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Fernandez, F. A., M. R. Buchanan, J. Hirsh, J. W. Fenton II und F. A. Ofosu. „Catalysis of Thrombin Inhibition Provides an Index for Estimating the Antithrombotic Potential of Glycosaminoglycans in Rabbits“. Thrombosis and Haemostasis 57, Nr. 03 (1987): 286–93. http://dx.doi.org/10.1055/s-0038-1651118.
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SummaryPrevious studies have demonstrated that standard anticoagulant tests are poor indices of the antithrombotic potential of glycosaminoglycans which are weak catalysts of the thrombinantithrombin III reaction. In this study we investigated whether the catalysis of thrombin inhibition by plasma could serve as a reliable index for assessing the antithrombotic effectiveness of glycosaminoglycans. Equal volumes of 125I-thrombin and control or test plasma were incubated for up to 10 min at 37° C. Inactivation of thrombin was then determined after 7.9% SDS-polyacrylamide gel electrophoresis and subsequent autoradiography. Increasing concentrations of heparin (>0.066 μg/mL or 0.01 USP units/mL) and dermatan sulfate (>0.1 μg/mL) could be readily demonstrated in undiluted plasma by enhanced formation of complexes of thrombin with antithrombin III and heparin cofactor II respectively. However, the detection of any catalytic effect of the two glycosaminoglycans decreased significantly with increasing plasma dilutions. When ex vivo plasmas obtained from rabbits that had been injected with the minimum dose of any one of seven glycosaminoglycans required to achieve their optimal antithrombotic effect were assessed for their ability to catalyse thrombin inhibition, there was approximately a 2-fold increase in the amount of thrombin inactivated 30 s after the thrombin had been added to the plasma. The enhanced inhibition of thrombin was achieved by catalysis of antithrombin III and/or heparin cofactor II activities. These results suggest that measurement of the catalysis of thrombin inactivation in undiluted plasma is a sensitive and reliable index for estimating the antithrombotic potential of glycosaminoglycans in rabbits.
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Ljungdahl, Per O. „Amino-acid-induced signalling via the SPS-sensing pathway in yeast“. Biochemical Society Transactions 37, Nr. 1 (20.01.2009): 242–47. http://dx.doi.org/10.1042/bst0370242.
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Yeast cells rely on the SPS-sensing pathway to respond to extracellular amino acids. This nutrient-induced signal transduction pathway regulates gene expression by controlling the activity of two redundant transcription factors: Stp1 and Stp2. These factors are synthesized as latent cytoplasmic proteins with N-terminal regulatory domains. Upon induction by extracellular amino acids, the plasma membrane SPS-sensor catalyses an endoproteolytic processing event that cleaves away the regulatory N-terminal domains. The shorter forms of Stp1 and Stp2 efficiently target to the nucleus, where they bind and activate transcription of selected genes encoding a subset of amino acid permeases that function at the plasma membrane to catalyse the transport of amino acids into cells. In the present article, the current understanding of events in the SPS-sensing pathway that enable external amino acids to induce their own uptake are reviewed with a focus on two key issues: (i) the maintenance of Stp1 and Stp2 latency in the absence of amino acid induction; and (ii) the amino-acid-induced SPS-sensor-mediated proteolytic cleavage of Stp1 and Stp2.
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Ofosu, F. A., G. J. Modi, M. A. Blajchman, M. R. Buchanan und E. A. Johnson. „Increased sulphation improves the anticoagulant activities of heparan sulphate and dermatan sulphate“. Biochemical Journal 248, Nr. 3 (15.12.1987): 889–96. http://dx.doi.org/10.1042/bj2480889.
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Heparan sulphate and dermatan sulphate have both antithrombotic and anticoagulant properties. These are, however, significantly weaker than those of a comparable amount of standard pig mucosal heparin. Antithrombotic and anticoagulant effects of glycosaminoglycans depend on their ability to catalyse the inhibition of thrombin and/or to inhibit the activation of prothrombin. Since heparan sulphate and dermatan sulphate are less sulphated than unfractionated heparin, we investigated whether the decreased sulphation contributes to the lower antithrombotic and anticoagulant activities compared with standard heparin. To do this, we compared the anticoagulant activities of heparan sulphate and dermatan sulphate with those of their derivatives resulphated in vitro. The ratio of sulphate to carboxylate in these resulphated heparan sulphate and dermatan sulphate derivatives was approximately twice that of the parent compounds and similar to that of standard heparin. Anticoagulant effects were assessed by determining (a) the catalytic effects of each glycosaminoglycan on the inhibition of thrombin added to plasma, and (b) the ability of each glycosaminoglycan to inhibit the activation of 125I-prothrombin in plasma. The least sulphated glycosaminoglycans were least able to catalyse the inhibition of thrombin added to plasma and to inhibit the activation of prothrombin. Furthermore, increasing the degree of sulphation improved the catalytic effects of glycosaminoglycans on the inhibition of thrombin by heparin cofactor II in plasma. The degree of sulphation therefore appears to be an important functional property that contributes significantly to the anticoagulant effects of the two glycosaminoglycans.
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Atkinson, Helen M., Tracy A. Mewhort-Buist, Leslie R. Berry und Anthony K. C. Chan. „Anticoagulant mechanisms of covalent antithrombin-heparin investigated by thrombelastography“. Thrombosis and Haemostasis 102, Nr. 07 (2009): 62–68. http://dx.doi.org/10.1160/th08-11-0769.
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SummaryWe have developed an antithrombin-heparin covalent complex (ATH) which inhibits coagulation enzymes by two mechanisms: directly, or by catalytic activation of plasma antithrombin (AT). Anticoagulation by ATH was compared to unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) using a blood-based, tissue factor (TF)-activated thrombelastography (TEG) assay. Simplified TEG assays with plasma or purified plasma components were used to determine the contribution of the direct and catalytic mechanisms to ATH efficacy. Low anti-Xa concentrations of UFH inhibited clot formation significantly more than equivalent concentrations of ATH or LMWH in blood and plasma. ATH had reduced ability to catalyse AT-mediated thrombin (IIa) inhibition compared to UFH. However, at high anti-Xa concentrations, ATH had similar anticoagulant activity to UFH. ATH and non-covalent AT+UFH directly inhibited clotting to a similar degree in AT-deficient plasma. IIa-ATH complexes, which are limited to catalytic inhibition, displayed impaired anticoagulation compared to free ATH, and the magnitude of this effect increased significantly as anticoagulant concentration increased. Kinetic experiments indicated that the rate of reaction of AT with IIa is lower when catalysed by ATH versus UFH. In conclusion, at low anti-Xa doses catalytic inhibition is the primary mechanism of ATH anticoagulation, and the catalytic potential of ATH is reduced relative to UFH. However, the direct inhibitory activity of ATH is comparable to noncovalent AT+UFH, and at high anti-Xa doses the direct inhibitory activity of ATH may play a larger role in anticoagulation.
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Gutteridge, John M. C. „Plasma ascorbate levels and inhibition of the antioxidant activity of caeruloplasmin“. Clinical Science 81, Nr. 3 (01.09.1991): 413–17. http://dx.doi.org/10.1042/cs0810413.
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1. The copper-containing protein caeruloplasmin has several oxidase activities. 2. Its ability to catalyse the oxidation of ferrous ions to the ferric state (ferroxidase activity) makes it an important antioxidant in vivo. 3. Recent reports have suggested that oral supplementation with vitamin C can inhibit the oxidase activities of caeruloplasmin. 4. As expected, damage to DNA and membrane lipids was stimulated by mixtures of iron salt and ascorbate, and this damage could be inhibited by caeruloplasmin provided the molar ratio of ascorbate to caeruloplasmin was kept sufficiently low. 5. When the molar ratio of ascorbate to caeruloplasmin was greater than 200 substantial loss of ferroxidase antioxidant activity occurred. 6. It is unlikely, however, that oral supplementation with vitamin C can raise plasma levels sufficiently to inhibit caeruloplasmin activity in vivo.
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Day, Joanna M., Paul A. Foster, Helena J. Tutill, Fabien Schmidlin, Christopher M. Sharland, Jonathan D. Hargrave, Nigel Vicker, Barry V. L. Potter, Michael J. Reed und Atul Purohit. „STX2171, a 17β-hydroxysteroid dehydrogenase type 3 inhibitor, is efficacious in vivo in a novel hormone-dependent prostate cancer model“. Endocrine-Related Cancer 20, Nr. 1 (06.11.2012): 53–64. http://dx.doi.org/10.1530/erc-12-0231.
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17β-Hydroxysteroid dehydrogenases (17β-HSDs) catalyse the 17-position reduction/oxidation of steroids. 17β-HSD type 3 (17β-HSD3) catalyses the reduction of the weakly androgenic androstenedione (adione) to testosterone, suggesting that specific inhibitors of 17β-HSD3 may have a role in the treatment of hormone-dependent prostate cancer and benign prostate hyperplasia. STX2171 is a novel selective non-steroidal 17β-HSD3 inhibitor with an IC50 of ∼200 nM in a whole-cell assay. It inhibits adione-stimulated proliferation of 17β-HSD3-expressing androgen receptor-positive LNCaP(HSD3) prostate cancer cells in vitro. An androgen-stimulated LNCaP(HSD3) xenograft proof-of-concept model was developed to study the efficacies of STX2171 and a more established 17β-HSD3 inhibitor, STX1383 (SCH-451659, Schering-Plough), in vivo. Castrated male MF-1 mice were inoculated s.c. with 1×107 cells 24 h after an initial daily dose of testosterone propionate (TP) or vehicle. After 4 weeks, tumours had not developed in vehicle-dosed mice, but were present in 50% of those mice given TP. One week after switching the stimulus to adione, mice were dosed additionally with the vehicle or inhibitor for a further 4 weeks. Both TP and adione efficiently stimulated tumour growth and increased plasma testosterone levels; however, in the presence of either 17β-HSD3 inhibitor, adione-dependent tumour growth was significantly inhibited and plasma testosterone levels reduced. Mouse body weights were unaffected. Both inhibitors also significantly lowered plasma testosterone levels in intact mice. In conclusion, STX2171 and STX1383 significantly lower plasma testosterone levels and inhibit androgen-dependent tumour growth in vivo, indicating that 17β-HSD3 inhibitors may have application in the treatment of hormone-dependent prostate cancer.
