highly stable and unlikely to break the bond and react with -SO3H ions. H-CSAC conversions were 23.04 %, 35.52 % and 34.2 7% at 333.15 K, 343.15 K and 353.15 K, respectively. From this research, rice straw can be used as carbon precursor to produce hybrid carbon-silica catalyst and has shown catalytic activity in biodiesel production. Rate equation obtained is also presented.

  14. Construction of a Trp- commercial baker's yeast strain by using food-safe-grade dominant drug resistance cassettes.

    Science.gov (United States)

    Estruch, Francisco; Prieto, José Antonio

    2003-12-01

    We have designed a food-safe-grade module for gene disruptions in commercial baker's yeast strains, which contains the G418 resistance cassette, KanMX4, flanked by direct repeats from the MEL1 gene of Saccharomyces cerevisiae. This module was used to obtain a Trp(-) auxotrophic mutant of the polyploid HY strain by successive targeting to the TRP1 locus and later in vivo excision of the kan(r) marker. Southern blot analysis indicated that HY contains five copies of the TRP1 gene. However, after four disruption rounds, a strain named HYtrpM(4), unable to grow in the absence of tryptophan, was selected. Southern and Northern analysis of HYtrpM(4) cells showed that a remaining functional wild-type copy was still present, suggesting that the level of phosphoribosylanthranylate isomerase activity, resulting from a single copy of TRP1, is too low to sustain growth. Accordingly, a high reversion frequency of the Trp(-) phenotype, through gene conversion, was found in cells of the mutant strain. Nevertheless, this was not a drawback for its use as a recipient strain of heterologous genes. Indeed, YEpACT-X24 transformants were stable after 25 generations and expressed and secreted high levels of active recombinant xylanase. These data indicate that the new Trp(-) strain can be used to generate a stable recombinant yeast that fulfils all the requirements and market criteria for commercial utilisation.

  15. Catalytic activity of various pepsin reduced Au nanostructures towards reduction of nitroarenes and resazurin

    International Nuclear Information System (INIS)

    Pepsin, a digestive protease enzyme, could function as a reducing as well as stabilizing agent for the synthesis of Au nanostructures of various size and shape under different reaction conditions. The simple tuning of the pH of the reaction medium led to the formation of spherical Au nanoparticles, anisotropic Au nanostructures such as triangles, hexagons, etc., as well as ultra small fluorescent Au nanoclusters. The activity of the enzyme was significantly inhibited after its participation in the formation of Au nanoparticles due to conformational changes in the native structure of the enzyme which was studied by fluorescence, circular dichroism (CD), and infra red spectroscopy. However, the Au nanoparticle-enzyme composites served as excellent catalyst for the reduction of p-nitrophenol and resazurin, with the catalytic activity varying with size and shape of the nanoparticles. The presence of pepsin as the surface stabilizer played a crucial role in the activity of the Au nanoparticles as reduction catalysts, as the approach of the reacting molecules to the nanoparticle surface was actively controlled by the stabilizing enzyme

  16. Catalytic activity of various pepsin reduced Au nanostructures towards reduction of nitroarenes and resazurin

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Bhagwati; Mandani, Sonam; Sarma, Tridib K., E-mail: tridib@iiti.ac.in [Indian Institute of Technology Indore, Discipline of Chemistry, School of Basic Sciences (India)

    2015-01-15

    Pepsin, a digestive protease enzyme, could function as a reducing as well as stabilizing agent for the synthesis of Au nanostructures of various size and shape under different reaction conditions. The simple tuning of the pH of the reaction medium led to the formation of spherical Au nanoparticles, anisotropic Au nanostructures such as triangles, hexagons, etc., as well as ultra small fluorescent Au nanoclusters. The activity of the enzyme was significantly inhibited after its participation in the formation of Au nanoparticles due to conformational changes in the native structure of the enzyme which was studied by fluorescence, circular dichroism (CD), and infra red spectroscopy. However, the Au nanoparticle-enzyme composites served as excellent catalyst for the reduction of p-nitrophenol and resazurin, with the catalytic activity varying with size and shape of the nanoparticles. The presence of pepsin as the surface stabilizer played a crucial role in the activity of the Au nanoparticles as reduction catalysts, as the approach of the reacting molecules to the nanoparticle surface was actively controlled by the stabilizing enzyme.

  17. Catalytic stimulation by restrained active-site floppiness--the case of high density lipoprotein-bound serum paraoxonase-1.

    Science.gov (United States)

    Ben-David, Moshe; Sussman, Joel L; Maxwell, Christopher I; Szeler, Klaudia; Kamerlin, Shina C L; Tawfik, Dan S

    2015-03-27

    Despite the abundance of membrane-associated enzymes, the mechanism by which membrane binding stabilizes these enzymes and stimulates their catalysis remains largely unknown. Serum paraoxonase-1 (PON1) is a lipophilic lactonase whose stability and enzymatic activity are dramatically stimulated when associated with high-density lipoprotein (HDL) particles. Our mutational and structural analyses, combined with empirical valence bond simulations, reveal a network of hydrogen bonds that connect HDL binding residues with Asn168--a key catalytic residue residing >15Å from the HDL contacting interface. This network ensures precise alignment of N168, which, in turn, ligates PON1's catalytic calcium and aligns the lactone substrate for catalysis. HDL binding restrains the overall motion of the active site and particularly of N168, thus reducing the catalytic activation energy barrier. We demonstrate herein that disturbance of this network, even at its most far-reaching periphery, undermines PON1's activity. Membrane binding thus immobilizes long-range interactions via second- and third-shell residues that reduce the active site's floppiness and pre-organize the catalytic residues. Although this network is critical for efficient catalysis, as demonstrated here, unraveling these long-rage interaction networks is challenging, let alone their implementation in artificial enzyme design.

  18. Surface structure and catalytic activity of electrodeposited Ni-Fe-Co-Mo alloy electrode by partially leaching Mo and Fe

    Institute of Scientific and Technical Information of China (English)

    LUO Bei-ping; GONG Zhu-qing; REN Bi-ye; YANG Yu-fang; CHEN Meng-jun

    2006-01-01

    Ni-Fe-Mo-Co alloy electrode was prepared in a citrate solution by electrodeposition, and then Mo and Fe were partially leached out from the electrode in 30% KOH solution. The unique surface micromorphology of a hive-like structure was obtained with an average pore size of about 50 nm. The electrode has a very large real surface area and a stable structure. The effects of sodium molybdate concentration on the composition, surface morphology, and structure of electrodes were analyzed by EDS, SEM and XRD. The polarization curves of the different electrodes show that the catalytic activity of electrodes is strongly correlated with the mole fraction of alloy elements (Ni, Fe, Mo, Co), and the addition of cobalt element to Ni-Fe-Mo alloy improves the catalytic activity. The Ni35.63Fe24.67Mo23.52Co16.18 electrode has the best activity for hydrogen evolution reaction(HER), with an over-potential of 66.2 mV, in 30% KOH at 80 ℃ and 200 mA/cm2. The alloy maintains its good catalytic activity for HER during continuous or intermittent electrolysis. Its electrochemical activity and catalytic stability are much higher than the other iron-group with Mo alloy electrodes.

  19. Tumor endothelial expression of P-glycoprotein upon microvesicular transfer of TrpC5 derived from adriamycin-resistant breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Dong, YePing; Pan, QiongXi; Jiang, Li; Chen, Zhen; Zhang, FangFang; Liu, YanJun; Xing, Hui; Shi, Mei; Li, Jiao; Li, XiYuan; Zhu, YaoDan; Chen, Yun; Bruce, Iain C.; Jin, Jian, E-mail: jinjian31@126.com; Ma, Xin, E-mail: maxin@jiangnan.edu.cn

    2014-03-28

    Highlights: • TrpC5 was mainly accumulated in microvesicles of drug-resistant MCF-7/ADM cells. • Microvesicles from MCF-7/ADM transferred TrpC5 to endothelial cells. • TrpC5 inhibition reduced P-glycoprotein accumulation on tumor blood vessels in vivo. - Abstract: Treatment of carcinoma commonly fails due to chemoresistance. Studies have shown that endothelial cells acquire resistance via the tumor microenvironment. Microvesicle (MV) shedding from the cell membrane to the microenvironment plays an important role in communication between cells. The aim of the present study was to determine whether MCF-7 adriamycin-resistant cells (MCF-7/ADM) shed MVs that alter the characteristics of human microvessel endothelial cells (HMECs). MVs from tumor cells transferred a Ca{sup 2+}-permeable channel TrpC5 to HMECs, inducing the expression of P-glycoprotein (P-gp) by activation of the transcription factor NFATc3 (nuclear factor of activated T cells isoform c3). Expression of the mdr1 gene was blocked by the TrpC5-blocking antibody T5E3, and the production of P-gp in HMECs was reduced by blockade of TrpC5. Thus, we postulate that endothelial cells acquire the resistant protein upon exposure to TrpC5-containg MVs in the microenvironment, and express P-gp in the TrpC5–NFATc3 signal pathway.

  20. Elastase-like Activity Is Dominant to Chymotrypsin-like Activity in 20S Proteasome's β5 Catalytic Subunit.

    Science.gov (United States)

    Bensinger, Dennis; Neumann, Theresa; Scholz, Christoph; Voss, Constantin; Knorr, Sabine; Kuckelkorn, Ulrike; Hamacher, Kay; Kloetzel, Peter-Michael; Schmidt, Boris

    2016-07-15

    The ubiquitin/proteasome system is the major protein degradation pathway in eukaryotes with several key catalytic cores. Targeting the β5 subunit with small-molecule inhibitors is an established therapeutic strategy for hematologic cancers. Herein, we report a mouse-trap-like conformational change that influences molecular recognition depending on the substitution pattern of a bound ligand. Variation of the size of P1 residues from the highly β5-selective proteasome inhibitor BSc2118 allows for discrimination between inhibitory strength and substrate conversion. We found that increasing molecular size strengthens inhibition, whereas decreasing P1 size accelerates substrate conversion. Evaluation of substrate hydrolysis after silencing of β5 activity reveals significant residual activity for large residues exclusively. Thus, classification of the β5 subunit as chymotrypsin-like and the use of the standard tyrosine-containing substrate should be reconsidered. PMID:27111844

  1. Evaluation of Performance Catalytic Ozonation Process with Activated Carbon in the Removal of Humic Acids from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Gh. Asgari

    2011-01-01

    Full Text Available Introduction & Objective: In recent years, the use of alternative disinfectants and the control of natural organic matters are two approaches that are typically applied in water treatment utilities to reduce the formation of chlorinated disinfection by-products. Catalytic ozonation is a new technology used to promote the efficiency of ozonation. The goal of this study was to survey the feasibility application of activated carbon as a catalyst in ozonation process for removal of humic acids from aqueous solution. Materials & Methods: This experimental study has been done in laboratory of water and wastewater chemistry, Tarbiat Modarres University. The solid structure and chemical composition of activated carbon were analyzed by X-ray fluorescence (XRF. Ozonation and catalytic ozonation experiments were performed in a semi-batch reactor and the mass of ozone produced was measured by iodometric titration methods. Concentration changes of humic acid in samples with a concentration of 15 mg/l were determined by using spectrophotometer at an absorbance wavelength of 254 nm. To evaluate the performance of catalytic ozonation in humic acid removal, total organic carbon and trihalomethane formation potential were evaluated and the results were analyzed by Excel software. Results: Catalytic ozone results showed that using activated carbon as a catalyst increased humic acid decomposition up to 11 times and removal efficiency increased with increasing pH (4-12 and catalyst dosage (0.25-1.5 g/250cc. The experimental results showed that catalytic ozonation was most effective in less time (10 min with considerable efficiency (95% compared to the sole ozonation process (SOP. Conclusion: The results indicated that the catalytic ozonation process, compared to SOP, was less affected by radical scavenger, and total organic carbon, and trihalomethane formation potential removal achieved were 30% and 83%, respectively. (Sci J Hamadan Univ Med Sci 2011;17(4:25-33

  2. Enhancing the Activity of Peptide-Based Artificial Hydrolase with Catalytic Ser/His/Asp Triad and Molecular Imprinting.

    Science.gov (United States)

    Wang, Mengfan; Lv, Yuqi; Liu, Xiaojing; Qi, Wei; Su, Rongxin; He, Zhimin

    2016-06-01

    In this study, an artificial hydrolase was developed by combining the catalytic Ser/His/Asp triad with N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF), followed by coassembly of the peptides into nanofibers (CoA-HSD). The peptide-based nanofibers provide an ideal supramolecular framework to support the functional groups. Compared with the self-assembled catalytic nanofibers (SA-H), which contain only the catalytic histidine residue, the highest activity of CoA-HSD occurs when histidine, serine, and aspartate residues are at a ratio of 40:1:1. This indicates that the well-ordered nanofiber structure and the synergistic effects of serine and aspartate residues contribute to the enhancement in activity. Additionally, for the first time, molecular imprinting was applied to further enhance the activity of the peptide-based artificial enzyme (CoA-HSD). p-NPA was used as the molecular template to arrange the catalytic Ser/His/Asp triad residues in the proper orientation. As a result, the activity of imprinted coassembled CoA-HSD nanofibers is 7.86 times greater than that of nonimprinted CoA-HSD and 13.48 times that of SA-H. PMID:27191381

  3. Confirmation of Isolated Cu2+ Ions in SSZ-13 Zeolite as Active Sites in NH3-Selective Catalytic Reduction

    NARCIS (Netherlands)

    Deka, U.; Juhin, A.F.; Eilertsen, E.A.; Emerich, H.; Green, M.A.; Korhonen, S.T.; Weckhuysen, B.M.; Beale, A.M.

    2012-01-01

    NH3-Selective Catalytic Reduction (NH3-SCR) is a widely used technology for NOx reduction in the emission control systems of heavy duty diesel vehicles. Copper-based ion exchanged zeolites and in particular Cu-SSZ-13 (CHA framework) catalysts show both exceptional activity and hydrothermal stability

  4. Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

    Institute of Scientific and Technical Information of China (English)

    Dai-shi Guo; Zi-feng Ma; Chun-sheng Yin; Qi-zhong Jiang

    2008-01-01

    TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared.The structural and acid properties of these materials were investigated by XRD,N2 adsorption-desorption,element analysis,thermal analysis,Raman and FTIR measurements.Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone.It was found that the obtained materials possess well-ordered mesostructure,and the grafted TiO2 components were in highly dispersed amorphous form.T/MCM41 without sulfation contained only Lewis acid sites,while Br(o)nsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41.T/MCM-41 was not active for the cyclization reaction of pseudoionone,but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities.The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15,and better than that of d-ST/MCM-41,although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content.The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.

  5. Fabrication and Catalytic Activity of Thermally Stable Gold Nanoparticles on Ultrastable Y (USY Zeolites

    Directory of Open Access Journals (Sweden)

    Keiko Iida

    2013-07-01

    Full Text Available Au was deposited on ultrastable Y (USY zeolites using an ion-exchange method. Up to 5.5 wt% Au was introduced into the NH4-form of USY zeolites. In contrast, deposition of Au hardly took place on the H- and Na-forms of Y-type zeolites, NH4-forms of mordenite, and ZSM-5. Treatment of the Au-loaded USY zeolite in a H2 atmosphere, afforded Au0 nanoparticles. These particles were thermally stable even at 973 K, where their mean particle diameter was 3.7 nm. In contrast, highly aggregated Au particles were observed after thermal treatment at temperatures lower than 523 K, followed by storage in air for a month. The resulting particle sizes were in good correlation with the IR band intensity of the adsorbed CO and the catalytic activity of Au in the aerobic oxidation of benzyl alcohol. The Au nanoparticles showed highest activity when the Au/USY zeolite was thermally treated at 673–973 K. A negligible deactivation was observed after repeating the reaction at least 12 times. In the case of Au/TiO2 catalyst prepared by the deposition-precipitation method, the highest activity was observed at 573 K, which was lower than the temperature used for the Au/USY zeolites. This study demonstrated the potential use of the NH4-form of USY zeolites for supporting Au.

  6. Antitumour, antimicrobial and catalytic activity of gold nanoparticles synthesized by different pH propolis extracts

    Energy Technology Data Exchange (ETDEWEB)

    Gatea, Florentina; Teodor, Eugenia Dumitra, E-mail: eu-teodor@yahoo.com [National Institute for Biological Sciences, Centre of Bioanalysis (Romania); Seciu, Ana-Maria [National Institute for Biological Sciences, Cellular and Molecular Biology Department (Romania); Covaci, Ovidiu Ilie [SARA Pharm Solutions (Romania); Mănoiu, Sorin [National Institute for Biological Sciences, Cellular and Molecular Biology Department (Romania); Lazăr, Veronica [University of Bucharest, Faculty of Biology (Romania); Radu, Gabriel Lucian [University “Politehnica” Bucharest, Faculty of Applied Chemistry and Materials Science (Romania)

    2015-07-15

    The Romanian propolis was extracted in five different media, respectively, in water (pH 6.8), glycine buffer (pH 2.5), acetate buffer (pH 5), phosphate buffer (pH 7.4) and carbonate buffer (pH 9.2). The extracts presented different amounts of flavonoids and phenolic acids, increasing pH leading to higher concentrations of active compounds. Five variants of gold nanoparticles suspensions based on different pH Romanian propolis aqueous extracts were successfully synthesized. The obtained nanoparticles presented dimensions between 20 and 60 nm in dispersion form and around 18 nm in dried form, and different morphologies (spherical, hexagonal, triangular). Fourier transform infrared spectroscopy proved the attachment of organic compounds from propolis extracts to the colloidal gold suspensions and X-ray diffraction certified that the suspensions contain metallic gold. The obtained propolis gold nanoparticles do not exhibit any antibacterial or antifungal activity, but presented different catalytic activities and toxicity on tumour cells.

  7. Mechanism of TRIM25 Catalytic Activation in the Antiviral RIG-I Pathway.

    Science.gov (United States)

    Sanchez, Jacint G; Chiang, Jessica J; Sparrer, Konstantin M J; Alam, Steven L; Chi, Michael; Roganowicz, Marcin D; Sankaran, Banumathi; Gack, Michaela U; Pornillos, Owen

    2016-08-01

    Antiviral response pathways induce interferon by higher-order assembly of signaling complexes called signalosomes. Assembly of the RIG-I signalosome is regulated by K63-linked polyubiquitin chains, which are synthesized by the E3 ubiquitin ligase, TRIM25. We have previously shown that the TRIM25 coiled-coil domain is a stable, antiparallel dimer that positions two catalytic RING domains on opposite ends of an elongated rod. We now show that the RING domain is a separate self-association motif that engages ubiquitin-conjugated E2 enzymes as a dimer. RING dimerization is required for catalysis, TRIM25-mediated RIG-I ubiquitination, interferon induction, and antiviral activity. We also provide evidence that RING dimerization and E3 ligase activity are promoted by binding of the TRIM25 SPRY domain to the RIG-I effector domain. These results indicate that TRIM25 actively participates in higher-order assembly of the RIG-I signalosome and helps to fine-tune the efficiency of the RIG-I-mediated antiviral response. PMID:27425606

  8. Antitumour, antimicrobial and catalytic activity of gold nanoparticles synthesized by different pH propolis extracts

    International Nuclear Information System (INIS)

    The Romanian propolis was extracted in five different media, respectively, in water (pH 6.8), glycine buffer (pH 2.5), acetate buffer (pH 5), phosphate buffer (pH 7.4) and carbonate buffer (pH 9.2). The extracts presented different amounts of flavonoids and phenolic acids, increasing pH leading to higher concentrations of active compounds. Five variants of gold nanoparticles suspensions based on different pH Romanian propolis aqueous extracts were successfully synthesized. The obtained nanoparticles presented dimensions between 20 and 60 nm in dispersion form and around 18 nm in dried form, and different morphologies (spherical, hexagonal, triangular). Fourier transform infrared spectroscopy proved the attachment of organic compounds from propolis extracts to the colloidal gold suspensions and X-ray diffraction certified that the suspensions contain metallic gold. The obtained propolis gold nanoparticles do not exhibit any antibacterial or antifungal activity, but presented different catalytic activities and toxicity on tumour cells

  9. Characterization of the structure and catalytic activity of Legionella pneumophila VipF.

    Science.gov (United States)

    Young, Byron H; Caldwell, Tracy A; McKenzie, Aidan M; Kokhan, Oleksandr; Berndsen, Christopher E

    2016-10-01

    The pathogenic bacteria Legionella pneumophila is known to cause Legionnaires' Disease, a severe pneumonia that can be fatal to immunocompromised individuals and the elderly. Shohdy et al. identified the L. pneumophila vacuole sorting inhibitory protein VipF as a putative N-acetyltransferase based on sequence homology. We have characterized the basic structural and functional properties of VipF to confirm this original functional assignment. Sequence conservation analysis indicates two putative CoA-binding regions within VipF. Homology modeling and small angle X-ray scattering suggest a monomeric, dual-domain structure joined by a flexible linker. Each domain contains the characteristic beta-splay motif found in many acetyltransferases, suggesting that VipF may contain two active sites. Docking experiments suggest reasonable acetyl-CoA binding locations within each beta-splay motif. Broad substrate screening indicated that VipF is capable of acetylating chloramphenicol and both domains are catalytically active. Given that chloramphenicol is not known to be N-acetylated, this is a surprising finding suggesting that VipF is capable of O-acetyltransferase activity. Proteins 2016; 84:1422-1430. © 2016 Wiley Periodicals, Inc. PMID:27315603

  10. Synthesis and bio-catalytic activity of isostructural cobalt(III)-phenanthroline complexes

    Indian Academy of Sciences (India)

    Dhananjay Dey; Arnab Basu Roy; Anandan Ranjani; Loganathan Gayathri; Saravanan Chandraleka; Dharumadurai Dhanasekaran; Mohammad Abdulkader Akbarsha; Chung-Yu Shen; Hui-Lien Tsai; Milan Maji; Niranjan Kole; Bhaskar Biswas

    2015-04-01

    We have synthesized two isostructural mononuclear cobalt(III) complexes [1]NO3·3H2O and [1]NO3·CH3CO2H·H2O {[1]+ = [Co(1,10-phenanthroline)2Cl2]+} and characterized by single crystal X-ray structural analyses. Mass spectral studies of the complexes indicate both the compounds to produce identical cationic species viz., [Co(phen)2Cl2]+ in methanol solution. [1]+ has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in methanol medium, which revealed that the cationic complex efficiently inhibits catalytic activity with kcat value 9.65 × 102 h−1. [1]+ cleaved pBR 322 DNA without addition of an activating agent. Further, the anti-cancer activity of [1]+ on human hepatocarcinoma cell line (HepG2) has been examined. The induction of apoptosis induced in the cell line was assessed base on the changes in cell morphology, which showed the efficacy of [1]+ to induce apoptosis in 53% of cells during 24 h treatment. Interestingly, the observed IC50 values reveal that [1]+ brings about conformational change on DNA strongly and exhibits remarkable cytotoxicity.

  11. Immobilized Cu (II)—Amino Acid Complexes as Prospective Highly Efficient Catalytic Materials: Synthesis, Structural Characterization and Catalytic Activities

    Science.gov (United States)

    Pálinkó, István; Ordasi, Adrien; Kiss, János T.; Labádi, Imre

    2008-11-01

    In this work the covalent anchoring of N-or C-protected Cu(II)—L-tyrosine complexes onto a swellable resin or surface-modified silica gel is described. Experimental conditions (solvents, the availability of ligands) of the synthesis were varied; the structures (by IR spectroscopy) and the superoxide dismutase activities of the anchored complexes were studied.

  12. Lentivirus-induced 'Smart' dendritic cells: Pharmacodynamics and GMP-compliant production for immunotherapy against TRP2-positive melanoma.

    Science.gov (United States)

    Sundarasetty, B S; Chan, L; Darling, D; Giunti, G; Farzaneh, F; Schenck, F; Naundorf, S; Kuehlcke, K; Ruggiero, E; Schmidt, M; von Kalle, C; Rothe, M; Hoon, D S B; Gerasch, L; Figueiredo, C; Koehl, U; Blasczyk, R; Gutzmer, R; Stripecke, R

    2015-09-01

    Monocyte-derived conventional dendritic cells (ConvDCs) loaded with melanoma antigens showed modest responses in clinical trials. Efficacy studies were hampered by difficulties in ConvDC manufacturing and low potency. Overcoming these issues, we demonstrated higher potency of lentiviral vector (LV)-programmed DCs. Monocytes were directly induced to self-differentiate into DCs (SmartDC-TRP2) upon transduction with a tricistronic LV encoding for cytokines (granulocyte macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4)) and a melanoma antigen (tyrosinase-related protein 2 (TRP2)). Here, SmartDC-TRP2 generated with monocytes from five advanced melanoma patients were tested in autologous DC:T cell stimulation assays, validating the activation of functional TRP2-specific cytotoxic T lymphocytes (CTLs) for all patients. We described methods compliant to good manufacturing practices (GMP) to produce LV and SmartDC-TRP2. Feasibility of monocyte transduction in a bag system and cryopreservation following a 24-h standard operating procedure were achieved. After thawing, 50% of the initial monocyte input was recovered and SmartDC-TRP2 self-differentiated in vitro, showing uniform expression of DC markers, detectable LV copies and a polyclonal LV integration pattern not biased to oncogenic loci. GMP-grade SmartDC-TRP2 expanded TRP2-specific autologous CTLs in vitro. These results demonstrated a simpler GMP-compliant method of manufacturing an effective individualized DC vaccine. Such DC vaccine, when in combination with checkpoint inhibition therapies, might provide higher specificity against melanoma. PMID:25965393

  13. Prostaglandin H synthase-mediated bioactivation of the amino acid pyrolysate product Trp P-2

    Energy Technology Data Exchange (ETDEWEB)

    Petry, T.W.; Krauss, R.S.; Eling, T.E.

    1986-08-01

    We report evidence that the mutagen and carcinogen 3-amino-1-methyl-5H pyrido(4,3b)indole (Trp P-2) is a substrate for co-oxidation by prostaglandin H synthase (PHS) in ram seminal vesicle (RSV) microsomes. Trp P-2 serves as a reducing cofactor for the hydroperoxidase activity of PHS as shown by the concentration-dependent inhibition of the hydroperoxidase catalyzed incorporation of molecular oxygen into phenylbutazone. Spectral data suggest that this metabolism results in disruption of the double bond conjugation within the nucleus of the molecule. A single metabolite peak which was dependent upon arachidonic acid and substrate concentration was separated from the parent compound by h.p.l.c. following incubation with RSV microsomes. Co-oxidation of Trp P-2 produced reactive intermediates which bound covalently to microsomal protein (9 nmol/mg) and to calf thymus DNA (475 pmol/mg). Binding was inhibited by indomethacin, and supported by substitution of hydrogen peroxide for arachidonic acid. These data suggest a possible role for PHS in the in situ activation of Trp P-2 to its ultimate carcinogenic form in tissues which contain PHS.

  14. Facile Synthesis of Fe-Doped Titanate Nano tubes with Enhanced Photo catalytic Activity for Castor Oil Oxidation

    International Nuclear Information System (INIS)

    Iron-doped titanate nano tubes were synthesized by hydrothermal method, and the photo catalytic activity was greatly enhanced by iron doping. Followed by the discovery of carbon nano tubes, synthesis of one-dimensional (1D) nano materials has attracted great interest because of their exceptional electrical and mechanical properties [1-4]. Some inorganic 1D nano materials including ZnO, VOx, and TiO2 have been synthesized in recent years [5-8]. Among these materials, titanic compound nanotubes have stimulated particular interest. Titanic nano crystals have been extensively studied in photo catalytic or photoelectrochemical systems and so forth [9-12], and fabrication of tubular structures offers an effective approach to adjust their properties, which are crucial in practical applications. For example, the photo catalytic activity of TiO2 could be enhanced by the tubular structures because of their large specific surface, which leads to a higher potential of applications in environmental purification and generation of hydrogen gas and so forth [13]. Recently, particular interest is devoted to obtain H2Ti3O7-type nano tubes synthesized by hydrothermal method [14-16], and these nano tubes show excellent ion-exchange ability and photo catalytic activities and may be applied to photo catalysis, photoluminescence, and dye-sensitized solar cells [3]. However, their structures are still not well understood. The photo catalytic property is originated from the charge carriers produced by the excitation process on the particle surface, and the photo catalytic efficiency is determined by the transfer rate and recombination rate of carriers [17]. However, the carriers are usually unstable and easy to recombine. To improve the photo catalytic efficiency, the transfer rate must be enhanced and recombination rate should be reduced. Introducing other elements especially the transition metal ions into the matrix has been proved to be an effective method to improve the photo catalytic

  15. Efficient Catalytic Ozonation over Reduced Graphene Oxide for p-Hydroxylbenzoic Acid (PHBA) Destruction: Active Site and Mechanism.

    Science.gov (United States)

    Wang, Yuxian; Xie, Yongbing; Sun, Hongqi; Xiao, Jiadong; Cao, Hongbin; Wang, Shaobin

    2016-04-20

    Nanocarbons have been demonstrated as promising environmentally benign catalysts for advanced oxidation processes (AOPs) upgrading metal-based materials. In this study, reduced graphene oxide (rGO) with a low level of structural defects was synthesized via a scalable method for catalytic ozonation of p-hydroxylbenzoic acid (PHBA). Metal-free rGO materials were found to exhibit a superior activity in activating ozone for catalytic oxidation of organic phenolics. The electron-rich carbonyl groups were identified as the active sites for the catalytic reaction. Electron spin resonance (ESR) and radical competition tests revealed that superoxide radical ((•)O2(-)) and singlet oxygen ((1)O2) were the reactive oxygen species (ROS) for PHBA degradation. The intermediates and the degradation pathways were illustrated from mass spectroscopy. It was interesting to observe that addition of NaCl could enhance both ozonation and catalytic ozonation efficiencies and make ·O2(-) as the dominant ROS. Stability of the catalysts was also evaluated by the successive tests. Loss of specific surface area and changes in the surface chemistry were suggested to be responsible for catalyst deactivation. PMID:27007603

  16. Catalytic Activity of Mono- and Bi-Metallic Nanoparticles Synthesized via Microemulsions

    Directory of Open Access Journals (Sweden)

    Ramona Y.G. König

    2014-07-01

    Full Text Available Water-in-oil (w/o microemulsions were used as a template for the synthesis of mono- and bi-metallic nanoparticles. For that purpose, w/o-microemulsions containing H2PtCl6, H2PtCl6 + Pb(NO32 and H2PtCl6 + Bi(NO3, respectively, were mixed with a w/o-microemulsion containing the reducing agent, NaBH4. The results revealed that it is possible to synthesize Pt, PtPb and PtBi nanoparticles of ~3–8 nm in diameter at temperatures of about 30°C. The catalytic properties of the bimetallic PtBi and PtPb nanoparticles were studied and compared with monometallic platinum nanoparticles. Firstly, the electrochemical oxidation of formic acid to carbon monoxide was investigated, and it was found that the resistance of the PtBi and PtPb nanoparticles against the catalyst-poisoning carbon monoxide was significantly higher compared to the Pt nanoparticles. Secondly, investigating the reduction of 4-nitrophenol to 4-aminophenol,we found that the bimetallic NPs are most active at 23 °C, while the order of the activity changes at higher temperatures, i.e., that the Pt nanoparticles are the most active ones at 36 and 49 °C. Furthermore, we observed a strong influence of the support, which was either a polymer or Al2O3. Thirdly, for the hydrogenation of allylbenzene to propylbenzene, the monometallic Pt NPs turned out to be the most active catalysts, followed by the PtPb and PtBi NPs. Comparing the two bimetallic nanoparticles, one sees that the PtPb NPs are significantly more active than the respective PtBi NPs.

  17. Nanostructured Samarium Doped Fluorapatites and Their Catalytic Activity towards Synthesis of 1,2,4-Triazoles.

    Science.gov (United States)

    Gangu, Kranthi Kumar; Maddila, Suresh; Maddila, Surya Narayana; Jonnalagadda, Sreekantha B

    2016-01-01

    An investigation was conducted into the influence of the amino acids as organic modifiers in the facile synthesis of metal incorporated fluorapatites (FAp) and their properties. The nanostructured Sm doped fluorapatites (Sm-FAp) were prepared by a co-precipitation method using four different amino acids, namely glutamic acid, aspartic acid, glycine and histidine. The materials were characterized by various techniques including X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), N₂-adsorption/desorption isotherm, temperature programmed desorption (TPD) and fluorescence spectrophotometry. Under similar conditions, Sm-FAp prepared using different amino acids exhibited distinctly different morphological structures, surface area and pore properties. Their activity as catalysts was assessed and Sm-FAp/Glycine displayed excellent efficiency in the synthesis of 1,2,4-triazole catalyzing the reaction between 2-nitrobenzaldehyde and thiosemicarbazide with exceptional selectivity and 98% yield in a short time interval (10 min). The study provides an insight into the role of organic modifiers as controllers of nucleation, growth and aggregation which significantly influence the nature and activity of the catalytic sites on Sm-FAp. Sm-FAp could also have potential as photoactive material. PMID:27669208

  18. Nanostructured Samarium Doped Fluorapatites and Their Catalytic Activity towards Synthesis of 1,2,4-Triazoles

    Directory of Open Access Journals (Sweden)

    Kranthi Kumar Gangu

    2016-09-01

    Full Text Available An investigation was conducted into the influence of the amino acids as organic modifiers in the facile synthesis of metal incorporated fluorapatites (FAp and their properties. The nanostructured Sm doped fluorapatites (Sm-FAp were prepared by a co-precipitation method using four different amino acids, namely glutamic acid, aspartic acid, glycine and histidine. The materials were characterized by various techniques including X-ray diffraction (XRD, Fourier transform infra-red spectroscopy (FT-IR, field emission scanning electron microscopy (FE-SEM, energy-dispersive X-ray spectroscopy (EDX, high resolution transmission electron microscopy (HR-TEM, N2-adsorption/desorption isotherm, temperature programmed desorption (TPD and fluorescence spectrophotometry. Under similar conditions, Sm-FAp prepared using different amino acids exhibited distinctly different morphological structures, surface area and pore properties. Their activity as catalysts was assessed and Sm-FAp/Glycine displayed excellent efficiency in the synthesis of 1,2,4-triazole catalyzing the reaction between 2-nitrobenzaldehyde and thiosemicarbazide with exceptional selectivity and 98% yield in a short time interval (10 min. The study provides an insight into the role of organic modifiers as controllers of nucleation, growth and aggregation which significantly influence the nature and activity of the catalytic sites on Sm-FAp. Sm-FAp could also have potential as photoactive material.

  19. Small molecule regulation of self-association and catalytic activity in a supramolecular coordination complex.

    Science.gov (United States)

    McGuirk, C Michael; Stern, Charlotte L; Mirkin, Chad A

    2014-03-26

    Herein, we report the synthesis and characterization of the first weak-link approach (WLA) supramolecular construct that employs the small molecule regulation of intermolecular hydrogen bonding interactions for the in situ control of catalytic activity. A biaryl urea group, prone to self-aggregation, was functionalized with a phosphinoalkyl thioether (P,S) hemilabile moiety and incorporated into a homoligated Pt(II) tweezer WLA complex. This urea-containing construct, which has been characterized by a single crystal X-ray diffraction study, can be switched in situ from a rigid fully closed state to a flexible semiopen state via Cl(-) induced changes in the coordination mode at the Pt(II) structural node. FT-IR and (1)H NMR spectroscopy studies were used to demonstrate that while extensive urea self-association persists in the flexible semiopen complex, these interactions are deterred in the rigid, fully closed complex because of geometric and steric restraints. Consequently, the urea moieties in the fully closed complex are able to catalyze a Diels-Alder reaction between cyclopentadiene and methyl vinyl ketone to generate 2-acetyl-5-norbornene. The free urea ligand and the semiopen complex show no such activity. The successful incorporation and regulation of a hydrogen bond donating catalyst in a WLA construct open the doors to a vast and rapidly growing catalogue of allosteric catalysts for applications in the detection and amplification of organic analytes.

  20. Iridium-decorated multiwall carbon nanotubes and its catalytic activity with Shell 405 in hydrazine decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, V.; Vasanthkumar, M. S., E-mail: vasanth.physics@gmail.com [Indian Institute of Science, Department of Physics (India)

    2015-10-15

    Iridium-functionalized multiwalled carbon nanotubes (Ir-MWNT) are the future catalyst support material for hydrazine fuel decomposition. The present work demonstrates decoration of iridium particle on iron-encapsulated multiwalled carbon nanotubes (MWNT) by wet impregnation method in the absence of any stabilizer. Electron microscopy studies reveal the coated iridium particle size in the range of 5–10 nm. Elemental analysis by energy dispersive X-ray diffraction confirms 21 wt% of Ir coated over MWNT. X-ray photoelectron spectroscopy (XPS) shows 4f{sub 5/2} and 4f{sub 7/2} lines of iridium and confirms the metallic nature. The catalytic activity of Ir-MWNT/Shell 405 combination is performed in 1 N hydrazine micro-thrusters. The thruster performance shows increase in chamber pressure and decrease in chamber temperature when compared to Shell 405 alone. This enhanced performance is due to high thermal conducting nature of MWNTs and the presence of Ir active sites over MWNTs.