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Bagoly, Zsuzsa, Vera Sheptovitsky, Rima Dardik, Judith Lahav, Eli Karniel und Aida Inbal. „Coagulation factor XIII serves as protein disulfide isomerase“. Thrombosis and Haemostasis 101, Nr. 05 (2009): 840–44. http://dx.doi.org/10.1160/th08-09-0605.
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SummaryTissue transglutaminase was reported to act as protein disulfide isomerase (PDI). We studied whether plasma transglutaminase – coagulation factor XIII (FXIII) – has PDI activity as well. PDI activity was measured by determining the ability to renature reduced-denatured RNase (rdRNase). We found that FXIII can re-nature rdRNase, with efficiency comparable to commercial PDI. This PDI activity was inhibited by bacitracin. Like tissue transglu-taminase, FXIII-mediated PDI activity is independent of its transglutaminase activity and is located on the A subunit. Surface-associated PDI has been previously shown to catalyse two distinct functions: transnitrosation with subsequent release of intracellular nitric oxide and disulfide bond rearrangement during platelet integrin ligation. Our results imply that FXIII-PDI activity may have a role in platelet function.
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Wang, Zhen, Dong Hao Wang, Yuliya Goykhman, Yuanyuan Yan, Peter Lawrence, Kumar S. D. Kothapalli und J. Thomas Brenna. „The elongation of very long-chain fatty acid 6 gene product catalyses elongation of n-13 : 0 and n-15 : 0 odd-chain SFA in human cells“. British Journal of Nutrition 121, Nr. 3 (03.01.2019): 241–48. http://dx.doi.org/10.1017/s0007114518003185.
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AbstractNormal odd-chain SFA (OCSFA), particularly tridecanoic acid (n-13 : 0), pentadecanoic acid (n-15 : 0) and heptadecanoic acid (n-17 : 0), are normal components of dairy products, beef and seafood. The ratio of n-15 : 0:n-17 : 0 in ruminant foods (dairy products and beef) is 2:1, while in seafood and human tissues it is 1:2, and their appearance in plasma is often used as a marker for ruminant fat intake. Human elongases encoded by elongation of very long-chain fatty acid (ELOVL)1, ELOVL3, ELOVL6 and ELOVL7 catalyse biosynthesis of the dominant even-chain SFA; however, there are no reports of elongase function on OCSFA. ELOVL transfected MCF7 cells were treated with n-13 : 0, n-15 : 0 or n-17 : 0 (80 µm) and products analysed. ELOVL6 catalysed elongation of n-13 : 0→n-15 : 0 and n-15 : 0→n-17 : 0; and ELOVL7 had modest activity toward n-15 : 0 (n-15 : 0→n-17 : 0). No elongation activity was detected for n-17 : 0→n-19 : 0. Our data expand ELOVL specificity to OCSFA, providing the first molecular evidence demonstrating ELOVL6 as the major elongase acting on OCSFA n-13 : 0 and n-15 : 0 fatty acids. Studies of food intake relying on OCSFA as a biomarker should consider endogenous human metabolism when relying on OCSFA ratios to indicate specific food intake.
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SIGAL, Yury J., Mark I. McDERMOTT und Andrew J. MORRIS. „Integral membrane lipid phosphatases/phosphotransferases: common structure and diverse functions“. Biochemical Journal 387, Nr. 2 (05.04.2005): 281–93. http://dx.doi.org/10.1042/bj20041771.
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Phospholipids and sphingolipids play critical roles in signal transduction, intracellular membrane trafficking, and control of cell growth and survival. We discuss recent progress in the identification and characterization of a family of integral membrane proteins with central roles in bioactive lipid metabolism and signalling. These five groups of homologous proteins, which we collectively term LPTs (lipid phosphatases/phosphotransferases), are characterized by a core domain containing six transmembrane-spanning α-helices connected by extramembrane loops, two of which interact to form the catalytic site. LPT family members are localized to all major membrane compartments of the cell. The transmembrane topology of these proteins places their active site facing the lumen of endomembrane compartments or the extracellular face of the plasma membrane. Sequence conservation between the active site of the LPPs (lipid phosphate phosphatases), SPPs (sphingosine phosphate phosphatases) and the recently identified SMSs (sphingomyelin synthases) with vanadium-dependent fungal oxidases provides a framework for understanding their common catalytic mechanism. LPPs hydrolyse LPA (lysophosphatidic acid), S1P (sphingosine 1-phosphate) and structurally-related substrates. Although LPPs can dephosphorylate intracellularly generated substrates to control intracellular lipid metabolism and signalling, their best understood function is to regulate cell surface receptor-mediated signalling by LPA and S1P by inactivating these lipids at the plasma membrane or in the extracellular space. SPPs are intracellularly localized S1P-selective phosphatases, with key roles in the pathways of sphingolipid metabolism linked to control of cell growth and survival. The SMS enzymes catalyse the interconversion of phosphatidylcholine and ceramide with sphingomyelin and diacylglycerol, suggesting a pivotal role in both housekeeping lipid synthesis and regulation of bioactive lipid mediators. The remaining members of the LPT family, the LPR/PRGs (lipid phosphatase-related proteins/plasticity-related genes) and CSS2s (type 2 candidate sphingomyelin synthases), are presently much less well studied. These two groups include proteins that lack critical amino acids within the catalytic site, and could therefore not use the conserved LPT reaction mechanism to catalyse lipid phosphatase or phosphotransferase reactions. In this review, we discuss recent ideas about their possible biological activities and functions, which appear to involve regulation of cellular morphology and, possibly, lipid metabolism and signalling in the nuclear envelope.
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WEIJL, N. I., T. J. ELSENDOORN, R. M. W. MOISON, E. G. W. M. LENTJES, R. BRAND, H. M. BERGER und S. OSANTO. „Non-protein bound iron release during chemotherapy in cancer patients“. Clinical Science 106, Nr. 5 (01.05.2004): 475–84. http://dx.doi.org/10.1042/cs20030271.
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Non-protein bound iron (NPBI) is able to catalyse oxidative reactions, causing damage to vital structures. Adverse effects induced by cisplatin seem, in part, to be mediated by free radicals. In the present study, we have measured plasma NPBI, various other iron parameters and antioxidants in 28 cancer patients undergoing cisplatin-based chemotherapy at various time points before and during chemotherapy. No NPBI was present prior to therapy, but within 1–4 days following the first administration of chemotherapy, mean NPBI rose significantly to 10.6±6.6 µmol/l (range, 0.6–21.3 µmol/l) in 18 (64.3%) of the 28 patients measured. The rise in NPBI was accompanied by a significant rise in total plasma iron and ferritin and a marked decrease in the latent iron-binding capacity. Concomitantly, plasma vitamins C and E decreased significantly, indicating consumption of antioxidants. Similar observations were also made during the fourth chemotherapy cycle. The increase in NPBI preceded and correlated significantly with chemotherapy toxicity, such as a decrease in leucocyte count and haemoglobin, with a transient rise in various liver enzymes and with known cisplatin-related toxicity, i.e. the loss of renal and hearing function. In conclusion, cisplatin chemotherapy induces oxidative damage which rapidly leads to release of iron from intracellular proteins and the appearance of NPBI. Bone marrow, red blood cells, liver and kidney seem to be a likely source of NPBI. The observed high levels of NPBI may be a major causative determinant in chemotherapy-induced toxicity.
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SAFADI-CHAMBERLAIN, Farida, Li-Ping WANG, Shawn G. PAYNE, Chang-Uk LIM, Suzanne STRATFORD, Jose Antonio CHAVEZ, Michael H. FOX, Sarah SPIEGEL und Scott A. SUMMERS. „Effect of a membrane-targeted sphingosine kinase 1 on cell proliferation and survival“. Biochemical Journal 388, Nr. 3 (07.06.2005): 827–34. http://dx.doi.org/10.1042/bj20041726.
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Numerous extracellular stimuli activate SK1 (sphingosine kinase type 1) to catalyse the production of sphingosine 1-phosphate, a bioactive lipid that functions as both an extracellular ligand for a family of G-protein-linked receptors and as a putative intracellular messenger. Phorbol esters, calcium or immunoglobulin receptors stimulate SK1 by promoting its translocation to the plasma membrane, which brings it into proximity both to its substrate (i.e. sphingosine) and to activating acidic phospholipids (e.g. phosphatidylserine). To evaluate the consequence of SK translocation, we generated an SK1-derivative tagged with a myristoylation sequence (Myr-SK1) on its N-terminus and overexpressed the construct in 3T3-L1 fibroblasts using recombinant retrovirus. Myr-SK1 overexpression increased SK activity by more than 50-fold in crude membranes, while only stimulating cytoplasmic SK activity by 4-fold. In contrast, the overexpression of WT-SK1 (wild-type SK1), as well as that of a construct containing a false myristoylation sequence (A2-Myr-SK1), markedly increased SK activity in both membrane and cytoplasmic compartments. Immunofluorescence confirmed that Myr-SK1 preferentially localized at the plasma membrane, whereas WT-SK1 and A2-Myr-SK1 partitioned in cytoplasmic/perinuclear cellular regions. Surprisingly, Myr-SK1 overexpression significantly decreased the rates of cell proliferation by delaying exit from G0/G1 phase. Moreover, expression of Myr-SK1 but not WT-SK1 or A2-Myr-SK1 protected cells from apoptosis induced by serum withdrawal. Collectively, these findings reveal that altering the subcellular location of SK1 has marked effects on cell function, with plasma membrane-associated SK having a potent inhibitory effect on the G1–S phase transition.
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PARK, Hee-Sae, S. Min LEE, Jin Hyup LEE, Yun-Sook KIM, Young-Seuk BAE und Jeen-Woo PARK. „Phosphorylation of the leucocyte NADPH oxidase subunit p47phox by casein kinase 2: conformation-dependent phosphorylation and modulation of oxidase activity“. Biochemical Journal 358, Nr. 3 (10.09.2001): 783–90. http://dx.doi.org/10.1042/bj3580783.
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The leucocyte NADPH oxidase of neutrophils is a membrane-bound enzyme that catalyses the reduction of oxygen to O−2 at the expense of NADPH. The enzyme is dormant in resting neutrophils but becomes active when the cells are exposed to the appropriate stimuli. During oxidase activation, the highly basic cytosolic oxidase component p47phox becomes phosphorylated on several serines and migrates to the plasma membrane. Protein kinase CK2 is an essential serine/threonine kinase present in all eukaryotic organisms. The leucocyte NADPH oxidase subunit p47phox has several putative CK2 phosphorylation sites. In the present study, we report that CK2 is able to catalyse the phosphorylation of p47phoxin vitro. Phosphoamino acid analysis of phosphorylated p47phox by CK2 indicated that the phosphorylation occurs on serine residues. CNBr mapping and phosphorylation of peptides containing the putative site of CK2 indicated that the main phosphorylated residues are Ser-208 and Ser-283 in the Src homology 3 (SH3) domains, and Ser-348 in the C-terminal domain of p47phox. Dependence of phosphorylation on the conformation of p47phox is supported by the finding that p47phox undergoes better phosphorylation by CK2 in the presence of arachidonic acid, a known activator of NADPH oxidase which induces conformational changes in p47phox. In addition, 5,6-dichloro-1-β-o-ribofuranosyl benzimidazole, a CK2 inhibitor, potentiates formyl-Met-Leu-Phe-induced NADPH oxidase activity in DMSO-differentiated HL-60 cells. Taken together, we propose that CK2 is the p47phox kinase, and that phosphorylation of p47phox by CK2 regulates the deactivation of NADPH oxidase.
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Li, Yudong, Michael Hinshelwood und Gottlieb S. Oehrlein. „Investigation of Ni catalyst activation during plasma-assisted methane oxidation“. Journal of Physics D: Applied Physics 55, Nr. 15 (19.01.2022): 155202. http://dx.doi.org/10.1088/1361-6463/ac4724.
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Abstract Atmospheric pressure plasma has shown promise in improving thermally activated catalytic reactions through a process termed plasma-catalysis synergy. In this work, we investigated atmospheric pressure plasma jet (APPJ)-assisted CH4 oxidation over a Ni/SiO2 .Al2O3 catalyst. Downstream gas-phase products from CH4 conversion were quantified by Fourier transform infrared spectroscopy. The catalyst near-surface region was characterized by in-situ diffuse reflectance infrared Fourier transform spectroscopy. The catalyst was observed to be activated at elevated temperature (500 °C) if it was exposed to the APPJ operated at large plasma power. ‘Catalyst activation’ signifies that the purely thermal conversion of CH4 using catalysts which had been pre-exposed to plasma became more intense and produced consistently CO product, even if the plasma was extinguished. Without the application of the APPJ to the Ni catalyst surface this was not observed at 500 °C. The study of different exposure conditions of the activated catalyst indicates that the reduction of the catalyst by the APPJ is likely the cause of the catalyst activation. We also observed a systematic shift of the vibrational frequency of adsorbed CO on Ni catalyst when plasma operating conditions and catalyst temperatures were varied and discussed possible explanations for the observed changes. This work provides insights into the plasma-catalyst interaction, especially catalyst modification in the plasma catalysis process, and potentially demonstrates the possibility of utilizing the surface CO as a local probe to understand the plasma-catalyst interaction and shed light on the complexity of plasma catalysis.
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Pingel, S., R. A. Field, M. L. S. Güther, M. Duszenko und M. A. J. Ferguson. „The hydrophobic mannoside Manα1-6Manα1-S-(CH2)7-CH3 acts as an acceptor for the UDP-Gal:glycosylphosphatidylinositol anchor α1,3-galactosyltransferase of Trypanosoma brucei“. Biochemical Journal 309, Nr. 3 (01.08.1995): 877–82. http://dx.doi.org/10.1042/bj3090877.
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The variant surface glycoproteins (VSGs) of Trypanosoma brucei are attached to the plasma membrane via a glycosylphosphatidylinositol (GPI) membrane anchor. This anchor contains the core sequence ethanolamine-PO4-6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcN alpha 1-6myo-inositol, which is conserved in all GPI anchors, and a unique alpha Gal side chain attached to the 3-position of the alpha Man residue adjacent to the alpha GlcN residue. Here we report that trypanosome membranes can catalyse the transfer of Gal from UDP-Gal to the hydrophobic thioglycoside Man alpha 1-6Man alpha 1-S-(CH2)7-CH3. Characterization of the galactosylated products by electrospray mass spectrometry, exoglycosidase digestion and periodate-oxidation studies revealed that the major product was Man alpha 1-6(Gal alpha 1-3)Man alpha 1-S-(CH2)7-CH3. The similarity of this product to part of the mature VSG GPI anchor suggests that the thioglycoside is able to act as an acceptor for the trypanosome-specific UDP-Gal-GPI anchor alpha 1,3-galactosyltransferase.
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Brieger, David, und Joan Dawes. „Low Molecular Weight Heparin Is Responsible for the Anti-Xa Activity of Desmin 370“. Thrombosis and Haemostasis 75, Nr. 02 (1996): 286–91. http://dx.doi.org/10.1055/s-0038-1650262.
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SummaryDermatan sulphate does not catalyse the inactivation of factor Xa. However, the low molecular weight (LMW) dermatan sulphate Desmin 370 has been shown to generate circulating anti-Xa activity following administration to humans. Using a single batch of Desmin 370, we measured 3 U/mg of anti-Xa activity by amidolytic assay in vitro. The material responsible for this activity had a lower molecular weight range (6000 and 1800 Da) than Desmin 370 and was more highly sulphated than the bulk of the drug. Heparinase digestion of Desmin 370 eliminated 90% of the in vitro anti-Xa activity without significantly interfering with its ability to potentiate inactivation of thrombin by HCII, suggesting that the anti-Xa activity is not due to dermatan sulphate and is probably heparin. When 125I-labelled Desmin 370 together with 40 mg/kg carrier drug was administered intravenously to a rabbit, anti-Xa activity was readily detectable in the plasma for up to 10 h and had a longer half-life than the sulphated radiolabel. Most of this anticoagulant activity was recovered from the plasma by Polybrene affinity chromatography and was probably a sulphated glycosaminoglycan. Administration of the heparinase-digested drug to a rabbit resulted in 70% less anti-Xa activity than the undigested drug. We conclude that Desmin 370 contains detectable quantities of biologically active low molecular weight heparin, which is responsible for persistent anti-Xa activity following intravenous administration.
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BHARADWAJ, Mausumi, Dwaipayan BHARADWAJ und Ratha N. HATI. „Characterization of a membrane protease from rat submaxillary-gland mitochondria that possess thrombin-like activity“. Biochemical Journal 313, Nr. 1 (01.01.1996): 193–99. http://dx.doi.org/10.1042/bj3130193.
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A membrane protease possessing thrombin-like activity was purified to homogeneity from mitochondria of rat submaxillary gland. The molecular mass of the enzyme was determined to be 45 kDa by SDS/PAGE under reducing conditions and by gel filtration on a Sephadex G-100 column. The enzyme is a glycoprotein and has an isoelectric point of 3.25. Maximum activity was observed at pH 10.5. Inhibition by di-isopropyl fluorophosphate, benzamidine, aprotinin and antipain suggested the enzyme to be a serine protease. Other inhibitors such as EDTA, soya-bean trypsin inhibitor, lima-bean trypsin inhibitor, TosLysCH2Cl and chymostatin did not alter the activity. The enzyme showed affinity towards different synthetic substrates (p-nitroanilide derivatives) containing arginine at the P1 position. Kinetic studies revealed that kcat./Km was highest with the substrate N-Bz-Phe-Val-Arg-p-nitroanilide. The enzyme exhibits significant plasma-coagulating activity. The coagulation initiated by the enzyme was not altered by concanavalin A, indicating that the carbohydrate moiety of the enzyme is not essential for this reaction. Further, this enzyme can catalyse the formation of fibrin clots from purified fibrinogen, which describes its thrombin-like activity. However, an antibody raised against the purified enzyme inhibited the plasma-clotting as well as fibrinogen-clotting activity of the enzyme. Fibrinogen coagulation by the enzyme was blocked in the presence of aprotinin, a protease inhibitor. Release of fibrinopeptides A and B from bovine fibrinogen by the enzyme has been shown by HPLC analysis. Our studies reveal that the enzyme reported here differs from trypsin, chymotrypsin and other mitochondrial proteases reported so far.
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Katki, Khurshed A., Gomathy Viswanathan und John M. Noronha. „Role of Folate in the Modulation of Lipids, Lipoproteins and Eicosanoids in Hypertension and Diabetes“. Pteridines 6, Nr. 2 (Mai 1995): 63–68. http://dx.doi.org/10.1515/pteridines.1995.6.2.63.