  1. Microwave-assisted facile green synthesis of silver nanoparticles and spectroscopic investigation of the catalytic activity

    Indian Academy of Sciences (India)

    Siby Joseph; Beena Mathew

    2015-06-01

    Silver nanoparticles have been successfully synthesized in aqueous medium by a green, rapid and costefficient synthetic approach based on microwave irradiation. In this study, iota-carrageenan (I-carrageenan) is used both as reducing and stabilizing agent. The formation of nanoparticles is determined using UV–vis, Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) and high-resolution-transmission electron microscopic (HR-TEM) analysis. Transmission electron microscopic (TEM) images show that the nanoparticles are of spherical shape with an average diameter of 18.2 nm. I-carrageenan-stabilized silver nanoparticles show outstanding catalytic activity for the reduction of 4-nitrophenol in the presence of NaBH4 in aqueous medium. The reaction follows pseudo-first-order kinetics and the reaction rate increases with the increase in amount of the catalyst. The study of the temperature dependence of reaction rate gives activation energy of 42.81 kJ mol−1. The synthesized silver nanoparticles are anticipated to be a promising material for pollution abatement.

  2. Improved acylation of phytosterols catalyzed by Candida antarctica lipase A with superior catalytic activity

    DEFF Research Database (Denmark)

    Panpipat, Worawan; Xu, Xuebing; Guo, Zheng

    2013-01-01

    This work reported a novel approach to synthesize phytosterol (ˇ-sitosterol as a model) fatty acid esters by employing Candida antarctica lipase A (CAL A) which shows a superior catalytic activity to other lipases. A series of ˇ-sitosteryl fatty acid esters (C2–C18) have been successfully prepared...... with structural identification of products by 1H NMR and Fourier transform-infrared spectroscopy (FTIR). Compared to other immobilized lipases, CAL A achieves 6–14 times faster esterification of ˇ-sitosterol with myristic acid. CAL A shows low activity toward short chain fatty acids (C2–C6), and remarkably high...... spectrum of log P values, was observed. 93–98% yield of ˇ-sitosteryl esters could be achieved with hexane as solvent, fatty acid (C8–C18)/ˇ-sitosterol (1:1, mol:mol), 5–10% CAL A load at 40–50 ◦C for 24 h. This work demonstrated the promising potential of CAL A in bioprocess of phytosterols for value...

  3. Adenylate kinase from Streptococcus pneumoniae is essential for growth through its catalytic activity

    Directory of Open Access Journals (Sweden)

    Trung Thanh Thach

    2014-01-01

    Full Text Available Streptococcus pneumoniae (pneumococcus infection causes more than 1.6 million deaths worldwide. Pneumococcal growth is a prerequisite for its virulence and requires an appropriate supply of cellular energy. Adenylate kinases constitute a major family of enzymes that regulate cellular ATP levels. Some bacterial adenylate kinases (AdKs are known to be critical for growth, but the physiological effects of AdKs in pneumococci have been poorly understood at the molecular level. Here, by crystallographic and functional studies, we report that the catalytic activity of adenylate kinase from S. pneumoniae (SpAdK serotype 2 D39 is essential for growth. We determined the crystal structure of SpAdK in two conformations: ligand-free open form and closed in complex with a two-substrate mimic inhibitor adenosine pentaphosphate (Ap5A. Crystallographic analysis of SpAdK reveals Arg-89 as a key active site residue. We generated a conditional expression mutant of pneumococcus in which the expression of the adk gene is tightly regulated by fucose. The expression level of adk correlates with growth rate. Expression of the wild-type adk gene in fucose-inducible strains rescued a growth defect, but expression of the Arg-89 mutation did not. SpAdK increased total cellular ATP levels. Furthermore, lack of functional SpAdK caused a growth defect in vivo. Taken together, our results demonstrate that SpAdK is essential for pneumococcal growth in vitro and in vivo.

  4. Structure of the Photo-catalytically Active Surface of SrTiO 3

    Energy Technology Data Exchange (ETDEWEB)

    Plaza, Manuel; Huang, Xin; Ko, J. Y. Peter; Shen, Mei; Simpson, Burton H.; Rodríguez-López, Joaquín; Ritzert, Nicole L.; Letchworth-Weaver, Kendra; Gunceler, Deniz; Schlom, Darrell G.; Arias, Tomás A.; Brock, Joel D.; Abruña, Héctor D.

    2016-06-29

    A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the "gold standard" for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiO3 electrode during water splitting, before and after "training" with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induced water splitting. A novel first-principles joint density functional theory simulation, constrained to the X-ray data via a generalized penalty function, identifies an anatase-like structure as the more active, trained surface.

  5. Ratio-controlled synthesis of CuNi octahedra and nanocubes with enhanced catalytic activity.

    Science.gov (United States)

    Wang, Menglin; Wang, Liangbing; Li, Hongliang; Du, Wenpeng; Khan, Munir Ullah; Zhao, Songtao; Ma, Chao; Li, Zhenyu; Zeng, Jie

    2015-11-11

    Non-noble bimetallic nanocrystals (NCs) have been widely explored due to not only their low cost and abundant content in the Earth's crust but also their outstanding performance in catalytic reactions. However, controllable synthesis of non-noble alloys remains a significant challenge. Here we report a facile synthesis of CuNi octahedra and nanocubes with controllable shapes and tunable compositions. Its success relies on the use of borane morpholine as a reducing agent, which upon decomposition generates a burst of H2 molecules to induce rapid formation of the nuclei. Specifically, octahedra switched to nanocubes with an increased amount of borane morpholine. In addition, the ratio of CuNi NCs could be facilely tuned by changing the molar ratio of both precursors. The obtained CuNi NCs exhibited high activity in aldehyde-alkyne-amine coupling reactions, and their performance is strongly facet- and composition-dependent due to the competition of the surface energy (enhanced by increasing the percent of Ni) and active sites (derived from Cu atoms). PMID:26498199

  6. Iridium-decorated multiwall carbon nanotubes and its catalytic activity with Shell 405 in hydrazine decomposition

    International Nuclear Information System (INIS)

    Iridium-functionalized multiwalled carbon nanotubes (Ir-MWNT) are the future catalyst support material for hydrazine fuel decomposition. The present work demonstrates decoration of iridium particle on iron-encapsulated multiwalled carbon nanotubes (MWNT) by wet impregnation method in the absence of any stabilizer. Electron microscopy studies reveal the coated iridium particle size in the range of 5–10 nm. Elemental analysis by energy dispersive X-ray diffraction confirms 21 wt% of Ir coated over MWNT. X-ray photoelectron spectroscopy (XPS) shows 4f5/2 and 4f7/2 lines of iridium and confirms the metallic nature. The catalytic activity of Ir-MWNT/Shell 405 combination is performed in 1 N hydrazine micro-thrusters. The thruster performance shows increase in chamber pressure and decrease in chamber temperature when compared to Shell 405 alone. This enhanced performance is due to high thermal conducting nature of MWNTs and the presence of Ir active sites over MWNTs

  7. Structure of the Photo-catalytically Active Surface of SrTiO3.

    Science.gov (United States)

    Plaza, Manuel; Huang, Xin; Ko, J Y Peter; Shen, Mei; Simpson, Burton H; Rodríguez-López, Joaquín; Ritzert, Nicole L; Letchworth-Weaver, Kendra; Gunceler, Deniz; Schlom, Darrell G; Arias, Tomás A; Brock, Joel D; Abruña, Héctor D

    2016-06-29

    A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the "gold standard" for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiO3 electrode during water splitting, before and after "training" with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induced water splitting. A novel first-principles joint density functional theory simulation, constrained to the X-ray data via a generalized penalty function, identifies an anatase-like structure as the more active, trained surface. PMID:27281231

  8. The tryptophan synthase β-subunit paralogs TrpB1 and TrpB2 in Thermococcus kodakarensis are both involved in tryptophan biosynthesis and indole salvage.

    Science.gov (United States)

    Hiyama, Takayoshi; Sato, Takaaki; Imanaka, Tadayuki; Atomi, Haruyuki

    2014-07-01

    The last two steps of l-tryptophan (Trp) biosynthesis are catalyzed by Trp synthase, a heterotetramer composed of TrpA and TrpB. TrpB catalyzes the condensation of indole, synthesized by TrpA, and serine to Trp. In the hyperthermophilic archaeon Thermococcus kodakarensis, trpA and trpB (trpB1) are located adjacently in the trpCDEGFB1A operon. Interestingly, several organisms possess a second trpB gene (trpB2) encoding TrpB2, located outside of the trp operon in T. kodakarensis. Until now, the physiological function of trpB2 has not been examined genetically. In the present study, we report the biochemical and physiological analyses of TrpB2 from T. kodakarensis. Kinetic analysis indicated that TrpB2 catalyzed the TrpB reaction but did not interact with TrpA as in the case of TrpB1. When growth phenotypes were examined for gene disruption strains, the double-deletion mutant (ΔtrpB1ΔtrpB2) displayed Trp auxotrophy, whereas individual single mutants (ΔtrpB1 and ΔtrpB2 strains) did not. It has been proposed previously that, in Thermotoga maritima, TrpB2 provides an alternate route to generate Trp from serine and free indole (indole salvage). To accurately examine the capacity of TrpB1 and TrpB2 in Trp synthesis via indole salvage, we constructed ΔtrpEB1 and ΔtrpEB2 strains using strain KUW1 (ΔpyrFΔtrpE) as a host, eliminating the route for endogenous indole synthesis. Indole complemented the Trp auxotrophies of ΔtrpEB1 (ΔpyrFΔtrpEΔtrpB1) and ΔtrpEB2 (ΔpyrFΔtrpEΔtrpB2) to similar levels. The results indicate that TrpB1 and TrpB2 both contribute to Trp biosynthesis in T. kodakarensis and can utilize free indole, and that indole salvage does not necessarily rely on TrpB2 to a greater extent. PMID:24835339

  9. Surface Acidity as Descriptor of Catalytic Activity for Oxygen Evolution Reaction in Li-O2 Battery.

    Science.gov (United States)

    Zhu, Jinzhen; Wang, Fan; Wang, Beizhou; Wang, Youwei; Liu, Jianjun; Zhang, Wenqing; Wen, Zhaoyin

    2015-10-28

    Unraveling the descriptor of catalytic activity, which is related to physical properties of catalysts, is a major objective of catalysis research. In the present study, the first-principles calculations based on interfacial model were performed to study the oxygen evolution reaction mechanism of Li2O2 supported on active surfaces of transition-metal compounds (TMC: oxides, carbides, and nitrides). Our studies indicate that the O2 evolution and Li(+) desorption energies show linear and volcano relationships with surface acidity of catalysts, respectively. Therefore, the charging voltage and desorption energies of Li(+) and O2 over TMC could correlate with their corresponding surface acidity. It is found that certain materials with an appropriate surface acidity can achieve the high catalytic activity in reducing charging voltage and activation barrier of rate-determinant step. According to this correlation, CoO should have as active catalysis as Co3O4 in reducing charging overpotential, which is further confirmed by our comparative experimental studies. Co3O4, Mo2C, TiC, and TiN are predicted to have a relatively high catalytic activity, which is consistent with the previous experiments. The present study enables the rational design of catalysts with greater activity for charging reactions of Li-O2 battery.

  10. Catalytically active bovine serum amine oxidase bound to fluorescent and magnetically drivable nanoparticles

    Directory of Open Access Journals (Sweden)

    Bidollari E

    2012-05-01

    Full Text Available Giulietta Sinigaglia1, Massimiliano Magro1, Giovanni Miotto1, Sara Cardillo1, Enzo Agostinelli2,3, Radek Zboril4, Eris Bidollari2,3, Fabio Vianello11Department of Biological Chemistry, University of Padua, Padua, Italy; 2Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biochemical Sciences "A. Rossi Fanelli", SAPIENZA University of Rome, Rome, Italy; 3CNR, Institute Biology and Molecular Pathology, Rome, Italy; 4Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University, Olomouc, Czech RepublicAbstract: Novel superparamagnetic surface-active maghemite nanoparticles (SAMNs characterized by a diameter of 10 ± 2 nm were modified with bovine serum amine oxidase, which used rhodamine B isothiocyanate (RITC adduct as a fluorescent spacer-arm. A fluorescent and magnetically drivable adduct comprised of bovine serum copper-containing amine oxidase (SAMN–RITC–BSAO that immobilized on the surface of specifically functionalized magnetic nanoparticles was developed. The multifunctional nanomaterial was characterized using transmission electron microscopy, infrared spectroscopy, mass spectrometry, and activity measurements. The results of this study demonstrated that bare magnetic nanoparticles form stable colloidal suspensions in aqueous solutions. The maximum binding capacity of bovine serum amine oxidase was approximately 6.4 mg g-1 nanoparticles. The immobilization procedure reduced the catalytic activity of the native enzyme to 30% ± 10% and the Michaelis constant was increased by a factor of 2. We suggest that the SAMN–RITC–BSAO complex, characterized by a specific activity of 0.81 IU g-1, could be used in the presence of polyamines to create a fluorescent magnetically drivable H2O2 and aldehydes-producing system. Selective tumor cell destruction is suggested as a potential future application of this system.Keywords: amine oxidase, hydrogen peroxide production, superparamagnetic

  11. DEVELOPMENT OF HIGH ACTIVITY, COAL-DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Joseph M. Calo

    2000-07-21

    This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, the following has been accomplished: (1) Steady-state reactivity studies in the packed bed reactor were extended to the NO/CO-carbon reaction system as a function of temperature and NO and CO concentrations. It was found that the NO reaction rate increased in the presence of CO, and the apparent activation energy decreased to about 75 {+-} 8 kJ/mol. In addition, the influence of mass transfer limitations were noted at low NO and CO concentrations. (2) The packed bed reactor/gas flow system has been applied to performing post-reaction temperature programmed desorption (TPD) studies of intermediate surface complexes following steady-state reaction. It was found that the amount of CO-evolving intermediate surface complexes exceeded that of the N{sub 2}-evolving surface complexes, and that both increased with reaction temperature. The TPD spectra indicates that both types of complexes desorb late, suggesting that they have high desorption activation energies. Plans for the next reporting period include extending the temperature programmed desorption studies in the packed bed reactor system to the NO/CO reaction system, including exposure to just CO, as well as NO/CO mixtures.

  12. Genetic factors affecting gene transcription and catalytic activity of UDP-glucuronosyltransferases in human liver.

    Science.gov (United States)

    Liu, Wanqing; Ramírez, Jacqueline; Gamazon, Eric R; Mirkov, Snezana; Chen, Peixian; Wu, Kehua; Sun, Chang; Cox, Nancy J; Cook, Edwin; Das, Soma; Ratain, Mark J

    2014-10-15

    The aim of this study was to discover cis- and trans-acting factors significantly affecting mRNA expression and catalytic activity of human hepatic UDP-glucuronosyltransferases (UGTs). Transcription levels of five major hepatic UGT1A (UGT1A1, UGT1A3, UGT1A4, UGT1A6 and UGT1A9) and five UGT2B (UGT2B4, UGT2B7, UGT2B10, UGT2B15 and UGT2B17) genes were quantified in human liver tissue samples (n = 125) using real-time PCR. Glucuronidation activities of 14 substrates were measured in 47 livers. We genotyped 167 tagSNPs (single-nucleotide polymorphisms) in UGT1A (n = 43) and UGT2B (n = 124), as well as the known functional UGT1A1*28 and UGT2B17 CNV (copy number variation) polymorphisms. Transcription levels of 15 transcription factors (TFs) known to regulate these UGTs were quantified. We found that UGT expression and activity were highly variable among the livers (median and range of coefficient of variations: 135%, 74-217% and 52%, 39-105%, respectively). CAR, PXR and ESR1 were found to be the most important trans-regulators of UGT transcription (median and range of correlation coefficients: 46%, 6-58%; 47%, 9-58%; and 52%, 24-75%, respectively). Hepatic UGT activities were mainly determined by UGT gene transcription levels. Twenty-one polymorphisms were significantly (FDR-adjusted P transcription and testosterone glucuronidation rate, in addition to that attributable to the UGT2B17 CNV. Our study discovered novel pharmacogenetic markers and provided detailed insight into the genetic network regulating hepatic UGTs.

  13. Synthesis of a Novel Carbon Based Acid Catalyst and Its Catalytic Activity for the Acetalization and Ketalization

    Institute of Scientific and Technical Information of China (English)

    LIANG Xue-Zheng; GAO Shan; CHEN Wen-Ping; WANG Wen-Juan; YANG Jian-Guo

    2007-01-01

    A novel carbon based strong solid acid catalyst has been synthesized successfully.The catalytic activity for acetalization and ketalization was investigated.The results showed that the novel catalyst was very efficient with the average yield over 92%.The novel heterogeneous catalyst also has the advantages of high activity,wide applicability even to the preparation of 7 membered ring acetals and ketals,strikingly simple workup procedure,non-pollution and reusability,which will contribute to the green process greatly.

  14. A fungal P450 (CYP5136A3 capable of oxidizing polycyclic aromatic hydrocarbons and endocrine disrupting alkylphenols: role of Trp(129 and Leu(324.

    Directory of Open Access Journals (Sweden)

    Khajamohiddin Syed

    Full Text Available The model white rot fungus Phanerochaete chrysosporium, which is known for its versatile pollutant-biodegradation ability, possesses an extraordinarily large repertoire of P450 monooxygenases in its genome. However, the majority of these P450s have hitherto unknown function. Our initial studies using a genome-wide gene induction strategy revealed multiple P450s responsive to individual classes of xenobiotics. Here we report functional characterization of a cytochrome P450 monooxygenase, CYP5136A3 that showed common responsiveness and catalytic versatility towards endocrine-disrupting alkylphenols (APs and mutagenic/carcinogenic polycyclic aromatic hydrocarbons (PAHs. Using recombinant CYP5136A3, we demonstrated its oxidation activity towards APs with varying alkyl side-chain length (C3-C9, in addition to PAHs (3-4 ring size. AP oxidation involves hydroxylation at the terminal carbon of the alkyl side-chain (ω-oxidation. Structure-activity analysis based on a 3D model indicated a potential role of Trp(129 and Leu(324 in the oxidation mechanism of CYP5136A3. Replacing Trp(129 with Leu (W129L and Phe (W129F significantly diminished oxidation of both PAHs and APs. The W129L mutation caused greater reduction in phenanthrene oxidation (80% as compared to W129F which caused greater reduction in pyrene oxidation (88%. Almost complete loss of oxidation of C3-C8 APs (83-90% was observed for the W129L mutation as compared to W129F (28-41%. However, the two mutations showed a comparable loss (60-67% in C9-AP oxidation. Replacement of Leu(324 with Gly (L324G caused 42% and 54% decrease in oxidation activity towards phenanthrene and pyrene, respectively. This mutation also caused loss of activity towards C3-C8 APs (20-58%, and complete loss of activity toward nonylphenol (C9-AP. Collectively, the results suggest that Trp(129 and Leu(324 are critical in substrate recognition and/or regio-selective oxidation of PAHs and APs. To our knowledge, this is the first

  15. Mesoporous Silica Supported Pd-MnOx Catalysts with Excellent Catalytic Activity in Room-Temperature Formic Acid Decomposition

    Science.gov (United States)

    Jin, Min-Ho; Oh, Duckkyu; Park, Ju-Hyoung; Lee, Chun-Boo; Lee, Sung-Wook; Park, Jong-Soo; Lee, Kwan-Young; Lee, Dong-Wook

    2016-01-01

    For the application of formic acid as a liquid organic hydrogen carrier, development of efficient catalysts for dehydrogenation of formic acid is a challenging topic, and most studies have so far focused on the composition of metals and supports, the size effect of metal nanoparticles, and surface chemistry of supports. Another influential factor is highly desired to overcome the current limitation of heterogeneous catalysis for formic acid decomposition. Here, we first investigated the effect of support pore structure on formic acid decomposition performance at room temperature by using mesoporous silica materials with different pore structures such as KIE-6, MCM-41, and SBA-15, and achieved the excellent catalytic activity (TOF: 593 h−1) by only controlling the pore structure of mesoporous silica supports. In addition, we demonstrated that 3D interconnected pore structure of mesoporous silica supports is more favorable to the mass transfer than 2D cylindrical mesopore structure, and the better mass transfer provides higher catalytic activity in formic acid decomposition. If the pore morphology of catalytic supports such as 3D wormhole or 2D cylinder is identical, large pore size combined with high pore volume is a crucial factor to achieve high catalytic performance. PMID:27666280

  16. Synthesis of Rh/Macro-Porous Alumina Over Micro-Channel Plate and Its Catalytic Activity Tests for Diesel Reforming.

    Science.gov (United States)

    Seong, Yeon Baek; Kim, Yong Sul; Park, No-Kuk; Lee, Tae Jin

    2015-11-01

    Macro-porous Al2O3 as the catalytic support material was synthesized using colloidal polystyrene spheres over a micro-channel plate. The colloidal polystyrene spheres were used as a template for the production of an ordered macro porous material using an alumina nitrate solution as the precursor for Al2O3. The close-packed colloidal crystal array template method was applied to the formulation of ordered macro-porous Al2O3 used as a catalytic support material over a micro-channel plate. The solvent in the mixture solution, which also contained the colloidal polystyrene solution, aluminum nitrate solution and the precursor of the catalytic active materials (Rh), was evaporated in a vacuum oven at 50 degrees C. The ordered polystyrene spheres and aluminum salt of the solid state were deposited over a micro channel plate, and macro-porous Al2O3 was formed after calcination at 600 degrees C to remove the polystyrene spheres. The catalytic activity of the Rh/macro-porous alumina supported over the micro-channel plate was tested for diesel reforming.

  17. IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 4. Reference procedure for the measurement of catalytic concentration of alanine aminotransferase.

    Science.gov (United States)

    Schumann, Gerhard; Bonora, Roberto; Ceriotti, Ferruccio; Férard, Georges; Ferrero, Carlo A; Franck, Paul F H; Gella, F Javier; Hoelzel, Wieland; Jørgensen, Poul Jørgen; Kanno, Takashi; Kessner, Art; Klauke, Rainer; Kristiansen, Nina; Lessinger, Jean-Marc; Linsinger, Thomas P J; Misaki, Hideo; Panteghini, Mauro; Pauwels, Jean; Schiele, Françoise; Schimmel, Heinz G; Weidemann, Gerhard; Siekmann, Lothar

    2002-07-01

    This paper is the fourth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 2.

  18. IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 6. Reference procedure for the measurement of catalytic concentration of gamma-glutamyltransferase.

    Science.gov (United States)

    Schumann, Gerhard; Bonora, Roberto; Ceriotti, Ferruccio; Férard, Georges; Ferrero, Carlo A; Franck, Paul F H; Gella, F Javier; Hoelzel, Wieland; Jørgensen, Poul Jørgen; Kanno, Takashi; Kessner, Art; Klauke, Rainer; Kristiansen, Nina; Lessinger, Jean-Marc; Linsinger, Thomas P J; Misaki, Hideo; Panteghini, Mauro; Pauwels, Jean; Schiele, Françoise; Schimmel, Heinz G; Weidemann, Gerhard; Siekmann, Lothar

    2002-07-01

    This paper is the sixth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 1.

  19. Heterogeneous catalytic ozonation of dibutyl phthalate in aqueous solution in the presence of iron-loaded activated carbon.

    Science.gov (United States)

    Huang, Yuanxing; Cui, Chenchen; Zhang, Daofang; Li, Liang; Pan, Ding

    2015-01-01

    Iron-loaded activated carbon was prepared and used as catalyst in heterogeneous catalytic ozonation of dibutyl phthalate (DBP). The catalytic activity of iron-loaded activated carbon was investigated under various conditions and the mechanisms of DBP removal were deduced. Characterization of catalyst indicated that the iron loaded on activated carbon was mainly in the form of goethite, which reduced its surface area, pore volume and pore diameter. The presence of metals on activated carbon positively contributed to its catalytic activity in ozonation of DBP. Iron loading content of 15% and initial water pH of 8 achieved highest DBP removal among all the tried conditions. Catalyst dosage of 10 mg L(-1) led to approximately 25% of increase in DBP (initial concentration 2 mg L(-1)) removal in 60 min as compared with ozone alone, and when catalyst dosage increased to 100 mg L(-1), the DBP removal was further improved by 46%. Based on a comparison of reaction rates for direct and indirect transformation of DBP, the increased removal of DBP in this study likely occurred via transformation of ozone into hydroxyl radicals on the catalyst surface.

  20. Role of the NC-loop in catalytic activity and stability in lipase from Fervidobacterium changbaicum.

    Directory of Open Access Journals (Sweden)

    Binchun Li

    Full Text Available Flexible NC-loops between the catalytic domain and the cap domain of the α/β hydrolase fold enzymes show remarkable diversity in length, sequence, and configuration. Recent investigations have suggested that the NC-loop might be involved in catalysis and substrate recognition in many enzymes from the α/β hydrolase fold superfamily. To foster a deep understanding of its role in catalysis, stability, and divergent evolution, we here systemically investigated the function of the NC-loop (residues 131-151 in a lipase (FClip1 from thermophilic bacterium Fervidobacterium changbaicum by loop deletion, alanine-scanning mutagenesis and site-directed mutagenesis. We found that the upper part of the NC-loop (residues 131-138 was of great importance to enzyme catalysis. Single substitutions in this region could fine-tune the activity of FClip1 as much as 41-fold, and any deletions from this region rendered the enzyme completely inactive. The lower part of the NC-loop (residues 139-151 was capable of enduring extensive deletions without loss of activity. The shortened mutants in this region were found to show both improved activity and increased stability simultaneously. We therefore speculated that the NC-loop, especially the lower part, would be a perfect target for enzyme engineering to optimize the enzymatic properties, and might present a hot zone for the divergent evolution of α/β hydrolases. Our findings may provide an opportunity for better understanding of the mechanism of divergent evolution in the α/β hydrolase fold superfamily, and may also guide the design of novel biocatalysts for industrial applications.

  1. Towards a Physical Description for the Origin of Enhanced Catalytic Activity of Corroding Magnesium Surfaces

    International Nuclear Information System (INIS)

    The so-called “negative difference effect” (NDE) exhibited by corroding magnesium (Mg) surfaces, where the rate of hydrogen evolution increases with the extent of anodic polarization, has been well documented. Recently this behaviour has been explained by a theory involving an increase in the cathodic exchange current density that occurs during anodic polarization, rather than the popular theory involving the formation of a univalent Mg+ ion and its subsequent chemical reaction with water to produce hydrogen. The present study reports on the results of transmission electron microscopy (TEM) conducted on focused ion beam (FIB) prepared cross-section lamellae of the dark film formed on a corroding area of a Mg surface from which hydrogen evolved. The film was found to consist of an outer columnar mixed magnesium oxide-hydroxide layer on top of a magnesium oxide-rich inner layer. X-ray energy dispersive spectroscopy (EDS) reveals iron (Fe)-rich particles embedded in the columnar outer layer. Subsequent cathodic polarization measurements showed that the corroded surface became cathodically activated relative to a non-corroded surface. These observations demonstrate that a surface film enriched in more noble metals can catalyze the cathodic process, provide physical evidence towards support of the enhanced catalytic surface theory explaining the NDE, and validate the chemistry and structure of the surface film that forms upon corroding regions during anodic polarization

  2. Band gap calculation and photo catalytic activity of rare earths doped rutile TiO2

    Institute of Scientific and Technical Information of China (English)

    BIAN Liang; SONG Mianxin; ZHOU Tianliang; ZHAO Xiaoyong; DAI Qingqing

    2009-01-01

    The density of states (DOS) of 17 kinds of rare earths (RE) doped futile TiO2 was by using fast-principles density functional the-ory (DFF) calculation. The band gap widths of RE doped rutile TiO2 were important factors for altering their absorbing wavelengths. The results show that RE ions could obviously reduce the band gap widths and form of energy of rutile TiO2 except Lu, Y, Yb and Sc, and the order of absorbing wavelengths of RE doped rutile TiO2 were the same as that of the results of calculation. The ratio of RE dopant was an-other important factor for the photo catalytic activity of RE doped rutile TiO2, and there was an optimal ratio of dopant. There was a constant for predigesting the calculation difficulty, respectively, which were 0.5mol.% and 100 mol-1 under supposition. The band gap widths of RE doped rutile TiO2 by DFT calculation were much larger than that by experiment. Finally, by transferring the calculation values to experiment values, it could be found and predicted that RE enlarged obviously the absorbing wavelengh of futile TiO2. In addition, the degree of RE ions edging out the Ti atom using the parameters of RE elements was computed.

  3. Facile synthesis of porous Pd nanoflowers with excellent catalytic activity towards CO oxidation☆

    Institute of Scientific and Technical Information of China (English)

    Tareque Odoom-Wubah; Mingming Du; Williams Brown Osei; Daohua Sun; Jiale Huang; Qingbiao Li

    2015-01-01

    Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cel s (PPCs) dosage, ascorbic acid (AA), Pd(NO3)2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the as-synthesized PdNFs could be tuned by adjusting the amount of Pd(NO3)2 solution and dosage of PPCs used. Char-acterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO2 supports to obtain bio-PdNF/TiO2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100%conversion at 100 °C and remaining stable over a period of 52 h of reaction time.

  4. Plasma Enhanced Chemical Vapor Deposition Nanocrystalline Tungsten Carbide Thin Film and Its Electro-catalytic Activity

    Institute of Scientific and Technical Information of China (English)

    Huajun ZHENG; Chunan MA; Jianguo HUANG; Guohua LI

    2005-01-01

    Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition (PECVD) at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS), respectively. The results show that the film prepared at CH4/WF6concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20~35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V (vs SCE).

  5. A supramolecular ruthenium macrocycle with high catalytic activity for water oxidation that mechanistically mimics photosystem II

    Science.gov (United States)

    Schulze, Marcus; Kunz, Valentin; Frischmann, Peter D.; Würthner, Frank

    2016-06-01

    Mimicking the ingenuity of nature and exploiting the billions of years over which natural selection has developed numerous effective biochemical conversions is one of the most successful strategies in a chemist's toolbox. However, an inability to replicate the elegance and efficiency of the oxygen-evolving complex of photosystem II (OEC-PSII) in its oxidation of water into O2 is a significant bottleneck in the development of a closed-loop sustainable energy cycle. Here, we present an artificial metallosupramolecular macrocycle that gathers three Ru(bda) centres (bda = 2,2‧-bipyridine-6,6‧-dicarboxylic acid) that catalyses water oxidation. The macrocyclic architecture accelerates the rate of water oxidation via a water nucleophilic attack mechanism, similar to the mechanism exhibited by OEC-PSII, and reaches remarkable catalytic turnover frequencies >100 s–1. Photo-driven water oxidation yields outstanding activity, even in the nM concentration regime, with a turnover number of >1,255 and turnover frequency of >13.1 s–1.

  6. A supramolecular ruthenium macrocycle with high catalytic activity for water oxidation that mechanistically mimics photosystem II.

    Science.gov (United States)

    Schulze, Marcus; Kunz, Valentin; Frischmann, Peter D; Würthner, Frank

    2016-06-01

    Mimicking the ingenuity of nature and exploiting the billions of years over which natural selection has developed numerous effective biochemical conversions is one of the most successful strategies in a chemist's toolbox. However, an inability to replicate the elegance and efficiency of the oxygen-evolving complex of photosystem II (OEC-PSII) in its oxidation of water into O2 is a significant bottleneck in the development of a closed-loop sustainable energy cycle. Here, we present an artificial metallosupramolecular macrocycle that gathers three Ru(bda) centres (bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) that catalyses water oxidation. The macrocyclic architecture accelerates the rate of water oxidation via a water nucleophilic attack mechanism, similar to the mechanism exhibited by OEC-PSII, and reaches remarkable catalytic turnover frequencies >100 s(-1). Photo-driven water oxidation yields outstanding activity, even in the nM concentration regime, with a turnover number of >1,255 and turnover frequency of >13.1 s(-1).

  7. Understanding Catalytic Activity Trends for NO Decomposition and CO Oxidation using Density Functional Theory and Microkinetic Modeling

    DEFF Research Database (Denmark)

    Falsig, Hanne

    towards rationalizing trends in catalytic activity of transition metal catalysts for NO decomposition by combining microkinetic modelling with density functional theory calculations. We establish the full potential energy diagram for the direct NO decomposition reaction over stepped transition......The main aim of this thesis is to understand the catalytic activity of transition metals and noble metals for the direct decomposition of NO and the oxidation of CO. The formation of NOx from combustion of fossil and renewable fuels continues to be a dominant environmental issue. We take one step......-metal surfaces by combining a database of adsorption energies on stepped metal surfaces with known Brønsted–Evans–Polanyi (BEP) relations for the activation barriers of dissociation of diatomic molecules over stepped transition- and noble-metal surfaces. The potential energy diagram directly points to why Pd...

  8. Initiation of decay of Bacillus subtilis trp leader RNA.

    Science.gov (United States)

    Deikus, Gintaras; Bechhofer, David H

    2007-07-13

    Transcription termination in the leader region of the Bacillus subtilis trp operon is regulated by binding of the 11-mer TRAP complex to nascent trp RNA, which results in formation of a terminator structure. Rapid decay of trp leader RNA, which is required to release the TRAP complex and maintain a sufficient supply of free TRAP, is mediated by polynucleotide phosphorylase (PNPase). Using purified B. subtilis PNPase, we showed that, when TRAP was present, PNPase binding to the 3' end of trp leader RNA and PNPase digestion of trp leader RNA from the 3' end were inefficient. These results suggested that initiation of trp leader RNA may begin with an endonuclease cleavage upstream of the transcription terminator structure. Such cleavage was observed in vivo. Mutagenesis of nucleotides at the cleavage site abolished processing and resulted in a 4-fold increase in trp leader RNA half-life. This is the first mapping of a decay-initiating endonuclease cleavage site on a native B. subtilis RNA. PMID:17507374

  9. Promotion of catalytic activity for methanol electro-oxidation on CoPc-Pt/C co-catalysts

    Institute of Scientific and Technical Information of China (English)

    WU JingJie; XU YiMin; PAN Mu; MA WenTao; TANG HaoLin

    2009-01-01

    The catalytic activity for methanol electro-oxidation on CoPc-Pt/C co-catalysts, prepared by impregnation method, was studied in details through electrochemical methods. Cyclic voltammetry (CV) result demonstrates that CoPc has higher forward anodic peak current density and jf/jb value (forward anodic peak current density/backward anodic peak current density) than Pt/C. Chronoamperometry (CA) analysis indicates that CoPc-Pt/C exhibits both excellent transient current density and stable current density for methanol electro-oxidation compared with Pt/C. Two main mechanisms related to the promotion of catalytic activity are as follows: CoPc-Pt/C has the activity of tolerance to carbonaceous intermediates, thus inhibiting the self-poisoning of catalysts; CoPc-Pt/C owns prominent intrinsic catalytic activity indicated by the apparent activation energy for methanol oxidation on CoPc-Pt/C, which is 18 kJ/mol, less than that on Pt and PtRu catalysts as reported.

  10. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale

    Science.gov (United States)

    Shan, Shiyao; Petkov, Valeri; Prasai, Binay; Wu, Jinfang; Joseph, Pharrah; Skeete, Zakiya; Kim, Eunjoo; Mott, Derrick; Malis, Oana; Luo, Jin; Zhong, Chuan-Jian

    2015-11-01

    The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo phase

  11. Transient Receptor Potential (TRP) Channels and Taste Sensation

    OpenAIRE

    Ishimaru, Y.; Matsunami, H

    2009-01-01

    Humans have 5 basic taste sensations: sweet, bitter, sour, salty, and umami (taste of 1-amino acids). Among 33 genes related to transient receptor potential (TRP) channels, 3—including TRP-melastatin 5 (TRPM5), polycystic kidney disease-1-like 3 (PKD1L3), and polycystic kidney disease-2-like 1 (PKD2L1)—are specifically and abundantly expressed in taste receptor cells. TRP-melastatin 5 is co-expressed with taste receptors T1Rs and T2Rs, and functions as a common downstream component in sweet, ...

  12. Identification of residues in the heme domain of soluble guanylyl cyclase that are important for basal and stimulated catalytic activity.