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Summary Besides elevated levels of lipids and lipoproteins, ievels of the physiological amino acid homocysteine as well as whole blood folates are now known to play a role in atherogenesis. The role of folates in atherosclerosis is rather peculiar in that it helps to catalyse the remethylation of homocysteine (a proatherogenic agent) to methionine thus preventing the accumulation of homocysteine in plasma and hence its antiatherogenic role. We estimated whole blood folate levels of 69 normotensive, 34 diabetic and 94 hypertensive individuals and have attempted to correlate these values with lipid and non-lipid parameters. Whole blood levels of simple, conjugated and total folates were significantly higher among the diabetics as well as the hypertensives when compared to the normotensives. In all the study groups, levels of conjugated folates correlated significantly to those of total folates even after adjustments for age and body mass index were introduced. Among the normotensive individuals the significance of the inverse correlation between simple folates and total cholesterol/high density lipoprotein cholesterol ratio was lost after adjusting for age and body mass index. Levels of total and conjugated folates were positively correlated to plasma levels of thromboxane B2 among the diabetics. In the same group the positive correlation between total folates and thromboxane B2 and that between total folates and the eicosanoid ratio remained significant even after adjustments for age and body mass index were introduced. None of the other metabolic variables correlated with whole blood levels of simple folates in any of the study groups.
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Gao, Yan, Wenchao Jiang, Tao Luan, Hui Li, Wenke Zhang, Wenchen Feng und Haolin Jiang. „High-Efficiency Catalytic Conversion of NOx by the Synergy of Nanocatalyst and Plasma: Effect of Mn-Based Bimetallic Active Species“. Catalysts 9, Nr. 1 (18.01.2019): 103. http://dx.doi.org/10.3390/catal9010103.
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Three typical Mn-based bimetallic nanocatalysts of Mn−Fe/TiO2, Mn−Co/TiO2, Mn−Ce/TiO2 were synthesized via the hydrothermal method to reveal the synergistic effects of dielectric barrier discharge (DBD) plasma and bimetallic nanocatalysts on NOx catalytic conversion. The plasma-catalyst hybrid catalysis was investigated compared with the catalytic effects of plasma alone and nanocatalyst alone. During the catalytic process of catalyst alone, the catalytic activities of all tested catalysts were lower than 20% at ambient temperature. While in the plasma-catalyst hybrid catalytic process, NOx conversion significantly improved with discharge energy enlarging. The maximum NOx conversion of about 99.5% achieved over Mn−Ce/TiO2 under discharge energy of 15 W·h/m3 at ambient temperature. The reaction temperature had an inhibiting effect on plasma-catalyst hybrid catalysis. Among these three Mn-based bimetallic nanocatalysts, Mn−Ce/TiO2 displayed the optimal catalytic property with higher catalytic activity and superior selectivity in the plasma-catalyst hybrid catalytic process. Furthermore, the physicochemical properties of these three typical Mn-based bimetallic nanocatalysts were analyzed by N2 adsorption, Transmission Electron Microscope (TEM), X-ray diffraction (XRD), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The multiple characterizations demonstrated that the plasma-catalyst hybrid catalytic performance was highly dependent on the phase compositions. Mn−Ce/TiO2 nanocatalyst presented the optimal structure characteristic among all tested samples, with the largest surface area, the minished particle sizes, the reduced crystallinity, and the increased active components distributions. In the meantime, the ratios of Mn4+/(Mn2+ + Mn3+ + Mn4+) in the Mn−Ce/TiO2 sample was the highest, which was beneficial to plasma-catalyst hybrid catalysis. Generally, it was verified that the plasma-catalyst hybrid catalytic process with the Mn-based bimetallic nanocatalysts was an effective approach for high-efficiency catalytic conversion of NOx, especially at ambient temperature.
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TAYLOR, M. C., und J. M. KELLY. „Iron metabolism in trypanosomatids, and its crucial role in infection“. Parasitology 137, Nr. 6 (15.02.2010): 899–917. http://dx.doi.org/10.1017/s0031182009991880.
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SUMMARYIron is almost ubiquitous in living organisms due to the utility of its redox chemistry. It is also dangerous as it can catalyse the formation of reactive free radicals – a classical double-edged sword. In this review, we examine the uptake and usage of iron by trypanosomatids and discuss how modulation of host iron metabolism plays an important role in the protective response. Trypanosomatids require iron for crucial processes including DNA replication, antioxidant defence, mitochondrial respiration, synthesis of the modified base J and, in African trypanosomes, the alternative oxidase. The source of iron varies between species. Bloodstream-form African trypanosomes acquire iron from their host by uptake of transferrin, andLeishmania amazonensisexpresses a ZIP family cation transporter in the plasma membrane. In other trypanosomatids, iron uptake has been poorly characterized. Iron-withholding responses by the host can be a major determinant of disease outcome. Their role in trypanosomatid infections is becoming apparent. For example, the cytosolic sequestration properties of NRAMP1, confer resistance against leishmaniasis. Conversely, cytoplasmic sequestration of iron may be favourable rather than detrimental toTrypanosoma cruzi. The central role of iron in both parasite metabolism and the host response is attracting interest as a possible point of therapeutic intervention.
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VAN UUM, Stan H. M., Brian R. WALKER, Ad R. M. M. HERMUS, C. G. J. (Fred) SWEEP, Paul SMITS, Peter W. DE LEEUW und Jacques W. M. LENDERS. „Effect of glycyrrhetinic acid on 11β-hydroxysteroid dehydrogenase activity in normotensive and hypertensive subjects“. Clinical Science 102, Nr. 2 (11.01.2002): 203–11. http://dx.doi.org/10.1042/cs1020203.
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The 11β-hydroxysteroid dehydrogenase (11β-HSD) isoenzymes catalyse the interconversion of cortisol and cortisone. Type 1 11β-HSD mainly converts cortisone into active cortisol. Type 2 11β-HSD inactivates cortisol in mineralocorticoid target tissues, and its activity can be inhibited by glycyrrhetinic acid (GA). Inactivation of cortisol to cortisone is impaired in a subgroup of patients with primary hypertension. To study where this defect is located, we measured cortisol and cortisone concentrations in arterial plasma, in saliva and across the forearm at baseline and after administration of GA in normotensive and hypertensive subjects. GA (500mg) or placebo was administered orally to 20 normotensive subjects in a placebo-controlled double-blind fashion. Further, we compared the effect of GA in 20 patients with primary hypertension with that in 20 normotensive subjects. Cortisol and cortisone were measured in plasma from the brachial artery and vein and in saliva. Samples were obtained at 0, 90 and 150min. Forearm blood flow (FBF) was measured simultaneously. Forearm production of corticosteroid hormones was assessed by multiplying the arteriovenous difference in corticosteroid concentration by FBF. The cortisol/cortisone ratio in arterial plasma remained at baseline levels after placebo (4.9±1.2; mean±S.D.), while after GA the ratio increased similarly in normotensive subjects (12.3±3.4) and in hypertensive patients (12.2±3.7). A similar effect of GA on the salivary cortisol/cortisone ratio was found. In both normotensive subjects and hypertensive patients no forearm production of cortisol or cortisone could be demonstrated, either at baseline or after administration of GA. Thus, both before and after GA administration, we did not find any difference in systemic and salivary 11β-HSD type 2 activity between subjects with primary hypertension and normotensive controls. Further, both at baseline and after GA administration we were not able to demonstrate net inactivation or re-activation of cortisol and cortisone by the 11β-HSD isoenzymes in the forearm in either normotensive or primary hypertensive subjects.
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Whitehead, J. Christopher. „Plasma catalysis: A solution for environmental problems“. Pure and Applied Chemistry 82, Nr. 6 (20.04.2010): 1329–36. http://dx.doi.org/10.1351/pac-con-10-02-39.
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The combination of a nonthermal, atmospheric plasma with a catalyst is investigated as a means of destroying pollutants in waste gas streams. Using the examples of dichloromethane (DCM) and toluene in air streams, it is shown that the destruction of the pollutant can be increased whilst lowering the operating temperature, giving increasing energy efficiency. Unwanted by-products can also be reduced selectively by appropriate choice of catalyst and of the plasma–catalyst configuration. By studying the temperature dependence of plasma catalysis, some ideas can be obtained about the nature of the interaction between plasma and catalyst in the processing.
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Zaychenko, Ilya Vladimirovich, Sergey Aleksandrovich Gordin, Anna Sergeevna Sizintseva, Vera Sergeevna Sokolova und Viktoria Vasilyevna Bazheryanu. „Nonthermal plasma for capturing CO2 as a path to ecologically clean energy“. E3S Web of Conferences 470 (2023): 01031. http://dx.doi.org/10.1051/e3sconf/202347001031.
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One of the serious environmental problems of our time is the impact on global climate change of the atmospheric pollution processes with greenhouse gases. Carbon dioxide is the most significant component of the anthropogenic impact on the heat balance of the earth. Therefore, reducing the concentration of greenhouse gases in the atmosphere is becoming increasingly important. Non-thermal plasma technology is considered as an attractive alternative for converting greenhouse gases into syngas and other valuable chemicals at lower temperatures. Highly active species generated in such a plasma are favourable for both initiation and propagation of chemical reactions. The combined effect of plasma and heterogeneous catalysis for fuel production from CH4 reforming has attracted increasing attention. The coupling between plasma and catalyst become complex when the catalyst is placed directly in the plasma. Both chemical and physical properties of the plasma and catalyst can be changed by the presence of each other. In this paper we studied resent progress in non-thermal plasma-catalysis research for CO2 capturing application.
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Pham, Thien, Ha Bui und Ahmed Khacef. „Oxidation of propene from air by atmospheric plasma-catalytic hybrid system“. Journal of the Serbian Chemical Society 83, Nr. 5 (2018): 641–49. http://dx.doi.org/10.2298/jsc171014012p.
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The pulsed dielectric barrier discharge (DBD) combined with the palladium supported on alumina beads, was investigated for propene (C3H6) removal from air. The effects of thermal-catalysis, plasma-catalysis (in-plasma catalysis and post-plasma catalysis), and plasma-alone on the propene removal were compared. Results are presented in the terms of C3H6 removal efficiency, energy consumption, and by-products production. Temperature dependence studies (20?250?C) show that in all conditions of input plasma energy density explored (23?148 J L-1), the plasma-catalysis systems exhibit better propene conversion efficiencies than the thermal catalysis at low temperature (60% at 20?C). Plasma-alone treatment has a similar effectiveness compared to plasma-catalysis at room temperature, but it leads to the formation of high by-products concentrations. It appears that in the plasma-catalyst system, C3H6 removal was the most efficient, whatever was the configuration used, and it was helpful to minimize by-products formation.
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Liu, Chang-jun, Jijun Zou, Kailu Yu, Dangguo Cheng, You Han, Jason Zhan, Chalita Ratanatawanate und Ben W. L. Jang. „Plasma application for more environmentally friendly catalyst preparation“. Pure and Applied Chemistry 78, Nr. 6 (01.01.2006): 1227–38. http://dx.doi.org/10.1351/pac200678061227.
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The present status of catalyst preparation using nonthermal plasma treatment has been summarized in this paper. Improved dispersion, better low-temperature activity, enhanced stability, and better anti-carbon deposition performance can be achieved with nonthermal plasma-treated catalysts. The improvement in catalyst preparation with nonthermal plasma treatment can reduce or avoid the use of hazardous chemicals. Nonthermal plasma catalyst treatment has especially induced a new development of nonthermal plasma for catalyst reduction. The reduction using hydrogen at high temperatures or using hazardous liquid chemicals can be replaced by the developed plasma reduction process. The mechanism for nonthermal plasma treatment has been presented. An analog between the man-made gas discharge plasmas and the environment inside the zeolite pores and around catalyst surface defects is also proposed.
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Korichi, Noussaiba, Olivier Aubry, Hervé Rabat, Benoît Cagnon und Dunpin Hong. „Paracetamol Degradation by Catalyst Enhanced Non-Thermal Plasma Process for a Drastic Increase in the Mineralization Rate“. Catalysts 10, Nr. 9 (21.08.2020): 959. http://dx.doi.org/10.3390/catal10090959.
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In order to remediate the very poor mineralization of paracetamol in water, even when well degraded by using a Non-Thermal Plasma (NTP) process at a very low dissipated power, a plasma-catalyst coupling process was tested and investigated. A homemade glass fiber supported Fe3+ catalyst was immersed in the liquid to be treated in a Dielectric Barrier Discharge plasma reactor. The plasma-catalysis process, at the same low dissipated power, achieved a mineralization rate of 54% with a full conversion rate of paracetamol at 25 mg L−1 in initial concentration after 60 min treatment, thanks to Fenton-like effects. The synergetic effects of the plasma-catalysis coupling process also improved the Energy Yield by a factor of two. The catalyst before and after use for treatment was characterized by Brunauer-Emmett-Teller and Thermogravimetric analysis. High-Performance Liquid Chromatography was used to measure the concentration of treated solution and to investigate the intermediates. Two of them, namely 1,4-hydroquinone and 1,4-benzoquinone, were formally identified. Some intermediates are presented in this paper as a function of treatment time and their UV absorbance spectra. NTP processes with and without catalyst coupling were compared in terms of acidity, conductivity, and nitrate concentrations in the treated solution.
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Gehring, Markus, Tobias Kutsch, Osmane Camara, Alexandre Merlen, Hermann Tempel, Hans Kungl und Rüdiger-A. Eichel. „The effect of cobalt on morphology, structure, and ORR activity of electrospun carbon fibre mats in aqueous alkaline environments“. Beilstein Journal of Nanotechnology 12 (19.10.2021): 1173–86. http://dx.doi.org/10.3762/bjnano.12.87.
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An innovative approach for the design of air electrodes for metal–air batteries are free-standing scaffolds made of electrospun polyacrylonitrile fibres. In this study, cobalt-decorated fibres are prepared, and the influence of carbonisation temperature on the resulting particle decoration, as well as on fibre structure and morphology is discussed. Scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, and inductively coupled plasma optical emission spectrometry are used for characterisation. The modified fibre system is compared to a benchmark system without cobalt additives. Cobalt is known to catalyse the formation of graphite in carbonaceous materials at elevated temperatures. As a result of cobalt migration in the material the resulting overall morphology is that of turbostratic carbon. Nitrogen removal and nitrogen-type distribution are enhanced by the cobalt additives. At lower carbonisation temperatures cobalt is distributed over the surface of the fibres, whereas at high carbonisation temperatures it forms particles with diameters up to 300 nm. Free-standing, current-collector-free electrodes assembled from carbonised cobalt-decorated fibre mats display promising performance for the oxygen reduction reaction in aqueous alkaline media. High current densities at an overpotential of 100 mV and low overpotentials at current densities of 333 μA·cm−2 were found for all electrodes made from cobalt-decorated fibre mats carbonised at temperatures between 800 and 1000 °C.
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Bayly, G. R., W. A. Bartlett und A. F. Jones. „A Non-Isotopic Method for Estimating 11β Hydroxysteroid Dehydrogenase Activity In Vivo“. Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 34, Nr. 5 (September 1997): 521–26. http://dx.doi.org/10.1177/000456329703400505.
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11 β-hydroxysteroid dehydrogenase (11βHSD) has both dehydrogenase (11βDH) and reductase (11βR) activities, which catalyse the interconversion of Cortisol and cortisone, and prednisolone and prednisone. This enzyme confers specificity on the mineralocorticoid receptor by local oxidation of Cortisol to cortisone. Using radiolabeled Cortisol 11βHSD activity has been shown to be lower in some cases of essential hypertension. This study investigated a novel approach to estimating 11βHSD activity in vivo. Plasma steroid kinetics were investigated following oral hydrocortisone (a substrate for 11βDH) and prednisone (a substrate for 11βR) in five normotensive volunteers after dexamethasone suppression of endogenous steroid production. This approach was evaluated by inducing partial deficiency of 11βHSD in the volunteers who took liquorice (to inhibit 11βDH) and then carbenoxolone (to inhibit both 11βDH and 11βR). The ratio of Cortisol to prednisolone (formed from prednisone) provided a measure of the activity of both 11βDH and 11βR. At 75min after the steroid bolus the ratio increased from 1·1 (0·6–1·3) (median, range) under control conditions to 1·2 (0·8–1·7) after liquorice ( P = 0·01, n = 5), and 2·0 (1·3–5·9) after carbenoxolone ( P = 0·02, n = 5). It may therefore be applied to the measurement of 11βHSD activity in vivo in large numbers of hypertensive patients without the use of radioisotopes.
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Stere, Cristina, Sarayute Chansai, Rahman Gholami, Kanlayawat Wangkawong, Amit Singhania, Alexandre Goguet, Burapat Inceesungvorn und Christopher Hardacre. „A design of a fixed bed plasma DRIFTS cell for studying the NTP-assisted heterogeneously catalysed reactions“. Catalysis Science & Technology 10, Nr. 5 (2020): 1458–66. http://dx.doi.org/10.1039/d0cy00036a.
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A newly developed DRIFTS cell for the in situ study of non-thermal plasma-assisted heterogeneously catalysed reactions is presented and evaluated using methane oxidation over a Pd/Al2O3 catalyst.
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Hülsey, Max J., Chia Wei Lim und Ning Yan. „Promoting heterogeneous catalysis beyond catalyst design“. Chemical Science 11, Nr. 6 (2020): 1456–68. http://dx.doi.org/10.1039/c9sc05947d.
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Kim, Jongsik, David B. Go und Jason C. Hicks. „Synergistic effects of plasma–catalyst interactions for CH4 activation“. Physical Chemistry Chemical Physics 19, Nr. 20 (2017): 13010–21. http://dx.doi.org/10.1039/c7cp01322a.
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Zhu, Tao, Yan Dong Wan, Yan Fang, Xu Chen, Dong Yao Xu, Xu Wen He und Xin Qian Shu. „Nano-Materials Coupled with Non-Thermal Plasma Application in Environmental Protection“. Advanced Materials Research 287-290 (Juli 2011): 1599–602. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1599.
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Nano-catalyst was prepared in the lab. Non-thermal plasma was generated by dielectric barrier discharge (DBD). Through nano-catalyst coupled with non-thermal plasma, a series of experiments for toluene decomposition were carried out. Based on reactor input energy density and removal efficiency and energy efficiency and inhibition for O3 formation, the load amount MnOx catalyst on the surface of γ-Al2O3 pellets were compared in the experiment. The results show the catalysis performance of 10 wt% MnOx/γ-Al2O3 coupled with non-thermal plasma resulted in higher removal efficiency of toluene and better energy efficiency. At the same time, 10 wt% MnOx/γ-Al2O3 operated on a better inhibition for O3 formation in the gas exhaust.
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Aceto, Domenico, Maria Carmen Bacariza, Arnaud Travert, Carlos Henriques und Federico Azzolina-Jury. „Thermal and Plasma-Assisted CO2 Methanation over Ru/Zeolite: A Mechanistic Study Using In-Situ Operando FTIR“. Catalysts 13, Nr. 3 (27.02.2023): 481. http://dx.doi.org/10.3390/catal13030481.
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CO2 methanation is an attractive reaction to convert CO2 into a widespread fuel such as methane, being the combination of catalysts and a dielectric barrier discharge (DBD) plasma responsible for synergistic effects on the catalyst’s performances. In this work, a Ru-based zeolite catalyst, 3Ru/CsUSY, was synthesized by incipient wetness impregnation and characterized by TGA, XRD, H2-TPR, N2 sorption and CO2-TPD. Catalysts were tested under thermal and plasma-assisted CO2 methanation conditions using in-situ operando FTIR, with the aim of comparing the mechanism under both types of catalysis. The incorporation of Ru over the CsUSY zeolite used as support induced a decrease of the textural properties and an increase of the basicity and hydrophobicity, while no zeolite structural damage was observed. Under thermal conditions, a maximum CO2 conversion of 72% and CH4 selectivity above 95% were registered. These promising results were ascribed to the presence of small Ru0 nanoparticles over the support (16 nm), catalyst surface hydrophobicity and the presence of medium-strength basic sites in the catalyst. Under plasma-catalytic conditions, barely studied in similar setups in literature, CO2 was found to be excited by the plasma, facilitating its adsorption on the surface of 3Ru/CsUSY in the form of oxidized carbon species such as formates, aldehydes, carbonates, or carbonyls, which are afterwards progressively hydrogenated to methane. Adsorption and surface reaction of key intermediates, namely formate and aldehydic groups, was observed even on the support alone, an occurrence not reported before for thermal catalysis. Overall, similar reaction mechanisms were proposed for both thermal and plasma-catalysis conditions.