    Directory of Open Access Journals (Sweden)

    Padmamalini Baskaran

    Full Text Available Nitric oxide signals through activation of soluble guanylyl cyclase (sGC, a heme-containing heterodimer. NO binds to the heme domain located in the N-terminal part of the β subunit of sGC resulting in increased production of cGMP in the catalytic domain located at the C-terminal part of sGC. Little is known about the mechanism by which the NO signaling is propagated from the receptor domain (heme domain to the effector domain (catalytic domain, in particular events subsequent to the breakage of the bond between the heme iron and Histidine 105 (H105 of the β subunit. Our modeling of the heme-binding domain as well as previous homologous heme domain structures in different states point to two regions that could be critical for propagation of the NO activation signal. Structure-based mutational analysis of these regions revealed that residues T110 and R116 in the αF helix-β1 strand, and residues I41 and R40 in the αB-αC loop mediate propagation of activation between the heme domain and the catalytic domain. Biochemical analysis of these heme mutants allows refinement of the map of the residues that are critical for heme stability and propagation of the NO/YC-1 activation signal in sGC.

  13. Enhancement in the Catalytic Activity of Pd/USY in the Heck Reaction Induced by H2 Bubbling

    Directory of Open Access Journals (Sweden)

    Miki Niwa

    2010-12-01

    Full Text Available Pd was loaded on ultra stable Y (USY zeolites prepared by steaming NH4-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H2 bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc2. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H2O gave the highest activity (TOF = 61,000 h−1, which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OHstrong generated as a result of steaming had a profound effect on the catalytic activity of Pd.

  14. Mustard oils and cannabinoids excite sensory nerve fibres through the TRP channel ANKTM1.

    Science.gov (United States)

    Jordt, Sven-Eric; Bautista, Diana M; Chuang, Huai-Hu; McKemy, David D; Zygmunt, Peter M; Högestätt, Edward D; Meng, Ian D; Julius, David

    2004-01-15

    Wasabi, horseradish and mustard owe their pungency to isothiocyanate compounds. Topical application of mustard oil (allyl isothiocyanate) to the skin activates underlying sensory nerve endings, thereby producing pain, inflammation and robust hypersensitivity to thermal and mechanical stimuli. Despite their widespread use in both the kitchen and the laboratory, the molecular mechanism through which isothiocyanates mediate their effects remains unknown. Here we show that mustard oil depolarizes a subpopulation of primary sensory neurons that are also activated by capsaicin, the pungent ingredient in chilli peppers, and by Delta(9)-tetrahydrocannabinol (THC), the psychoactive component of marijuana. Both allyl isothiocyanate and THC mediate their excitatory effects by activating ANKTM1, a member of the TRP ion channel family recently implicated in the detection of noxious cold. These findings identify a cellular and molecular target for the pungent action of mustard oils and support an emerging role for TRP channels as ionotropic cannabinoid receptors. PMID:14712238

  15. Down-regulation of tyrosinase, TRP-1, TRP-2 and MITF expressions by citrus press-cakes in murine B16 F10 melanoma

    Institute of Scientific and Technical Information of China (English)

    Sang Suk Kim; Min-Jin Kim; Young Hun Choi; Byung Kuk Kim; Kwang Sik Kim; Kyung Jin Park; Suk Man Park; Nam Ho Lee; Chang-Gu Hyun

    2013-01-01

    Objective: To investigate the suitability of citrus-press cakes, by-products of the juice industry as a source for the whitening agents for cosmetic industry. Methods:Ethylacetate extracts of citrus-press cakes (CCE) were examined for their anti-melanogenic potentials in terms of the inhibition of melanin production and mechanisim of melanogenesis by using Western Blot analysis with tyrosinese, tyrosinase-related protein-1 (TRP-1), TRP2, and microphthalmia-associated transcription factor (MITF) proteins. To apply the topical agents, citrus-press cakes was investigated the safety in human skin cell line. Finally flavonoid analysis of CCE was also determined by HPLC analysis. Results: Results indicated that CCE were shown to down-regulate melanin content in a dose-dependent pattern. The CCE inhibited tyrosinase, TRP-2, and MITF expressions in a dose-dependent manner. To test the applicability of CCE to human skin, we used MTT assay to assess the cytotoxic effects of CCE on human keratinocyte HaCaT cells. The CCE exhibited low cytotoxicity at 50 µg/mL. Characterization of the citrus-press cakes for flavonoid contents using HPLC showed varied quantity of rutin, narirutin, and hesperidin. Conclusions:Considering the anti-melanogenic activity and human safety, CCE is considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.

  16. DEVELOPMENT OF HIGH ACTIVITY, COAL-DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Joseph M. Calo

    2000-07-24

    This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, TPD studies were conducted following steady-state reaction in NO/CO mixtures in helium. From these studies, the following points have been concluded: (1) The total amount of CO and N{sub 2} evolved following reaction in NO increases with reaction temperature. The TPD spectra are skewed to high temperatures, indicating more stable surface complexes with high desorption activation energies. (2) The total amount of CO evolved following exposure of the char sample to CO at reaction temperatures decreases with reaction temperature, similar to chemisorption behavior. The CO TPD spectra are shifted to lower temperatures, indicating more labile oxygen surface complexes with lower desorption activation energies. (3) The total amount of CO evolved following reaction in NO/CO mixtures decreases with reaction temperature, while the evolved N{sub 2} still increases with reaction temperature. The CO TPD spectra appear more similar to those obtained following exposure to pure CO, while the N{sub 2} TPD spectra are more similar to those obtained followed reaction in just CO. Based on the preceding observations, a simple mechanism was formulated whereby two different types of surface complexes are formed by NO and CO; the former are more stable, and the latter more labile. This produces two parallel routes for the NO-carbon reaction: (a) the C(O) complexes formed directly by NO desorb as CO; and (b) The C(CO) complexes formed by CO, react with NO to produce CO{sub 2

  17. Evidence for Participation of Remote Residues in the Catalytic Activity of Co-type Nitrile Hydratase from Pseudomonas putida†

    OpenAIRE

    Brodkin, Heather R.; Novak, Walter R. P.; Milne, Amy C.; D’Aquino, J. Alejandro; Karabacak, N. M.; Agar, Jeffrey N.; Payne, Mark S.; Petsko, Gregory A; Ondrechen, Mary Jo; Ringe, Dagmar

    2011-01-01

    Active sites may be regarded as layers of residues, whereby the residues that interact directly with substrate also interact with residues in a second shell, and these in turn interact with residues in a third shell. These residues in the second and third layers may have distinct roles in maintaining the essential chemical properties of the first-shell catalytic residues, particularly their spatial arrangement relative to the substrate binding pocket, and their electrostatic and dynamic prope...

  18. Modulating TRAP-mediated transcription termination by AT during transcription of the leader region of the Bacillus subtilis trp operon.

    Science.gov (United States)

    Sharma, Shraddha; Gollnick, Paul

    2014-05-01

    An 11-subunit protein called trp RNA binding Attenuation Protein (TRAP) controls attenuation of the tryptophan biosynthetic (trpEDCFBA) operon in Bacillus subtilis. Tryptophan-activated TRAP binds to 11 (G/U)AG repeats in the 5' leader region of trp mRNAs, and downregulates expression of the operon by promoting transcription termination prior to the structural genes. Anti-TRAP (AT) is an antagonist that binds to tryptophan-activated TRAP and prevents TRAP from binding to RNA, thereby upregulating expression of the trp genes. AT forms trimers, and multiple trimers bind to a TRAP 11mer. It is not known how many trimers must bind to TRAP in order to interfere with RNA binding. Studies of isolated TRAP and AT showed that AT can prevent TRAP from binding to the trp leader RNA but cannot dissociate a pre-formed TRAP-RNA complex. Here, we show that AT can prevent TRAP-mediated termination of transcription by inducing dissociation of TRAP from the nascent RNA when it has bound to fewer than all 11 (G/U)AG repeats. The 5'-most region of the TRAP binding site in the nascent transcript is most susceptible to dissociation from TRAP. We also show that one AT trimer bound to TRAP 11mer reduces the affinity of TRAP for RNA and eliminates TRAP-mediated transcription termination in vitro. PMID:24682818

  19. Effect of structure and surface properties on the catalytic activity of nanodiamond in the conversion of 1,2-dichloroethane

    Science.gov (United States)

    Tveritinova, E. A.; Zhitnev, Yu. N.; Kulakova, I. I.; Maslakov, K. I.; Nesterova, E. A.; Kharlanov, A. N.; Ivanov, A. S.; Savilov, S. V.; Lunin, V. V.

    2015-04-01

    The catalytic activity of a detonation nanodiamond and its Ni-containing forms in the conversion of 1,2-dichloroethane is studied and compared with the activity of other carbon and nanocarbon materials: carbon nanotubes, "Dalan" synthetic diamond, and fluorinated graphite. The surface and structure of the carbon materials are characterized using XRD, diffuse reflectance IR spectroscopy, XPS, BET, and TPR. The catalytic properties of the materials are studied using the pulsed microcatalytic method. It is found that the synthetic diamond, the nanodiamond, and its Ni-containing forms are catalysts for dichloroethane conversion in a nitrogen atmosphere, where the main product is ethylene. It is noted that the catalytic activity of deactivated diamond catalysts is restored after hydrogen treatment. It is shown that the carbon structure of the nanodiamond and the "Dalan" synthetic diamond with hydrogen groups located on it plays a key role in the dichloroethane conversion. It is found that the nanodiamond acts simultaneously as a catalyst and an adsorbent of chlorine-containing products of dichloroethane conversion.

  20. Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

    Science.gov (United States)

    Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

    2015-06-18

    A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts. PMID:26266615

  1. Catalytic activities of fungal oxidases in hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate-based microemulsion.

    Science.gov (United States)

    Zhou, Gui-Ping; Zhang, Yun; Huang, Xi-Rong; Shi, Chuan-Hong; Liu, Wei-Feng; Li, Yue-Zhong; Qu, Yin-Bo; Gao, Pei-Ji

    2008-10-01

    For hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]), an H(2)O-in-[BMIM][PF(6)] microemulsion could be formed in the presence of nonionic surfactant Triton X-100 (TX-100). In such a medium, both lignin peroxidase (LiP) and laccase could express their catalytic activity with the optimum molar ratio of H(2)O to TX-100 at 8.0 for LiP and >20 for laccase, and the optimum pH values at 3.2 for LiP and 4.2 for laccase, respectively. As compared with pure or water saturated [BMIM][PF(6)], in which the two oxidases had negligible catalytic activity due to the strong inactivating effect of [BMIM][PF(6)] on both enzymes, the use of the [BMIM][PF(6)]-based microemulsion had some advantages. Not only the catalytic activities of both fungal oxidases greatly enhanced, but also the apparent viscosity of the medium decreased. PMID:18602799

  2. VaSP1, catalytically active serine proteinase from Vipera ammodytes ammodytes venom with unconventional active site triad.

    Science.gov (United States)

    Kurtović, Tihana; Brgles, Marija; Leonardi, Adrijana; Lang Balija, Maja; Sajevic, Tamara; Križaj, Igor; Allmaier, Günter; Marchetti-Deschmann, Martina; Halassy, Beata

    2014-01-01

    VaSP1, a serine proteinase from Vipera ammodytes ammodytes venom, is a glycosylated monomer of 31.5 kDa, as determined by MALDI mass spectrometry, showing multiple isoelectric points between pH 6.5 and pH 8.5. Partial amino acid sequencing of VaSP1 by Edman degradation and MS/MS analysis identified sequences which allowed its classification among the so-called snake venom serine proteinase homologues, members of the peptidase S1 family, however being devoid of the canonical catalytic triad. Only few representatives of this group have been identified so far with just two of them characterised in detail at the protein level. Despite substitution of His57 with Arg, VaSP1 possesses proteolytic activity which can be inhibited by Pefabloc, benzamidine, Zn²⁺ ions, DTT and trypsin inhibitor II, a Kunitz/BPTI group member. It hydrolyses N(α)-benzoyl-Phe-Val-Arg-p-NA, exhibiting Michaelis-Menten behaviour with K(m) = 48.2 μM and V(m) = 0.019 nM s⁻¹. The pH for optimal activity on tested substrate is around 9.0. VaSP1 also cleaves insulin B-chain, digesting it at positions His¹⁰-Leu¹¹, Ala¹⁴-Leu¹⁵ and Tyr¹⁶-Leu¹⁷. Furthermore, the novel serine proteinase is active towards wide array of proteins involved in haemostasis where its degradation of fibrinogen, fibrin, prothrombin, factor X and plasminogen in vivo probably results in depletion of coagulation factors in blood circulation. The possibility that VaSP1 possesses anticoagulant properties has been further indicated by its ability to prolong prothrombin time and activated partial thromboplastin time.

  3. Surface composition and catalytic activity of La-Fe mixed oxides for methane oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fengxiang [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Li, Zhanping [Analysis Center, Tsinghua University, Beijing 100084 (China); Ma, Hongwei [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China); Gao, Zhiming, E-mail: zgao@bit.edu.cn [School of Chemistry, Beijing Institute of Technology, Liangxiang East Road, Beijing 102488 (China)

    2015-10-01

    Graphical abstract: - Highlights: • The sample with La/Fe atomic ratio of 0.94 is single phase perovskite La{sub 0.94}FeO{sub 3−d}. • The excess ironic oxide exists on the surface of the perovskite crystallites. • La{sup 3+} ions are enriched on surface of the oxides even for the La{sub 0.68}Fe sample. - Abstract: Four La-Fe oxide samples with La/Fe atomic ratio y = 1.02 ∼ 0.68 (denoted as LayFe) were prepared by the citrate method. The samples had a decreased specific surface area with the La/Fe atomic ratio decreasing. XRD pattern proved that the sample La{sub 0.94}Fe is single phase perovskite La{sub 0.94}FeO{sub 3−d}. Phase composition of the samples was estimated by the Rietveld refinement method. XPS analyses indicate that La{sup 3+} ions are enriched on surface of crystallites for all the samples, and surface carbonate ions are relatively abundant on the samples La{sub 1.02}Fe and La{sub 0.94}Fe. Catalytic activity for methane oxidation per unit surface area of the samples is in the order of La{sub 0.68}Fe > La{sub 0.76}Fe > La{sub 0.94}Fe > La{sub 1.02}Fe both in the presence and in the absence of gaseous oxygen. A reason for this order would be the higher concentration of Fe{sup 3+} ion on the surface of the samples La{sub 0.68}Fe and La{sub 0.76}Fe.

  4. TRP Channels as Therapeutic Targets in Diabetes and Obesity

    Science.gov (United States)

    Zsombok, Andrea; Derbenev, Andrei V.

    2016-01-01

    During the last three to four decades the prevalence of obesity and diabetes mellitus has greatly increased worldwide, including in the United States. Both the short- and long-term forecasts predict serious consequences for the near future, and encourage the development of solutions for the prevention and management of obesity and diabetes mellitus. Transient receptor potential (TRP) channels were identified in tissues and organs important for the control of whole body metabolism. A variety of TRP channels has been shown to play a role in the regulation of hormone release, energy expenditure, pancreatic function, and neurotransmitter release in control, obese and/or diabetic conditions. Moreover, dietary supplementation of natural ligands of TRP channels has been shown to have potential beneficial effects in obese and diabetic conditions. These findings raised the interest and likelihood for potential drug development. In this mini-review, we discuss possibilities for better management of obesity and diabetes mellitus based on TRP-dependent mechanisms. PMID:27548188

  5. Determination of the catalytic activity of binuclear metallohydrolases using isothermal titration calorimetry.

    Science.gov (United States)

    Pedroso, Marcelo M; Ely, Fernanda; Lonhienne, Thierry; Gahan, Lawrence R; Ollis, David L; Guddat, Luke W; Schenk, Gerhard

    2014-03-01

    Binuclear metallohydrolases are a large and diverse family of enzymes that are involved in numerous metabolic functions. An increasing number of members find applications as drug targets or in processes such as bioremediation. It is thus essential to have an assay available that allows the rapid and reliable determination of relevant catalytic parameters (k cat, K m, and k cat/K m). Continuous spectroscopic assays are frequently only possible by using synthetic (i.e., nonbiological) substrates that possess a suitable chromophoric marker (e.g., nitrophenol). Isothermal titration calorimetry, in contrast, affords a rapid assay independent of the chromophoric properties of the substrate-the heat associated with the hydrolytic reaction can be directly related to catalytic properties. Here, we demonstrate the efficiency of the method on several selected examples of this family of enzymes and show that, in general, the catalytic parameters obtained by isothermal titration calorimetry are in good agreement with those obtained from spectroscopic assays.

  6. Investigation on preparation of CuO-SnO2-CeO2/γ-Al2O3 catalysts for catalytic wet air oxidation process and their catalytic activity for degradation of phenol

    Institute of Scientific and Technical Information of China (English)

    SUN Xiao-jun; ZHANG Mi-lin; WAN Jia-feng; XIA Zhi; LIU Xiao-hui; LIU hui

    2008-01-01

    Catalytic Wet Air Oxidation process is an efficient measure for treatment of wastewater with great strength which is not biodegradable. Heterocatalysts now become the key investigation subject of catalytic wet air oxidation process due to their good stability and easy separation. In the paper, CuO-SnOE-CeO2/γ-Al2O3 catalysts are prepared by impregnation method, with SnO2 as a doping component, CuO as an active component, CeO2 as a structure stabilizer, γ-Al2O3 as a substrate. XPS test is carried out to investigate the effect of Sn on the chemical surrounding of Cu and O element on the catalyst surface and their catalytic activity. It is shown that the right do-ping of Sn can increase Cu+ content on the catalyst surface, as a result the quantity of adsorption oxygen is also increased. It is found that Cu + content on the catalyst surface is one of the primary factors that determin catalytic activity of catalyst through analyzing the catalytic wet air oxidation process of phenol.

  7. The effect of chelating/combustion agent on catalytic activity and magnetic properties of Dy doped Ni-Zn ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Samoila, P.; Slatineanu, T. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, 11 Carol I Boulevard 700506 (Romania); Postolache, P. [Faculty of Physics, Alexandru Ioan Cuza University of Iasi, 11 Carol I Boulevard 700506 (Romania); Iordan, A.R. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, 11 Carol I Boulevard 700506 (Romania); Palamaru, M.N., E-mail: palamaru@uaic.ro [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, 11 Carol I Boulevard 700506 (Romania)

    2012-09-14

    The spinel ferrite Ni{sub 0.8}Zn{sub 0.2}Fe{sub 1.98}Dy{sub 0.02}O{sub 4} was prepared by sol-gel low temperature autocombustion method using four different chelating/combustion agents: citric acid, tartaric acid, urea and cellulose. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, the catalytic H{sub 2}O{sub 2} decomposition and the magnetic behavior were employed to investigate the influence of the combustion agents on structural characteristics, catalytic activity and magnetic properties. Spinel-type phase in the nano-scale domain was accomplished during sol-gel synthesis and was confirmed by XRD and IR. The best catalytic activity is belonging to the sample obtained using urea, which shows the smallest grain size (SEM), the highest specific surface area (BET measurements) and DyFeO{sub 3} phase (XRD), while ferrimagnetic behavior prevails for all the samples independently of fuel agent. Highlights: Black-Right-Pointing-Pointer Ni-Zn ferrite doped with Dy as catalyst and magnetic material. Black-Right-Pointing-Pointer Four chelating/combustion agents were used in sol-gel method. Black-Right-Pointing-Pointer Citric acid and cellulose allowed spinel monophase formation confirmed by XRD. Black-Right-Pointing-Pointer Catalytic activity of ferrite samples is affected by synthesis conditions. Black-Right-Pointing-Pointer Magnetic behavior is not changed significantly as a function of fuel agent.

  8. Catalytic oxidative desulfurization of diesel utilizing hydrogen peroxide and functionalized-activated carbon in a biphasic diesel-acetonitrile system

    Energy Technology Data Exchange (ETDEWEB)

    Haw, Kok-Giap; Bakar, Wan Azelee Wan Abu; Ali, Rusmidah; Chong, Jiunn-Fat [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Kadir, Abdul Aziz Abdul [Department of Petroleum Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2010-09-15

    This paper presents the development of granular functionalized-activated carbon as catalysts in the catalytic oxidative desulfurization (Cat-ODS) of commercial Malaysian diesel using hydrogen peroxide as oxidant. Granular functionalized-activated carbon was prepared from oil palm shell using phosphoric acid activation method and carbonized at 500 C and 700 C for 1 h. The activated carbons were characterized using various analytical techniques to study the chemistry underlying the preparation and calcination treatment. Nitrogen adsorption/desorption isotherms exhibited the characteristic of microporous structure with some contribution of mesopore property. The Fourier Transform Infrared Spectroscopy results showed that higher activation temperature leads to fewer surface functional groups due to thermal decomposition. Micrograph from Field Emission Scanning Electron Microscope showed that activation at 700 C creates orderly and well developed pores. Furthermore, X-ray Diffraction patterns revealed that pyrolysis has converted crystalline cellulose structure of oil palm shell to amorphous carbon structure. The influence of the reaction temperature, the oxidation duration, the solvent, and the oxidant/sulfur molar ratio were examined. The rates of the catalytic oxidative desulfurization reaction were found to increase with the temperature, and H{sub 2}O{sub 2}/S molar ratio. Under the best operating condition for the catalytic oxidative desulfurization: temperature 50 C, atmospheric pressure, 0.5 g activated carbon, 3 mol ratio of hydrogen peroxide to sulfur, 2 mol ratio of acetic acid to sulfur, 3 oxidation cycles with 1 h for each cycle using acetonitrile as extraction solvent, the sulfur content in diesel was reduced from 2189 ppm to 190 ppm with 91.3% of total sulfur removed. (author)

  9. Catalytic activity and stability of glucose oxidase/horseradish peroxidase co-confined in macroporous silica foam.

    Science.gov (United States)

    Cao, Xiaodong; Li, Ying; Zhang, Zhiqiang; Yu, Jiachao; Qian, Jing; Liu, Songqin

    2012-12-21

    Investigation of the catalytic activity and stability of enzymes in confined nano/microspace provides valuable contributions to the fundamental understanding of biological reactions taking place on a mesoscopic scale within confined spaces. In this paper, macroporous silica foam (MSF) is used as a nanoreactor to co-confine glucose oxidase (GOD) and horseradish peroxidase (HRP). Then, the enzymatic cascade reactions, which act in tandem inside nanoreactors, for oxidation of glucose and 3,3',5,5'-tetramethylbenzidine (TMB) were studied. The catalytic kinetic parameters of apparent Michaelis constant (K(m)(app)) and maximum rate (V(max)) were obtained from Lineweaver-Burk plot by UV-vis spectrometry. Results showed that the catalytic activity of the co-confined enzymes is reduced compared to that of free enzymes in solution at room temperature. The stabilities of co-confined enzymes in denaturing agents, such as guanidinium chloride (GdmCl) and urea, were higher than those of free enzymes in solution. When employing a co-confined bienzyme system as a biosensor for the detection of glucose, a wider linear range of glucose was obtained for the co-confined bienzyme system than for free enzymes in solution. PMID:23096254

  10. Synthesis, Characterization and catalytic activity of triorganotin(IV) carboxylates for the production of biodiesel from rocket seed oil

    International Nuclear Information System (INIS)

    Organotin(IV) carboxylates have a wide range of industrial applications such as antifouling paints, PVC stabilization, ion carries in electrochemical membranes and homogeneous catalysts. The catalytic application of organotin carboxylates are in the field of silicone curing, polyurethane formation and esterification. Only a limited literature is available regarding the use of organotin carboxylates in the transesterification of vegetable oil to produce biodiesel . The present study deals with the synthesis of some new triorganotin(IV) carboxylates for their subsequent use as catalyst for transesterification of rocket seed oil to produce biodiesel. The three new triorganotin(IV) i.e. (Me/sub 3/SnL) (1),(Bu/sub 3/Snl) (2) and (Ph/sub 3/SnL) (3), were synthesized by refluxing sodium salt of ligand (NaL), where L=O/sub 2/C(CH/sub 3/)C=CHC/sub 6/H/sub 4/F with trimethyl, tributyl and triphenyl tin(IV) chlorides, respectively for 10 hrs. The synthesized compounds were characterized by instrumental techniques like FT-IR and NMR (1H, 13C). The catalytic activity of these compounds was assessed for transesterification of triglycerides in rocket seed oil to produce biodiesel. All the tested compounds showed good catalytic activity in the order 1> 2 > 3. (author)

  11. Catalytic modification of conventional SOFC anodes with a view to reducing their activity for direct internal reforming of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Boder, M.; Dittmeyer, R. [Research Group Technical Chemistry, Karl-Winnacker-Institut, DECHEMA e.V., Theodor-Heuss-Allee 25, D-60486 Frankfurt (Germany)

    2006-04-18

    When using natural gas as fuel for the solid oxide fuel cell (SOFC), direct internal reforming lowers the requirement for cell cooling and, theoretically, offers advantages with respect to capital cost and efficiency. The high metal content of a nickel/zirconia anode and the high temperature, however, cause the endothermic reforming reaction to take place very fast. The resulting drop of temperature at the inlet produces thermal stresses, which may lower the system efficiency and limit the stack lifetime. To reduce the reforming rate without lowering the electrochemical activity of the cell, a wet impregnation procedure for modifying conventional cermets by coverage with a less active metal was developed. As the coating material copper was chosen. Copper is affordable, catalytically inert for the reforming reaction and exhibits excellent electronic conductivity. The current density-voltage characteristics of the modified units showed that it is possible to maintain a good electrochemical performance of the cells despite the catalytic modification. A copper to nickel ratio of 1:3 resulted in a strong diminution of the catalytic reaction rate. This indicates that the modification could be a promising method to improve the performance of solid oxide fuel cells with direct internal reforming of hydrocarbons. (author)

  12. Activation of Al–Cu–Fe quasicrystalline surface: fabrication of a fine nanocomposite layer with high catalytic performance

    Directory of Open Access Journals (Sweden)

    Satoshi Kameoka

    2014-01-01

    Full Text Available A fine layered nanocomposite with a total thickness of about 200 nm was formed on the surface of an Al63Cu25Fe12 quasicrystal (QC. The nanocomposite was found to exhibit high catalytic performance for steam reforming of methanol. The nanocomposite was formed by a self-assembly process, by leaching the Al–Cu–Fe QC using a 5 wt% Na2CO3 aqueous solution followed by calcination in air at 873 K. The quasiperiodic nature of the QC played an important role in the formation of such a structure. Its high catalytic activity originated from the presence of highly dispersed copper and iron species, which also suppressed the sintering of nanoparticles.

  13. Sulfur-Functionalized N-Heterocyclic Carbene Complexes of Pd(II: Syntheses, Structures and Catalytic Activities

    Directory of Open Access Journals (Sweden)

    Dan Yuan

    2012-03-01

    Full Text Available N-heterocyclic carbenes (NHCs can be easily modified by introducing functional groups at the nitrogen atoms, which leads to versatile coordination chemistry as well as diverse catalytic applications of the resulting complexes. This article summarizes our contributions to the field of NHCs bearing different types of sulfur functions, i.e., thioether, sulfoxide, thiophene, and thiolato. The experimental evidence for the truly hemilabile coordination behavior of a Pd(II thioether-NHC complex has been reported as well. In addition, complexes bearing rigid CSC-pincer ligands have been synthesized and the reasons for pincer versus pseudo-pincer formation investigated. Incorporation of the electron-rich thiolato function resulted in the isolation of structurally diverse complexes. The catalytic activities of selected complexes have been tested in Suzuki-Miyaura, Mizoroki-Heck and hydroamination reactions.

  14. 3D hierarchical walnut-like CuO nanostructures: Preparation, characterization and their efficient catalytic activity for CO oxidation

    Science.gov (United States)

    Yao, Weitang; Zhang, Yujuan; Duan, Tao; Zhu, Wenkun; Yi, Zao; Cui, Xudong

    2016-07-01

    In this work, 3D hierarchical walnut-shaped, 2D nanosheet and 3D microspheres single phase CuO nanostructures are functioning as catalysts and supporting materials, differing from the conventional ways. The novel nanostructures were synthesized via hydrothermal method under a stainless steel autoclave. The as-prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and H2 temperature-programmed reduction (H2-TPR). The walnut-shaped structures with high O/Cu atomic ratio (1.22) exhibit high oxygen adsorption capacity and greatly enhanced catalytic activity. These results will be enrich the techniques for tuning the morphologies of metal oxide micro/nanostructures and open a new field in catalytic applications.

  15. Energy Efficient Catalytic Activation of Hydrogen peroxide for Green Chemical Processes: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Terrence J.; Horwitz, Colin

    2004-11-12

    A new, highly energy efficient approach for using catalytic oxidation chemistry in multiple fields of technology has been pursued. The new catalysts, called TAML® activators, catalyze the reactions of hydrogen peroxide and other oxidants for the exceptionally rapid decontamination of noninfectious simulants (B. atrophaeus) of anthrax spores, for the energy efficient decontamination of thiophosphate pesticides, for the facile, low temperature removal of color and organochlorines from pulp and paper mill effluent, for the bleaching of dyes from textile mill effluents, and for the removal of recalcitrant dibenzothiophene compounds from diesel and gasoline fuels. Highlights include the following: 1) A 7-log kill of Bacillus atrophaeus spores has been achieved unambiguously in water under ambient conditions within 15 minutes. 2) The rapid total degradation under ambient conditions of four thiophosphate pesticides and phosphonate degradation intermediates has been achieved on treatment with TAML/peroxide, opening up potential applications of the decontamination system for phosphonate structured chemical warfare agents, for inexpensive, easy to perform degradation of stored and aged pesticide stocks (especially in Africa and Asia), for remediation of polluted sites and water bodies, and for the destruction of chemical warfare agent stockpiles. 3) A mill trial conducted in a Pennsylvanian bleached kraft pulp mill has established that TAML catalyst injected into an alkaline peroxide bleach tower can significantly lower color from the effluent stream promising a new, more cost effective, energy-saving approach for color remediation adding further evidence of the value and diverse engineering capacity of the approach to other field trials conducted on effluent streams as they exit the bleach plant. 4) Dibenzothiophenes (DBTs), including 4,6-dimethyldibenzothiophene, the most recalcitrant sulfur compounds in diesel and gasoline, can be completely removed from model gasoline

  16. Catalytic Activity and Stability of Oxides: The Role of Near-Surface Atomic Structures and Compositions.

    Science.gov (United States)

    Feng, Zhenxing; Hong, Wesley T; Fong, Dillon D; Lee, Yueh-Lin; Yacoby, Yizhak; Morgan, Dane; Shao-Horn, Yang

    2016-05-17

    the physical origin of segregation is discussed in comparison with (La1-ySry)2CoO4±δ/La1-xSrxCo0.2Fe0.8O3-δ. Sr enrichment in many electrocatalysts, such as La1-xSrxMO3-δ (M = Cr, Co, Mn, or Co and Fe) and Sm1-xSrxCoO3, has been probed using alternative techniques, including low energy ion scattering, secondary ion mass spectrometry, and X-ray fluorescence-based methods for depth-dependent, element-specific analysis. We highlight a strong connection between cation segregation and electrocatalytic properties, because cation segregation enhances oxygen transport and surface oxygen exchange kinetics. On the other hand, the formation of cation-enriched secondary phases can lead to the blocking of active sites, inhibiting oxygen exchange. With help from density functional theory, the links between cation migration, catalyst stability, and catalytic activity are provided, and the oxygen p-band center relative to the Fermi level can be identified as an activity descriptor. Based on these findings, we discuss strategies to increase a catalyst's activity while maintaining stability to design efficient, cost-effective electrocatalysts. PMID:27149528

  17. Catalytic catechol oxidation by copper complexes : development of a structure-activity relationship

    NARCIS (Netherlands)

    Ording-Wenker, Erica C M; Siegler, Maxime A; Lutz, Martin; Bouwman, Elisabeth

    2015-01-01

    A large library of Cu(II) complexes with mononucleating and dinucleating ligands was synthesized to investigate their potential as catalysts for the catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC). X-ray structure determination for a number of these complexes revealed relatively large Cu

  18. A single active catalytic site is sufficient to promote transport in P-glycoprotein.

    Science.gov (United States)

    Bársony, Orsolya; Szalóki, Gábor; Türk, Dóra; Tarapcsák, Szabolcs; Gutay-Tóth, Zsuzsanna; Bacsó, Zsolt; Holb, Imre J; Székvölgyi, Lóránt; Szabó, Gábor; Csanády, László; Szakács, Gergely; Goda, Katalin

    2016-01-01

    P-glycoprotein (Pgp) is an ABC transporter responsible for the ATP-dependent efflux of chemotherapeutic compounds from multidrug resistant cancer cells. Better understanding of the molecular mechanism of Pgp-mediated transport could promote rational drug design to circumvent multidrug resistance. By measuring drug binding affinity and reactivity to a conformation-sensitive antibody we show here that nucleotide binding drives Pgp from a high to a low substrate-affinity state and this switch coincides with the flip from the inward- to the outward-facing conformation. Furthermore, the outward-facing conformation survives ATP hydrolysis: the post-hydrolytic complex is stabilized by vanadate, and the slow recovery from this state requires two functional catalytic sites. The catalytically inactive double Walker A mutant is stabilized in a high substrate affinity inward-open conformation, but mutants with one intact catalytic center preserve their ability to hydrolyze ATP and to promote drug transport, suggesting that the two catalytic sites are randomly recruited for ATP hydrolysis. PMID:27117502

  19. Catalytic dioxygen activation by Co(II) complexes employing a coordinatively versatile ligand scaffold.

    Science.gov (United States)

    Sharma, Savita K; May, Philip S; Jones, Matthew B; Lense, Sheri; Hardcastle, Kenneth I; MacBeth, Cora E

    2011-02-14

    The ligand bis(2-isobutyrylamidophenyl)amine has been prepared and used to stabilize both mononuclear and dinuclear cobalt(II) complexes. The nuclearity of the cobalt product is regulated by the deprotonation state of the ligand. Both complexes catalytically oxidize triphenylphosphine to triphenylphosphine oxide in the presence of O(2).

  20. Breathtaking TRP Channels: TRPA1 and TRPV1 in Airway Chemosensation and Reflex Control

    OpenAIRE

    Bessac, Bret F.; Jordt, Sven-Eric

    2008-01-01

    New studies have revealed an essential role for TRPA1, a sensory neuronal TRP ion channel, in airway chemosensation and inflammation. TRPA1 is activated by chlorine, reactive oxygen species and noxious constituents of smoke and smog, initiating irritation and airway reflex responses. Together with TRPV1, the capsaicin receptor, TRPA1 may contribute to chemical hypersensitivity, chronic cough and airway inflammation in asthma, COPD and reactive airway dysfunction syndrome.

  1. Breathtaking TRP channels: TRPA1 and TRPV1 in airway chemosensation and reflex control.

    Science.gov (United States)

    Bessac, Bret F; Jordt, Sven-Eric

    2008-12-01

    New studies have revealed an essential role for TRPA1, a sensory neuronal TRP ion channel, in airway chemosensation and inflammation. TRPA1 is activated by chlorine, reactive oxygen species, and noxious constituents of smoke and smog, initiating irritation and airway reflex responses. Together with TRPV1, the capsaicin receptor, TRPA1 may contribute to chemical hypersensitivity, chronic cough, and airway inflammation in asthma, COPD, and reactive airway dysfunction syndrome. PMID:19074743

  2. TRAP binding to the Bacillus subtilis trp leader region RNA causes efficient transcription termination at a weak intrinsic terminator.