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JENG, Y. Arco, Paula SAVAGE, Michael E. BEIL, Charles W. BRUSEO, Denton HOYER, Cynthia A. FINK und Angelo J. TRAPANI. „CGS 34226, a thiol-based dual inhibitor of endothelin converting enzyme-1 and neutral endopeptidase 24.11“. Clinical Science 103, s2002 (01.09.2002): 98S—101S. http://dx.doi.org/10.1042/cs103s098s.
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Endothelins (ETs) are potent vasoconstrictors and have been implicated in the pathogenesis of various cardiovascular and renal diseases. In contrast, atrial natriuretic peptide (ANP) is a potent vasorelaxant and diuretic agent, which is mainly degraded by neutral endopeptidase 24.11 (NEP) in vivo. Thus, compounds that can suppress the biosynthesis of ETs by inhibiting endothelin converting enzymes (ECEs), which catalyse the final step of post-translational processing of the vasoconstrictors, while simultaneously potentiating the levels of ANP by inhibiting NEP may have novel therapeutic utility. Through targeted screening of our compound library and subsequent optimization, CGS 34226 was identified as a potent, dual inhibitor of ECE-1 and NEP, inhibiting the enzymes with respective IC50 values of 11 and 4.6nM. In vivo, CGS 34226 suppressed the big endothelin-1 (big ET-1)-induced pressor response dose-dependently. At 15 and 90min after an intravenous dose of 30mg/kg in anaesthetized rats, this compound inhibited the big ET-1-induced effect by 79% and 65% respectively. In addition, CGS 34226 increased plasma ANP immunoreactivity by 120% up to 4h after an intravenous dose of 10mg/kg in conscious rats infused with ANP at a rate of 450ng/kg per min, intravenously. These results show that CGS 34226 is a potent dual inhibitor of ECE-1 and NEP in vitro and in vivo and that the compound may represent a novel agent for the treatment of cardiovascular and renal dysfunction.
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He, Wenyu, Bin Xu, Lin Lang, Wenshen Yang, Huacai Liu, Hao Zhan, Jianjun Xie, Xiuli Yin und Chuangzhi Wu. „Exploring Simultaneous Upgrading and Purification of Biomass−Gasified Gases Using Plasma Catalysis“. Catalysts 13, Nr. 4 (31.03.2023): 686. http://dx.doi.org/10.3390/catal13040686.
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Tar and substantial CH4 and CO2 are contained in gasified fuels, which pose an obstacle to direct chemical synthesis, and this is a predominant challenge for biomass gasification technology. Herein, a packed−bed dielectric barrier discharge (DBD) reactor was built for simultaneous CH4 dry reforming and tar removal with a La−Ni/γ−Al2O3 catalyst. The interaction between CH4 dry reforming and tar removal in plasma catalysis was investigated. The results indicated that plasma catalysis can achieve high−efficiency simultaneous tar removal and CH4 dry reforming, as indicated by the reactants’ conversion (14% increase for CCH4 and CCO2 at 450 °C in the presence of tar and a 37% increase for the tar removal rate at 360 °C when CH4 and CO2 were introduced), and the mechanism for mutual promotion of CH4 dry reforming and tar removal was elucidated through catalyst characterization results. In addition, a possible reaction mechanism for tar removal via plasma catalysis was proposed. These findings provide valuable insights for simultaneous upgrading and purification of gases generated by biomass gasification.
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Ge, F., und RJ Guillory. „Identification of the NADPH‐binding protein of the neutrophil superoxide‐generating oxidase of guinea pigs“. Biotechnology and Applied Biochemistry 19, Nr. 1 (Februar 1994): 111–28. http://dx.doi.org/10.1111/j.1470-8744.1994.tb00289.x.
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A cell‐free system prepared from polymorphonuclear neutrophils is capable of NADPH‐dependent generation of superoxide anion, but requires the simultaneous presence of plasma membranes, cytosol, arachidonate and guanosine 5′‐[gamma‐thio]triphosphate (GTP[S]). The isolated membranes from such a preparation are able to catalyse NADPH‐dependent superoxide formation independently of added cytosol and activators. Such activated membranes, activated in the cell‐free system, must consequently contain all of the essential components required by the oxidase for superoxide formation, including the NADPH‐binding component. Arylazido‐beta‐alanyl‐[32P]NADPH (3′‐O‐(3‐[N‐(4‐azido‐2‐nitrophenyl)‐amino] propionyl)‐[32P]NADPH), an NADPH analogue and photoaffinity probe, is shown to act in the dark as a substrate for the oxidase activity in the activated membranes and an irreversible photodependent inhibitor following photoirradiation. The photoaffinity probe has been used to identify the specific NADPH‐binding component of the oxidase in the activated membranes. In contrast with the sensitivity of the activated membranes, photoirradiation of arylazido‐beta‐alanyl‐[32P]‐NADPH under identical conditions, but with non‐activated membranes, did not prevent subsequent activation of the treated membranes by cytosol, arachidonate and GTP[S]. However, photoirradiation of the cytosolic fraction in the presence of arylazido‐beta‐alanyl‐[32P]NADPH resulted in an inhibition of the cytosol's ability to activate superoxide generation upon subsequent incubation with plasma membranes in the presence of arachidonate and GTP[S]. These observations are taken as a strong indication that the NADPH‐binding protein of the oxidase is a cytosolic factor which associates with the plasma membrane upon activation. The superoxide‐generating activity of the activated membranes was inhibited irreversibly in a concentration‐ and photo‐dependent manner by arylazido‐beta‐alanyl‐NADPH. The arylazido‐beta‐alanyl‐NADPH‐photodependent inhibition of superoxide generation in the activated membranes correlated with the photodependent labelling of a protein of 55.6 kDa by the arylazido‐beta‐alanyl‐NADPH. Specificity of labelling was indicated by a lack of labelling of the 55.6 kDa region in the non‐activated membranes and protection of the photodependent inhibition and labelling of the 55.6 kDa protein by NADPH. It is proposed that the arylazido‐beta‐alanyl‐NADPH‐labelled 55.6 kDa protein present on the activated membranes is the NADPH‐binding protein of the neutrophil superoxide‐generating oxidase.
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Buchori, Luqman, Istadi Istadi, Purwanto Purwanto, Anggun Kurniawan und Teuku Irfan Maulana. „Preliminary Testing of Hybrid Catalytic-Plasma Reactor for Biodiesel Production Using Modified-Carbon Catalyst“. Bulletin of Chemical Reaction Engineering & Catalysis 11, Nr. 1 (10.03.2016): 59. http://dx.doi.org/10.9767/bcrec.11.1.416.59-65.
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<p>Preliminary testing of hybrid catalytic-plasma reactor for biodiesel production through transesterification of soybean oil with methanol over modified-carbon catalyst was investigated. This research focused on synergetic roles of non-thermal plasma and catalysis in the transesterification process. The amount of modified-carbon catalyst with grain size of 1.75 mm was placed into fixed tubular reactor within discharge zone. The discharge zone of the hybrid catalytic-plasma reactor was defined in the volume area between high voltage and ground electrodes. Weight Hourly Space Velocity (WHSV) of 1.85 h-1 of reactant feed was studied at reaction temperature of 65 oC and at ambient pressure. The modified-carbon catalyst was prepared by impregnation of active carbon within H2SO4 solution followed by drying at 100 oC for overnight and calcining at 300 oC for 3 h. It was found that biodiesel yield obtained using the hybrid catalytic-plasma reactor was 92.39% and 73.91% when using active carbon and modified-carbon catalysts, respectively better than without plasma. Therefore, there were synergetic effects of non-thermal plasma and catalysis roles for driving the transesterification process. Copyright © 2016 BCREC GROUP. All rights reserved</p><p><em>Received: 10<sup>th</sup> November 2015; Revised: 16<sup>th</sup> January 2016; Accepted: 16<sup>th</sup> January 2016</em></p><p><strong>How to Cite:</strong> Buchori, L., Istadi, I., Purwanto, P., Kurniawan, A., Maulana, T.I. (2016). Preliminary Testing of Hybrid Catalytic-Plasma Reactor for Biodiesel Production Using Modified-Carbon Catalyst.<em> Bulletin of Chemical Reaction Engineering & Catalysis</em>, 11 (1): 59-65. (doi:10.9767/bcrec.11.1.416.59-65) </p><p><strong>Permalink/DOI</strong>: <a href="http://dx.doi.org/10.9767/bcrec.11.1.416.59-65">http://dx.doi.org/10.9767/bcrec.11.1.416.59-65</a></p><p> </p><p> </p>
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K. P. Veerapandian, Savita, Nathalie De Geyter, Jean-Marc Giraudon, Jean-François Lamonier und Rino Morent. „The Use of Zeolites for VOCs Abatement by Combining Non-Thermal Plasma, Adsorption, and/or Catalysis: A Review“. Catalysts 9, Nr. 1 (17.01.2019): 98. http://dx.doi.org/10.3390/catal9010098.
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Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite as adsorbent and catalyst in combination with non-thermal plasma for VOC abatement in flue gas. The superior surface properties of zeolites in combination with its excellent catalytic properties obtained by metal loading make it an ideal packing material for adsorption plasma catalytic removal of VOCs. This work highlights the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolites via plasma.
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Kumari, Sudesh, Babajide Patrick Ajayi, Bijandra Kumar, Jacek B. Jasinski, Mahendra K. Sunkara und Joshua M. Spurgeon. „A low-noble-metal W1−xIrxO3−δ water oxidation electrocatalyst for acidic media via rapid plasma synthesis“. Energy & Environmental Science 10, Nr. 11 (2017): 2432–40. http://dx.doi.org/10.1039/c7ee02626a.
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Rapid plasma oxidation of a mixed-metal oxide catalyst with Ir metal content as low as 1% showed promising water oxidation catalysis in acid with significantly improved performance over an analogous thermally oxidized material.
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Kaige Chen, Kaige Chen, Ruoyu Chen Ruoyu Chen, Zhe Tang Zhe Tang, Hui Cang Hui Cang und Qi Xu Qi Xu. „Plasma-Treated Ce/TiO2-Palygorskite Catalyst for the NH3-SCR of NOx“. Journal of the chemical society of pakistan 41, Nr. 1 (2019): 90. http://dx.doi.org/10.52568/000724/jcsp/41.01.2019.
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Ce/TiO2-Palygorskite ternary composites were fabricated as an efficient catalyst for medium and low temperature NH3-SCR reaction and the optimal mass proportion (Ti:Pal=1:3) of this catalyst was confirmed by the catalytic performance test, in order to improve the surface dispersion , which needed to be further disposed by the Non-thermal plasma , after that, it was activated by thermal treatment at 400⁰C for 4 h. Based on the results obtained by XRD, FE-SEM, TEM, NH3-TPD, UV-vis (DRS), XPS, the treatment of plasma was much essential for the transformation from Ce4+ to Ce3+ on the surface of Ce/TiO2-palygorskite, to increase surface chemisorbed oxygen, and the improved dispersion, which were highly favorable for denitration. At about 350⁰C, the best NO conversion was respectively 90.59 % and 96.78 % for the untreated and treated catalysts, the latter possessed higher N2 selectivity. Besides, according to the research results on alkali metals poisoning resistance of these catalysts, it was discovered, the treated-catalyst poisoned by sodium salt had the best resistance performance, which might be related with the modification of the Non-thermal plasma, leading to more dispersed surface acid sites, to get more active sites, meanwhile, the toxicity of K was stronger than Na.
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Li, Ju, Cunhua Ma, Shengjie Zhu, Feng Yu, Bin Dai und Dezheng Yang. „A Review of Recent Advances of Dielectric Barrier Discharge Plasma in Catalysis“. Nanomaterials 9, Nr. 10 (09.10.2019): 1428. http://dx.doi.org/10.3390/nano9101428.
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Dielectric barrier discharge plasma is one of the most popular methods to generate nanthermal plasma, which is made up of a host of high-energy electrons, free radicals, chemically active ions and excited species, so it has the property of being prone to chemical reactions. Due to these unique advantages, the plasma technology has been widely used in the catalytic fields. Compared with the conventional method, the heterogeneous catalyst prepared by plasma technology has good dispersion and smaller particle size, and its catalytic activity, selectivity and stability are significantly improved. In addition, the interaction between plasma and catalyst can achieve synergistic effects, so the catalytic effect is further improved. The review mainly introduces the characteristics of dielectric barrier discharge plasma, development trend and its recent advances in catalysis; then, we sum up the advantages of using plasma technology to prepare catalysts. At the same time, the synergistic effect of plasma technology combined with catalyst on methanation, CH4 reforming, NOx decomposition, H2O2 synthesis, Fischer–Tropsch synthesis, volatile organic compounds removal, catalytic sterilization, wastewater treatment and degradation of pesticide residues are discussed. Finally, the properties of plasma in catalytic reaction are summarized, and the application prospect of plasma in the future catalytic field is prospected.
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Fjellvåg, A. Slagtern, D. Waller, J. Skjelstad und A. Olafsen Sjåstad. „Grain Reconstruction of Palladium and Palladium-Nickel Alloys for Platinum Catchment“. Johnson Matthey Technology Review 63, Nr. 4 (01.10.2019): 236–46. http://dx.doi.org/10.1595/205651319x15597236291099.
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Platinum-rhodium gauzes are frequently used to catalyse the high temperature ammonia oxidation step for production of synthetic nitrogen-based fertilisers. The gauzes suffer from Pt loss in the form of platinum dioxide (PtO2), due to the highly exothermic nature of the oxidation reaction. Industrially this is mitigated by installing one or more palladium-nickel catchment gauzes directly downstream of the combustion gauzes, to capture the lost Pt. The Pd-Ni catchment gauzes undergo severe structural modification during operation. In this study, we undertake a systematic study in a laboratory-scale furnace system to determine the role of each of the constituent gases O2, H2O and PtO2 on the structural changes of the Pd-Ni gauzes. In addition, some samples are exposed to real industrial conditions in an ammonia combustion pilot plant reactor. Fresh and spent catchment gauzes are analysed by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and inductively coupled plasma mass spectroscopy/optical emission spectroscopy (ICP-MS/OES). By combining analysis of samples from furnace and pilot scale experiments, the main findings are that Pd-Ni gauzes undergo internal oxidation to nickel(II) oxide (NiO); which in the presence of steam results in Ni depletion and that PtO2 vapour causes severe grain reconstruction. Furthermore, in laboratory-scale experiments no significant Pd loss is observed, which is in contrast to observations from the pilot plant where the samples are exposed to real post-ammonia oxidation conditions. Pd loss is likely attributed to some gas species contained in the real post-ammonia oxidation gas stream.
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BRAUN, Norbert, Sabine FENGLER, Christian EBELING, Jörg SERVOS und Herbert ZIMMERMANN. „Sequencing, functional expression and characterization of rat NTPDase6, a nucleoside diphosphatase and novel member of the ecto-nucleoside triphosphate diphosphohydrolase family“. Biochemical Journal 351, Nr. 3 (24.10.2000): 639–47. http://dx.doi.org/10.1042/bj3510639.
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We have isolated and characterized the cDNA encoding nucleoside triphosphate diphosphohydrolase 6 (NTPDase6), a novel member of the ecto-nucleoside triphosphate diphosphohydrolase family. The rat-brain-derived cDNA has an open reading frame of 1365bp encoding a protein of 455 amino acid residues, a calculated molecular mass of 49971Da and a predicted N-terminal hydrophobic sequence. It shares 86% sequence identity with the human CD39L2 sequence and 48% and 51% identity respectively with sequences of the two related human and murine nucleoside diphosphatases (CD39L4, NTPDase5/ER-UDPase). The mRNA was expressed in all tissues investigated, revealing two major transcripts with differing abundances. PCR analysis suggests a single open reading frame. A Myc-His-tagged NTPDase6 was expressed in Chinese hamster ovary (CHO) and PC12 cells for immunological analysis and protein isolation. The protein was contained in membrane fractions of transfected CHO cells and occurred in a soluble form in the cell culture supernatants. NTPDase6 preferentially hydrolysed nucleoside 5′-diphosphates. With different substrates the order of activity was GDP>IDP≫UDP,CDP≫ADP. Nucleoside 5′-triphosphates were hydrolysed only to a minor extent and no hydrolysis of nucleoside 5′-monophosphates was observed. The enzyme was strongly and equally activated by Ca2+ and Mg2+ and had a Km for GDP of 211µM. The immunohistochemical analysis of transfected CHO and PC12 cells suggests that NTPDase6 is associated with the Golgi apparatus and to a small extent also with the plasma membrane. The enzyme might support glycosylation reactions in the Golgi apparatus and, when released from cells, might catalyse the hydrolysis of extracellular nucleotides.
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Mauray, Sandrine, Claude Sternberg, Jocelyne Theveniaux, Jean Millet, Corinne Sinquin, Jacqueline Tapon-Bretaudiére und Anne-Marie Fischer. „Venous Antithrombotic and Anticoagulant Activities of a Fucoïdan Fraction“. Thrombosis and Haemostasis 74, Nr. 05 (1995): 1280–85. http://dx.doi.org/10.1055/s-0038-1649927.
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SummaryFucoïdans catalyse thrombin inhibition by antithrombin (AT) and heparin cofactor II (HCII); their affinity for each serpin varies according to the seaweed species from which they are extracted, as well as their chemical composition and molecular weight. We extracted a homogeneous fucoïdan fraction from Ascophyllum nodosum, a brown seaweed, and tested its anticoagulant and antithrombotic activities. At a fucoïdan concentration of 3.75 µg/ml, thrombin inhibition mediated by AT showed an apparent second-order rate constant (kapp) of 2 × 108 M-1 min-1, compared to 1.5 × 106 M-1 min-1 for the uncatalyzed reaction. The kapp value of thrombin inhibition via HCII was 1.17 × 109 M-1 min-1 at a fucoïdan concentration of 50 µg/ml, compared to 1.72 × 105 M-1 min-1 for the uncatalyzed reaction. In a Wessler model of venous thrombosis, the fucoïdan fraction, injected intravenously to rabbits 10 min before thrombosis induction, exhibited antithrombotic activity: 1.8 mg/kg was the dose which inhibited F Xa-induced thrombus formation by 80% (ED80), compared to a heparin ED80 of 0.1 mg/kg. At this ED80 the antithrombotic effect of the fucoïdan persisted longer than that of heparin (30 min versus 15 min). The thrombin clotting time (TCT) was significantly prolonged (73 s versus control 29 s, compared to 53 s with heparin) 10 min after a fucoïdan bolus infusion giving a plasma fucoïdan concentration of 14.6 ± 2.7 µg/ml. The bleeding time was slightly increased after fucoïdan infusion at the ED80. Fucoïdan extracted from marine flora thus shows promise as an antithrombotic drug.
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Abiev, Rufat Sh, Dmitry A. Sladkovskiy, Kirill V. Semikin, Dmitry Yu Murzin und Evgeny V. Rebrov. „Non-Thermal Plasma for Process and Energy Intensification in Dry Reforming of Methane“. Catalysts 10, Nr. 11 (22.11.2020): 1358. http://dx.doi.org/10.3390/catal10111358.