    Science.gov (United States)

    Potter, Kristine D; Merlino, Natalie M; Jacobs, Timothy; Gollnick, Paul

    2011-03-01

    The Bacillus subtilis trpEDCFBA operon is regulated by a transcription attenuation mechanism controlled by the trp RNA-binding attenuation protein (TRAP). TRAP binds to 11 (G/U)AG repeats in the trp leader transcript and prevents formation of an antiterminator, which allows formation of an intrinsic terminator (attenuator). Previously, formation of the attenuator RNA structure was believed to be solely responsible for signaling RNA polymerase (RNAP) to halt transcription. However, base substitutions that prevent formation of the antiterminator, and thus allow the attenuator structure to form constitutively, do not result in efficient transcription termination. The observation that the attenuator requires the presence of TRAP bound to the nascent RNA to cause efficient transcription termination suggests TRAP has an additional role in causing termination at the attenuator. We show that the trp attenuator is a weak intrinsic terminator due to low GC content of the hairpin stem and interruptions in the U-stretch following the hairpin. We also provide evidence that termination at the trp attenuator requires forward translocation of RNA polymerase and that TRAP binding to the nascent transcript can induce this activity. PMID:21097886

  3. The rate of TRAP binding to RNA is crucial for transcription attenuation control of the B. subtilis trp operon.

    Science.gov (United States)

    Barbolina, Maria V; Kristoforov, Roman; Manfredo, Amanda; Chen, Yanling; Gollnick, Paul

    2007-07-27

    The trp RNA-binding attenuation protein (TRAP) regulates expression of the tryptophan biosynthetic and transport genes in Bacillus subtilis in response to changes in the levels of intracellular tryptophan. Transcription of the trpEDCFBA operon is controlled by an attenuation mechanism involving two overlapping RNA secondary structures in the 5' leader region of the trp transcript; TRAP binding promotes formation of a transcription terminator structure that halts transcription prior to the structural genes. TRAP consists of 11 identical subunits and is activated to bind RNA by binding up to 11 molecules of L-tryptophan. The TRAP binding site in the leader region of the trp operon mRNA consists of 11 (G/U)AG repeats. We examined the importance of the rate of TRAP binding to RNA for the transcription attenuation mechanism. We compared the properties of two types of TRAP 11-mers: homo-11-mers composed of 11 wild-type subunits, and hetero-11-mers with only one wild-type subunit and ten mutant subunits defective in binding either RNA or tryptophan. The hetero-11-mers bound RNA with only slightly diminished equilibrium binding affinity but with slower on-rates as compared to WT TRAP. The hetero-11-mers showed significantly decreased ability to induce transcription termination in the trp leader region when examined using an in vitro attenuation system. Together these results indicate that the rate of TRAP binding to RNA is a crucial factor in TRAP's ability to control attenuation. PMID:17555767

  4. Catalytic activity of nuclear PLC-beta(1) is required for its signalling function during C2C12 differentiation.

    Science.gov (United States)

    Ramazzotti, Giulia; Faenza, Irene; Gaboardi, Gian Carlo; Piazzi, Manuela; Bavelloni, Alberto; Fiume, Roberta; Manzoli, Lucia; Martelli, Alberto M; Cocco, Lucio

    2008-11-01

    Here we report that PLC-beta(1) catalytic activity plays a role in the increase of cyclin D3 levels and induces the differentiation of C2C12 skeletal muscle cells. PLC-beta(1) mutational analysis revealed the importance of His(331) and His(378) for the catalysis. The expression of PLC-beta(1) and cyclin D3 proteins is highly induced during the process of skeletal myoblast differentiation. We have previously shown that PLC-beta(1) activates cyclin D3 promoter during the differentiation of myoblasts to myotubes, indicating that PLC-beta(1) is a crucial regulator of the mouse cyclin D3 gene. We show that after insulin treatment cyclin D3 mRNA levels are lower in cells overexpressing the PLC-beta(1) catalytically inactive form in comparison to wild type cells. We describe a novel signalling pathway elicited by PLC-beta(1) that modulates AP-1 activity. Gel mobility shift assay and supershift performed with specific antibodies indicate that the c-jun binding site is located in a cyclin D3 promoter region specifically regulated by PLC-beta(1) and that c-Jun binding activity is significantly increased by insulin and PLC-beta(1) overexpression. Mutation of AP-1 site decreased the basal cyclin D3 promoter activity and eliminated its induction by insulin and PLC-beta(1). These results hint at the fact that PLC-beta(1) catalytic activity signals a c-jun/AP-1 target gene, i.e. cyclin D3, during myogenic differentiation.

  5. Understanding Trends in Catalytic Activity: The Effect of Adsorbate-Adsorbate Interactions for CO Oxidation Over Transition Metals

    DEFF Research Database (Denmark)

    Grabow, Lars; Larsen, Britt Hvolbæk; Nørskov, Jens Kehlet

    2010-01-01

    Using high temperature CO oxidation as the example, trends in the reactivity of transition metals are discussed on the basis of density functional theory (DFT) calculations. Volcano type relations between the catalytic rate and adsorption energies of important intermediates are introduced...... and the effect of adsorbate-adsorbate interaction on the trends is discussed. We find that adsorbate-adsorbate interactions significantly increase the activity of strong binding metals (left side of the volcano) but the interactions do not change the relative activity of different metals and have a very small...... influence on the position of the top of the volcano, that is, on which metal is the best catalyst....

  6. Impact of Substituents Attached to N-Heterocyclic Carbenes on the Catalytic Activity of Copper Complexes in the Reduction of Carbonyl Compounds with Triethoxysilane

    Institute of Scientific and Technical Information of China (English)

    PENG, Jiajian; CHEN, Lingzhen; XU, Zheng; HU, Yingqian; LI, Jiayun; BAI, Ying; QIU, Huayu; LAI, Guoqiao

    2009-01-01

    By using functionalized imidazolium salts such as 1-allyl-3-alkylimidazolium or 1-alkyi-3-vinylimidazolium salts as carbene ligand precursors, the reduction of aryl ketones with triethoxysilane may be catalyzed by copper salt/imidazolium salt/KO~tBu systems. The functional substituents attached to the N-heterocyclic carbene (NHC) serve to enhance the catalytic activity. Different copper salts also have an effect on the catalytic activity, with copper(Ⅱ) acetate monohydrate being superior to copper(I) chloride.

  7. Influence of heme-thiolate in shaping the catalytic properties of a bacterial nitric-oxide synthase.

    Science.gov (United States)

    Hannibal, Luciana; Somasundaram, Ramasamy; Tejero, Jesús; Wilson, Adjele; Stuehr, Dennis J

    2011-11-11

    Nitric-oxide synthases (NOS) are heme-thiolate enzymes that generate nitric oxide (NO) from L-arginine. Mammalian and bacterial NOSs contain a conserved tryptophan (Trp) that hydrogen bonds with the heme-thiolate ligand. We mutated Trp(66) to His and Phe (W66H, W66F) in B. subtilis NOS to investigate how heme-thiolate electronic properties control enzyme catalysis. The mutations had opposite effects on heme midpoint potential (-302, -361, and -427 mV for W66H, wild-type (WT), and W66F, respectively). These changes were associated with rank order (W66H < WT < W66F) changes in the rates of oxygen activation and product formation in Arg hydroxylation and N-hydroxyarginine (NOHA) oxidation single turnover reactions, and in the O(2) reactivity of the ferrous heme-NO product complex. However, enzyme ferrous heme-O(2) autoxidation showed an opposite rank order. Tetrahydrofolate supported NO synthesis by WT and the mutant NOS. All three proteins showed similar extents of product formation (L-Arg → NOHA or NOHA → citrulline) in single turnover studies, but the W66F mutant showed a 2.5 times lower activity when the reactions were supported by flavoproteins and NADPH. We conclude that Trp(66) controls several catalytic parameters by tuning the electron density of the heme-thiolate bond. A greater electron density (as in W66F) improves oxygen activation and reactivity toward substrate, but decreases heme-dioxy stability and lowers the driving force for heme reduction. In the WT enzyme the Trp(66) residue balances these opposing effects for optimal catalysis.

  8. Catalytic activity of hydrophobic Pt/C/PTFE catalysts of different PTFE content for hydrogen-water liquid exchange reaction

    International Nuclear Information System (INIS)

    10%Pt/C catalysts were prepared by liquid reduction method. PTFE and Pt/ C catalysts were adhered to porous metal and hydrophobic Pt/C/PTFE catalysts were prepared. The structure and size of Pt crystal particles of Pt/C catalysts were analyzed by XRD, and their mean size was 3.1 nm. The dispersion state of Pt/C and PTFE was analyzed by SEM, and they had good dispersion mostly, but PTFE membrane could be observed on local parts of Pt/C/PTFE surface. Because of low hydrophobicity, Pt/C/ PTFE catalysts have low activity when the mass ratio of PTFE and Pt/C is 0.5: 1, and their catalytic activity increases markedly when the ratio is 1:1. When the ratio increases again, more Pt active sites would be covered by PTFE and interior diffusion effect would increase, which result in the decrease of catalytic activity of Pt/C/PTFE. By PTFE pretreatment of porous metal carrier, the activity of Pt/C/PTFE catalysts decreases when the mass ratio of PTFE and Pt/C is 0.5:1, and their activity decreases when the mass ratio is 1:1. (authors)

  9. Indolmycin-mediated inhibition and stimulation of transcription at the trp promoter of Escherichia coli.

    OpenAIRE

    Bogosian, G; Haydock, P V; Somerville, R L

    1983-01-01

    Escherichia coli cells harboring a non-attenuated trp-lac operon fusion were used to evaluate the effects of indolmycin on the initiation of transcription at the trp promoter. Indolmycin caused repression in trpR+ strains and in trpR deletion mutants, although higher effector concentrations were required in the latter situation. Plasmid-mediated elevation in tryptophanyl-tRNA synthetase reversed the inhibitory effect of indolmycin. Indolmycin did not facilitate the binding of purified Trp rep...

  10. Synthesis, characterization and catalytic activity of indium substituted nanocrystalline Mobil Five (MFI) zeolite

    International Nuclear Information System (INIS)

    Highlights: • In situ modification of the MFI zeolite by incorporation of indium. • The samples were characterized by XRD, FTIR, TGA, UV–vis (DRS), SAA, EDX and SEM. • The incorporation of indium was confirmed by XRD, FT-IR, UV–vis (DRS), EDX and TGA. • Hydroxylation of phenol reaction was studied on the synthesized catalysts. - Abstract: A series of indium doped Mobil Five (MFI) zeolite were synthesized hydrothermally with silicon to aluminium and indium molar ratio of 100 and with aluminium to indium molar ratios of 1:1, 2:1 and 3:1. The MFI zeolite phase was identified by XRD and FT-IR analysis. In XRD analysis the prominent peaks were observed at 2θ values of around 6.5° and 23° with a few additional shoulder peaks in case of all the indium incorporated samples suggesting formation of pure phase of the MFI zeolite. All the samples under the present investigation were found to exhibit high crystallinity (∼92%). The crystallite sizes of the samples were found to vary from about 49 to 55 nm. IR results confirmed the formation of MFI zeolite in all cases showing distinct absorbance bands near 1080, 790, 540, 450 and 990 cm−1. TG analysis of In-MFI zeolites showed mass losses in three different steps which are attributed to the loss due to adsorbed water molecules and the two types TPA+ cations. Further, the UV–vis (DRS) studies reflected the position of the indium metal in the zeolite framework. Surface area analysis of the synthesized samples was carried out to characterize the synthesized samples The analysis showed that the specific surface area ranged from ∼357 to ∼361 m2 g−1 and the pore volume of the synthesized samples ranged from 0.177 to 0.182 cm3 g−1. The scanning electron microscopy studies showed the structure of the samples to be rectangular and twinned rectangular shaped. The EDX analysis was carried out for confirmation of Si, Al and In in zeolite frame work. The catalytic activities of the synthesized samples were

  11. Synthesis and catalytic activity of Ln(III) complexes with an unsymmetrical Schiff base including multigroups

    Institute of Scientific and Technical Information of China (English)

    YAO; Kemin; (

    2003-01-01

    [1]Elder, R. C., Tridentate and unsymmetrical tetradentate Schiff base ligands from salicylaldehydes and dimeric nickel(II) complexes, Aust. J. Chem., 1978, 31:35-45.[2]Atkins, R., Brewer, G., Kokot, G. et al., Copper(II) and nickel(II) complexesof unsymmetrical tetradentate Schiff base ligand, Inorg. Chem., 1985, 24: 127-134.[3]Meng Qingjin, Wang Ruixue, Bu Xiuren et al., New Ni (II) complexes with mixedtrimeric double Schiff ligands, Chemical Journal of Chinese Universities (in Chinese), 1990, 10: 1126-1130.[4]Yao Kemin, Zhou Wen, Lu Gui et al., Synthesis, mechanism and NMR spectra of lanthanide complexes with a novel unsymmetrical Schiff base, Science in China, Series B, 1999, 42(2): 164-169.[5]Yao Kemin, Li Ning, Huang Qiaohong et al., Synthesis and catalytic activity of novel heteronuclear Ln(III)-Cu(II) complexes with noncyclic polyether-amino acid Schiff base, Science in China, Series B, 1999, 42 (1) : 54-81.[6]Li Ning, Yao Kemin, Lou Kaiyan, Synthesis of La(III), Y(III) complexes with polyglycol aldehyde-amino acid Schiff base and their high resolution solid state 13C NMR spectra, Science in China, Series B, 1999, 42(6): 599-604.[7]Lam Berf, J. B., Shurvell, H. F., Verbet, L. et al., Organic Structural Analysis, New York: Macmillan Publishing Co. Inc., 1975, 234-250.[8]Yao Kemin, Cai Lezhen, Shen Liangfang et al., Synthesis and characterization of lanthanide perchlorates with noncyclic polyethylene glycols and their 13C-NMRspectra, Polyhedron, 1992,11(7): 2245-2251.[9]Dewar, M. J. S., Zoebisch, E. G., Healy, E. F., AM1: A new general purpose quantum mechanical molecular model, J. Amer. Chem. Soc., 1985, 107: 3902-3909.[10]Feifer, P., Avnjr, D., Chemistry in noninteger dimensions between two and three, I. Fractal theory of heterogeneous surfaces, J. Chem. Phys., 1983, 79(7): 3558-3565.[11]Yang Haifeng, Wang Hui, Duan Jinxia et al., Ab initio research of organic ligand Schiff base 4-[(2-hydroxyphenyl) imine]-2

  12. Synthesis, characterization and catalytic activity of indium substituted nanocrystalline Mobil Five (MFI) zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Kishor Kr. [Department of Chemistry, ADP College, Nagaon, Assam 782002 (India); Nandi, Mithun [Department of Chemistry, Gauhati University, Guwahati, Assam 781014 (India); Talukdar, Anup K., E-mail: anup_t@sify.com [Department of Chemistry, Gauhati University, Guwahati, Assam 781014 (India)

    2015-06-15

    Highlights: • In situ modification of the MFI zeolite by incorporation of indium. • The samples were characterized by XRD, FTIR, TGA, UV–vis (DRS), SAA, EDX and SEM. • The incorporation of indium was confirmed by XRD, FT-IR, UV–vis (DRS), EDX and TGA. • Hydroxylation of phenol reaction was studied on the synthesized catalysts. - Abstract: A series of indium doped Mobil Five (MFI) zeolite were synthesized hydrothermally with silicon to aluminium and indium molar ratio of 100 and with aluminium to indium molar ratios of 1:1, 2:1 and 3:1. The MFI zeolite phase was identified by XRD and FT-IR analysis. In XRD analysis the prominent peaks were observed at 2θ values of around 6.5° and 23° with a few additional shoulder peaks in case of all the indium incorporated samples suggesting formation of pure phase of the MFI zeolite. All the samples under the present investigation were found to exhibit high crystallinity (∼92%). The crystallite sizes of the samples were found to vary from about 49 to 55 nm. IR results confirmed the formation of MFI zeolite in all cases showing distinct absorbance bands near 1080, 790, 540, 450 and 990 cm{sup −1}. TG analysis of In-MFI zeolites showed mass losses in three different steps which are attributed to the loss due to adsorbed water molecules and the two types TPA{sup +} cations. Further, the UV–vis (DRS) studies reflected the position of the indium metal in the zeolite framework. Surface area analysis of the synthesized samples was carried out to characterize the synthesized samples The analysis showed that the specific surface area ranged from ∼357 to ∼361 m{sup 2} g{sup −1} and the pore volume of the synthesized samples ranged from 0.177 to 0.182 cm{sup 3} g{sup −1}. The scanning electron microscopy studies showed the structure of the samples to be rectangular and twinned rectangular shaped. The EDX analysis was carried out for confirmation of Si, Al and In in zeolite frame work. The catalytic activities of

  13. Molecular basis of epithelial Ca2+ and Mg2+ transport: insights from the TRP channel family

    DEFF Research Database (Denmark)

    Dimke, Henrik Anthony; Hoenderop, Joost G J; Bindels, René J M

    2011-01-01

    active transcellular movement of divalent cations from the lumen into the enterocyte. Furthermore, in bone, TRPV channels play important roles by influencing the osteoclastic resorption process, thereby contributing importantly to overall bone mineral content. The divalent cation-permeable TRPV5 and TRPM......Maintenance of plasma Ca(2+) and Mg(2+) levels is of vital importance for many physiological functions. This is achieved via a coordinated interplay between the intestine, bone and kidney by amending the rate of absorption, storage and excretion, respectively. Discovery of the transient receptor...... potential (TRP) family identified several new ion channels acting as gatekeepers of Ca(2+) and Mg(2+) transport in these epithelia, greatly increasing our understanding of the molecular processes that facilitate the movement of these minerals. In the intestine, TRP channels contribute to the saturable...

  14. Synthesis of chitosan supported palladium nanoparticles and its catalytic activity towards 2-nitrophenol reduction

    Science.gov (United States)

    Dhanavel, S.; Nivethaa, E. A. K.; Esther, G.; Narayanan, V.; Stephen, A.

    2016-05-01

    Chitosan supported Palladium nanoparticles were synthesized by a simple cost effective chemical reduction method using NaBH4. The prepared nanocomposite was characterized by X-Ray diffraction analysis, FESEM and Energy dispersive spectroscopy analysis of X-rays (EDAX). The catalytic performance of the nanocomposite was evaluated on the reduction of 2-Nitrophenol to the 2-Amino phenol with rate constant 1.08 × 10-3 S-1 by NaBH4 using Spectrophotometer.

  15. Catalytic activity of MoS2 nanotubes in the hydrodesulphurization reaction of dibenzothiophene

    OpenAIRE

    F. Leonard-Deepak; R. Pérez-Hernández; Cruz-Reyes, J; Fuentes, S.; M.J. Yacaman

    2011-01-01

    In the need for developing better fuels and as a consequence better hydrodesulphurization catalysts (HDS), new generations of catalysts are necessary to reduce substantially the sulfur content in diesel and gasoline fuels. HDS are catalytic processes that involve Mo or W- based catalysts, often doped with other transition metals. We synthesized MoS 2 nanotubes by reacting MoO 3 with thiourea and used them as catalysts for the hydrodesulfurization of dibenzothiophene in a batch reactor. X-ray ...

  16. Catalytic activities of ultra-small β-FeOOH nanorods in ozonation of 4-chlorophenol.

    Science.gov (United States)

    Oputu, Ogheneochuko; Chowdhury, Mahabubur; Nyamayaro, Kudzanai; Fatoki, Olalekan; Fester, Veruscha

    2015-09-01

    We report the catalytic properties of ultra-small β-FeOOH nanorods in ozonation of 4-chlorophenol (4-CP). XRD, TEM, EDS, SAED, FTIR and BET were used to characterize the prepared material. Interaction between O3 and β-FeOOH was evident from the FTIR spectra. The removal efficiency of 4-CP was significantly enhanced in the presence of β-FeOOH compared to ozone alone. Removal efficiency of 99% and 67% was achieved after 40min in the presence of combined ozone and catalyst and ozone only, respectively. Increasing catalyst load increased COD removal efficiency. Maximum COD removal of 97% was achieved using a catalyst load of 0.1g/100mL of 4-CP solution. Initial 4-CP concentration was not found to be rate limiting below 2×10(-3)mol/L. The catalytic properties of the material during ozonation process were found to be pronounced at lower initial pH of 3.5. Two stage first order kinetics was applied to describe the kinetic behavior of the nanorods at low pH. The first stage of catalytic ozonation was attributed to the heterogeneous surface breakdown of O3 by β-FeOOH, while the second stage was attributed to homogeneous catalysis initiated by reductive dissolution of β-FeOOH at low pH. PMID:26354696

  17. The importance of hinge sequence for loop function and catalytic activity in the reaction catalyzed by triosephosphate isomerase.

    Science.gov (United States)

    Xiang, J; Sun, J; Sampson, N S

    2001-04-01

    We have determined the sequence requirements for the N-terminal protein hinge of the active-site lid of triosephosphate isomerase. The codons for the hinge (PVW) were replaced with a genetic library of all possible 8000 amino acid combinations. The most active of these 8000 mutants were selected using in vivo complementation of a triosephosphate isomerase-deficient strain of Escherichia coli, DF502. Approximately 0.3 % of the mutants complement DF502 with an activity that is between 10 and 70 % of wild-type activity. They all contain Pro at the first position. Furthermore, the sequences of these hinge mutants reveal that hydrophobic packing is very important for efficient formation of the enediol intermediate. However, the reduced catalytic activities observed are not due to increased rates of loop opening. To explore the relationship between the N-terminal and C-terminal hinges, three semi-active mutants from the N-terminal hinge selection experiment (PLH, PHS and PTF), and six active C-terminal hinge mutants from previous work (NSS, LWA, YSL, KTK, NPN, KVA) were combined to form 18 "double-hinge" mutants. The activities of these mutants suggest that the N-terminal and C-terminal hinge structures affect one another. It appears that specific side-chain interactions are important for forming a catalytically active enzyme, but not for preventing release of the unstable enediol intermediate from the active site of the enzyme. The independence of intermediate release on amino acid sequence is consistent with the absence of a "universal" hinge sequence in structurally related enzymes.

  18. Calpain-Mediated Processing of Adenylate Cyclase Toxin Generates a Cytosolic Soluble Catalytically Active N-Terminal Domain.

    Directory of Open Access Journals (Sweden)

    Kepa B Uribe

    Full Text Available Bordetella pertussis, the whooping cough pathogen, secretes several virulence factors among which adenylate cyclase toxin (ACT is essential for establishment of the disease in the respiratory tract. ACT weakens host defenses by suppressing important bactericidal activities of the phagocytic cells. Up to now, it was believed that cell intoxication by ACT was a consequence of the accumulation of abnormally high levels of cAMP, generated exclusively beneath the host plasma membrane by the toxin N-terminal catalytic adenylate cyclase (AC domain, upon its direct translocation across the lipid bilayer. Here we show that host calpain, a calcium-dependent Cys-protease, is activated into the phagocytes by a toxin-triggered calcium rise, resulting in the proteolytic cleavage of the toxin N-terminal domain that releases a catalytically active "soluble AC". The calpain-mediated ACT processing allows trafficking of the "soluble AC" domain into subcellular organella. At least two strategic advantages arise from this singular toxin cleavage, enhancing the specificity of action, and simultaneously preventing an indiscriminate activation of cAMP effectors throughout the cell. The present study provides novel insights into the toxin mechanism of action, as the calpain-mediated toxin processing would confer ACT the capacity for a space- and time-coordinated production of different cAMP "pools", which would play different roles in the cell pathophysiology.

  19. Catalytically active telomerase holoenzyme is assembled in the dense fibrillar component of the nucleolus during S phase.

    Science.gov (United States)

    Lee, Ji Hoon; Lee, Yang Sin; Jeong, Sun Ah; Khadka, Prabhat; Roth, Jürgen; Chung, In Kwon

    2014-02-01

    The maintenance of human telomeres requires the ribonucleoprotein enzyme telomerase, which is composed of telomerase reverse transcriptase (TERT), telomerase RNA component, and several additional proteins for assembly and activity. Telomere elongation by telomerase in human cancer cells involves multiple steps including telomerase RNA biogenesis, holoenzyme assembly, intranuclear trafficking, and telomerase recruitment to telomeres. Although telomerase has been shown to accumulate in Cajal bodies for association with telomeric chromatin, it is unclear where and how the assembly and trafficking of catalytically active telomerase is regulated in the context of nuclear architecture. Here, we show that the catalytically active holoenzyme is initially assembled in the dense fibrillar component of the nucleolus during S phase. The telomerase RNP is retained in nucleoli through the interaction of hTERT with nucleolin, a major nucleolar phosphoprotein. Upon association with TCAB1 in S phase, the telomerase RNP is transported from nucleoli to Cajal bodies, suggesting that TCAB1 acts as an S-phase-specific holoenzyme component. Furthermore, depletion of TCAB1 caused an increase in the amount of telomerase RNP associated with nucleolin. These results suggest that the TCAB1-dependent trafficking of telomerase to Cajal bodies occurs in a step separate from the holoenzyme assembly in nucleoli. Thus, we propose that the dense fibrillar component is the provider of active telomerase RNP for supporting the continued proliferation of cancer and stem cells.

  20. Catalytic activity and effect of modifiers on Ni-based catalysts for the dry reforming of methane

    Energy Technology Data Exchange (ETDEWEB)

    Barroso-Quiroga, Maria Martha; Castro-Luna, Adolfo Eduardo [Facultad de Ingenieria y Ciencias Economico-Sociales INTEQUI-CONICET-UNSL, Av. 25 de Mayo 384 (5730) Villa Mercedes (S.L.) (Argentina)

    2010-06-15

    Ni catalysts supported on different ceramic oxides (Al{sub 2}O{sub 3}, CeO{sub 2}, La{sub 2}O{sub 3}, ZrO{sub 2}) were prepared by wet impregnation. The catalytic behavior toward hydrogen production through the dry reforming of methane using a fixed-bed reactor was evaluated under certain experimental conditions, and the catalyst supported on ZrO{sub 2} showed the highest stable activity during the period of time studied. The catalyst supported on CeO{sub 2} has a relatively good activity, but shows signs of deactivation after a certain time during the reaction. This catalyst was chosen to be studied after the addition of 0.5 wt% Li and K as activity modifiers. The introduction of the alkaline metals produces a reduction of the catalytic activity but a better stability over the reactant conversion time. The reverse water-gas shift reaction influences the global system of reactions, and as the results indicate, should be considered near equilibrium. (author)

  1. Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice.

    Science.gov (United States)

    Wu, Xudong; Indzhykulian, Artur A; Niksch, Paul D; Webber, Roxanna M; Garcia-Gonzalez, Miguel; Watnick, Terry; Zhou, Jing; Vollrath, Melissa A; Corey, David P

    2016-01-01

    Members of the TRP superfamily of ion channels mediate mechanosensation in some organisms, and have been suggested as candidates for the mechanotransduction channel in vertebrate hair cells. Some TRP channels can be ruled out based on lack of an inner ear phenotype in knockout animals or pore properties not similar to the hair-cell channel. Such studies have excluded Trpv4, Trpa1, Trpml3, Trpm1, Trpm3, Trpc1, Trpc3, Trpc5, and Trpc6. However, others remain reasonable candidates. We used data from an RNA-seq analysis of gene expression in hair cells as well as data on TRP channel conductance to narrow the candidate group. We then characterized mice lacking functional Trpm2, Pkd2, Pkd2l1, Pkd2l2 and Pkd1l3, using scanning electron microscopy, auditory brainstem response, permeant dye accumulation, and single-cell electrophysiology. In all of these TRP-deficient mice, and in double and triple knockouts, mechanotransduction persisted. Together with published studies, these results argue against the participation of any of the 33 mouse TRP channels in hair cell transduction. PMID:27196058

  2. Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice.

    Directory of Open Access Journals (Sweden)

    Xudong Wu

    Full Text Available Members of the TRP superfamily of ion channels mediate mechanosensation in some organisms, and have been suggested as candidates for the mechanotransduction channel in vertebrate hair cells. Some TRP channels can be ruled out based on lack of an inner ear phenotype in knockout animals or pore properties not similar to the hair-cell channel. Such studies have excluded Trpv4, Trpa1, Trpml3, Trpm1, Trpm3, Trpc1, Trpc3, Trpc5, and Trpc6. However, others remain reasonable candidates. We used data from an RNA-seq analysis of gene expression in hair cells as well as data on TRP channel conductance to narrow the candidate group. We then characterized mice lacking functional Trpm2, Pkd2, Pkd2l1, Pkd2l2 and Pkd1l3, using scanning electron microscopy, auditory brainstem response, permeant dye accumulation, and single-cell electrophysiology. In all of these TRP-deficient mice, and in double and triple knockouts, mechanotransduction persisted. Together with published studies, these results argue against the participation of any of the 33 mouse TRP channels in hair cell transduction.

  3. Increased biomass yield of Lactococcus lactis by reduced overconsumption of amino acids and increased catalytic activities of enzymes.

    Directory of Open Access Journals (Sweden)

    Kaarel Adamberg

    Full Text Available Steady state cultivation and multidimensional data analysis (metabolic fluxes, absolute proteome, and transcriptome are used to identify parameters that control the increase in biomass yield of Lactococcus lactis from 0.10 to 0.12 C-mol C-mol(-1 with an increase in specific growth rate by 5 times from 0.1 to 0.5 h(-1. Reorganization of amino acid consumption was expressed by the inactivation of the arginine deiminase pathway at a specific growth rate of 0.35 h(-1 followed by reduced over-consumption of pyruvate directed amino acids (asparagine, serine, threonine, alanine and cysteine until almost all consumed amino acids were used only for protein synthesis at maximal specific growth rate. This balanced growth was characterized by a high glycolytic flux carrying up to 87% of the carbon flow and only amino acids that relate to nucleotide synthesis (glutamine, serine and asparagine were consumed in higher amounts than required for cellular protein synthesis. Changes in the proteome were minor (mainly increase in the translation apparatus. Instead, the apparent catalytic activities of enzymes and ribosomes increased by 3.5 times (0.1 vs 0.5 h(-1. The apparent catalytic activities of glycolytic enzymes and ribosomal proteins were seen to follow this regulation pattern while those of enzymes involved in nucleotide metabolism increased more than the specific growth rate (over 5.5 times. Nucleotide synthesis formed the most abundant biomonomer synthetic pathway in the cells with an expenditure of 6% from the total ATP required for biosynthesis. Due to the increase in apparent catalytic activity, ribosome translation was more efficient at higher growth rates as evidenced by a decrease of protein to mRNA ratios. All these effects resulted in a 30% decrease of calculated ATP spilling (0.1 vs 0.5 h(-1. Our results show that bioprocesses can be made more efficient (using a balanced metabolism by varying the growth conditions.

  4. Stable Alkynyl Glycosyl Carbonates: Catalytic Anomeric Activation and Synthesis of a Tridecasaccharide Reminiscent of Mycobacterium tuberculosis Cell Wall Lipoarabinomannan.

    Science.gov (United States)

    Mishra, Bijoyananda; Neralkar, Mahesh; Hotha, Srinivas

    2016-06-27

    Oligosaccharide synthesis is still a challenging task despite the advent of modern glycosidation techniques. Herein, alkynyl glycosyl carbonates are shown to be stable glycosyl donors that can be activated catalytically by gold and silver salts at 25 °C in just 15 min to produce glycosides in excellent yields. Benzoyl glycosyl carbonate donors are solid compounds with a long shelf life. This operationally simple protocol was found to be highly efficient for the synthesis of nucleosides, amino acids, and phenolic and azido glycoconjugates. Repeated use of the carbonate glycosidation method enabled the highly convergent synthesis of tridecaarabinomannan in a rapid manner. PMID:26879797

  5. New Element Organic Frameworks Based on Sn, Sb, and Bi, with Permanent Porosity and High Catalytic Activity

    Directory of Open Access Journals (Sweden)

    Julia Fritsch

    2010-03-01

    Full Text Available We present new element organic frameworks based on Sn, Sb and Bi atoms connected via organic linkers by element-carbon bonds. The open frameworks are characterized by specific surface areas (BET of up to 445 m2 g-1 and a good stability under ambient conditions resulting from a highly hydrophobic inner surface. They show good performance as heterogeneous catalysts in the cyanosylilation of benzaldehyde as a test reaction. Due to their catalytic activity, this class of materials might be able to replace common homogeneous element-organic and often highly toxic catalysts especially in the food industry.

  6. Effect of preparation method on the catalytic activity of Au/CeO_2 for VOCs oxidation

    Institute of Scientific and Technical Information of China (English)

    李锦卫; 黎维彬

    2010-01-01

    The Au/CeO2 catalysts were synthesized by co-precipitation (CP), deposition-precipitation (DP) and metallic colloids deposition (MCD) method, and tested for oxidation of volatile organic compounds (VOCs). It was revealed that the Au/CeO2 catalyst prepared by DP method was the most efficient catalyst towards the total oxidation of toluene. The Au/CeO2 catalysts had obviously high catalytic activity, and the best results was obtained on 3 wt.% Au/CeO2 catalyst prepared by DP method. These catalysts were chara...

  7. Near-Monodisperse Ni-Cu Bimetallic Nanocrystals of Variable Composition: Controlled Synthesis and Catalytic Activity for H2 Generation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yawen; Huang, Wenyu; Habas, Susan E.; Kuhn, John N.; Grass, Michael E.; Yamada, Yusuke; Yang, Peidong; Somorjai, Gabor A.

    2008-07-22

    Near-monodisperse Ni{sub 1-x}Cu{sub x} (x = 0.2-0.8) bimetallic nanocrystals were synthesized by a one-pot thermolysis approach in oleylamine/1-octadecene, using metal acetylacetonates as precursors. The nanocrystals form large-area 2D superlattices, and display a catalytic synergistic effect in the hydrolysis of NaBH{sub 4} to generate H{sub 2} at x = 0.5 in a strongly basic medium. The Ni{sub 0.5}Cu{sub 0.5} nanocrystals show the lowest activation energy, and also exhibit the highest H{sub 2} generation rate at 298 K.

  8. Syntheses, characterizations, and catalytic activities of mesostructured aluminophosphates with tailorable acidity assembled with various preformed zeolite nanoclusters

    KAUST Repository

    Suo, Hongri

    2015-02-25

    © 2015, Springer Science+Business Media New York. A series of ordered hexagonal mesoporous zeolites have been successfully synthesized by the assembly of various preformed aluminosilicates zeolite (MFI, FAU, BEA etc.) with surfactants (cetyltrimethylammonium chloride) under hydrothermal conditions. These unique samples were further characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption, infrared spectroscopy. Characterization results showed that these samples contain primary and secondary structural building units of various zeolites, which may be responsible for their distinguished acidic strength, suggesting that the acidic strength of these mesoporous silicoaluminophosphates could be tailored and controlled. Furthermore, the prepared samples were catalytically active in the cracking of cumene.

  9. Comparison of Two Preparation Methods on Catalytic Activity and Selectivity of Ru-Mo/HZSM5 for Methane Dehydroaromatization

    Directory of Open Access Journals (Sweden)

    Lucia M. Petkovic

    2014-01-01

    Full Text Available Catalytic performance of Mo/HZSM5 and Ru-Mo/HZSM5 catalysts prepared by vaporization-deposition of molybdenum trioxide and impregnation with ammonium heptamolybdate was analyzed in terms of catalyst activity and selectivity, nitrogen physisorption analyses, temperature-programmed oxidation of carbonaceous residues, and temperature-programmed reduction. Vaporization-deposition rendered the catalyst more selective to ethylene and coke than the catalyst prepared by impregnation. This result was assigned to lower interaction of molybdenum carbide with the zeolite acidic sites.

  10. Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation

    International Nuclear Information System (INIS)

    The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with [14C]iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined

  11. Copper sulfide nanoparticle-decorated graphene as a catalytic amplification platform for electrochemical detection of alkaline phosphatase activity.

    Science.gov (United States)

    Peng, Juan; Han, Xiao-Xia; Zhang, Qing-Chun; Yao, Hui-Qin; Gao, Zuo-Ning

    2015-06-01

    Copper sulfide nanoparticle-decorated graphene sheet (CuS/GR) was successfully synthesized and used as a signal amplification platform for electrochemical detection of alkaline phosphatase activity. First, CuS/GR was prepared through a microwave-assisted hydrothermal approach. The CuS/GR nanocomposites exhibited excellent electrocatalytic activity toward the oxidation of ALP hydrolyzed products such as 1-naphthol, which produced a current response. Thus, a catalytic amplification platform based on CuS/GR nanocomposite for electrochemical detection of ALP activity was designed using 1-naphthyl phosphate as a model substrate. The current response increased linearly with ALP concentration from 0.1 to 100 U L(-1) with a detection limit of 0.02 U L(-1). The assay was applied to estimate ALP activity in human serum samples with satisfactory results. This strategy may find widespread and promising applications in other sensing systems that involves ALP.

  12. Simultaneous realization of high catalytic activity and stability for catalytic cracking of n-heptane on highly exposed (010) crystal planes of nanosheet ZSM-5 zeolite.

    Science.gov (United States)

    Xiao, Xia; Zhang, Yaoyuan; Jiang, Guiyuan; Liu, Jia; Han, Shanlei; Zhao, Zhen; Wang, Ruipu; Li, Cong; Xu, Chunming; Duan, Aijun; Wang, Yajun; Liu, Jian; Wei, Yuechang

    2016-08-01

    Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.

  13. Membrane lipid modulations remove divalent open channel block from TRP-like and NMDA channels.

    Science.gov (United States)

    Parnas, Moshe; Katz, Ben; Lev, Shaya; Tzarfaty, Vered; Dadon, Daniela; Gordon-Shaag, Ariela; Metzner, Henry; Yaka, Rami; Minke, Baruch

    2009-02-25

    Open channel block is a process in which ions bound to the inside of a channel pore block the flow of ions through that channel. Repulsion of the blocking ions by depolarization is a known mechanism of open channel block removal. For the NMDA channel, this mechanism is necessary for channel activation and is involved in neuronal plasticity. Several types of transient receptor potential (TRP) channels, including the Drosophila TRP and TRP-like (TRPL) channels, also exhibit open channel block. Therefore, removal of open channel block is necessary for the production of the physiological response to light. Because there is no membrane depolarization before the light response develops, it is not clear how the open channel block is removed, an essential step for the production of a robust light response under physiological conditions. Here we present a novel mechanism to alleviate open channel block in the absence of depolarization by membrane lipid modulations. The results of this study show open channel block removal by membrane lipid modulations in both TRPL and NMDA channels of the photoreceptor cells and CA1 hippocampal neurons, respectively. Removal of open channel block is characterized by an increase in the passage-rate of the blocking cations through the channel pore. We propose that the profound effect of membrane lipid modulations on open channel block alleviation, allows the productions of a robust current in response to light in the absence of depolarization.

  14. Evolutionary divergence in the catalytic activity of the CAM-1, ROR1 and ROR2 kinase domains.

    Directory of Open Access Journals (Sweden)

    Travis W Bainbridge

    Full Text Available Receptor tyrosine kinase-like orphan receptors (ROR 1 and 2 are atypical members of the receptor tyrosine kinase (RTK family and have been associated with several human diseases. The vertebrate RORs contain an ATP binding domain that deviates from the consensus amino acid sequence, although the impact of this deviation on catalytic activity is not known and the kinase function of these receptors remains controversial. Recently, ROR2 was shown to signal through a Wnt responsive, β-catenin independent pathway and suppress a canonical Wnt/β-catenin signal. In this work we demonstrate that both ROR1 and ROR2 kinase domains are catalytically deficient while CAM-1, the C. elegans homolog of ROR, has an active tyrosine kinase domain, suggesting a divergence in the signaling processes of the ROR family during evolution. In addition, we show that substitution of the non-consensus residues from ROR1 or ROR2 into CAM-1 and MuSK markedly reduce kinase activity, while restoration of the consensus residues in ROR does not restore robust kinase function. We further demonstrate that the membrane-bound extracellular domain alone of either ROR1 or ROR2 is sufficient for suppression of canonical Wnt3a signaling, and that this domain can also enhance Wnt5a suppression of Wnt3a signaling. Based on these data, we conclude that human ROR1 and ROR2 are RTK-like pseudokinases.

  15. Green synthesis of gold nanoparticles using Trigonella foenum-graecum and its size-dependent catalytic activity

    Science.gov (United States)

    Aswathy Aromal, S.; Philip, Daizy

    2012-11-01

    The development of new synthesis methods for monodispersed nanocrystals using cheap and nontoxic chemicals, environmentally benign solvents and renewable materials remains a challenge to the scientific community. Most of the current methods involve known protocols which may be potentially harmful to either environment or human health. Recent research has been focused on green synthesis methods to produce new nanomaterials, ecofriendly and safer with sustainable commercial viability. The present work reports the green synthesis of gold nanoparticles using the aqueous extract of fenugreek (Trigonella foenum-graecum) as reducing and protecting agent. The pathway is based on the reduction of AuCl4- by the extract of fenugreek. This method is simple, efficient, economic and nontoxic. Gold nanoparticles having different sizes in the range from 15 to 25 nm could be obtained by controlling the synthesis parameters. The nanoparticles have been characterized by UV-Visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. The high crystallinity of nanoparticles is evident from clear lattice fringes in the HRTEM images, bright circular spots in the SAED pattern and peaks in the XRD pattern. FTIR spectrum indicates the presence of different functional groups present in the biomolecule capping the nanoparticles. The synthesized gold nanoparticles show good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol by excess NaBH4. The catalytic activity is found to be size-dependent, the smaller nanoparticles showing faster activity.

  16. Triosephosphate isomerase of Taenia solium (TTPI): phage display and antibodies as tools for finding target regions to inhibit catalytic activity.

    Science.gov (United States)

    Sanabria-Ayala, Víctor; Belmont, Iaraset; Abraham, Landa

    2015-01-01

    Previous studies demonstrated that antibodies against triosephosphate isomerase of Taenia solium (TTPI) can alter its enzymatic catalysis. In the present study, we used antibodies produced against the NH2-terminal region of TTPI (1/3NH2TTPI) and the phage display technology to find target regions to inhibit TTPI activity. As a first step, we obtained polyclonal antibodies against non-conserved regions from the 1/3NH2TTPI, which had an inhibitory effect of about 74 % on catalytic activity. Afterward, they were used to screen a library of phage-displayed dodecapeptides; as a result, 41 phage mimotope clones were isolated and grouped according to their amino acid sequence, finding the consensus A1 (VPTXPI), A2 (VPTXXI), B (LTPGQ), and D (DPLPR). Antibodies against selected phage mimotope clones were obtained by rabbit's immunization; these ones clearly recognized TTPI by both Western blot and ELISA. However, only the mimotope PDTS16 (DSVTPTSVMAVA) clone, which belongs to the VPTXXI consensus, raised antibodies capable of inhibiting the TTPI catalytic activity in 45 %. Anti-PDTS16 antibodies were confronted to several synthetic peptides that encompass the 1/3NH2TTPI, and they only recognized three, which share the motif FDTLQK belonging to the helix-α1 in TTPI. This suggests that this motif is the main part of the epitope recognized by anti-PDTS16 antibodies and revealed its importance for TTPI catalysis.

  17. Catalytic activity vs. size correlation in platinum catalysts of PEM fuel cells prepared on carbon black by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Nores-Pondal, F.J.; Granada, M.; Corti, H.R. [Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), General Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Vilella, I.M.J.; de Miguel, S.R.; Scelza, O.A. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE), Facultad de Ingenieria Quimica (Universidad Nacional del Litoral) - CONICET, Santiago del Estero 2654, 3000 Santa Fe (Argentina); Troiani, H. [Departamento de Fisica, Centro Atomico Bariloche, Comision Nacional de Energia Atomica (CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2009-10-15

    In this work nanoparticulated platinum catalysts have been prepared on carbon Vulcan XC-72 using three methods starting with chloroplatinic acid as a precursor: (i) formic acid as a reductor agent; (ii) impregnation method followed by reduction in hydrogen atmosphere at moderated temperature; and (iii) microwave-assisted reduction in ethylene glycol. The catalytic and size studies were also performed on a commercial Pt catalyst (E-Tek, De Nora). The characterization of the particle size and distribution was performed by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characterizations of the catalytic and electrocatalytic properties of the catalysts were determined by studying the cyclohexane dehydrogenation reaction (CHD) and the behavior under cyclic voltammetry (CV) in sulfuric acid solutions. The measured electrochemical activity, along with the hydrogen chemisorption of the catalysts allows the estimation of effective particle sizes, which are much larger than those measured by TEM and XRD. The catalysts prepared by reduction with formic acid and ethylene glycol (microwave-assisted) show electrochemical activities very close to those of the commercial catalyst, and are almost insensitive to the Pt dispersion or Pt particle size. The chemical activity in CHD correlates well with the metallic dispersion determined by hydrogen chemisorption, indicating similar accesibility of H{sub 2} and cyclohexane to the catalyst surface. (author)

  18. Effect of Calcination Temperature on Catalytic Activity and Textual Property of Cu/HMOR Catalysts in Dimethyl Ether Carbonylation Reaction

    Institute of Scientific and Technical Information of China (English)

    Xue Zhang; Yu-ping Li; Song-bai Qiu; Tie-jun Wang; Long-long Ma; Qi Zhang; Ming-yue Ding

    2013-01-01

    The effect of calcination temperature on the catalytic activity for the dimethyl ether (DME) carbonylation into methyl acetate (MA) was investigated over mordenite supported copper (Cu/HMOR) prepared by ion-exchange process.The results showed that the catalytic activity was obviously affected by the calcination temperature.The maximal DME conversion of 97.2% and the MA selectivity of 97.9% were obtained over the Cu/HMOR calcined at 430 ℃ under conditions of 210 ℃,1.5 MPa,and GSHV of 4883 h-1.The obtained Cu/HMOR catalysts were characterized by powder X-ray diffraction,N2 absorption,NH3 temperature program desorption,CO temperature program desorption,and Raman techniques.Proper calcination temperature was effective to promote copper ions migration and diffusion,and led the support HMOR to possess more acid activity sites,which exhibited the complete decomposing of copper nitrate,large surface area and optimum micropore structure,more amount of CO adsorption site and proper amount of weak acid centers.

  19. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    Science.gov (United States)

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  20. Highly stable and re-dispersible nano Cu hydrosols with sensitively size-dependent catalytic and antibacterial activities

    Science.gov (United States)

    Zhang, Yu; Zhu, Pengli; Li, Gang; Wang, Wenzhao; Chen, Liang; Lu, Daoqiang Daniel; Sun, Rong; Zhou, Feng; Wong, Chingping

    2015-08-01

    Highly stable monodispersed nano Cu hydrosols were facilely prepared by an aqueous chemical reduction method through selecting copper hydroxide (Cu(OH)2) as the copper precursor, poly(acrylic acid) (PAA) and ethanol amine (EA) as the complexing agents, and hydrazine hydrate as the reducing agent. The size of the obtained Cu colloidal nanoparticles was controlled from 0.96 to 26.26 nm by adjusting the dosage of the copper precursor. Moreover, the highly stable nano Cu hydrosols could be easily concentrated and re-dispersed in water meanwhile maintaining good dispersibility. A model catalytic reaction of reducing p-nitrophenol with NaBH4 in the presence of nano Cu hydrosols with different sizes was performed to set up the relationship between the apparent kinetic rate constant (kapp) and the particle size of Cu catalysts. The experimental results indicate that the corresponding kapp showed an obvious size-dependency. Calculations revealed that kapp was directly proportional to the surface area of Cu catalyst nanoparticles, and also proportional to the reciprocal of the particle size based on the same mass of Cu catalysts. This relationship might be a universal principle for predicting and assessing the catalytic efficiency of Cu nanoparticles. The activation energy (Ea) of this catalytic reaction when using 0.96 nm Cu hydrosol as a catalyst was calculated to be 9.37 kJ mol-1, which is considered an extremely low potential barrier. In addition, the synthesized nano Cu hydrosols showed size-dependent antibacterial activities against Pseudomonas aeruginosa (P. aeruginosa) and the minimal inhibitory concentration of the optimal sample was lower than 5.82 μg L-1.Highly stable monodispersed nano Cu hydrosols were facilely prepared by an aqueous chemical reduction method through selecting copper hydroxide (Cu(OH)2) as the copper precursor, poly(acrylic acid) (PAA) and ethanol amine (EA) as the complexing agents, and hydrazine hydrate as the reducing agent. The size of the

  1. Enhanced Intrinsic Catalytic Activity of λ-MnO2 by Electrochemical Tuning and Oxygen Vacancy Generation.

    Science.gov (United States)

    Lee, Sanghan; Nam, Gyutae; Sun, Jie; Lee, Jang-Soo; Lee, Hyun-Wook; Chen, Wei; Cho, Jaephil; Cui, Yi

    2016-07-18

    Chemically prepared λ-MnO2 has not been intensively studied as a material for metal-air batteries, fuel cells, or supercapacitors because of their relatively poor electrochemical properties compared to α- and δ-MnO2 . Herein, through the electrochemical removal of lithium from LiMn2 O4 , highly crystalline λ-MnO2 was prepared as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of the material was further improved by introducing oxygen vacancies (OVs) that could be achieved by increasing the calcination temperature during LiMn2 O4 synthesis; a concentration of oxygen vacancies in LiMn2 O4 could be characterized by its voltage profile as the cathode in a lithiun-metal half-cell. λ-MnO2-z prepared with the highest OV exhibited the highest diffusion-limited ORR current (5.5 mA cm(-2) ) among a series of λ-MnO2-z electrocatalysts. Furthermore, the number of transferred electrons (n) involved in the ORR was >3.8, indicating a dominant quasi-4-electron pathway. Interestingly, the catalytic performances of the samples were not a function of their surface areas, and instead depended on the concentration of OVs, indicating enhancement in the intrinsic catalytic activity of λ-MnO2 by the generation of OVs. This study demonstrates that differences in the electrochemical behavior of λ-MnO2 depend on the preparation method and provides a mechanism for a unique catalytic behavior of cubic λ-MnO2 . PMID:27254822

  2. Effects of Silylation on Zn-IM5 and Its Catalytic Activity for Butane Aromatization

    Institute of Scientific and Technical Information of China (English)

    Yu Lei; Yi Dezhi; Lu Yannan; Shi Li; Chen Junwen; Meng Xuan

    2016-01-01

    Effects of silylation on surface properties and catalytic performance of Zn-IM5 for butane aromatization were studied in this paper. Collidine-IR and NH3-TPD analyses revealed that the silylation treatment not only decreased the quantity of both strong and weak acid sites but also led to a slightly reduced intensity of weak acidity. Silylation of the catalyst promoted the selec-tivity of BTX by narrowing the channel and cutting the acidity. The effect of temperature of silylation and amount of Si loading were evaluated. The best condition has speciifed a temperature of 50℃and a SiO2 loading of 4.0%.

  3. Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide.

    Science.gov (United States)

    Lu, Zhenpin; Hausmann, Heike; Becker, Sabine; Wegner, Hermann A

    2015-04-29

    A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent. PMID:25871326

  4. The "gate keeper" role of Trp222 determines the enantiopreference of diketoreductase toward 2-chloro-1-phenylethanone.

    Directory of Open Access Journals (Sweden)

    Hairong Ma

    Full Text Available Trp222 of diketoreductase (DKR, an enzyme responsible for reducing a variety of ketones to chiral alcohols, is located at the hydrophobic dimeric interface of the C-terminus. Single substitutions at DKR Trp222 with either canonical (Val, Leu, Met, Phe and Tyr or unnatural amino acids (UAAs (4-cyano-L-phenylalanine, 4-methoxy-L-phenylalanine, 4-phenyl-L-phenyalanine, O-tert-butyl-L-tyrosine inverts the enantiotope preference of the enzyme toward 2-chloro-1-phenylethanone with close side chain correlation. Analyses of enzyme activity, substrate affinity and ternary structure of the mutants revealed that substitution at Trp222 causes a notable change in the overall enzyme structure, and specifically in the entrance tunnel to the active center. The size of residue 222 in DKR is vital to its enantiotope preference. Trp222 serves as a "gate keeper" to control the direction of substrate entry into the active center. Consequently, opposite substrate-binding orientations produce respective alcohol enantiomers.

  5. Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Tonkyn, Russell G.; Kim, Do Heui; Szanyi, Janos; Peden, Charles HF

    2010-10-21

    Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction (SCR) of NOx with NH3 were observed, in comparison to Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C), but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by-products (i.e., NO2 and N2O) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest activity and N2 formation selectivity in the oxidation of NH3. The results of this study strongly suggest that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment systems for either mobile or stationary sources.

  6. Effects of tryptophan starvation on levels of the trp RNA-binding attenuation protein (TRAP) and anti-TRAP regulatory protein and their influence on trp operon expression in Bacillus subtilis.

    Science.gov (United States)

    Yang, Wen-Jen; Yanofsky, Charles

    2005-03-01

    The anti-TRAP protein (AT), encoded by the rtpA gene of Bacillus subtilis, can bind to and inhibit the tryptophan-activated trp RNA-binding attenuation protein (TRAP). AT binding can prevent TRAP from promoting transcription termination in the leader region of the trp operon, thereby increasing trp operon expression. We show here that AT levels continue to increase as tryptophan starvation becomes more severe, whereas the TRAP level remains relatively constant and independent of tryptophan starvation. Assuming that the functional form of AT is a trimer, we estimate that the ratios of AT trimers per TRAP molecule are 0.39 when the cells are grown under mild tryptophan starvation conditions, 0.83 under more severe starvation conditions, and approximately 2.0 when AT is expressed maximally. As the AT level is increased, a corresponding increase is observed in the anthranilate synthase level. When AT is expressed maximally, the anthranilate synthase level is about 70% of the level observed in a strain lacking TRAP. In a nutritional shift experiment where excess phenylalanine and tyrosine could potentially starve cells of tryptophan, both the AT level and anthranilate synthase activity were observed to increase. Expression of the trp operon is clearly influenced by the level of AT. PMID:15743934

  7. Preparation and photo-catalytic activities of FeOOH/ZnO/MMT composite

    Science.gov (United States)

    Zhou, Yao; Liu, Fusheng; Yu, Shitao

    2015-11-01

    Montmorillonite (MMT) was used as the carrier for synthesis of FeOOH and FeOOH/ZnO nano-material. FeOOH and FeOOH/ZnO were synthesized by the aqueous solutions of Fe(NO3)3-HNO3 and Zn(NO3)2-NaOH/Fe(NO3)3-HNO3 with the carrier of montmorillonite respectively. Transmission electron-microscopy (TEM) and X-ray diffraction (XRD) were used to study the morphology form and structure of the nano-materials. TEM was also used to demonstrate that FeOOH/ZnO can be formed with the appropriate interface. According to UV-vis absorption spectra, FeOOH/ZnO has a better response to visible light than FeOOH and ZnO, which indicates there is some coupling effect between FeOOH and ZnO. Pentachlorophenol (PCP) was used as a representative organic pollutant to evaluate the photo-catalytic efficiency of the FeOOH/ZnO and FeOOH catalysts in visible light (λ > 400 nm). The photo-catalytic efficiency of FeOOH/ZnO/MMT is better than FeOOH/MMT. According to FTIR, changes of pH and TOC, the degradation mechanism was also discussed. PCP was degraded to aromatic ketone and chloro-hydrocarbon compounds and then to H2O, CO2 and HCl.

  8. Substrate-mediated enhanced activity of Ru nanoparticles in catalytic hydrogenation of benzene

    KAUST Repository

    Liu, Xin

    2012-01-01

    The impact of carbon substrate-Ru nanoparticle interactions on benzene and hydrogen adsorption that is directly related to the performance in catalytic hydrogenation of benzene has been investigated by first-principles based calculations. The stability of Ru 13 nanoparticles is enhanced by the defective graphene substrate due to the hybridization between the dsp states of the Ru 13 particle with the sp 2 dangling bonds at the defect sites. The local curvature formed at the interface will also raise the Ru atomic diffusion barrier, and prohibit the particle sintering. The strong interfacial interaction results in the shift of averaged d-band center of the deposited Ru nanoparticle, from -1.41 eV for a freestanding Ru 13 particle, to -1.17 eV for the Ru/Graphene composites, and to -1.54 eV on mesocellular foam carbon. Accordingly, the adsorption energies of benzene are increased from -2.53 eV for the Ru/mesocellular foam carbon composites, to -2.62 eV on freestanding Ru 13 particles, to -2.74 eV on Ru/graphene composites. A similar change in hydrogen adsorption is also observed, and all these can be correlated to the shift of the d-band center of the nanoparticle. Thus, Ru nanoparticles graphene composites are expected to exhibit both high stability and superior catalytic performance in hydrogenation of arenes. © 2012 The Royal Society of Chemistry.

  9. FACILE GREEN SYNTHESIS OF GOLD NANOPARTICLES WITH GREAT CATALYTIC ACTIVITY USING ULVA FASCIATA

    Directory of Open Access Journals (Sweden)

    V. Sugantha Kumari

    2014-03-01

    Full Text Available We report a facile, green, and high yielding approache for the synthesis and stabilization of monodisperse gold nanoparticles (AuNPs using green seaweed Ulva fasciata extract. Characterization of the obtained AuNPs was performed using UV-visible, Fourier transform infrared (FTIR, X-ray diffraction (XRD and transmission electron microscopy (TEM. UV-visible absorption spectroscopy was used to determine the yield of the gold nanoparticles. The UV-visible absorption spectrum showed a characteristic optical peak of AuNPs at 541 nm. The X-ray diffraction pattern suggested the formation and crystallinity of AuNPs. Spherical AuNPs synthesized with an average particle size of 10 ± 3 nm were confirmed by TEM. FTIR analysis supported the role of phytochemicals of Ulva fasciata extract for bioreduction and stabilization of AuNPs. Moreover, the synthesized AuNPs exhibit remarkable catalytic efficiency by using the reduction of 4-nitroaniline by potassium borohydride in aqueous solution using UV-visible absorption spectroscopy. Catalytic reduction followed pseudo-first-order kinetics with respect to 4-Nitrophenol.

  10. Observation of Different Catalytic Activity of Various 1-Olefins during Ethylene/1-Olefin Copolymerization with Homogeneous Metallocene Catalysts

    Directory of Open Access Journals (Sweden)

    Mingkwan Wannaborworn

    2011-01-01

    Full Text Available This research aimed to investigate the copolymerization of ethylene and various 1-olefins. The comonomer lengths were varied from 1-hexene (1-C6 up to 1-octadecene (1-C18 in order to study the effect of comonomer chain length on the activity and properties of the polymer in the metallocene/MAO catalyst system. The results indicated that two distinct cases can be described for the effect of 1-olefin chain length on the activity. Considering the short chain length comonomers, such as 1-hexene, 1-octene and 1-decene, it is obvious that the polymerization activity decreased when the length of comonomer was higher, which is probably due to increased steric hindrance at the catalytic center hindering the insertion of ethylene monomer to the active sites, hence, the polymerization rate decreased. On the contrary, for the longer chain 1-olefins, namely 1-dodecene, 1-tetradecene and 1-octadecene, an increase in the comonomer chain length resulted in better activity due to the opening of the gap aperture between Cp(centroid-M-Cp-(centroid, which forced the coordination site to open more. This effect facilitated the polymerization of the ethylene monomer at the catalytic sites, and thus, the activity increased. The copolymers obtained were further characterized using thermal analysis, X-ray diffraction spectroscopy and 13C-NMR techniques. It could be seen that the melting temperature and comonomer distribution were not affected by the 1-olefin chain length. The polymer crystallinity decreased slightly with increasing comonomer chain length. Moreover, all the synthesized polymers were typical LLDPE having random comonomer distribution.

  11. Understanding the enhanced catalytic activity of Cu1@Pd3(111) in formic acid dissociation, a theoretical perspective

    Science.gov (United States)

    He, Feng; Li, Kai; Xie, Guangyou; Wang, Ying; Jiao, Menggai; Tang, Hao; Wu, Zhijian

    2016-06-01

    The bimetallic Cu1@Pd3(111) catalyst has been synthesized recently and exhibits better catalytic activity and durability compared with pure Pd(111) as anode catalyst in direct formic acid fuel cells (DFAFCs). In this work, we studied the reaction mechanism of formic acid dissociation on both Pd(111) and Cu1@Pd3(111) by using the density functional method. Our calculations showed that the surface adsorption of the poisoning species CO on Cu1@Pd3(111) is weakened mainly by the strain effect rather than the Cusbnd Pd ligand effect. The Cu1@Pd3(111) can effectively promote the catalytic activity for formic acid dissociation by decreasing the barrier of CO2 formation from the preferential trans-COOH intermediate and increasing the barrier of CO formation from the reduction of CO2. We found that the H atom accumulation, electron accumulation and low electrode potential could accelerate the catalyst deactivation due to the contamination of the poisoning species CO. Furthermore, under low anode potential, the Cu1@Pd3(111) has better durability than pure Pd(111), which can be attributed to the unfavorable CO formation and the favorable CO desorption.

  12. Modeling and Simulation of the Hydrogenation of α-Methylstyrene on Catalytically Active Metal Foams as Tubular Reactor Packing

    Directory of Open Access Journals (Sweden)

    Farzad Lali

    2016-01-01

    Full Text Available This work presents a one-dimensional reactor model for a tubular reactor packed with a catalytically active foam packing with a pore density of 30 PPI in cocurrent upward flow in the example of hydrogenation reaction of α-methylstyrene to cumene. This model includes material, enthalpy, and momentum balances as well as continuity equations. The model was solved within the parameter space applied for experimental studies under assumption of a bubbly flow. The method of orthogonal collocation on finite elements was applied. For isothermal and polytropic processes and steady state conditions, axial profiles for concentration, temperature, fluid velocities, pressure, and liquid holdup were computed and the conversions for various gas and liquid flow rates were validated with experimental results. The obtained results were also compared in terms of space time yield and catalytic activity with experimental results and stirred tank and also with random packed bed reactor. The comparison shows that the application of solid foams as reactor packing is advantageous compared to the monolithic honeycombs and random packed beds.

  13. Preparation and Characterization of Cu loaded TiO2 Nano tube Arrays and their Photo catalytic Activity

    International Nuclear Information System (INIS)

    This paper described the preparation of Cu loaded TiO2 nano tube arrays. Firstly, TiO2 nano tube arrays were formed by anodization. Afterwards, the formed nano tube arrays were incorporated with Cu by wet impregnation method. The soaking time and concentration were varied to obtain an optimum set of parameter for Cu incorporation in TiO2 nano tubes. After anodization, all samples were annealed at 400 degree Celsius for 4 hours to obtain anatase phase. The nano tube arrays were characterized by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD) and x-ray photoelectron spectra (XPS). An average diameter 63.02 nm and length 12.15 μm were obtained for TiO2 nano tubes. The photo catalytic activity of these nano tubes were investigated with methyl orange (MO) and the TiO2 nano tube prepared in 0.01 M of Cu (NO3)2 solution within 3 hours demonstrates the highest photo catalytic activity with 83.6 % degradation of methyl orange. (author)

  14. Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

    Science.gov (United States)

    Wang, Xin; Zhao, Zhe; Ou, Dingrong; Tu, Baofeng; Cui, Daan; Wei, Xuming; Cheng, Mojie

    2016-11-01

    Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported.

  15. High-temperature hydrothermal synthesis of crystalline mesoporous TiO2 with superior photo catalytic activities

    International Nuclear Information System (INIS)

    Mesoporous titanium dioxide with crystalline mesopore walls (M-TiO2-ns) have been successfully synthesized through the self-assembly of poly 4-Vinylpyridine template and tetrabutyl titanate precursor based on their complex bond interaction under high temperature (180 °C) hydrothermal conditions. X-ray diffraction shows that M-TiO2-ns have highly crystalline mesopore walls with anatase phase characters; N2 sorption-desorption isotherms, SEM and TEM images show that M-TiO2-ns have high BET surface areas (85 and 120 m2/g, respectively), large pore volumes (0.32 and 0.34 cm3/g, respectively) and crystalline mesopore walls, which exhibit monolithic morphology with crystal sizes around 3-5 μm. Interestingly, M-TiO2-ns exhibit much higher catalytic activities and good recyclability in both induced reduction of decabromodiphenyl and oxidation of Rhodamine B under UV light than those of nonporous crystalline TiO2 and M-TiO2 templated by hydrocarbon surfactant of F127, which is even comparable with that of commercial P25. Combination of the unique characters such as crystallinity, stable mesostructure, large BET surface areas and superior photo catalytic activities make M-TiO2-ns a kind of potentially important material for removing of organic pollutions in environment through green photo irradiation processes.

  16. SIRT1 catalytic activity has little effect on tumor formation and metastases in a mouse model of breast cancer.

    Directory of Open Access Journals (Sweden)

    Katherine V Clark-Knowles

    Full Text Available The protein deacetylase SIRT1 has been implicated in the regulation of a large number of cellular processes that are thought to be required for cancer initiation and progression. There are conflicting data that make it unclear whether Sirt1 functions as an oncogene or tumor suppressor. To assess the effect of SIRT1 on the emergence and progression of mammary tumors, we crossed mice that harbor a point mutation that abolishes SIRT1 catalytic activity with mice carrying the polyoma middle T transgene driven by the murine mammary tumor virus promoter (MMTV-PyMT. The absence of SIRT1 catalytic activity neither accelerated nor blocked the formation of tumors and metastases in this model. There was a lag in tumor latency that modestly extended survival in Sirt1 mutant mice that we attribute to a delay in mammary gland development and not to a direct effect of SIRT1 on carcinogenesis. These results are consistent with previous evidence suggesting that Sirt1 is not a tumor promoter or a tumor suppressor.

  17. The tumor suppressor gene Trp53 protects the mouse lens against posterior subcapsular cataracts and the BMP receptor Acvr1 acts as a tumor suppressor in the lens

    Directory of Open Access Journals (Sweden)

    Luke A. Wiley

    2011-07-01

    We previously found that lenses lacking the Acvr1 gene, which encodes a bone morphogenetic protein (BMP receptor, had abnormal proliferation and cell death in epithelial and cortical fiber cells. We tested whether the tumor suppressor protein p53 (encoded by Trp53 affected this phenotype. Acvr1 conditional knockout (Acvr1CKO mouse fiber cells had increased numbers of nuclei that stained for p53 phosphorylated on serine 15, an indicator of p53 stabilization and activation. Deletion of Trp53 rescued the Acvr1CKO cell death phenotype in embryos and reduced Acvr1-dependent apoptosis in postnatal lenses. However, deletion of Trp53 alone increased the number of fiber cells that failed to withdraw from the cell cycle. Trp53CKO and Acvr1;Trp53DCKO (double conditional knockout, but not Acvr1CKO, lenses developed abnormal collections of cells at the posterior of the lens that resembled posterior subcapsular cataracts. Cells from human posterior subcapsular cataracts had morphological and molecular characteristics similar to the cells at the posterior of mouse lenses lacking Trp53. In Trp53CKO lenses, cells in the posterior plaques did not proliferate but, in Acvr1;Trp53DCKO lenses, many cells in the posterior plaques continued to proliferate, eventually forming vascularized tumor-like masses at the posterior of the lens. We conclude that p53 protects the lens against posterior subcapsular cataract formation by suppressing the proliferation of fiber cells and promoting the death of any fiber cells that enter the cell cycle. Acvr1 acts as a tumor suppressor in the lens. Enhancing p53 function in the lens could contribute to the prevention of steroid- and radiation-induced posterior subcapsular cataracts.

  18. mTOR Ser-2481 Autophosphorylation Monitors mTORC-specific Catalytic Activity and Clarifies Rapamycin Mechanism of Action*

    Science.gov (United States)

    Soliman, Ghada A.; Acosta-Jaquez, Hugo A.; Dunlop, Elaine A.; Ekim, Bilgen; Maj, Nicole E.; Tee, Andrew R.; Fingar, Diane C.

    2010-01-01

    The mammalian target of rapamycin (mTOR) Ser/Thr kinase signals in at least two multiprotein complexes distinguished by their different partners and sensitivities to rapamycin. Acute rapamycin inhibits signaling by mTOR complex 1 (mTORC1) but not mTOR complex 2 (mTORC2), which both promote cell growth, proliferation, and survival. Although mTORC2 regulation remains poorly defined, diverse cellular mitogens activate mTORC1 signaling in a manner that requires sufficient levels of amino acids and cellular energy. Before the identification of distinct mTOR complexes, mTOR was reported to autophosphorylate on Ser-2481 in vivo in a rapamycin- and amino acid-insensitive manner. These results suggested that modulation of mTOR intrinsic catalytic activity does not universally underlie mTOR regulation. Here we re-examine the regulation of mTOR Ser-2481 autophosphorylation (Ser(P)-2481) in vivo by studying mTORC-specific Ser(P)-2481 in mTORC1 and mTORC2, with a primary focus on mTORC1. In contrast to previous work, we find that acute rapamycin and amino acid withdrawal markedly attenuate mTORC1-associated mTOR Ser(P)-2481 in cycling cells. Although insulin stimulates both mTORC1- and mTORC2-associated mTOR Ser(P)-2481 in a phosphatidylinositol 3-kinase-dependent manner, rapamycin acutely inhibits insulin-stimulated mTOR Ser(P)-2481 in mTORC1 but not mTORC2. By interrogating diverse mTORC1 regulatory input, we find that without exception mTORC1-activating signals promote, whereas mTORC1-inhibitory signals decrease mTORC1-associated mTOR Ser(P)-2481. These data suggest that mTORC1- and likely mTORC2-associated mTOR Ser-2481 autophosphorylation directly monitors intrinsic mTORC-specific catalytic activity and reveal that rapamycin inhibits mTORC1 signaling in vivo by reducing mTORC1 catalytic activity. PMID:20022946

  19. Incorporation of lanthanum into SBA-15 and its catalytic activity in trichloroethylene combustion

    Institute of Scientific and Technical Information of China (English)

    LI Dao; CHEN Guoping; WANG Xingyi

    2008-01-01

    s: The direct synthesis of La-SBA- 15 mesoporous material by two-step synthesis method was reported. The effect of pH value dur-ing the process on the incorporation of La into the framework of SBA-15 was investigated, and XRD, UV-vis, FT-IR, and ICP were used to characterize the obtained La-SBA-15. The experimental results showed that a large amount of La could enter SBA-15 framework under suitable pH value while a highly ordered mesostructure of samples containing La was retained. In addition, the obtained La-SBA-15 exhib-ited good catalytic performance in the combustion of trichioroethylene.

  20. Surface Characteristics and Catalytic Activity of Copper Deposited Porous Silicon Powder

    Directory of Open Access Journals (Sweden)

    Muhammad Yusri Abdul Halim

    2014-12-01

    Full Text Available Porous structured silicon or porous silicon (PS powder was prepared by chemical etching of silicon powder in an etchant solution of HF: HNO3: H2O (1:3:5 v/v. An immersion time of 4 min was sufficient for depositing Cu metal from an aqueous solution of CuSO4 in the presence of HF. Scanning electron microscopy (SEM analysis revealed that the Cu particles aggregated upon an increase in metal content from 3.3 wt% to 9.8 wt%. H2-temperature programmed reduction (H2-TPR profiles reveal that re-oxidation of the Cu particles occurs after deposition. Furthermore, the profiles denote the existence of various sizes of Cu metal on the PS. The Cu-PS powders show excellent catalytic reduction on the p-nitrophenol regardless of the Cu loadings.

  1. Catalytic activity of carbon nanotubes in the conversion of aliphatic alcohols

    Science.gov (United States)

    Zhitnev, Yu. N.; Tveritinova, E. A.; Chernyak, S. A.; Savilov, S. V.; Lunin, V. V.

    2016-06-01

    Carbon nanotubes (CNTs) obtained via the catalytic pyrolysis of hexane at 750°C were studied as the catalysts in conversion of C2-C4 alcohols. The efficiency of CNTs as catalysts in dehydration and dehydrogenation of ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol was studied by means of pulse microcatalysis. The surface and structural characteristics of CNTs are investigated via SEM, TEM, DTA, BET, and XPS. CNTs are shown to be effective catalysts in the conversion of alcohols and do not require additional oxidative treatment. The regularities of the conversion of aliphatic alcohols, related to the properties of the CNTs surface and the structure of the alcohols are identified.

  2. Novel Cage-Like Hexanuclear Nickel(II Silsesquioxane. Synthesis, Structure, and Catalytic Activity in Oxidations with Peroxides

    Directory of Open Access Journals (Sweden)

    Alexey N. Bilyachenko

    2016-05-01

    Full Text Available New hexanuclear nickel(II silsesquioxane [(PhSiO1.512(NiO6(NaCl] (1 was synthesized as its dioxane-benzonitrile-water complex (PhSiO1,512(NiO6(NaCl(C4H8O213(PhCN2(H2O2 and studied by X-ray and topological analysis. The compound exhibits cylinder-like type of molecular architecture and represents very rare case of polyhedral complexation of metallasilsesquioxane with benzonitrile. Complex 1 exhibited catalytic activity in activation of such small molecules as light alkanes and alcohols. Namely, oxidation of alcohols with tert-butylhydroperoxide and alkanes with meta-chloroperoxybenzoic acid. The oxidation of methylcyclohexane gave rise to the isomeric ketones and unusual distribution of alcohol isomers.

  3. Catalytic activity correlation of Ni(Ⅱ),Co(Ⅱ) and Pd(Ⅱ)complexes to metal atom net charge

    Institute of Scientific and Technical Information of China (English)

    ZHANG XiongFei; DUAN BaoGen; SUN WenHua; HSU Shaw Ling; YANG XiaoZhen

    2009-01-01

    The metal atom net charge correlation (MANCC) method was developed in prediction of catalyst activity of asymmetric late-transition metal complexes, 2-quinoxalinyl-6-iminopyridine Ni(Ⅱ), 2-imino-1, 10-phenanthroline Co(Ⅱ) and 2-methoxycarbonyl-6-iminopyridine Pd(Ⅱ) complexes, from the net charge of the metal atom for ethylene polymerization. Dreiding force field was modified according to the X-ray diffraction data. We found that the asymmetric structure of the complexes resulted in a charge differ-ence between two halogen atoms coordinated to the metal atom. In order to remove such contribution we introduced the effective charge Qeff which was obtained by the charge equilibration (QEq) approach. The results verified the successful introduction of Qeff and showed that the catalytic activities of dif-ferent complexes are related to central metal atom effective charge.

  4. Catalytic activity correlation of Ni(Ⅱ),Co(Ⅱ) and Pd(Ⅱ) complexes to metal atom net charge

    Institute of Scientific and Technical Information of China (English)

    HSU; Shaw; Ling

    2009-01-01

    The metal atom net charge correlation(MANCC) method was developed in prediction of catalyst activity of asymmetric late-transition metal complexes,2-quinoxalinyl-6-iminopyridine Ni(Ⅱ),2-imino-1,10-phenanthroline Co(Ⅱ) and 2-methoxycarbonyl-6-iminopyridine Pd(Ⅱ) complexes,from the net charge of the metal atom for ethylene polymerization.Dreiding force field was modified according to the X-ray diffraction data.We found that the asymmetric structure of the complexes resulted in a charge differ-ence between two halogen atoms coordinated to the metal atom.In order to remove such contribution we introduced the effective charge Qeff,which was obtained by the charge equilibration(QEq) approach.The results verified the successful introduction of Qeff and showed that the catalytic activities of different complexes are related to central metal atom effective charge.