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Plasma-assisted dry reforming of methane (DRM) is considered as a potential way to convert natural gas into fuels and chemicals under near ambient temperature and pressure; particularly for distributed processes based on renewable energy. Both catalytic and photocatalytic technologies have been applied for DRM to investigate the CH4 conversion and the energy efficiency of the process. For conventional catalysis; metaldoped Ni-based catalysts are proposed as a leading vector for further development. However; coke deposition leads to fast deactivation of catalysts which limits the catalyst lifetime. Photocatalysis in combination with non-thermal plasma (NTP), on the other hand; is an enabling technology to convert CH4 to more reactive intermediates. Placing the catalyst directly in the plasma zone or using post-plasma photocatalysis could generate a synergistic effect to increase the formation of the desired products. In this review; the recent progress in the area of NTP-(photo)catalysis applications for DRM has been described; with an in-depth discussion of novel plasma reactor types and operational conditions including employment of ferroelectric materials and nanosecond-pulse discharges. Finally, recent developments in the area of optical diagnostic tools for NTP, such as optical emission spectroscopy (OES), in-situ FTIR, and tunable diode laser absorption spectroscopy (TDLAS), are reviewed.
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Liu, Su, Jiabin Zhou, Dan Liu und Ke Du. „Modified Mn/ZSM-5 for Non-Thermal Plasma Mineralization of VOCs and DFT Simulation Using a Novel Y-Type ZSM-5 Model“. Catalysts 12, Nr. 8 (17.08.2022): 906. http://dx.doi.org/10.3390/catal12080906.
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Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) were used to introduce possible oxygen defects into the Mn/ZSM-5 to prepare modified catalysts, which were evaluated in VOCs degradation activity using a Double Dielectric Barrier Discharge (DDBD) plasma device. Additionally, a novel Y-type ZSM-5 model was employed in the DFT simulation. The new Y-type ZSM-5 model used in this paper is a more realistic aperiodic model. It showed that introducing possible oxygen defects can substantially enhance degradation efficiency. Taking the catalyst with oxygen defects introduced by plasma as an example, the conversion (CO2 selectivity) of the methanol, acetone, and toluene could reach 100% (100%), 97.7% (99.1%), 91.2% (93.9%), respectively, at an initial concentration of 2000 ppm and specific input energy of 9 kJ/L. The results demonstrated that modification could significantly enhance the activity of the catalyst in decomposing VOCs at room temperature using non-thermal plasma catalysis. Theoretical simulation of density functional theory (DFT) revealed that the adsorption of adsorbate on the catalyst becomes easier after possible oxygen defects are introduced.
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Gorbanev, Yury, Yannick Engelmann, Kevin van’t Veer, Evgenii Vlasov, Callie Ndayirinde, Yanhui Yi, Sara Bals und Annemie Bogaerts. „Al2O3-Supported Transition Metals for Plasma-Catalytic NH3 Synthesis in a DBD Plasma: Metal Activity and Insights into Mechanisms“. Catalysts 11, Nr. 10 (13.10.2021): 1230. http://dx.doi.org/10.3390/catal11101230.
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N2 fixation into NH3 is one of the main processes in the chemical industry. Plasma catalysis is among the environmentally friendly alternatives to the industrial energy-intensive Haber-Bosch process. However, many questions remain open, such as the applicability of the conventional catalytic knowledge to plasma. In this work, we studied the performance of Al2O3-supported Fe, Ru, Co and Cu catalysts in plasma-catalytic NH3 synthesis in a DBD reactor. We investigated the effects of different active metals, and different ratios of the feed gas components, on the concentration and production rate of NH3, and the energy consumption of the plasma system. The results show that the trend of the metal activity (common for thermal catalysis) does not appear in the case of plasma catalysis: here, all metals exhibited similar performance. These findings are in good agreement with our recently published microkinetic model. This highlights the virtual independence of NH3 production on the metal catalyst material, thus validating the model and indicating the potential contribution of radical adsorption and Eley-Rideal reactions to the plasma-catalytic mechanism of NH3 synthesis.
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Zhu, Tao, Yan Dong Wan, Chun Hui Zhang, Ming Han Sun, Xu Wen He, Dong Yao Xu und Xin Qian Shu. „VOCs Decomposition Using Multiple Catalysis in Non-Thermal Plasma Processing“. Advanced Materials Research 152-153 (Oktober 2010): 973–77. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.973.
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A series of experiments were performed for toluene removal from a gaseous influent at normal temperature and atmospheric pressure by adsorption & non-thermal plasma strength & nano-catalysis technology. Non-thermal plasma was generated by dielectric barrier discharge. Sorbent & nano-catalyst were called combined catalyst which included MnO2/γ-Al2O3 and nano-Ba0.8Sr0.2Zr0.1Ti0.9O3 catalyst. MnO2/γ-Al2O3 has an advantage for ozone removal, while nano-Ba0.8Sr0.2Zr0.1Ti0.9O3 is a kind of good material for improving energy utilize rate. The results showed the synergistic technology resulted in greater enhancement of toluene removal efficiency and energy efficiency and a better inhibition for O3 formation in the gas exhaust. Based on data analysis of FT-IR, the experiment discussed decomposition mechanism and reaction process of toluene. The results showed that synergic effect could control byproducts effectively.
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Li, Yuwei, Hao Yuan, Xiongfeng Zhou, Jianping Liang, Yueyue Liu, Dalei Chang und Dezheng Yang. „Degradation of Benzene Using Dielectric Barrier Discharge Plasma Combined with Transition Metal Oxide Catalyst in Air“. Catalysts 12, Nr. 2 (08.02.2022): 203. http://dx.doi.org/10.3390/catal12020203.
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In this paper, a uniform and stable dielectric barrier discharge plasma is presented for degradation of benzene combined with a transition metal oxide catalyst. The discharge images, waveforms of discharge current, and the optical emission spectra are measured to investigate the plasma characteristics. The effects of catalyst types, applied voltage, driving frequency, and initial VOCs concentration on the degradation efficiency of benzene are studied. It is found that the addition of the packed dielectric materials can effectively improve the uniformity of discharge and enhance the intensity of discharge, thus promoting the benzene degradation efficiency. At 22 kV, the degradation efficiencies of dielectric barrier discharge plasma packed with CuO, ZnO and Fe3O4 are 93.6%, 93.2% and 76.2%, respectively. When packing with ZnO, the degradation efficiency of the dielectric barrier discharge plasma is improved from 86.8% to 94.9%, as the applied voltage increases from 16 kV to 24 kV. The catalysts were characterized by XPS, XRD and SEM. The synergistic mechanism and the property of the catalyst are responsible for benzene degradation in the plasma–catalysis system. In addition, the main physiochemical processes and possible degradation mechanism of benzene are discussed.
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Sonar, Shilpa, Jean-Marc Giraudon, Savita Kaliya Perumal Veerapandian, Jean-François Lamonier, Rino Morent, Axel Löfberg und Nathalie De Geyter. „Adsorption Followed by Plasma Assisted Catalytic Conversion of Toluene into CO2 on Hopcalite in an Air Stream“. Catalysts 11, Nr. 7 (14.07.2021): 845. http://dx.doi.org/10.3390/catal11070845.
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The abatement of toluene was studied in a sequential adsorption-plasma catalysis (APC) process. Within this process, Hopcalite was used as bifunctional material: as adsorbent (storage stage) and as catalyst via the oxidation of adsorbed toluene (discharge stage). It was observed that the desorption and oxidation activity of the adsorbed toluene was significantly affected the process variables. In addition, the adsorption time influenced the CO2 selectivity and CO2 yield by changing the interaction between the catalyst and the plasma generated species. At least four APC sequences were performed for each examined condition suggesting that Hopcalite is very stable under plasma exposure during all the sequences. Consequently, these results could contribute to advance the plasma–catalyst system with an optimal VOC oxidation efficiency. The catalytic activity, amount of toluene adsorbed, amount of toluene desorbed and product formation have been quantified by FT-IR. Moreover, the catalyst was characterized by XRD, H2-TPR, N2 adsorption–desorption analysis and XPS. Hopcalite shows a good CO2 selectivity and CO2 yield when the APC process is performed with an adsorption time of 20 min and a plasma treatment with a discharge power of 46 W which leads to a low energy cost of 11.6 kWh·m−3 and energy yields of toluene and CO2 of 0.18 (±0.01) g·kWh−1 and 0.48 (±0.06) g·kWh−1 respectively.
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Govender, Byron Bradley, Samuel Ayodele Iwarere und Deresh Ramjugernath. „Plasma-Catalytic Fischer–Tropsch Synthesis at Very High Pressure“. Catalysts 11, Nr. 3 (25.02.2021): 297. http://dx.doi.org/10.3390/catal11030297.
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This study explored Fischer–Tropsch synthesis (FTS) by combining a non-thermal plasma (NTP), generated by an arc discharge reactor at pressures >> 1 MPa, coupled with a mullite-coated 2 wt%-Co/5 wt%-Al2O3 catalyst. The FTS product yields and electrical energy consumption for the pure plasma (no catalyst) and plasma-catalytic FTS processes were compared under the scope of various reactor operating parameters, namely, pressure (0.5 to 10 MPa), current (250 to 450 mA) and inter-electrode gap (0.5 to 2 mm). The major products, obtained in low concentrations for both processes, were gaseous C1–C3 hydrocarbons, synthesised in the order: methane >> ethane > ethylene > propane. The hydrocarbon product yields were observed to increase, while the specific required energy generally decreased with increasing pressure, decreasing current and increasing inter-electrode gap. Plasma-catalysis improved the FTS performance, with the optimum conditions as: (i) 10 MPa at 10 s and 2 MPa at 60 s for the pressure variation study with the longer treatment time producing higher yields; (ii) 250 mA for the current variation study; (iii) 2 mm for the inter-electrode gap variation study. Plasma-catalysis at a gap of 2 mm yielded the highest concentrations of methane (15,202 ppm), ethane (352 ppm), ethylene (121 ppm) and propane (20 ppm), thereby indicating the inter-electrode gap as the most influential parameter.