  5. Gadolinium and ruthenium red attenuate remote hind limb preconditioning-induced cardioprotection: possible role of TRP and especially TRPV channels.

    Science.gov (United States)

    Randhawa, Puneet Kaur; Jaggi, Amteshwar Singh

    2016-08-01

    Remote ischemic preconditioning is a well reported therapeutic strategy that induces cardioprotective effects but the underlying intracellular mechanisms have not been widely explored. The current study was designed to investigate the involvement of TRP and especially TRPV channels in remote hind limb preconditioning-induced cardioprotection. Remote hind limb preconditioning stimulus (4 alternate cycles of inflation and deflation of 5 min each) was delivered using a blood pressure cuff tied on the hind limb of the anesthetized rat. Using Langendorff's system, the heart was perfused and subjected to 30-min ischemia and 120-min reperfusion. The myocardial injury was assessed by measuring infarct size, lactate dehydrogenase (LDH), creatine kinase (CK), LVDP, +dp/dtmax, -dp/dtmin, heart rate, and coronary flow rate. Gadolinium, TRP blocker, and ruthenium red, TRPV channel blocker, were employed as pharmacological tools. Remote hind limb preconditioning significantly reduced the infarct size, LDH release, CK release and improved coronary flow rate, hemodynamic parameters including LVDP, +dp/dtmax, -dp/dtmin, and heart rate. However, gadolinium (7.5 and 15 mg kg(-1)) and ruthenium red (4 and 8 mg kg(-1)) significantly attenuated the cardioprotective effects suggesting the involvement of TRP especially TRPV channels in mediating remote hind limb preconditioning-induced cardioprotection. Remote hind limb preconditioning stimulus possibly activates TRPV channels on the heart or sensory nerve fibers innervating the heart to induce cardioprotective effects. Alternatively, remote hind limb preconditioning stimulus may also activate the mechanosensitive TRP and especially TRPV channels on the sensory nerve fibers innervating the skeletal muscles to trigger cardioprotective neurogenic signaling cascade. The cardioprotective effects of remote hind limb preconditioning may be mediated via activation of mechanosensitive TRP and especially TRPV channels. PMID:27118661

  6. Colorimetric kinetic determination of potassium ions based on the use of a specific aptamer and catalytically active gold nanoparticles

    International Nuclear Information System (INIS)

    We describe a simple, highly sensitive, and selective colorimetric kinetic assay for the determination of potassium(I) by exploiting the specific recognition capability of an appropriate aptamer and catalytic signal amplification by gold nanoparticles (AuNPs). Amplification is based on the reduction of 4-nitrophenol by borohydride which is catalyzed by AuNPs. This leads to a color change of the solution from yellow to colorless, and the color change can be recognized with bare eyes or via photometry. The K(I)-selective aptamer is placed on the AuNPs and forms a tightly bound G-quadruplex with K(I) which partially masks the surface of the AuNPs and prevents 4-nitrophenol to be reduced at the catalytically active surface of the AuNPs. Hence, the rate of decoloration is retarded. The assay displays high selectivity for K(I) over other cations, has a linear response in the 0.1 nM to 10 μM concentration range, and a detection limit as low as 0.06 nM. In addition, these findings pave the way to novel analytical methods based on the use of gold nanoparticle-catalyzed chemical reactions. (author)

  7. One-step preparation of Fe3O4/Pd@polypyrrole composites with enhanced catalytic activity and stability.

    Science.gov (United States)

    Zhang, Hui; Liu, Yang; Wu, Jie; Xin, Baifu

    2016-08-15

    Core/shell Fe3O4/Pd@polypyrrole (PPy) composites with a Fe3O4 core and a PPy shell embedding Pd nanoparticles were prepared in one-step. The diameter of highly dispersed Pd nanoparticles was as small as 2.9nm owing to coordination interaction generated between Pd(2+) ions and amino groups on PPy chains. The outer PPy shell was only 6.8nm: on one hand, the coverage was beneficial to improving the stability of resulting composites; on the other hand, the shell was thin enough to permit free contact between embedding Pd nanoparticles and reactants. Additionally, the as-prepared Fe3O4/Pd@PPy composites displayed good magnetic separation property due to incorporation of Fe3O4 nanospheres. Based on above merits, they served as suitable catalyst candidates. Their catalytic performance and reusability were evaluated by reduction of 4-nitrophenol with sodium borohydride as reducing agent. Compared with traditional Fe3O4/Pd composites, Fe3O4/Pd@PPy composites not only showed superior catalytic activity; but also exhibited much better stability in successive cycling tests.

  8. One-step preparation of Fe3O4/Pd@polypyrrole composites with enhanced catalytic activity and stability.

    Science.gov (United States)

    Zhang, Hui; Liu, Yang; Wu, Jie; Xin, Baifu

    2016-08-15

    Core/shell Fe3O4/Pd@polypyrrole (PPy) composites with a Fe3O4 core and a PPy shell embedding Pd nanoparticles were prepared in one-step. The diameter of highly dispersed Pd nanoparticles was as small as 2.9nm owing to coordination interaction generated between Pd(2+) ions and amino groups on PPy chains. The outer PPy shell was only 6.8nm: on one hand, the coverage was beneficial to improving the stability of resulting composites; on the other hand, the shell was thin enough to permit free contact between embedding Pd nanoparticles and reactants. Additionally, the as-prepared Fe3O4/Pd@PPy composites displayed good magnetic separation property due to incorporation of Fe3O4 nanospheres. Based on above merits, they served as suitable catalyst candidates. Their catalytic performance and reusability were evaluated by reduction of 4-nitrophenol with sodium borohydride as reducing agent. Compared with traditional Fe3O4/Pd composites, Fe3O4/Pd@PPy composites not only showed superior catalytic activity; but also exhibited much better stability in successive cycling tests. PMID:27232537

  9. Synthesis, electronic structure and catalytic activity of ruthenium-iodo-carbonyl complexes with thioether containing NNS donor ligand

    Science.gov (United States)

    Jana, Subrata; Jana, Mahendra Sekhar; Biswas, Sujan; Sinha, Chittaranjan; Mondal, Tapan Kumar

    2014-05-01

    The ruthenium carbonyl complexes 1 and 2 with redox noninnocent NNS donor ligand, 1-methyl-2-{(o-thiomethyl)phenylazo}imidazole (L) have been synthesized and characterized by various analytical and spectroscopic (IR, UV-Vis and 1H NMR) techniques. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.11 V for 1 and 0.76 V for 2 along with two successive one electron ligand reductions. Catalytic activity of the compounds has been investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential. DFT, NBO and TDDFT calculations in DFT/B3LYP/6-31G(d)/lanL2TZ(f) method are employed to interpret the structural and electronic features of the complexes.

  10. Gas cleaning and hydrogen sulfide removal for COREX coal gas by sorption enhanced catalytic oxidation over recyclable activated carbon desulfurizer.

    Science.gov (United States)

    Sun, Tonghua; Shen, Yafei; Jia, Jinping

    2014-02-18

    This paper proposes a novel self-developed JTS-01 desulfurizer and JZC-80 alkaline adsorbent for H2S removal and gas cleaning of the COREX coal gas in small-scale and commercial desulfurizing devices. JTS-01 desulfurizer was loaded with metal oxide (i.e., ferric oxides) catalysts on the surface of activated carbons (AC), and the catalyst capacity was improved dramatically by means of ultrasonically assisted impregnation. Consequently, the sulfur saturation capacity and sulfur capacity breakthrough increased by 30.3% and 27.9%, respectively. The whole desulfurizing process combined selective adsorption with catalytic oxidation. Moreover, JZC-80 adsorbent can effectively remove impurities such as HCl, HF, HCN, and ash in the COREX coal gas, stabilizing the system pressure drop. The JTS-01 desulfurizer and JZC-80 adsorbent have been successfully applied for the COREX coal gas cleaning in the commercial plant at Baosteel, Shanghai. The sulfur capacity of JTS-01 desulfurizer can reach more than 50% in industrial applications. Compared with the conventional dry desulfurization process, the modified AC desulfurizers have more merit, especially in terms of the JTS-01 desulfurizer with higher sulfur capacity and low pressure drop. Thus, this sorption enhanced catalytic desulfurization has promising prospects for H2S removal and other gas cleaning. PMID:24456468

  11. Biogenic synthesis of palladium nanoparticles using Pulicaria glutinosa extract and their catalytic activity towards the Suzuki coupling reaction.

    Science.gov (United States)

    Khan, Mujeeb; Khan, Merajuddin; Kuniyil, Mufsir; Adil, Syed Farooq; Al-Warthan, Abdulrahman; Alkhathlan, Hamad Z; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H

    2014-06-28

    Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report a facile and eco-friendly method for the synthesis of palladium (Pd) nanoparticles (NPs) using an aqueous solution of Pulicaria glutinosa, a plant widely found in a large region of Saudi Arabia, as a bioreductant. The as-prepared Pd NPs were characterized using ultraviolet-visible (UV-vis) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform-infrared spectroscopy (FT-IR). The hydroxyl groups of the plant extract (PE) molecules were found mainly responsible for the reduction and growth of Pd NPs. FT-IR analysis confirmed the dual role of the PE, both as a bioreductant as well as a capping ligand, which stabilizes the surface of Pd NPs. The crystalline nature of the Pd NPs was identified using XRD analysis which confirmed the formation of a face-centered cubic structure (JCPDS: 87-0641, space group: Fm3m (225)). Furthermore, the as-synthesized Pd NPs demonstrated excellent catalytic activity towards the Suzuki coupling reaction under aqueous and aerobic conditions. Kinetic studies of the catalytic reaction monitored using GC confirmed that the reaction completes in less than 5 minutes.

  12. Catalytic activity of phosphorus and steam modified HZSM-5 and the theoretical selection of phosphorus grafting model

    Institute of Scientific and Technical Information of China (English)

    Renqing Lü; Zuogang Cao; Xinhai Liu

    2008-01-01

    The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phospho-rus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction (XRD) results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption (TPD) of ammonia. The oxidation state of phosphorus shown by XPS is +5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type Ⅰ and type Ⅳ, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.

  13. Gas cleaning and hydrogen sulfide removal for COREX coal gas by sorption enhanced catalytic oxidation over recyclable activated carbon desulfurizer.

    Science.gov (United States)

    Sun, Tonghua; Shen, Yafei; Jia, Jinping

    2014-02-18

    This paper proposes a novel self-developed JTS-01 desulfurizer and JZC-80 alkaline adsorbent for H2S removal and gas cleaning of the COREX coal gas in small-scale and commercial desulfurizing devices. JTS-01 desulfurizer was loaded with metal oxide (i.e., ferric oxides) catalysts on the surface of activated carbons (AC), and the catalyst capacity was improved dramatically by means of ultrasonically assisted impregnation. Consequently, the sulfur saturation capacity and sulfur capacity breakthrough increased by 30.3% and 27.9%, respectively. The whole desulfurizing process combined selective adsorption with catalytic oxidation. Moreover, JZC-80 adsorbent can effectively remove impurities such as HCl, HF, HCN, and ash in the COREX coal gas, stabilizing the system pressure drop. The JTS-01 desulfurizer and JZC-80 adsorbent have been successfully applied for the COREX coal gas cleaning in the commercial plant at Baosteel, Shanghai. The sulfur capacity of JTS-01 desulfurizer can reach more than 50% in industrial applications. Compared with the conventional dry desulfurization process, the modified AC desulfurizers have more merit, especially in terms of the JTS-01 desulfurizer with higher sulfur capacity and low pressure drop. Thus, this sorption enhanced catalytic desulfurization has promising prospects for H2S removal and other gas cleaning.

  14. Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.

    Science.gov (United States)

    Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

    2014-08-20

    The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

  15. Preparation of CoFe2O4 Nano crystallites by Solvo thermal Process and Its Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate

    International Nuclear Information System (INIS)

    Nanometer cobalt ferrite (CoFe2O4) was synthesized by polyol-medium solvo thermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Further, the catalytic activity and kinetic parameters of CoFe2O4 nano crystallites on the thermal decomposition behavior of ammonium perchlorate (AP) have been investigated by thermogravimetry and differential scanning calorimetry analysis (TG-DSC). The results imply that the catalytic performance of CoFe2O4 nano crystallites is significant and the decrease in the activation energy and the increase in the rate constant for AP further confirm the enhancement in catalytic activity of CoFe2O4 nano crystallites. A mechanism based on an proton transfer process has also been proposed for AP in the presence of CoFe2O4 nano crystallites.

  16. An Aggressive Hypoxia Related Subpopulation of Melanoma Cells is TRP-2 Negative12

    OpenAIRE

    Lenggenhager, Daniela; Curioni-Fontecedro, Alessandra; Storz, Martina; Shakhova, Olga; Sommer, Lukas; Widmer, Daniel S.; Seifert, Burkhardt; Moch, Holger; Dummer, Reinhard; Mihic-Probst, Daniela

    2014-01-01

    Despite existing vaccination strategies targeting TRP-2, its function is not yet fully understood. TRP-2 is an enzyme involved in melanin biosynthesis and therefore discussed as a differentiation antigen. However, in mice Trp-2 was shown to be expressed in melanocyte stem cells of the hair follicle and therefore also considered as an indicator of stemness. A proper understanding of the TRP-2 function is crucial, considering a vaccination targeting cells with stemness properties would be highl...

  17. Sustainability of the Catalytic Activity of a Silica-Titania Composite (STC) for Long-Term Indoor Air Quality Control

    Science.gov (United States)

    Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.

    2011-01-01

    TiO2-assisted photocatalytic oxidation (PCO) is an emerging technology for indoor air quality control and is also being evaluated as an alternative trace contaminant control technology for crew habitats in space exploration. Though there exists a vast range of literature on the development of photocatalysts and associated reactor systems, including catalyst performance and performance-influencing factors, the critical question of whether photocatalysts can sustain their initial catalytic activity over an extended period of operation has not been adequately addressed. For a catalyst to effectively serve as an air quality control product, it must be rugged enough to withstand exposure to a multitude of low concentration volatile organic compounds (VOCs) over long periods of time with minimal loss of activity. The objective of this study was to determine the functional lifetime of a promising photocatalyst - the silica-titania composite (STC) from Sol Gel Solutions, LLC in a real-world scenario. A bench-scale STC-packed annular reactor under continuous irradiation by a UV-A fluorescent black-light blue lamp ((lambda)max = 365 nm) was exposed to laboratory air continuously at an apparent contact time of 0.27 sand challenged with a known concentration of ethanol periodically to assess any changes in catalytic activity. Laboratory air was also episodically spiked with halocarbons (e.g., octafluoropropane), organosulfur compounds (e.g., sulfur hexafluoride), and organosilicons (e.g., siloxanes) to simulate accidental releases or leaks of such VOCs. Total organic carbon (TOC) loading and contaminant profiles of the laboratory air were also monitored. Changes in STC photocatalytic performance were evaluated using the ethanol mineralization rate, mineralization efficiency, and oxidation intermediate (acetaldehyde) formation. Results provide insights to any potential catalyst poisoning by trace halocarbons and organosulfur compounds.

  18. Influence of different preparation conditions on catalytic activity of ag /gama-al/sub 2/o/sub 3/ for hydrogenation of coal slime pyrolysis

    International Nuclear Information System (INIS)

    This paper, introducing variable conditional factors with Ag/AL/sub 2/O/sub 3/ as catalyst, selects five variables to investigate the influences of experimental conditions on Ag/Al2O/sub 3/ catalytic activity and define the optimal process conditions. These variables include Ag loading amount, calcinations temperature, calcinations time, reduction temperature, reduction time. X ray diffraction (XRD), hydrogen temperature-programmed reduction (TPR), X ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM) were utilized to characterize the catalytic activity of Ag/-Al/sub 2/O/sub 3/, active center structure and state and those of carrier were emphatically studied, In the meantime the effects of active center and carrier on catalytic activity are studied. The results showed that: (1) In the range of 600 degree C-900 degree C, the catalytic activity of Ag/-Al/sub 2/O/sub 3/ with different loading showed little difference when changing loading amount, in the range of 900 degree C-1100 degree C, when the loading was 5%, the catalytic activity was very high; From the XRD and SEM characterizations, when the loading was 5%, it showed strong intensity diffraction peak of Ag crystal, crystal Ag is the most important activity center to promote hydrogen yield. (2) the catalytic activity of Ag/-Al/sub 2/O/sub 3/ at 450 degree C was considerably higher than that at 400 degree C and 500 degree C. By BET, XRD and SEM characterization, it can be seen, the diffraction peaks intensity of Ag crystal at 450 degree C is higher and sharper than that at 400 degree C and 500 degree C and with the increase of calcinations temperature, the specific surface area of catalysts also increased. (3) In the range of 600 degree C - 1000 degree C, the effects of calcinations time can be negligible, while, with temperature higher than 1000 degree C, 4-hour-calcinations-time catalyst exhibits a more noticeable catalytic activity than 3-hour and 5-hour catalyst do; From the XRD

  19. CATALYTIC WET PEROXIDE OXIDATION OF HYDROQUINONE WITH Co(Ⅱ)/ACTIVE CARBON CATALYST LOADED IN STATIC BED

    Institute of Scientific and Technical Information of China (English)

    LI Chunxiang; YAN Yongsheng; XU Wanzhen

    2008-01-01

    Catalysts based on Co(Ⅱ) supported on active carbon were prepared and loaded in static bed.The hydroquinone wouid be degraded completely after treated by Catalytic wet peroxide oxidation method with Co(Ⅱ)/active carbon catalyst.After activate treatment, the active carbon was immerged in cobaltoas nitrate solution, then put into a drying oven, Co(Ⅱ) could be loaded on the micro-surface of carbon.Taking the static bed as the equipment, the absorption of active carbon and catalysis of Co(Ⅱ) was used to reduce activation energy of hydroquinone.Thus hydroquinone could be drastically degraded and the effluent can be drained under the standard.Referring to Fenton reaction mechanism, experiment had been done to study the heterogeneous catalyzed oxidation mechanism of Co(Ⅱ).The degradation rate of hydroquinone effluent could be achieved to 92% when treated in four columns at H2O2 concentration 10%, reaction temperature 40℃, pH 5 and reaction time 2.5h.

  20. CATALYTIC WET PEROXIDE OXIDATION OF HYDROQUINONE WITH Co(II)/ACTIVE CARBON CATALYST LOADED IN STATIC BED

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Catalysts based on Co(II) supported on active carbon were prepared and loaded in static bed. The hydroquinone would be degraded completely after treated by Catalytic wet peroxide oxidation method with Co(II)/active carbon catalyst. After activate treatment, the active carbon was immerged in cobaltous nitrate solution, then put into a drying oven, Co(II) could be loaded on the micro-surface of carbon. Taking the static bed as the equipment, the absorption of active carbon and catalysis of Co(II) was used to reduce activation energy of hydroquinone. Thus hydroquinone could be drastically degraded and the effluent can be drained under the standard. Referring to Fenton reaction mechanism, experiment had been done to study the heterogeneous catalyzed oxidation mechanism of Co(II). The degradation rate of hydroquinone effluent could be achieved to 92% when treated in four columns at H2O2 concentration 10%, reaction temperature 40℃ , pH 5 and reaction time 2.5h.

  1. Catalytic performance of symmetrical and unsymmetrical sulfur-containing pincer complexes: synthesis and tandem catalytic activity of the first PCS-pincer palladium complex

    OpenAIRE

    Gagliardo, M.; Selander, N.; Mehendale, N.C.; van Koten, G; Klein Gebbink, R. J. M.; Szabó, K.J.

    2008-01-01

    The synthesis and catalytic applications of a new aryl-based unsymmetrical PCS-pincer complex are reported. Preparation of the robust air- and moisture-stable PCS-pincer palladium complex 5[X] started from the symmetrical ,-dibromo-meta-xylene and involved the selective substitution of one bromide by PPh2(BH3), followed by substitution of the second bromide by SPh and subsequent introduction of the palladium. The new PCS complexes (5[X]) were employed as catalysts in two important organic tra...

  2. File list: Oth.EmF.10.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.EmF.10.Trp53.AllCell mm9 TFs and others Trp53 Embryonic fibroblast SRX483599,SR...X270554,SRX270556 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.EmF.10.Trp53.AllCell.bed ...

  3. File list: Oth.ALL.20.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.ALL.20.Trp53.AllCell mm9 TFs and others Trp53 All cell types SRX483599,SRX27055...4,SRX335560,SRX270556 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.ALL.20.Trp53.AllCell.bed ...

  4. File list: Oth.ALL.05.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  5. File list: Oth.ALL.50.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.ALL.50.Trp53.AllCell mm9 TFs and others Trp53 All cell types SRX483599,SRX27055...4,SRX335560,SRX270556 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.ALL.50.Trp53.AllCell.bed ...

  6. File list: Oth.EmF.05.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  7. File list: Oth.ALL.10.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  8. File list: Oth.EmF.20.Trp53.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.EmF.20.Trp53.AllCell mm9 TFs and others Trp53 Embryonic fibroblast SRX483599,SR...X270554,SRX270556 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.EmF.20.Trp53.AllCell.bed ...

  9. TrpA1 Regulates Defecation of Food-Borne Pathogens under the Control of the Duox Pathway.

    Directory of Open Access Journals (Sweden)

    Eun Jo Du

    2016-01-01

    Full Text Available Pathogen expulsion from the gut is an important defense strategy against infection, but little is known about how interaction between the intestinal microbiome and host immunity modulates defecation. In Drosophila melanogaster, dual oxidase (Duox kills pathogenic microbes by generating the microbicidal reactive oxygen species (ROS, hypochlorous acid (HOCl in response to bacterially excreted uracil. The physiological function of enzymatically generated HOCl in the gut is, however, unknown aside from its anti-microbial activity. Drosophila TRPA1 is an evolutionarily conserved receptor for reactive chemicals like HOCl, but a role for this molecule in mediating responses to gut microbial content has not been described. Here we identify a molecular mechanism through which bacteria-produced uracil facilitates pathogen-clearing defecation. Ingestion of uracil increases defecation frequency, requiring the Duox pathway and TrpA1. The TrpA1(A transcript spliced with exon10b (TrpA1(A10b that is present in a subset of midgut enteroendocrine cells (EECs is critical for uracil-dependent defecation. TRPA1(A10b heterologously expressed in Xenopus oocytes is an excellent HOCl receptor characterized with elevated sensitivity and fast activation kinetics of macroscopic HOCl-evoked currents compared to those of the alternative TRPA1(A10a isoform. Consistent with TrpA1's role in defecation, uracil-excreting Erwinia carotovora showed higher persistence in TrpA1-deficient guts. Taken together, our results propose that the uracil/Duox pathway promotes bacteria expulsion from the gut through the HOCl-sensitive receptor, TRPA1(A10b, thereby minimizing the chances that bacteria adapt to survive host defense systems.

  10. Effect of Sb Segregation on Conductance and Catalytic Activity at Pt/Sb-Doped SnO2 Interface: A Synergetic Computational and Experimental Study

    DEFF Research Database (Denmark)

    Hu, Qiang; Colmenares Rausseo, Luis César; Martinez, Umberto;

    2015-01-01

    combined computational and experimental study. It was found that Sb-dopant atoms prefer to segregate toward the ATO/Pt interface. The deposited Pt catalysts, interestingly, not only promote Sb segregation, but also suppress the occurrence of Sb3+ species, a charge carrier neutralizer at the interface. The...... addition, the calculation results show that the presence of Sb dopants in ATO has little effect on the catalytic activity of deposited three-layer Pt toward the oxygen reduction reaction, although subsequent alloying of Pt and Sb could lower the corresponding catalytic activity. These findings help to...

  11. Tuning size and catalytic activity of nano-clusters of cobalt oxide

    Indian Academy of Sciences (India)

    R Venkat Narayan; Vinod Kanniah; Aruna Dhathathreyan

    2006-03-01

    Cobalt oxides were prepared by three different methods: (1) by reacting cobalt nitrate with oxalic acid, (2) co-precipitating cobalt nitrate with sodium carbonate, and (3) using sodium dodecyl sulphate as organic surfactant. All three samples were characterized before and after calcination by solvent extraction and the resulting products examined by IR spectroscopy. In the case of method 3, the removal of surfactant was followed by TGA studies. Products from all three methods were identified by XRD. Peaks in low angle XRD indicate the porous nature of the oxides. The morphology of the pores was studied by transmission electron microscopy. Some irregular pore structures were obtained for samples from methods 1 and 2, with an average size of 4-6 nm. Only the product from method 3 using SDS as template showed ordered structure and optimum size, and Brunauer-Emmet-Teller surface areas of the as-prepared, as well as the treated samples, exhibited H3 type hysteresis. The samples from the three methods were used as catalysts in the oxidation reaction of cyclohexane under mild conditions and the catalytic efficiency of the cobalt oxide was comparable with mesoporous cobalt oxides.

  12. Filtres à activité catalytique pour moteur Diesel Catalytic Activity Filters for Diesel Engines

    Directory of Open Access Journals (Sweden)

    Goldenberg E.

    2006-11-01

    Full Text Available A partir de l'examen des normes actuelles et envisagées dans le futur pour limiter les émissions de particules Diesel, et en considérant les propriétés physico-chimiques de ces particules, cet article expose les problèmes posés par la filtration des suies Diesel et leur élimination par combustion sur les différents types de filtres actuellement retenus. La régénération des filtres par combustion catalytique du dépôt est plus particulièrement discutée. From an examination of present regulations and ones being considered for the future to limit particle emissions by diesel engines, and considering the physicochemical properties of such particles, this article describes the problems raised by filtering soot from diesel engines and eliminating it by various types of filters now used. Filter regeneration by catalytic combustion of the deposit is considered in particular.

  13. Properties and catalytic activity of magnetic and acidic ionic liquids: experimental and molecular simulation.

    Science.gov (United States)

    Zhou, Cunshan; Yu, Xiaojie; Ma, Haile; Huang, Xingyi; Zhang, Henan; Jin, Jian

    2014-05-25

    The exploitation of dual functional magnetic and acidic ionic liquids (MAILs) for hydrolysis of cellulose to platform chemicals can solve some practical challenges through easy separation of products and efficient catalyst recyclability. In this work, seven Cnmim/FeCl4 MAILs were synthesized and investigated with combined experimental and molecular dynamics. The MAILs contained FeCl4(-) anions and exhibited a typical hard magnetic materials behavior with rather strong magnetic susceptibilities. These MAILs were stable up to 250-310°C, the decomposition was started up at 250/310-480-810°C in two steps with the formation of the undecomposed residue. The Gibbs energy for the reaction of glucose/xylose conversion to 5-hydroxymethylfurfural by metal chlorides in the CnmimCl ionic liquid was studied using the density functional theory calculations and the results that C3mim/WCl3 may be the most hopeful catalyst. The MAILs have the potential to open up promising new catalytic systems because of their easy product separation and efficient catalyst recyclability. PMID:24708984

  14. Detailed characterization of the cooperative mechanism of Ca(2+) binding and catalytic activation in the Ca(2+) transport (SERCA) ATPase.

    Science.gov (United States)

    Zhang, Z; Lewis, D; Strock, C; Inesi, G; Nakasako, M; Nomura, H; Toyoshima, C

    2000-08-01

    Expression of heterologous SERCA1a ATPase in Cos-1 cells was optimized to yield levels that account for 10-15% of the microsomal protein, as revealed by protein staining on electrophoretic gels. This high level of expression significantly improved our characterization of mutants, including direct measurements of Ca(2+) binding by the ATPase in the absence of ATP, and measurements of various enzyme functions in the presence of ATP or P(i). Mutational analysis distinguished two groups of amino acids within the transmembrane domain: The first group includes Glu771 (M5), Thr799 (M6), Asp800 (M6), and Glu908 (M8), whose individual mutations totally inhibit binding of the two Ca(2+) required for activation of one ATPase molecule. The second group includes Glu309 (M4) and Asn796 (M6), whose individual or combined mutations inhibit binding of only one and the same Ca(2+). The effects of mutations of these amino acids were interpreted in the light of recent information on the ATPase high-resolution structure, explaining the mechanism of Ca(2+) binding and catalytic activation in terms of two cooperative sites. The Glu771, Thr799, and Asp800 side chains contribute prominently to site 1, together with less prominent contributions by Asn768 and Glu908. The Glu309, Asn796, and Asp800 side chains, as well as the Ala305 (and possibly Val304 and Ile307) carbonyl oxygen, contribute to site 2. Sequential binding begins with Ca(2+) occupancy of site 1, followed by transition to a conformation (E') sensitive to Ca(2+) inhibition of enzyme phosphorylation by P(i), but still unable to utilize ATP. The E' conformation accepts the second Ca(2+) on site 2, producing then a conformation (E' ') which is able to utilize ATP. Mutations of residues (Asp813 and Asp818) in the M6/M7 loop reduce Ca(2+) affinity and catalytic turnover, suggesting a strong influence of this loop on the correct positioning of the M6 helix. Mutation of Asp351 (at the catalytic site within the cytosolic domain

  15. Size Control of Iron Oxide Nanoparticles Using Reverse Microemulsion Method: Morphology, Reduction, and Catalytic Activity in CO Hydrogenation

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Housaindokht

    2013-01-01

    Full Text Available Iron oxide nanoparticles were prepared by microemulsion method and evaluated in Fischer-Tropsch synthesis. The precipitation process was performed in a single-phase microemulsion operating region. Different HLB values of surfactant were prepared by mixing of sodium dodecyl sulfate (SDS and Triton X-100. Transmission electron microscopy (TEM, surface area, pore volume, average pore diameter, pore size distribution, and XRD patterns were used to analyze size distribution, shape, and structure of precipitated hematite nanoparticles. Furthermore, temperature programmed reduction (TPR and catalytic activity in CO hydrogenation were implemented to assess the performance of the samples. It was found that methane and CO2 selectivity and also the syngas conversion increased as the HLB value of surfactant decreased. In addition, the selectivity to heavy hydrocarbons and chain growth probability (α decreased by decreasing the catalyst crystal size.

  16. Facile synthesis of catalytically active CeO2-Gd2O3 solid solutions for soot oxidation

    Indian Academy of Sciences (India)

    D Naga Durgasri; T Vinodkumar; Benjaram M Reddy

    2014-03-01

    CeO2-Gd2O3 oxides were synthesized by a modified coprecipitation method and subjected to thermal treatments at different temperatures to understand their thermal behaviour. The obtained samples were characterized by XRD, BET, TEM, Raman and TPR techniques. Catalytic efficiencies for oxygen storage/release capacity (OSC) and soot oxidation were evaluated by a thermogravimetric (TG) method. XRD and Raman results indicated the formation of Ce0.8Gd0.2O2− (CG) solid solutions at lower calcination temperatures, and TEM studies confirmed nanosized nature of the particles. Raman studies further confirmed the presence of oxygen vacancies and lattice defects in the CG sample. TPR measurements indicated a facile reduction of ceria after Gd3+ addition. Activity studies revealed that incorporation of Gd3+ into the ceria matrix favoured the creation of more structural defects, which accelerates the oxidation rate of soot compared to pure ceria.

  17. Postassembly Transformation of a Catalytically Active Composite Material, Pt@ZIF-8, via Solvent-Assisted Linker Exchange.

    Science.gov (United States)

    Stephenson, Casey J; Hupp, Joseph T; Farha, Omar K

    2016-02-15

    2-Methylimidazolate linkers of Pt@ZIF-8 are exchanged with imidazolate using solvent-assisted linker exchange (SALE) to expand the apertures of the parent material and create Pt@SALEM-2. Characterization of the material before and after SALE was performed. Both materials are active as catalysts for the hydrogenation of 1-octene, whereas the hydrogenation of cis-cyclohexene occurred only with Pt@SALEM-2, consistent with larger apertures for the daughter material. The largest substrate, β-pinene, proved to be unreactive with H2 when either material was employed as a candidate catalyst, supporting the contention that substrate molecules, for both composites, must traverse the metal-organic framework component in order to reach the catalytic nanoparticles.

  18. Synthesis and Catalytic Activity of Cu-Incorporated MCM-41 with Spheres-within-a-Sphere Hollow Structure

    Institute of Scientific and Technical Information of China (English)

    SUN Zhen-Hua; WANG Li-Feng; LIU Ping-Ping; SUN Bo; JIANG Da-Zhen; XIAO Feng-Shou

    2006-01-01

    Cu-incorporated ordered hexagonal mesoporous silicates (Cu-MCM-41) with spheres-within-a-sphere hollow structure have been synthesized using thermoreversible polymer hydrogel methylcellulose (MC) and cationic surfactant as co-templates, which have been characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD), ransmission electron micrograph (TEM), and N2 adsorption-desorption isotherms. The obtained results indicate that the morphology of Cu-incorporated MCM-41 materials is "spheres-within-a-sphere" hollow structure,which is very similar to that of the alveolus. In benzene hydroxylation with H2O2, the hollow spheres show much higher catalytic activity than particles of Cu-MCM-41.Keywords hollow sphere, MCM-41, mesoporous material, benzene hydroxylation, hydrogel, methylcellulose E-mail: fsxiao @mail.jlu.edu.cn; Tel.: 0086-431-5168590; Fax: 0086-431-5168624revised and accepted July 5, 2006.

  19. Development of a New Generation of Stable, Tunable, and Catalytically Active Nanoparticles Produced by the Helium Nanodroplet Deposition Method.

    Science.gov (United States)

    Wu, Qiyuan; Ridge, Claron J; Zhao, Shen; Zakharov, Dmitri; Cen, Jiajie; Tong, Xiao; Connors, Eoghan; Su, Dong; Stach, Eric A; Lindsay, C Michael; Orlov, Alexander

    2016-08-01

    Nanoparticles (NPs) are revolutionizing many areas of science and technology, often delivering unprecedented improvements to properties of the conventional materials. However, despite important advances in NPs synthesis and applications, numerous challenges still remain. Development of alternative synthetic method capable of producing very uniform, extremely clean and very stable NPs is urgently needed. If successful, such method can potentially transform several areas of nanoscience, including environmental and energy related catalysis. Here we present the first experimental demonstration of catalytically active NPs synthesis achieved by the helium nanodroplet isolation method. This alternative method of NPs fabrication and deposition produces narrowly distributed, clean, and remarkably stable NPs. The fabrication is achieved inside ultralow temperature, superfluid helium nanodroplets, which can be subsequently deposited onto any substrate. This technique is universal enough to be applied to nearly any element, while achieving high deposition rates for single element as well as composite core-shell NPs. PMID:27409518

  20. Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

    Science.gov (United States)

    Pullamsetty, Ashok; Sundara, Ramaprabhu

    2016-10-01

    Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. PMID:27393888

  1. Increasing the catalytic activity of Bilirubin oxidase from Bacillus pumilus: Importance of host strain and chaperones proteins.

    Science.gov (United States)

    Gounel, Sébastien; Rouhana, Jad; Stines-Chaumeil, Claire; Cadet, Marine; Mano, Nicolas

    2016-07-20

    Aggregation of recombinant proteins into inclusion bodies (IBs) is the main problem of the expression of multicopper oxidase in Escherichia coli. It is usually attributed to inefficient folding of proteins due to the lack of copper and/or unavailability of chaperone proteins. The general strategies reported to overcome this issue have been focused on increasing the intracellular copper concentration. Here we report a complementary method to optimize the expression in E. coli of a promising Bilirubin oxidase (BOD) isolated from Bacillus pumilus. First, as this BOD has a disulfide bridge, we switched E.coli strain from BL21 (DE3) to Origami B (DE3), known to promote the formation of disulfide bridges in the bacterial cytoplasm. In a second step, we investigate the effect of co-expression of chaperone proteins on the protein production and specific activity. Our strategy allowed increasing the final amount of enzyme by 858% and its catalytic rate constant by 83%.

  2. Enhanced catalytic activity of gold nanoparticles doped in a mesoporous organic gel based on polymeric phloroglucinol carboxylic acid-formaldehyde.

    Science.gov (United States)

    Yang, Han; Nagai, Keiji; Abe, Toshiyuki; Homma, Hirofumi; Norimatsu, Takayoshi; Ramaraj, Ramasamy

    2009-09-01

    Gold nanoparticles were supported by a phloroglucinolcarboxylic acid-formaldehyde (PF) gel, a new organic gel with a 30 nm spheroid-like structure. The surface area of the PF gel with gold nanoparticles was 550 m(2)/g. Gold nanoparticles supported on a PF gel exhibited catalytic activity in the reduction of 4-nitrophenol with a reaction rate constant of 7.4 x 10(-3) s(-1), which is high in the reported heterogeneous reaction system. The adsorption behavior of 4-nitrophenol into the gel support was observed by ultraviolet-visible absorption spectroscopy. Gold nanoparticles in the PF network were characterized by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy observation. The high reduction rate would be attributed to the extraction and diffusion of the reactant through the pores of a PF gel support to encounter the highly dispersed gold nanoparticles on the surface and inside the material.

  3. Highly n-Type Titanium Oxide as an Electronically Active Support for Platinum in the Catalytic Oxidation of Carbon Monoxide

    KAUST Repository

    Baker, L. Robert

    2011-08-18

    The role of the oxide-metal interface in determining the activity and selectivity of chemical reactions catalyzed by metal particles on an oxide support is an important topic in science and industry. A proposed mechanism for this strong metal-support interaction is electronic activation of surface adsorbates by charge carriers. Motivated by the goal of using electronic activation to drive nonthermal chemistry, we investigated the ability of the oxide support to mediate charge transfer. We report an approximately 2-fold increase in the turnover rate of catalytic carbon monoxide oxidation on platinum nanoparticles supported on stoichiometric titanium dioxide (TiO2) when the TiO2 is made highly n-type by fluorine (F) doping. However, for nonstoichiometric titanium oxide (TiOX<2) the effect of F on the turnover rate is negligible. Studies of the titanium oxide electronic structure show that the energy of free electrons in the oxide determines the rate of reaction. These results suggest that highly n-type TiO2 electronically activates adsorbed oxygen (O) by electron spillover to form an active O- intermediate. © 2011 American Chemical Society.

  4. Iridium ultrasmall nanoparticles, worm-like chain nanowires, and porous nanodendrites: One-pot solvothermal synthesis and catalytic CO oxidation activity

    Science.gov (United States)

    Zhang, Tao; Li, Shuai-Chen; Zhu, Wei; Ke, Jun; Yu, Jing-Wen; Zhang, Zhi-Ping; Dai, Lin-Xiu; Gu, Jun; Zhang, Ya-Wen

    2016-06-01

    We report a facile one-pot solvothermal synthesis of monodisperse iridium (Ir) ultrasmall (1.5-2.5 nm in diameter) nanoparticles (NPs), worm-like chain nanowires (NWs), and porous nanodendrites (NDs), for which CO oxidation reaction has been employed as a probe reaction to investigate the effects of nanoparticle size and surface-capping organics on the catalytic activities. Time-dependent experiments revealed that an oriented attachment mechanism induced by the strong adsorption of halide anions (Br- and I-) on specific facet of Ir nanoclusters or by decreasing the reduction rate of Ir precursors with changing their concentrations during the synthesis was responsible for the formation of Ir NWs and NDs. Annealing tests indicated that an O2-H2 atmosphere treatment turned out to be an effective measure to clean up the surface-capping organics of Ir NPs supported on commercial SiO2. Catalytic CO oxidation reaction illustrated that a significant improvement in the catalytic activity of CO oxidation reaction was achieved together with the changing of activation energies after such atmosphere treatment for the supported catalysts of the ultrasmall Ir NPs. It is noteworthy that this enhancement in catalytic activity could be ascribed to the changes in the surface status (including populations of Ir species in metallic and oxidized states, removal of surface capping organics, the variety of active sites, and total effective active site number) for the supported nanocatalysts during the atmosphere treatment.

  5. Promoting Effect of CeO2 Addition on Activity and Catalytic Stability in Steam Reforming of Methane over Ni/Al2O3

    International Nuclear Information System (INIS)

    Hydrogen production by steam reforming of methane was studied over Ni catalysts supported on CeO2, Al2O3 and CeO2-Al2O3. These catalysts were prepared using the impregnation method and characterized by XRD. The effect of CeO2 promoter on the catalytic performance of Ni/Al2O3 catalyst for methane steam reforming reaction was investigated. In fact, CeO2 had a positive effect on the catalytic activity in this reaction. Experimental results demonstrated that Ni/CeO2-Al2O3 catalyst showed excellent catalytic activity and high reaction performance. In addition, the effects of reaction temperature and metal content on the conversion of CH4 and H2/CO ratio were also investigated. Results indicated that CH4 conversion increased significantly with the increase of the reaction temperature and metal content. (author)

  6. Molecular basis of TRAP-5'SL RNA interaction in the Bacillus subtilis trp operon transcription attenuation mechanism.

    Science.gov (United States)

    McGraw, Adam P; Mokdad, Ali; Major, François; Bevilacqua, Philip C; Babitzke, Paul

    2009-01-01

    Expression of the Bacillus subtilis trpEDCFBA operon is regulated by the interaction of tryptophan-activated TRAP with 11 (G/U)AG trinucleotide repeats that lie in the leader region of the nascent trp transcript. Bound TRAP prevents folding of an antiterminator structure and favors formation of an overlapping intrinsic terminator hairpin upstream of the trp operon structural genes. A 5'-stem-loop (5'SL) structure that forms just upstream of the triplet repeat region increases the affinity of TRAP-trp RNA interaction, thereby increasing the efficiency of transcription termination. Single-stranded nucleotides in the internal loop and in the hairpin loop of the 5'SL are important for TRAP binding. We show here that altering the distance between these two loops suggests that G7, A8, and A9 from the internal loop and A19 and G20 from the hairpin loop constitute two structurally discrete TRAP-binding regions. Photochemical cross-linking experiments also show that the hairpin loop of the 5'SL is in close proximity to the flexible loop region of TRAP during TRAP-5'SL interaction. The dimensions of B. subtilis TRAP and of a three-dimensional model of the 5'SL generated using the MC-Sym and MC-Fold pipeline imply that the 5'SL binds the protein in an orientation where the helical axis of the 5'SL is perpendicular to the plane of TRAP. This interaction not only increases the affinity of TRAP-trp leader RNA interaction, but also orients the downstream triplet repeats for interaction with the 11 KKR motifs that lie on TRAP's perimeter, increasing the likelihood that TRAP will bind in time to promote termination. PMID:19033375

  7. E. coli histidine triad nucleotide binding protein 1 (ecHinT is a catalytic regulator of D-alanine dehydrogenase (DadA activity in vivo.

    Directory of Open Access Journals (Sweden)

    Sanaa Bardaweel

    Full Text Available Histidine triad nucleotide binding proteins (Hints are highly conserved members of the histidine triad (HIT protein superfamily. Hints comprise the most ancient branch of this superfamily and can be found in Archaea, Bacteria, and Eukaryota. Prokaryotic genomes, including a wide diversity of both gram-negative and gram-positive bacteria, typically have one Hint gene encoded by hinT (ycfF in E. coli. Despite their ubiquity, the foundational reason for the wide-spread conservation of Hints across all kingdoms of life remains a mystery. In this study, we used a combination of phenotypic screening and complementation analyses with wild-type and hinT knock-out Escherichia coli strains to show that catalytically active ecHinT is required in E. coli for growth on D-alanine as a sole carbon source. We demonstrate that the expression of catalytically active ecHinT is essential for the activity of the enzyme D-alanine dehydrogenase (DadA (equivalent to D-amino acid oxidase in eukaryotes, a necessary component of the D-alanine catabolic pathway. Site-directed mutagenesis studies revealed that catalytically active C-terminal mutants of ecHinT are unable to activate DadA activity. In addition, we have designed and synthesized the first cell-permeable inhibitor of ecHinT and demonstrated that the wild-type E. coli treated with the inhibitor exhibited the same phenotype observed for the hinT knock-out strain. These results reveal that the catalytic activity and structure of ecHinT is essential for DadA function and therefore alanine metabolism in E. coli. Moreover, they provide the first biochemical evidence linking the catalytic activity of this ubiquitous protein to the biological function of Hints in Escherichia coli.

  8. Catalytically Active Guanylyl Cyclase B Requires Endoplasmic Reticulum-mediated Glycosylation, and Mutations That Inhibit This Process Cause Dwarfism.

    Science.gov (United States)

    Dickey, Deborah M; Edmund, Aaron B; Otto, Neil M; Chaffee, Thomas S; Robinson, Jerid W; Potter, Lincoln R

    2016-05-20

    C-type natriuretic peptide activation of guanylyl cyclase B (GC-B), also known as natriuretic peptide receptor B or NPR2, stimulates long bone growth, and missense mutations in GC-B cause dwarfism. Four such mutants (L658F, Y708C, R776W, and G959A) bound (125)I-C-type natriuretic peptide on the surface of cells but failed to synthesize cGMP in membrane GC assays. Immunofluorescence microscopy also indicated that the mutant receptors were on the cell surface. All mutant proteins were dephosphorylated and incompletely glycosylated, but dephosphorylation did not explain the inactivation because the mutations inactivated a "constitutively phosphorylated" enzyme. Tunicamycin inhibition of glycosylation in the endoplasmic reticulum or mutation of the Asn-24 glycosylation site decreased GC activity, but neither inhibition of glycosylation in the Golgi by N-acetylglucosaminyltransferase I gene inactivation nor PNGase F deglycosylation of fully processed GC-B reduced GC activity. We conclude that endoplasmic reticulum-mediated glycosylation is required for the formation of an active catalytic, but not ligand-binding domain, and that mutations that inhibit this process cause dwarfism. PMID:26980729

  9. Catalytically Active Guanylyl Cyclase B Requires Endoplasmic Reticulum-mediated Glycosylation, and Mutations That Inhibit This Process Cause Dwarfism.

    Science.gov (United States)

    Dickey, Deborah M; Edmund, Aaron B; Otto, Neil M; Chaffee, Thomas S; Robinson, Jerid W; Potter, Lincoln R

    2016-05-20

    C-type natriuretic peptide activation of guanylyl cyclase B (GC-B), also known as natriuretic peptide receptor B or NPR2, stimulates long bone growth, and missense mutations in GC-B cause dwarfism. Four such mutants (L658F, Y708C, R776W, and G959A) bound (125)I-C-type natriuretic peptide on the surface of cells but failed to synthesize cGMP in membrane GC assays. Immunofluorescence microscopy also indicated that the mutant receptors were on the cell surface. All mutant proteins were dephosphorylated and incompletely glycosylated, but dephosphorylation did not explain the inactivation because the mutations inactivated a "constitutively phosphorylated" enzyme. Tunicamycin inhibition of glycosylation in the endoplasmic reticulum or mutation of the Asn-24 glycosylation site decreased GC activity, but neither inhibition of glycosylation in the Golgi by N-acetylglucosaminyltransferase I gene inactivation nor PNGase F deglycosylation of fully processed GC-B reduced GC activity. We conclude that endoplasmic reticulum-mediated glycosylation is required for the formation of an active catalytic, but not ligand-binding domain, and that mutations that inhibit this process cause dwarfism.

  10. Structural and mechanistic analysis of engineered trichodiene synthase enzymes from Trichoderma harzianum: towards higher catalytic activities empowering sustainable agriculture.

    Science.gov (United States)

    Kumari, Indu; Chaudhary, Nitika; Sandhu, Padmani; Ahmed, Mushtaq; Akhter, Yusuf

    2016-06-01

    Trichoderma spp. are well-known bioagents for the plant growth promotion and pathogen suppression. The beneficial activities of the fungus Trichoderma spp. are attributed to their ability to produce and secrete certain secondary metabolites such as trichodermin that belongs to trichothecene family of molecules. The initial steps of trichodermin biosynthetic pathway in Trichoderma are similar to the trichothecenes from Fusarium sporotrichioides. Trichodiene synthase (TS) encoded by tri5 gene in Trichoderma catalyses the conversion of farnesyl pyrophosphate to trichodiene as reported earlier. In this study, we have carried out a comprehensive comparative sequence and structural analysis of the TS, which revealed the conserved residues involved in catalytic activity of the protein. In silico, modelled tertiary structure of TS protein showed stable structural behaviour during simulations. Two single-substitution mutants, i.e. D109E, D248Y and one double-substitution mutant (D109E and D248Y) of TS with potentially higher activities are screened out. The mutant proteins showed more stability than the wild type, an increased number of electrostatic interactions and better binding energies with the ligand, which further elucidates the amino acid residues involved in the reaction mechanism. These results will lead to devise strategies for higher TS activity to ultimately enhance the trichodermin production by Trichoderma spp. for its better exploitation in the sustainable agricultural practices.

  11. Structural and mechanistic analysis of engineered trichodiene synthase enzymes from Trichoderma harzianum: towards higher catalytic activities empowering sustainable agriculture.

    Science.gov (United States)

    Kumari, Indu; Chaudhary, Nitika; Sandhu, Padmani; Ahmed, Mushtaq; Akhter, Yusuf

    2016-06-01

    Trichoderma spp. are well-known bioagents for the plant growth promotion and pathogen suppression. The beneficial activities of the fungus Trichoderma spp. are attributed to their ability to produce and secrete certain secondary metabolites such as trichodermin that belongs to trichothecene family of molecules. The initial steps of trichodermin biosynthetic pathway in Trichoderma are similar to the trichothecenes from Fusarium sporotrichioides. Trichodiene synthase (TS) encoded by tri5 gene in Trichoderma catalyses the conversion of farnesyl pyrophosphate to trichodiene as reported earlier. In this study, we have carried out a comprehensive comparative sequence and structural analysis of the TS, which revealed the conserved residues involved in catalytic activity of the protein. In silico, modelled tertiary structure of TS protein showed stable structural behaviour during simulations. Two single-substitution mutants, i.e. D109E, D248Y and one double-substitution mutant (D109E and D248Y) of TS with potentially higher activities are screened out. The mutant proteins showed more stability than the wild type, an increased number of electrostatic interactions and better binding energies with the ligand, which further elucidates the amino acid residues involved in the reaction mechanism. These results will lead to devise strategies for higher TS activity to ultimately enhance the trichodermin production by Trichoderma spp. for its better exploitation in the sustainable agricultural practices. PMID:26207800

  12. Drought-Stimulated Activity of Plasma Membrane Nicotinamide Adenine Dinucleotide Phosphate Oxidase and Its Catalytic Properties in Rice

    Institute of Scientific and Technical Information of China (English)

    Zhuang-Qin Duan; Lei Bai; Zhi-Guang Zhao; Guo-Ping Zhang; Fang-Min Cheng; Li-Xi Jiang; Kun-Ming Chen

    2009-01-01

    The activity of plasma membrane (PM) nicoUnamide adenine dinucleotide phosphate (NADPH) oxidase and Its catalytic properties in rice was investigated under drought stress conditions. Drought stress led to decreased leaf relative water content (RWC) and, as a result of drought-induced oxidative stress, the activities of antioxidant enzymes increased significantly. More interestingly, the intensity of applied water stress was correlated with increased production of H_2O_2and O_2~- and elevated activity of PM NADPH oxidase, a key enzyme of reactive oxygen species generation in plants.Histochemlcal analyses also revealed increased H_2O_2 and O_2~- production in drought-stressed leaves. Application of dlphenylene iodonium (DPI), an Inhibitor of PM NADPH oxidasa, did not alleviate drought-induced production of H_2O_2 and O_2~-. Catalysis experiments indicated that the dce PM NADPH oxidass was partially fiavin-dependent. The pH and temperature optima for this enzyme were 9.8 and 40 ℃, respectively. In addition, drought stress enhanced the activity under alkaline pH and high temperature conditions. These results suggest that a complex regulatory mechanism, associated with the NADPH oxidase-H_2O_2 system, is involved in the response of rice to drought stress.

  13. The Ste5 scaffold directs mating signaling by catalytically unlocking the Fus3 MAP kinase for activation.

    Science.gov (United States)

    Good, Matthew; Tang, Grace; Singleton, Julie; Reményi, Attila; Lim, Wendell A

    2009-03-20

    The scaffold protein Ste5 is required to properly direct signaling through the yeast mating pathway to the mitogen-activated protein kinase (MAPK), Fus3. Scaffolds are thought to function by tethering kinase and substrate in proximity. We find, however, that the previously identified Fus3-binding site on Ste5 is not required for signaling, suggesting an alternative mechanism controls Fus3's activation by the MAPKK Ste7. Reconstituting MAPK signaling in vitro, we find that Fus3 is an intrinsically poor substrate for Ste7, although the related filamentation MAPK, Kss1, is an excellent substrate. We identify and structurally characterize a domain in Ste5 that catalytically unlocks Fus3 for phosphorylation by Ste7. This domain selectively increases the k(cat) of Ste7-->Fus3 phosphorylation but has no effect on Ste7-->Kss1 phosphorylation. The dual requirement for both Ste7 and this Ste5 domain in Fus3 activation explains why Fus3 is selectively activated by the mating pathway and not by other pathways that also utilize Ste7. PMID:19303851

  14. Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation

    Energy Technology Data Exchange (ETDEWEB)

    Droux, M.; Miginiac-Maslow, M.; Jacquot, J.P.; Gadal, P.; Crawford, N.A.; Kosower, N.S.; Buchanan, B.B.

    1987-07-01

    The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with (/sup 14/C)iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined.

  15. Tunneling of redox enzymes to design nano-probes for monitoring NAD(+) dependent bio-catalytic activity.

    Science.gov (United States)

    Akshath, Uchangi Satyaprasad; Bhatt, Praveena

    2016-11-15

    Monitoring of bio-catalytic events by using nano-probes is of immense interest due to unique optical properties of metal nanoparticles. In the present study, tunneling of enzyme activity was achieved using redox cofactors namely oxidized cytochrome-c (Cyt-c) and Co-enzyme-Q (Co-Q) immobilized on Quantum dots (QDs) which acted as a bio-probe for NAD(+) dependent dehydrogenase catalyzed reaction. We studied how electron transfer from substrate to non-native electron acceptors can differentially modify photoluminescence properties of CdTe QDs. Two probes were designed, QD-Ox-Cyt-c and QD-Ox-Co-Q, which were found to quench the fluorescence of QDs. However, formaldehyde dehydrogenase (FDH) catalyzed reduction of Cyt-c and Co-Q on the surface of QDs lead to fluorescence turn-on of CdTe QDs. This phenomenon was successfully used for the detection of HCHO in the range of 0.01-100,000ng/mL (LOD of 0.01ng/mL) using both QD-Ox-Cyt-c (R(2)=0.93) and QD-Ox-Co-Q (R(2)=0.96). Further probe performance and stability in samples like milk, wine and fruit juice matrix were studied and we could detect HCHO in range of 0.001-100,000ng/mL (LOD of 0.001ng/mL) with good stability and sensitivity of probe in real samples (R(2)=0.97). Appreciable recovery and detection sensitivity in the presence of metal ions suggests that the developed nano-probes can be used successfully for monitoring dehydrogenase based bio-catalytic events even in the absence of NAD(+). Proposed method is advantageous over classical methods as clean up/ derivatization of samples is not required for formaldehyde detection. PMID:27179565

  16. Pyridine-thermal synthesis and high catalytic activity of CeO2/CuO/CNT nanocomposites

    International Nuclear Information System (INIS)

    Carbon nanotubes (CNTs) were controllably coated with the uninterrupted CuO and CeO2 composite nanoparticles by a facile pyridine-thermal method and the high catalytic performance for CO oxidation was also found. The obtained nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction as well as X-ray photoelectron spectroscopy. It is found that the CuO/CeO2 composite nanoparticles are distributed uniformly on the surface of CNTs and the shell of CeO2/CuO/CNT nanocomposites is made of nanoparticles with a diameter of 30-60 nm. The possible formation mechanism is suggest as follows: the surface of CNTs is modified by the pyridine due to the π-π conjugate role so that the alkaline of pyridine attached on the CNT surface is more enhanced as compared to the one in the bulk solvent, and thus, these pyridines accept the proton from the water molecular preferentially, which result in the formation of the OH- ions around the surface of CNTs. Subsequently, the metal ions such as Ce3+ and Cu2+ in situ react with the OH- ions and the resultant nanoparticles deposit on the surface of CNTs, and finally the CeO2/CuO/CNT nanocomposites are obtained. The T50 depicting the catalytic activity for CO oxidation over CeO2/CuO/CNT nanocomposites can reach ∼113 deg. C, which is much lower than that of CeO2/CNT or CuO/CNT nanocomposites or CNTs.

  17. Synthesis, characterization, electronic structure and catalytic activity of new ruthenium carbonyl complexes of N-[(2-pyridyl)methylidene]-2-aminothiazole

    Science.gov (United States)

    Kundu, Subhankar; Sarkar, Deblina; Jana, Mahendra Sekhar; Pramanik, Ajoy Kumar; Jana, Subrata; Mondal, Tapan Kumar

    2013-03-01

    Reaction of ruthenium carbonyls, [Ru(CO)2Cl2]n/[Ru(CO)4I2] with bidentate Schiffs base ligands derived by the condensation of pyridine-2-carboxaldehyde with 2-aminothiazole in a 1:1 mole ratio in acetonitrile led to the formation of complexes having general formula [Ru(CO)2(L)X2] (X = Cl (1) and I (2)) (L = N-[(2-pyridyl)methylidene]-2-aminothiazole). The compounds have been characterized by various analytical and spectroscopic (IR, electronic and 1H NMR) studies. In acetonitrile solution the complexes exhibit a weak broad metal-ligand to ligand charge transfer (MLLCT) band along with ILCT transitions. The compounds are emissive in room temperature upon excitation in the ILCT band. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.44 V for 1 and 0.94 V for 2. Catalytic activity of these compounds is investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential of the complexes. DFT, NBO and TDDFT calculations are employed to explain the structural and electronic features and to support the spectroscopic assignments.

  18. Is TrpM5 a reliable marker for chemosensory cells? Multiple types of microvillous cells in the main olfactory epithelium of mice

    Directory of Open Access Journals (Sweden)

    Finger Thomas E

    2008-12-01

    Full Text Available Abstract Background In the past, ciliated receptor neurons, basal cells, and supporting cells were considered the principal components of the main olfactory epithelium. Several studies reported the presence of microvillous cells but their function is unknown. A recent report showed cells in the main olfactory epithelium that express the transient receptor potential channel TrpM5 claiming that these cells are chemosensory and that TrpM5 is an intrinsic signaling component of mammalian chemosensory organs. We asked whether the TrpM5-positive cells in the olfactory epithelium are microvillous and whether they belong to a chemosensory system, i.e. are olfactory neurons or trigeminally-innervated solitary chemosensory cells. Results We investigated the main olfactory epithelium of mice at the light and electron microscopic level and describe several subpopulations of microvillous cells. The ultrastructure of the microvillous cells reveals at least three morphologically different types two of which express the TrpM5 channel. None of these cells have an axon that projects to the olfactory bulb. Tests with a large panel of cell markers indicate that the TrpM5-positive cells are not sensory since they express neither neuronal markers nor are contacted by trigeminal nerve fibers. Conclusion We conclude that TrpM5 is not a reliable marker for chemosensory cells. The TrpM5-positive cells of the olfactory epithelium are microvillous and may be chemoresponsive albeit not part of the sensory apparatus. Activity of these microvillous cells may however influence functionality of local elements of the olfactory system.

  19. Absence of telomerase activity and telomerase catalytic subunit mRNA in melanocyte cultures

    OpenAIRE

    Dhaene, K.; Vancoillie, G; Lambert, J.; Naeyaert, J M; Van Marck, E

    2000-01-01

    The classic model of activation of telomerase, for which activity has been found in most cancers including cutaneous malignant melanoma (CMM), dictates that enzyme activity is generated by pathological reactivation of telomerase in telomerase-negative somatic cells. However, recent data demonstrated physiological up-regulation in some normal cell types when established as proliferating cultures, indicating that, in some cancer types, telomerase is expressed by the process of up-regulation in ...

  20. Studies relevant to the catalytic activation of carbon monoxide. Technical progress report, September 1991

    Energy Technology Data Exchange (ETDEWEB)

    Ford, P.C.

    1992-06-04

    Research activity during the 1991--1992 funding period has been concerned with the following topics relevant to carbon monoxide activation. (1) Exploratory studies of water gas shift catalysts heterogenized on polystyrene based polymers. (2) Mechanistic investigation of the nucleophilic activation of CO in metal carbonyl clusters. (3) Application of fast reaction techniques to prepare and to investigate reactive organometallic intermediates relevant to the activation of hydrocarbons toward carbonylation and to the formation of carbon-carbon bonds via the migratory insertion of CO into metal alkyl bonds.

  1. Use of Metallopeptide Based Mimics Demonstrates That the Metalloprotein Nitrile Hydratase Requires Two Oxidized Cysteinates for Catalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Shearer, J.; Callan, P; Amie, J

    2010-01-01

    Nitrile hydratases (NHases) are non-heme Fe{sup III} or non-corrin Co{sup III} containing metalloenzymes that possess an N{sub 2}S{sub 3} ligand environment with nitrogen donors derived from amidates and sulfur donors derived from cysteinates. A closely related enzyme is thiocyanate hydrolase (SCNase), which possesses a nearly identical active-site coordination environment as CoNHase. These enzymes are redox inactive and perform hydrolytic reactions; SCNase hydrolyzes thiocyanate anions while NHase converts nitriles into amides. Herein an active CoNHase metallopeptide mimic, [Co{sup III}NHase-m1] (NHase-m1 = AcNH-CCDLP-CGVYD-PA-COOH), that contains Co{sup III} in a similar N{sub 2}S{sub 3} coordination environment as CoNHase is reported. [Co{sup III}NHase-m1] was characterized by electrospray ionization-mass spectrometry (ESI-MS), gel-permeation chromatography (GPC), Co K-edge X-ray absorption spectroscopy (Co-S: 2.21 {angstrom}; Co-N: 1.93 {angstrom}), vibrational, and optical spectroscopies. We find that [Co{sup III}NHase-m1] will perform the catalytic conversion of acrylonitrile into acrylamide with up to 58 turnovers observed after 18 h at 25 C (pH 8.0). FTIR data used in concert with calculated vibrational data (mPWPW91/aug-cc-TZVPP) demonstrates that the active form of [Co{sup III}NHase-m1] has a ligated SO{sub 2} (? = 1091 cm{sup -1}) moiety and a ligated protonated SO(H) (? = 928 cm{sup -1}) moiety; when only one oxygenated cysteinate ligand (i.e., a mono-SO{sub 2} coordination motif) or the bis-SO{sub 2} coordination motif are found within [Co{sup III}NHase-m1] no catalytic activity is observed. Calculations of the thermodynamics of ligand exchange (B3LYP/aug-cc-TZVPP) suggest that the reason for this is that the SO{sub 2}/SO(H) equatorial ligand motif promotes both water dissociation from the Co{sup III}-center and nitrile coordination to the Co{sup III}-center. In contrast, the under- or overoxidized motifs will either strongly favor a five coordinate Co

  2. A facile strategy for the preparation of ZnS nanoparticles deposited on montmorillonite and their higher catalytic activity for rapidly colorimetric detection of H2O2.

    Science.gov (United States)

    Ding, Yanyuan; Sun, Lifang; Jiang, Yanling; Liu, Shunxiang; Chen, Mingxing; Chen, Miaomiao; Ding, Yanan; Liu, Qingyun

    2016-10-01

    In this paper, ZnS nanoparticles deposited on montmorillonite (ZnS-MMT) were prepared by a facile method at room temperature and characterized by powder X-ray diffraction (XRD), Energy-dispersive X-ray Detector (EDX) and transmission electron microscope (TEM), respectively. Significantly, the as-prepared ZnS-MMT nanocomposites have been proven to possess intrinsic peroxidase-like activity that can rapidly catalyze the reaction of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 and produce a blue color product in less than 30 seconds, which provides a sensitive colorimetric sensor to detect H2O2. Due to the synergistic effects between montmorillonite and ZnS nanoparticles, the obtained ZnS-MMT nanocomposites exhibit higher catalytic activity than that of MMT or ZnS alone. The catalytic behaviors of the ZnS-MMT nanocomposites showed a typical Michaelis-Menten kinetics. The catalytic activity and the catalytic mechanism were investigated using the procedures of steady-state kinetics and hydroxyl radical detection. ESR data revealed that the peroxidase-like activity of ZnS-MMT originated from the generation of OH radicals. PMID:27287113

  3. Synthesis and Catalytic Activity of Ruthenium-Indenylidene Complexes for Olefin Metathesis: Microscale Experiments for the Undergraduate Inorganic or Organometallic Laboratories

    Science.gov (United States)

    Pappenfus, Ted M.; Hermanson, David L.; Ekerholm, Daniel P.; Lilliquist, Stacie L.; Mekoli, Megan L.

    2007-01-01

    A series of experiments for undergraduate laboratory courses (e.g., inorganic, organometallic or advanced organic) have been developed. These experiments focus on understanding the design and catalytic activity of ruthenium-indenylidene complexes for olefin metathesis. Included in the experiments are the syntheses of two ruthenium-indenylidene…

  4. [Standardization of measurement of catalytic activity concentration of enzymes--current situation regarding the external quality assessment program provided by the Japan Medical Association].

    Science.gov (United States)

    Maekawa, Masato

    2010-01-01

    Measurement of the catalytic activity concentration of enzymes has been standardized using a traceability chain, consisting a reference measurement system for enzyme catalytic activity and reference standard-JSCC enzyme. The Japan Medical Association (JMA) has provided an external quality assessment (EQA) survey program for clinical laboratory testing. More than 3,100 clinical laboratories participated in 2008. The EQA program indicated that standardization of the measurement of the catalytic activity concentration of enzymes has been completed for AST, ALT, LD, ALP, gammaGT, and CK in more than 90% laboratories, and for Amy and ChE in nearly 80% of laboratories. Because such a large survey program must use artificial specimens, a matrix effect cannot be avoided, especially in dry chemistry. However, the bias produced by a matrix effect usually has a predictable tendency: it can be corrected. Next, after standardization of the measurement of the catalytic activity concentration of enzymes, we should develop and use common reference intervals. On completing the standardization, we can make standard medical decisions using reference measurement systems and rules.

  5. Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly(ethylene terephthalate):Ⅰ. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

    Institute of Scientific and Technical Information of China (English)

    Dan ZHANG; Shu Yong JIA; Yue WANG; Jie YAO; Yi ZENG; Gong Ying WANG

    2006-01-01

    A novel direct method for preparation of dimethyl carbonate and poly(ethylene terephthalate) from ethylene carbonate and dimethyl terephthalate has been demonstrated in the presence of metal acetate catalysts, lithium acetate dihydrate showed highest catalytic activity with 47.9% yield of dimethyl carbonate. This method was a green chemical process.

  6. Enhanced catalytic performance of zeolite ZSM-5 for conversion of methanol to dimethyl ether by combining alkaline treatment and partial activation

    NARCIS (Netherlands)

    Wei, Ying; de Jongh, Petra E.; Bonati, Matteo L. M.; Law, David J.; Sunley, Glenn J.; de Jong, Krijn P.

    2015-01-01

    Zeolite ZSM-5 (MFI) due to its excellent hydrothermal stability and high catalytic activity for methanol dehydration to dimethyl ether (MID) has been considered for use in combination with a methanol synthesis catalyst, such as Cu/ZnO/Al2O3, in the conversion of syngas to dimethyl ether. However, th

  7. Content of sulfates and their stability – key factors determining the catalytic activity of sulfated zirconia catalysts

    Directory of Open Access Journals (Sweden)

    ALEKSANDRA ZARUBICA

    2007-07-01

    Full Text Available Two series of sulfated zirconia catalysts were synthesized from various precursors using mono- or multi-step sequence preparations under laboratory con­ditions. Their activities/selectivities in the isomerization reaction of n-hexane were correlated to their textural, structural and morphological properties. The slightly higher activity of a commercially sulfated Zr(OH4-based catalyst is in agreement with the differences in the content of SO42-- ions and their thermal stability, textural and structural properties, i.e., crystallite size and possible imperfection of the incor­poration of sulfate groups in the multi-step synthesis of the catalyst having a nitrate origin. The employment of H2 as the carrier gas resulted in no catalytic activity, regardless of the catalyst precursor, preparation method and calcination tempera­ture. When the isomerization reaction was performed under He, the relatively short life-times of all catalyst samples were caused by fast deactivation due to coking in the absence of H2.

  8. Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst.

    Science.gov (United States)

    Baran, Talat; Inanan, Tülden; Menteş, Ayfer

    2016-07-10

    The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, (1)H NMR, (13)C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H2O2 decomposition reaction with considerable high activity using comparatively small loading catalyst (10mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature.

  9. Molecular cloning and catalytic activity of a membrane-bound prenyl diphosphate phosphatase from Croton stellatopilosus Ohba.

    Science.gov (United States)

    Nualkaew, Natsajee; Guennewich, Nils; Springob, Karin; Klamrak, Anuwatchakit; De-Eknamkul, Wanchai; Kutchan, Toni M

    2013-07-01

    Geranylgeraniol (GGOH), a bioactive acyclic diterpene with apoptotic induction activity, is the immediate precursor of the commercial anti-peptic, plaunotol (18-hydroxy geranylgeraniol), which is found in Croton stellatopilosus (Ohba). From this plant, a cDNA encoding a prenyl diphosphate phosphatase (CsPDP), which catalyses the dephosphorylation of geranylgeranyl diphosphate (GGPP) to GGOH, was isolated using a PCR approach. The full-length cDNA contained 888bp and encoded a 33.6 kDa protein (295 amino acids) that was phylogenetically grouped into the phosphatidic acid phosphatase (PAP) enzyme family. The deduced amino acid sequence showed 6 hydrophobic transmembrane regions with 57-85% homology to the sequences of other plant PAPs. The recombinant CsPDP and its 4 truncated constructs exhibited decreasing dephosphorylation activities relative to the lengths of the N-terminal deletions. While the full-length CsPDP successfully performed the two sequential monodephosphorylation steps on GGPP to form GGOH, the larger N-terminal deletion in the truncated enzymes appeared to specifically decrease the catalytic efficiency of the second monodephosphorylation step. The information presented here on the CsPDP cDNA and factors affecting the dephosphorylation activity of its recombinant protein may eventually lead to the discovery of the specific GGPP phosphatase gene and enzyme that are involved in the formation of GGOH in the biosynthetic pathway of plaunotol in C. stellatopilosus.

  10. Catalytic water co-existing with a product peptide in the active site of HIV-1 protease revealed by X-ray structure analysis.

    Directory of Open Access Journals (Sweden)

    Vishal Prashar

    Full Text Available BACKGROUND: It is known that HIV-1 protease is an important target for design of antiviral compounds in the treatment of Acquired Immuno Deficiency Syndrome (AIDS. In this context, understanding the catalytic mechanism of the enzyme is of crucial importance as transition state structure directs inhibitor design. Most mechanistic proposals invoke nucleophilic attack on the scissile peptide bond by a water molecule. But such a water molecule coexisting with any ligand in the active site has not been found so far in the crystal structures. PRINCIPAL FINDINGS: We report here the first observation of the coexistence in the active site, of a water molecule WAT1, along with the carboxyl terminal product (Q product peptide. The product peptide has been generated in situ through cleavage of the full-length substrate. The N-terminal product (P product has diffused out and is replaced by a set of water molecules while the Q product is still held in the active site through hydrogen bonds. The position of WAT1, which hydrogen bonds to both the catalytic aspartates, is different from when there is no substrate bound in the active site. We propose WAT1 to be the position from where catalytic water attacks the scissile peptide bond. Comparison of structures of HIV-1 protease complexed with the same oligopeptide substrate, but at pH 2.0 and at pH 7.0 shows interesting changes in the conformation and hydrogen bonding interactions from the catalytic aspartates. CONCLUSIONS/SIGNIFICANCE: The structure is suggestive of the repositioning, during substrate binding, of the catalytic water for activation and subsequent nucleophilic attack. The structure could be a snap shot of the enzyme active site primed for the next round of catalysis. This structure further suggests that to achieve the goal of designing inhibitors mimicking the transition-state, the hydrogen-bonding pattern between WAT1 and the enzyme should be replicated.

  11. Production of activated carbon and its catalytic application for oxidation of hydrogen sulphide

    Science.gov (United States)

    Azargohar, Ramin

    Hydrogen sulphide is an environmentally hazardous gas which is present in many gas streams associated with oil and gas industry. Oxidation of H 2S to sulphur in air produces no bulky or waste material and requires no further purification. Activated carbon is known as a catalyst for this reaction. In this research, a coal-based precursor (luscar char) and a biomass-based precursor (biochar) were used for production of activated carbons by two common methods of activation: physical and chemical activation in which steam and potassium hydroxide (KOH), respectively, were used. Experiments were designed by the statistical central composite design method. Two models were developed for the BET surface area and reaction yield of each activation process. These models showed the effects of operating conditions, such as activation temperature, mass ratio of activating agent to precursor, activation time, and nitrogen flowrate on the BET surface area and reaction yield for each activation method for each precursor. The optimum operating conditions were calculated using these models to produce activated carbons with relatively large BET surface area (> 500 m2/g) and high reaction yield (> 50 wt %). The BET surface area and reaction yield for activated carbons produced at optimum operating conditions showed maximum 7 and 7.4% difference, respectively, comparing to the values predicted by models. The activated carbons produced at optimum operating conditions were used as the base catalysts for the direct oxidation of 1 mol % hydrogen sulphide in nitrogen to sulphur at the temperature range of 160-205°C and pressure of 700 kPa. Originally activated carbons showed a good potential for oxidation of hydrogen sulphide by their selectivity for sulphur product and low amount of sulphur dioxide production. To improve the performance of steam-activated carbons, the catalysts were modified by acid-treatment followed by thermal desorption. This method increased the break-through times for

  12. Support effects and catalytic trends for water gas shift activity of transition metals

    DEFF Research Database (Denmark)

    Boisen, Astrid; Janssens, T.V.W.; Schumacher, Nana Maria Pii;

    2010-01-01

    CO and atomic oxygen on the metal; the latter is a good measure for the reactivity of the metal towards H2O. Generally, the activity of the catalysts with the Ce0.75Zr0.25O2 support is higher, compared to the corresponding MgAl2O4-supported catalysts. Exceptions are Cu and Au, which have a higher......Water gas shift activity measurements for 12 transition metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Re, Ir, Pt, Au) supported on inert MgAl2O4 and Ce0.75Zr0.25O2 are presented, to elucidate the influence of the active metal and the support. The activity is related to the adsorption energy of molecular...... activity on the MgAl2O4 support and are both characterized by weak CO adsorption. For the MgAl2O4-supported catalysts a volcano-type relation between the activity and the adsorption energy of atomic oxygen on the metal is obtained. The maximum activity is found for metals with a binding energy of oxygen...

  13. Atomization energy approach to the quantitative evaluation of catalytic activities of metal oxides during dehydrogenation of MgH{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Hirate, H., E-mail: hirate@silky.numse.nagoya-u.ac.jp [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8603 (Japan); Morinaga, M.; Yukawa, H. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8603 (Japan); Nakai, H. [Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo, 169-8555 (Japan)

    2011-09-15

    Research highlights: > Study of catalytic reaction on MgH{sub 2} and NaAlH{sub 4} using atomization energy concept. > Quantitative evaluation of catalytic activities of metal oxide for MgH{sub 2}. > Quantitative evaluation of catalytic activities of metal chlorides for NaAlH{sub 4}. > Observation of the O-H stretching mode on Nb{sub 2}O{sub 5}-catalyzed MgH{sub 2} in FT-IR. - Abstract: The hydrogen desorption reaction of magnesium hydride (MgH{sub 2}), MgH{sub 2} {yields} Mg + H{sub 2}, is accelerated by mixing catalytic metal oxides (e.g., Nb{sub 2}O{sub 5}). This catalytic effect is evaluated quantitatively using the atomization energy concept. The measured hydrogen desorption rate increases monotonously with increasing y x {Delta}E{sub O} values of metal oxides, M{sub x}O{sub y}. Here, {Delta}E{sub O,} is the atomization energy for the oxide ion in M{sub x}O{sub y}. This indicates that the oxide ion interacts mainly with hydrogen atom in MgH{sub 2}, in agreement with the observation of the O-H stretching mode in the FT-IR spectra during the dehydrogenation of the Nb{sub 2}O{sub 5}-catalyzed MgH{sub 2}. This approach is also proved to be useful for the catalytic analysis of metal chlorides (e.g., TiCl{sub 3}) on the decomposition reaction of NaAlH{sub 4} expressed as, NaAlH{sub 4} {yields} (1/3)Na{sub 3}AlH{sub 6} + (2/3)Al + H{sub 2}

  14. Human Dcp2: a catalytically active mRNA decapping enzyme located in specific cytoplasmic structures

    OpenAIRE

    van Dijk, Erwin; Cougot, Nicolas; Meyer, Sylke; Babajko, Sylvie; Wahle, Elmar; Séraphin, Bertrand

    2002-01-01

    We have cloned cDNAs for the human homologues of the yeast Dcp1 and Dcp2 factors involved in the major (5′–3′) and NMD mRNA decay pathways. While yeast Dcp1 has been reported to be the decapping enzyme, we show that recombinant human Dcp2 (hDcp2) is enzymatically active. Dcp2 activity appears evolutionarily conserved. Mutational and biochemical analyses indicate that the hDcp2 MutT/Nudix domain mediates this activity. hDcp2 generates m7GDP and 5′-phosphorylated mRNAs that are 5′–3′ exonucleas...

  15. Catalytical Activities of Reconstructed Hemoglobin with Different Central Ions in Prosthetic Group

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-yu; SUN Bao-wei; LI Yuan-zong; CHANG Wen-bao

    2003-01-01

    Hemoglobin(Hb) was de-prosthetized, which was then reconstructed with the prosthetic groups with different central metal ions including Fe(Ⅲ), Co(Ⅱ) and Mn(Ⅱ). The spectral properties along with the catalase and peroxidase activities of the reconstructed hemoglobin were compared with those of Hb and prosthetic groups with different ions. When the central ion is iron, the reconstituted Hb(rHb) has the highest catalase and peroxidase activities. Maybe it is the reason that iron is chosen as the central ion in the prosthetic groups of natural hemoproteins. Different from peroxidase activity, the catalase activity of hemin cannot be enhanced by the microenvironment of apoHb. This result shows that the structure of apoHb is more similar to that of apoHRP than that of apocatalase.

  16. Preparation, characterization and catalytic activity of mesoporous Ag2HPW12O40/SBA-15 and Ag2HPW12O40/TiO2 composites

    International Nuclear Information System (INIS)

    The current study reports the synthesis and characterization of tungstophosphoric acid and its acid silver salt supported on mesoporous molecular sieve SBA-15 and TiO2. Because silver salts are partially insoluble, the SBA-15 and TiO2 supported silver acid salts were prepared by two step sequential impregnations. The synthesized catalysts were characterized by various physicochemical methods such as Fourier transform infrared and Raman spectroscopy, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and nitrogen physisorption at −196 °C. It is observed that both active phases keep their Keggin-type structure after being supported on the supports while their specific surface area is considerably increased by deposition on mesoporous substrates. The results also indicated that the synthesized catalysts retained the morphology specific for each of the supports, while their thermal stability is increased in comparison with their active phases. The catalytic activity of the prepared catalysts was probed for the vapor phase dehydration of ethanol at 300 °C. Results revealed that all the catalysts show considerably improved catalytic activity in comparison to the bulk active phases. - Highlights: • SBA-15 and TiO2 supported Ag2HPW12O40 and H3PW12O40 were prepared. • Active phases are uniformly dispersed without changing morphology of the substrates. • Composites are more thermally stable than active phases. • Composites exhibit high catalytic activity for gas phase ethanol dehydration

  17. 2,4-Dichlorophenol hydroxylase for chlorophenol removal: Substrate specificity and catalytic activity.

    Science.gov (United States)

    Ren, Hejun; Li, Qingchao; Zhan, Yang; Fang, Xuexun; Yu, Dahai

    2016-01-01

    Chlorophenols (CPs) are common environmental pollutants. As such, different treatments have been assessed to facilitate their removal. In this study, 2,4-dichlorophenol (2,4-DCP) hydroxylase was used to systematically investigate the activity and removal ability of 19CP congeners at 25 and 0 °C. Results demonstrated that 2,4-DCP hydroxylase exhibited a broad substrate specificity to CPs. The activities of 2,4-DCP hydroxylase against specific CP congeners, including 3-CP, 2,3,6-trichlorophenol, 2-CP, and 2,3-DCP, were higher than those against 2,4-DCP, which is the preferred substrate of previously reported 2,4-DCP hydroxylase. To verify whether cofactors are necessary to promote hydroxylase activity against CP congeners, we added FAD and found that the added FAD induced a 1.33-fold to 5.13-fold significant increase in hydroxylase activity against different CP congeners. The metabolic pathways of the CP degradation in the enzymatic hydroxylation step were preliminarily proposed on the basis of the analyses of the enzymatic activities against 19CP congeners. We found that the high activity and removal rate of 2,4-DCP hydroxylase against CPs at 0 °C enhance the low-temperature-adaptability of this enzyme to the CP congeners; as such, the proposed removal process may be applied to biochemical, bioremediation, and industrial processes, particularly in cold environments. PMID:26672451

  18. Preparation and Catalytic Activity of SO42-/TiO-La2O3 in Synthesis of Butyl Butyrate

    Institute of Scientific and Technical Information of China (English)

    YANG Shui-jin; LUO Yi; BAI Ai-min; HU Zhen-zhu; CHEN Fang

    2004-01-01

    Butyl butyrate is a very important compound, which is transparent liquid and has the pear,apple flavor. Natural exist is in the fruit, such as apple, pear, banana, grape and strawberry, etc.Primarily used for to prepare the edible spice and is also widely used in industrial intermediate product, solvent and synthetic perfumery. Until now, there are many methods to synthesize it.Conventionally H2SO4 was reported, but it causes many problems, such as the erosion of equipment,easily causes the vice-reaction, difficulty for after-treatment, environment pollution etc. A new environmentally friendly catalyst, SO42-/TiO2-La2O3 was prepared. And catalytic activity of catalyst in esterification of n-butanoic acid and n-butyl alcohol with SO42-/TiO2-La2O3 as catalyst has been no report up to now. Therefore, studying on the synthetic catalyst has theoretical and practical significances. The catalytic activity of catalyst in esterification of n-butanoic acid and n-butyl alcohol was measured.In this paper, we fast reported the preparation of SO42-/riO2-La2O3 and discussed the factors influencing the synthesis catalyst. The catalyst rare earth solid superacid SO42-/TiO2-La2O3 was The precipitate was filtered and washed thoroughly with distilled water until chloride ions were free.furnace at 480 ℃ for 3 h, and finally stored in a desiccator until use.The factors influencing the synthesis were discussed and the best conditions were found out. The experiment indicated that this catalyst has the following advantage. The amount of catalyst was little and getting high yield, its product has a good quanlity and is favour of reducing erosion of equipment, avoiding environment pollution. The optimum conditions are: molar ratio of n-butanoic acid to n-butyl alcohol was 1:1.5, the quantity of catalyst was equal to 1.5% of feed stocks, the reaction temperature was 93-114 ℃, and the reaction time was 1.0 h. Rare earth solid superacid SO42-/TiO2-La2O3 is an excellent catalyst for

  19. Synthesis, Immobilization and Catalytic Activity of a Copper(II Complex with a Chiral Bis(oxazoline

    Directory of Open Access Journals (Sweden)

    Liliana Carneiro

    2014-08-01

    Full Text Available A chiral bis(oxazoline bearing CH2OH groups was synthesized from a commercial bis(oxazoline and characterized by 1H- and 13C-NMR, high resolution ESI-mass spectrometry and FTIR. The corresponding copper(II complex was immobilized onto the surface of a mesoporous carbonaceous material (Starbon® 700 in which the double bonds had been activated via conventional bromination. The materials were characterized by elemental analysis, ICP-OES, XPS, thermogravimetry and nitrogen adsorption at 77 K. The new copper(II bis(oxazoline was tested both in the homogeneous phase and once immobilized onto a carbonaceous support for the kinetic resolution of hydrobenzoin. Both were active, enantioselective and selective in the mono-benzoylation of hydrobenzoin, but better enantioselectivities were obtained in the homogeneous phase. The heterogeneous catalyst could be separated from the reaction media at the end of the reaction and reused in another catalytic cycle, but with loss of product yield and enantioselectivity.

  20. Robust non-carbon titanium nitride nanotubes supported Pt catalyst with enhanced catalytic activity and durability for methanol oxidation reaction

    International Nuclear Information System (INIS)

    By the combination of solvothermal alcoholysis and post-nitriding method, titanium nitride nanotubes (TiN NTs), with high surface area, hollow and interior porous structure are prepared successfully and used at a support for Pt nanoparticles. The TiN NTs supported Pt (Pt/TiN NTs) catalyst displays enhanced activity and durability towards methanol oxidation reaction (MOR) compared with the commercial Pt/C (E-TEK) catalyst. X ray diffraction (XRD), nitrogen adsorption/desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements are performed to investigate the physicochemical properties of the synthesized catalyst. SEM and TEM images reveal that the wall of the TiN NTs is porous and Pt nanoparticles supported on the dendritic TiN nanocrystals exhibit small size and good dispersion. Effects of inherent corrosion-resistant, tubular and porous nanostructures and electron transfer due to the strong metal–support interactions of TiN NTs contribute to the enhanced catalytic activity and stability of Pt/TiN NTs towards the MOR

  1. Biosynthesis of silver nanoparticles using Momordica charantia leaf broth: Evaluation of their innate antimicrobial and catalytic activities.

    Science.gov (United States)

    Ajitha, B; Reddy, Y Ashok Kumar; Reddy, P Sreedhara

    2015-05-01

    Silver nanoparticles (AgNPs) were prepared through green route with the aid of Momordica charantia leaf extract as both reductant and stabilizer. X-ray diffraction pattern (XRD) and selected area electron diffraction (SAED) fringes revealed the structure of AgNPs as face centered cubic (fcc). Morphological studies elucidate the nearly spherical AgNPs formation with particle size in nanoscale. Biosynthesized AgNPs were found to be photoluminescent and UV-Vis absorption spectra showed one surface plasmon resonance peak (SPR) at 424nm attesting the spherical nanoparticles formation. XPS study provides the surface chemical nature and oxidation state of the synthesized nanoparticles. FTIR spectra ascertain the reduction and capping nature of phytoconstituents of leaf extract in AgNPs synthesis. Further, these AgNPs showed effective antimicrobial activity against tested pathogens and thus applicable as potent antimicrobial agent. In addition, the synthesized AgNPs were observed to have an excellent catalytic activity on the reduction of methylene blue by M. charantia which was confirmed by the decrement in maximum absorbance values of methylene blue with respect to time and is ascribed to electron relay effect. PMID:25771428

  2. IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 °C. Part 9: reference procedure for the measurement of catalytic concentration of alkaline phosphatase International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Scientific Division, Committee on Reference Systems of Enzymes (C-RSE) (1)).

    Science.gov (United States)

    Schumann, Gerhard; Klauke, Rainer; Canalias, Francesca; Bossert-Reuther, Steffen; Franck, Paul F H; Gella, F-Javier; Jørgensen, Poul J; Kang, Dongchon; Lessinger, Jean-Marc; Panteghini, Mauro; Ceriotti, Ferruccio

    2011-09-01

    Abstract This paper is the ninth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 °C and the certification of reference preparations. Other parts deal with: Part 1. The concept of reference procedures for the measurement of catalytic activity concentrations of enzymes; Part 2. Reference procedure for the measurement of catalytic concentration of creatine kinase; Part 3. Reference procedure for the measurement of catalytic concentration of lactate dehydrogenase; Part 4. Reference procedure for the measurement of catalytic concentration of alanine aminotransferase; Part 5. Reference procedure for the measurement of catalytic concentration of aspartate aminotransferase; Part 6. Reference procedure for the measurement of catalytic concentration of γ-glutamyltransferase; Part 7. Certification of four reference materials for the determination of enzymatic activity of γ-glutamyltransferase, lactate dehydrogenase, alanine aminotransferase and creatine kinase at 37 °C; Part 8. Reference procedure for the measurement of catalytic concentration of α-amylase. The procedure described here is derived from the previously described 30 °C IFCC reference method. Differences are tabulated and commented on in Appendix 1.

  3. Catalytic irreversible inhibition of bacterial and plant arginine decarboxylase activities by novel substrate and product analogues.

    Science.gov (United States)

    Bitonti, A J; Casara, P J; McCann, P P; Bey, P

    1987-02-15

    Arginine decarboxylase (ADC) activity from Escherichia coli and two plant species (oats and barley) was inhibited by five new substrate (arginine) and product (agmatine) analogues. The five compounds, (E)-alpha-monofluoromethyldehydroarginine (delta-MFMA), alpha-monofluoromethylarginine (MFMA), alpha-monofluoromethylagatine (FMA), alpha-ethynylagmatine (EA) and alpha-allenylagmatine (AA), were all more potent inhibitors of ADC activity than was alpha-difluoromethylarginine (DFMA), the only irreversible inhibitor of this enzyme described previously. The inhibition caused by the five compounds was apparently enzyme-activated and irreversible, since the loss of enzyme activity followed pseudo-first-order kinetics, was time-dependent, the natural substrate of ADC (arginine) blocked the effects of the inhibitors, and the inhibition remained after chromatography of inhibited ADC on Sephadex G-25 or on overnight dialysis of the enzyme. DFMA, FMA, delta-MFMA and MFMA were effective at very low concentrations (10 nM-10 microM) at inhibiting ADC activity in growing E. coli. FMA was also shown to deplete putrescine effectively in E. coli, particularly when combined with an inhibitor of ornithine decarboxylase, alpha-monofluoromethyl-putrescine. The potential uses of the compounds for the study of the role of polyamine biosynthesis in bacteria and plants is discussed.

  4. Genetically engineered synthetic miniaturized versions of Plasmodium falciparum UvrD helicase are catalytically active.

    Science.gov (United States)

    Ansari, Abulaish; Tarique, Mohammed; Tuteja, Renu

    2014-01-01

    Helicases catalyze unwinding of double stranded nucleic acids in an energy-dependent manner. We have reported characterization of UvrD helicase from Plasmodium falciparum. We reported that the N-terminal and C-terminal fragments of PfUvrD contain characteristic ATPase and DNA helicase activities. Here we report the generation and characterization of a genetically engineered version of PfUvrD and its derivatives. This synthetic UvrD (sUD) contains all the conserved domains of PfUvrD but only the intervening linker sequences are shortened. sUD (∼ 45 kDa) and one of its smallest derivative sUDN1N2 (∼ 22 kDa) contain ATPase and DNA helicase activities. sUD and sUDN1N2 can utilize hydrolysis of all the NTPs and dNTPs, can also unwind blunt end duplex DNA substrate and unwind DNA duplex in 3 to 5 direction only. Some of the properties of sUD are similar to the PfUvrD helicase. Mutagenesis in the conserved motif Ia indicate that the mutants sUDM and sUDN1N2M lose all the enzyme activities, which further confirms that these activities are intrinsic to the synthesized proteins. These studies show that for helicase activity only the conserved domains are essentially required and intervening sequences have almost no role. These observations will aid in understanding the unwinding mechanism by a helicase. PMID:24608129

  5. Catalytic activity trends of oxygen reduction reaction for nonaqueous Li-air batteries.

    Science.gov (United States)

    Lu, Yi-Chun; Gasteiger, Hubert A; Shao-Horn, Yang

    2011-11-30

    We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO(4) 1,2-dimethoxyethane via rotating disk electrode measurements. The nonaqueous Li(+)-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a "volcano-type" trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O(2) cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li(+)-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications. PMID:22044022

  6. Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni{sub 2}P supported on active carbon

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yanli [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Sang, Huanxin [Tianjin Academy of Environmental Sciences, Tianjin 300191 (China); Wang, Kang [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang, Xitao, E-mail: wangxt@tju.edu.cn [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2014-10-15

    Graphical abstract: - Highlights: • Ni{sub 2}P catalyst is tested in dehydrogenation of isobutane for the first time. • The effects of Cs promoter on catalytic performance of Ni2P/AC were investigated. • Cs-Ni2P/AC exhibits high activity and selectivity for isobutane dehydrogenation. - Abstract: In this article, an environmentally friendly non-noble-metal class of Cs-Ni{sub 2}P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H{sub 2}-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni{sub 2}P particles, which decreases the strength of Ni-C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni{sub 2}P/AC catalysts display much higher catalytic performance as compared to Ni{sub 2}P/AC catalyst. Cs-Ni{sub 2}P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni{sub 2}P particles, transfer electron from Cs to Ni, and decrease acid site number and strength.

  7. Mechanism of action of ferrocene derivatives on the catalytic activity of topoisomerase IIalpha and beta--distinct mode of action of two derivatives.

    Science.gov (United States)

    Sai Krishna, A D; Panda, Gayatri; Kondapi, Anand K

    2005-06-15

    Topoisomerase II is found to be present in two isoforms alpha and beta, and both the isoforms are regulated in cancerous tissue. Development of isoform-specific topoisomerase II poisons has been of great interest for cancer-specific drug targeting. In the present investigation using quantitative structure-activity analysis of ferrocene derivatives, we show that two derivatives of ferrocene, azalactone ferrocene and thiomorpholide amido methyl ferrocene, can preferentially inhibit topoisomerase IIbeta activity. Thiomorpholide amido methyl ferrocene shows higher inhibition of catalytic activity (IC(50) = 50 microM) against topoisomerase IIbeta compared to azalactone ferrocene (IC(50) = 100 microM). The analysis of protein DNA intermediates formed in the presence of these two compounds suggests that azalactone ferrocene readily induces formation of cleavable complex in a dose-dependent manner, in comparison with thiomorpholide amido methyl ferrocene. Both the compounds show significant inhibition of DNA-dependent ATPase activity of enzyme. These results suggest that azalactone ferrocene inhibits DNA passage activity of enzyme leading to the formation of cleavable complex, while thiomorpholide amido methyl ferrocene competes with ATP binding resulting in the inhibition of catalytic activity of enzyme. In summary, thiomorpholide amido methyl ferrocene and azalactone ferrocene show distinctly different mechanisms in inhibition of catalytic activity of topoisomerase IIbeta. PMID:15907782

  8. The roles of the catalytic and noncatalytic activities of Rpd3L and Rpd3S in the regulation of gene transcription in yeast.

    Directory of Open Access Journals (Sweden)

    Daniella Yeheskely-Hayon

    Full Text Available In budding yeasts, the histone deacetylase Rpd3 resides in two different complexes called Rpd3L (large and Rpd3S (small that exert opposing effects on the transcription of meiosis-specific genes. By introducing mutations that disrupt the integrity and function of either Rpd3L or Rpd3S, we show here that Rpd3 function is determined by its association with either of these complexes. Specifically, the catalytic activity of Rpd3S activates the transcription of the two major positive regulators of meiosis, IME1 and IME2, under all growth conditions and activates the transcription of NDT80 only during vegetative growth. In contrast, the effects of Rpd3L depends on nutrients; it represses or activates transcription in the presence or absence of a nitrogen source, respectively. Further, we show that transcriptional activation does not correlate with histone H4 deacetylation, suggesting an effect on a nonhistone protein. Comparison of rpd3-null and catalytic-site point mutants revealed an inhibitory activity that is independent of either the catalytic activity of Rpd3 or the integrity of Rpd3L and Rpd3S.

  9. Briefly Bound to Activate: Transient Binding of a Second Catalytic Magnesium Activates the Structure and Dynamics of CDK2 Kinase for Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Zhao Qin; Jacobsen, Douglas M.; Young, Matthew A. (Michigan-Med)

    2014-10-02

    We have determined high-resolution crystal structures of a CDK2/Cyclin A transition state complex bound to ADP, substrate peptide, and MgF{sub 3}{sup -}. Compared to previous structures of active CDK2, the catalytic subunit of the kinase adopts a more closed conformation around the active site and now allows observation of a second Mg{sup 2+} ion in the active site. Coupled with a strong [Mg{sup 2+}] effect on in vitro kinase activity, the structures suggest that the transient binding of the second Mg{sup 2+} ion is necessary to achieve maximum rate enhancement of the chemical reaction, and Mg{sup 2+} concentration could represent an important regulator of CDK2 activity in vivo. Molecular dynamics simulations illustrate how the simultaneous binding of substrate peptide, ATP, and two Mg{sup 2+} ions is able to induce a more rigid and closed organization of the active site that functions to orient the phosphates, stabilize the buildup of negative charge, and shield the subsequently activated {gamma}-phosphate from solvent.

  10. Catalytic activity of triphasic cocrystallized system of high-silicon zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Yushchenko, V.V.; Topchieva, K.V.; Meged, N.F.; Trunova, V.I.; Meged, A.A.

    1985-08-01

    Triphasic cocrystallized zeolite (TPCZ), prepared from granulated silica gel in alkaline aluminate solution containing sodium and tetraethyammonium cations, was tested for its efficiency in cracked n-octane and for acidity by ammonia thermodesorption. The studies with TPCZ, consisting of 30% mordenite, 30% ZSM-5, and 40% ZSM-12, showed that the initial cracking activity falls during the first hour to a plateau with a rate constant of 3 ..mu..moles/g.sec at 450/sup 0/C, which is markedly below that of biphasic cocrystallized zeolite and ultrasil. After cooling and activation with hydrogen at 450/sup 0/C there was no decrease in the activity of TPCZ, although the activity was below that of fresh TPCZ. The desorption curve for TPCZ was below that for ultrasil, H-mordenite, and the biphasic zeolite. Tabulated data on the conversion products obtained with TPCZ showed time-independent changes in the products, with fresh TPCZ initially forming 420 moles of methane per 100 moles of n-octane, a figures which eventually dropped to 141 moles of methane. In terms of yields of C/sub 2/ to C/sub 5/ hydrocarbons, TPCZ differed from the other zeolites, a difference which was ascribed to ZSM-12. 6 references, 2 figures.

  11. A Catalytically Active Membrane Reactor for Fast, Highly Exothermic, Heterogeneous Gas Reactions. A Pilot Plant Study

    NARCIS (Netherlands)

    Veldsink, Jan W.; Versteeg, Geert F.; Swaaij, Wim P.M. van

    1995-01-01

    Membrane reactors have been frequently studied because of their ability to combine chemical activity and separation properties into one device. Due to their thermal stability and mechanical strength, ceramic membranes are preferred over polymeric ones, but small transmembrane fluxes obstruct a wides

  12. Synthesis of a tricyclic mescaline analogue by catalytic C-H bond activation.

    Science.gov (United States)

    Ahrendt, Kateri A; Bergman, Robert G; Ellman, Jonathan A

    2003-04-17

    [reaction: see text] A tetrahydrobis(benzofuran) mescaline analogue has been prepared in six steps and 38% overall yield from (4'-O-methyl)methyl gallate. The key step in this synthesis is a tandem cyclization reaction via directed C[bond]H activation followed by olefin insertion.

  13. Novel biohybrids of layered double hydroxide and lactate dehydrogenase enzyme: Synthesis, characterization and catalytic activity studies

    Science.gov (United States)

    Djebbi, Mohamed Amine; Braiek, Mohamed; Hidouri, Slah; Namour, Philippe; Jaffrezic-Renault, Nicole; Ben Haj Amara, Abdesslem

    2016-02-01

    The present work introduces new biohybrid materials involving layered double hydroxides (LDH) and biomolecule such as enzyme to produce bioinorganic system. Lactate dehydrogenase (Lac Deh) has been chosen as a model enzyme, being immobilized onto MgAl and ZnAl LDH materials via direct ion-exchange (adsorption) and co-precipitation methods. The immobilization efficiency was largely dependent upon the immobilization methods. A comparative study shows that the co-precipitation method favors the immobilization of great and tunable amount of enzyme. The structural behavior, chemical bonding composition and morphology of the resulting biohybrids were determined by X-ray diffraction (XRD) study, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM), respectively. The free and immobilized enzyme activity and kinetic parameters were also reported using UV-Visible spectroscopy. However, the modified LDH materials showed a decrease in crystallinity as compared to the unmodified LDH. The change in activity of the immobilized lactate dehydrogenase was considered to be due, to the reduced accessibility of substrate molecules to the active sites of the enzyme and the partial conformational change of the Lac Deh molecules as a result of the immobilization way. Finally, it was proven that there is a correlation between structure/microstructure and enzyme activity dependent on the immobilization process.

  14. Extended Synaptotagmin Interaction with the Fibroblast Growth Factor Receptor Depends on Receptor Conformation, Not Catalytic Activity.

    Science.gov (United States)

    Tremblay, Michel G; Herdman, Chelsea; Guillou, François; Mishra, Prakash K; Baril, Joëlle; Bellenfant, Sabrina; Moss, Tom

    2015-06-26

    We previously demonstrated that ESyt2 interacts specifically with the activated FGF receptor and is required for a rapid phase of receptor internalization and for functional signaling via the ERK pathway in early Xenopus embryos. ESyt2 is one of the three-member family of Extended Synaptotagmins that were recently shown to be implicated in the formation of endoplasmic reticulum (ER)-plasma membrane (PM) junctions and in the Ca(2+) dependent regulation of these junctions. Here we show that ESyt2 is directed to the ER by its putative transmembrane domain, that the ESyts hetero- and homodimerize, and that ESyt2 homodimerization in vivo requires a TM adjacent sequence but not the SMP domain. ESyt2 and ESyt3, but not ESyt1, selectively interact in vivo with activated FGFR1. In the case of ESyt2, this interaction requires a short TM adjacent sequence and is independent of receptor autophosphorylation, but dependent on receptor conformation. The data show that ESyt2 recognizes a site in the upper kinase lobe of FGFR1 that is revealed by displacement of the kinase domain activation loop during receptor activation.

  15. Synthesis of copper/nickel nanoparticles using newly synthesized Schiff-base metals complexes and their cytotoxicity/catalytic activities.

    Science.gov (United States)

    Aazam, Elham S; El-Said, Waleed Ahmed

    2014-12-01

    Transition metal complexes compounds with Schiff bases ligand representing an important class of compounds that could be used to develop new metal-based anticancer agents and as precursors of metal NPs. Herein, 2,3-bis-[(3-ethoxy-2-hydroxybenzylidene)amino]but-2-enedinitrile Schiff base ligand and its corresponding copper/nickel complexes were synthesized. Also, we reported a facile and rapid method for synthesis nickel/copper nanoparticles based on thermal reduction of their complexes. Free ligand, its metal complexes and metals nanoparticles have been characterized based on elemental analysis, transmission electron microscopy, powder X-ray diffraction, magnetic measurements and by various spectroscopic (UV-vis, FT-IR, (1)H NMR, GC-MS) techniques. Additionally, the in vitro cytotoxic activity of free ligand and its complexes compounds were assessed against two cancer cell lines (HeLa and MCF-7 cells)and one healthy cell line (HEK293 cell). The copper complex was found to be active against these cancer cell lines at very low LD50 than the free ligand, while nickel complex did not show any anticancer activity against these cell lines. Also, the antibacterial activity of as-prepared copper nanoparticles were screened against Escherichia coli, which demonstrated minimum inhibitory concentration and minimum bactericidal concentration values lower than those values of the commercial Cu NPs as well as the previous reported values. Moreover, the synthesized nickel nanoparticles demonstrated remarkable catalytic performance toward hydrogenation of nitrobenzene that producing clean aniline with high selectivity (98%). This reactivity could be attributed to the high degree of dispersion of Ni nanoparticles.

  16. Phospholipase C from Pseudomonas aeruginosa and Bacillus cereus;characterization of catalytic activity

    Institute of Scientific and Technical Information of China (English)

    Nooran Sherif Elleboudy; Mohammad Mabrouk Aboulwafa; Nadia Abdel-Haleem Hassouna

    2014-01-01

    Objective:To study characteristics of phospholipases C (PLCs), their importance for producing microorganisms as well as the potential of their use for industrial purposes. Methods:PLC from Bacillus cereus (B. cereus) D101 was selected as an example of Gram-positive PLCs and PLC from Pseudomonas aeruginosa (P. aeruginosa) D183 of Gram-negative ones. Enzymes were partially purified by ammonium sulfate precipitation followed by membrane dialysis. Partially purified preparations were used to study effect of different factors on activities as well as in substrate specificity tests which were conducted using a turbidimetric assay method. Results: Maximum activity was at pH 7 and 8 and 40℃for P. aeruginosa PLC, and pH 8-10 and 37℃for B. cereus PLC. Both PLCs were inhibited by Pi at 5 mM or higher, whereas, PLC from B. cereus only was inhibited by EDTA. Activity of P. aeruginosa PLC was not affected by removing Zn2+ions from reaction mixture or their replacement with Ca2+, Ba2+, Mg2+or Mn2+ions. Vis-à-vis, activity of B. cereus PLC was found to be metal ion dependent. PLCs from both isolates were relatively thermostable and showed maximum affinity toward phosphatidylcholine. Sphingomyelin and phosphatidylethanolamine were not good substrates and phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and cardiolipin could be considered non-substrates. Conclusions: Human body physiological conditions could favor activity of P. aeruginosa and B. cereus PLCs. These enzymes may participate in phosphate scavenging and virulence of producing isolates but not in autolysis. PLCs from both isolates are potential candidates for industrial use.

  17. Genetically engineered synthetic miniaturized versions of Plasmodium falciparum UvrD helicase are catalytically active.

    Directory of Open Access Journals (Sweden)

    Abulaish Ansari

    Full Text Available Helicases catalyze unwinding of double stranded nucleic acids in an energy-dependent manner. We have reported characterization of UvrD helicase from Plasmodium falciparum. We reported that the N-terminal and C-terminal fragments of PfUvrD contain characteristic ATPase and DNA helicase activities. Here we report the generation and characterization of a genetically engineered version of PfUvrD and its derivatives. This synthetic UvrD (sUD contains all the conserved domains of PfUvrD but only the intervening linker sequences are shortened. sUD (∼ 45 kDa and one of its smallest derivative sUDN1N2 (∼ 22 kDa contain ATPase and DNA helicase activities. sUD and sUDN1N2 can utilize hydrolysis of all the NTPs and dNTPs, can also unwind blunt end duplex DNA substrate and unwind DNA duplex in 3 to 5 direction only. Some of the properties of sUD are similar to the PfUvrD helicase. Mutagenesis in the conserved motif Ia indicate that the mutants sUDM and sUDN1N2M lose all the enzyme activities, which further confirms that these activities are intrinsic to the synthesized proteins. These studies show that for helicase activity only the conserved domains are essentially required and intervening sequences have almost no role. These observations will aid in understanding the unwinding mechanism by a helicase.

  18. Facile synthesis of polypyrrole functionalized nickel foam with catalytic activity comparable to Pt for the poly-generation of hydrogen and electricity

    Science.gov (United States)

    Tang, Tiantian; Li, Kan; Shen, Zhemin; Sun, Tonghua; Wang, Yalin; Jia, Jinping

    2016-01-01

    Polypyrrole functionalized nickel foam is facilely prepared through the potentiostatic electrodeposition. The PPy-functionalized Ni foam functions as a hydrogen-evolution cathode in a rotating disk photocatalytic fuel cell, in which hydrogen energy and electric power are generated by consuming organic wastes. The PPy-functionalized Ni foam cathode exhibits stable catalytic activities after thirteen continuous runs. Compared with net or plate structure, the Ni foam with a unique three-dimensional reticulate structure is conducive to the electrodeposition of PPy. Compared with Pt-group electrode, PPy-coated Ni foam shows a satisfactory catalytic performance for the H2 evolution. The combination of PPy and Ni forms a synergistic effect for the rapid trapping and removal of proton from solution and the catalytic reduction of proton to hydrogen. The PPy-functionalized Ni foam could be applied in photocatalytic and photoelectrochemical generation of H2. In all, we report a low cost, high efficient and earth abundant PPy-functionalized Ni foam with a satisfactory catalytic activities comparable to Pt for the practical application of poly-generation of hydrogen and electricity.

  19. Macromolecular peroxo complexes of Vanadium(V) and Molybdenum(VI): Catalytic activities and biochemical relevance

    Indian Academy of Sciences (India)

    Nashreen S Islam; Jeena Jyoti Boruah

    2015-05-01

    Our recent achievements concerning the synthesis and characterization of water soluble peroxo complexes of V(V) and Mo(VI) in macroligand environment, as well as some key features of biological relevance of these compounds, such as their hydrolytic stability, activity with phosphohydrolase enzyme vis-à-vis free peroxovanadium (pV) or peroxomolybdenum (pMo) complexes, and their activity in biomimetic oxidative bromination are presented here. Immobilization of pMo species on insoluble polymer matrices viz., amino acid functionalized Merrifield resins and poly(acrylonitrile) on the other hand, afforded a set of heterogeneous catalysts highly effective in facile organic transformations such as selective oxidation of organic sulfides and oxidative bromination of aromatic substrates by H2O2, at ambient temperature. The methodologies are straightforward, high-yielding, halogen-free and the catalysts afford easy regeneration. Our findings illustrate the various features which make the procedures sustainable and synthetically useful.

  20. Understanding the catalytic activity of gold nanoparticles through multi-scale simulations

    DEFF Research Database (Denmark)

    Brodersen, Simon Hedegaard; Vej-Hansen, Ulrik Grønbjerg; Larsen, Britt Hvolbæk;

    2011-01-01

    We investigate how the chemical reactivity of gold nanoparticles depends on the cluster size and shape using a combination of simulation techniques at different length scales, enabling us to model at the atomic level the shapes of clusters in the size range relevant for catalysis. The detailed......-coordinated active sites is found, and their reactivities are extracted from models based on Density Functional Theory calculations. This enables us to determine the chemical activity of clusters in the same range of particle sizes that is accessible experimentally. The variation of reactivity with particle size...... is in excellent agreement with experiments, and we conclude that the experimentally observed trends are mostly explained by the high reactivity of under-coordinated corner atoms on the gold clusters. Other effects, such as the effect of the substrate, may influence the reactivities significantly, but the presence...