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Articles de revues sur le sujet « Support de catalyseurs »

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Auteur : Grafiati
Publié le 22 juin 2024

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1

DEVYNCK, J., et F. BEDIOUI. « Catalyse électrochimique à l'aide de catalyseurs immobilisés sur support organique ou minéral ». Le Journal de Physique IV 04, no C1 (janvier 1994) : C1–131—C1–146. http://dx.doi.org/10.1051/jp4:1994109.

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Barrauit, JoËL, et Nazaire Biwole. « CONVERSATION DU GAZ DE SYNTHESE EN HYDROCARBURES LIQUIDES:INFLUENCE DU SUPPORT ET DES PROMOTEURS (La, Ce ET Mn) SUR LES CATALYSEURS AU COBALTS ». Bulletin des Sociétés Chimiques Belges 104, no 3 (1 septembre 2010) : 149–53. http://dx.doi.org/10.1002/bscb.19951040307.

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Delannay, F., E. N. Haeussler et B. Delmon. « Étude Par Spectrométrie De Diffusion Ionique De La Structure De La Bi-Couche D'Oxyde De Molybdene Et De Cobalt A La Surface Du Support Des Catalyseurs D'Hydrodésulfuration ». Bulletin des Sociétés Chimiques Belges 89, no 4 (1 septembre 2010) : 255–59. http://dx.doi.org/10.1002/bscb.19800890401.

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Mauret, P., P. Alphonse et M. Ramalanjaona. « Désactivation de catalyseurs au nickel non supporté ». Journal de Chimie Physique 84 (1987) : 895–99. http://dx.doi.org/10.1051/jcp/1987840895.

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Jaeger, Philippe. « Préparation de catalyseurs supportés. Preparation of supported catalysts ». Sciences Géologiques. Bulletin 46, no 1 (1993) : 281–89. http://dx.doi.org/10.3406/sgeol.1993.1911.

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Mabang, Théophile, Joseph Mbadcam Ketcha et Claudine Géron. « Préparation et caractérisation de catalyseurs au palladium supporté : monométalliques et bimétalliques ». Annales de Chimie Science des Matériaux 30, no 2 (28 avril 2005) : 149–70. http://dx.doi.org/10.3166/acsm.30.149-170.

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Zalma, Roger, Lionel Bonneau, Jeanine Fournier, Joëlle Guignard, Françoise Borg et Henri Pezerat. « Hydrodésazotation de l'indole sur catalyseur fer supporté sur amiante ». Canadian Journal of Chemistry 65, no 3 (1 mars 1987) : 523–27. http://dx.doi.org/10.1139/v87-091.

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The aim of this study is to examine hydrodenitrogenation (HDN) of indole on asbestos catalysts (chrysotile and crocidolite) under hydrogen pressure. HDN is carried out according to two competitive pathways, either via ortho-ethylaniline or via ortho-toluidine. This reaction is assisted by increase of temperature and pressure and by pre-reduction of the asbestos. Particles of Fe0on the fibre surface are formed from the original material. Their presence plays a role in the initial breaking of the C—N bond and in the hydrogenation reaction.
8

Bachari, Khaldoun, Rabah Bouarab et Ouiza Chérifi. « Production d’Hydrogène via le Procédé Catalytique CH4 + CO2 ». Journal of Renewable Energies 4, no 2 (31 décembre 2001) : 101–5. http://dx.doi.org/10.54966/jreen.v4i2.1002.

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La réaction de reformage du méthane par le CO2 en gaz de synthèse (H2, CO) a été étudiée sur catalyseurs à base de nickel, cobalt et de terres rares supportés. Les solides catalytiques ont été préparés par imprégnation sèche et caractérisés par absorption atomique et par la diffraction des rayons-X. La production d’hydrogène est remarquablement influencée par la nature de la phase métallique et des supports utilisés. L’ordre décroissent des conversions de CO2 et de CH4 ainsi que la production d’hydrogène des catalyseurs supportés sur silice est : Ru, Ni, Rh, Pt, Co. En revanche, l’activité des catalyseurs supportés sur l’alumine suit la séquence suivante : Rh , Ru, Pt.
9

Milgram, Lisa, Sarah Wheeler, Andrea Adamic, Mirhad Loncar, Micheal Guirguis et Betty Jo McCabe. « A Framework for Evaluating the Implementation of Biosimilar Drugs ». Canadian Journal of Hospital Pharmacy 76, no 2 (3 avril 2023) : 109–16. http://dx.doi.org/10.4212/cjhp.3272.

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Background: The introduction of biosimilar drugs has significant effects on health care systems, and a variety of approaches are required to support acceptance, adoption, and use of these drugs. Literature exists on the enablers of, and barriers to, biosimilar implementation, but frameworks that support the evaluation of biosimilar implementation strategies are currently lacking. Objective: To develop an evaluation framework for assessing the effects of biosimilar implementation strategies on patients, clinicians, and publicly funded drug programs. Methods: The scope of the evaluation was determined by a pan-Canadian working group through the creation of a logic model of activities and expected outcomes associated with biosimilar implementation. Each component of the logic model was considered under the RE-AIM framework, which led to a set of evaluation questions and indicators. Feedback to inform the final framework was sought from stakeholders through focus group sessions and written responses. Results: An evaluation framework was created that articulates evaluation questions and indicators across 5 priority areas: stakeholder engagement, patient experience, patient outcomes, clinician experience, and system sustainability and affordability. Stakeholder feedback was obtained through 9 focus group sessions with a total of 87 participants. Feedback was used to refine the framework on the basis of stakeholder priorities and feasibility. Conclusions: Through extensive stakeholder consultation, an evaluation framework was developed to measure and monitor the effects of biosimilar implementation on the 5 identified priority areas, as well as to inform future biosimilar implementations. This framework can be used as a starting point for evaluating the implementation of biosimilars across health care systems. RÉSUMÉ Contexte : L’apparition de médicaments biosimilaires a eu et continue d’avoir des effets importants sur les systèmes de soins de santé et diverses approches doivent être mises en place pour qu’ils soient acceptés, adoptés et utilisés. Il existe de la documentation sur les catalyseurs et les obstacles à leur mise en œuvre, mais les cadres entourant l’évaluation des stratégies de mise en œuvre des médicaments biosimilaires font actuellement défaut. Objectif : Développer un cadre d’évaluation pour estimer les retombées des stratégies de mise en œuvre des biosimilaires sur les patients, les cliniciens et les programmes de médicaments financés par les deniers publics. Méthodes : Un groupe de travail pancanadien a déterminé la portée de l’évaluation à l’aide d’un modèle logique des activités et des résultats attendus associés à la mise en œuvre des biosimilaires. Chaque composante du modèle logique a été examinée dans le cadre RE-AIM, ce qui a donné lieu à un ensemble de questions d’évaluation et des indicateurs d’évaluation. Des commentaires pour éclairer le cadre final ont été sollicités auprès des parties prenantes au moyen de groupes de discussion et de réponses écrites. Résultats : Un cadre d’évaluation a été défini. Il articule les questions d’évaluation et des indicateurs d’évaluation dans 5 domaines prioritaires : l’engagement des intervenants, l’expérience des patients, les résultats des patients, l’expérience des cliniciens et la durabilité et l’abordabilité du système. Les commentaires des intervenants ont été obtenus au cours de 9 séances de groupes de discussion avec un total de 87 participants. Les commentaires ont été utilisés pour affiner le cadre sur la base des priorités des parties prenantes et de la faisabilité. Conclusions : Une vaste consultation des parties prenantes a permis de définir un cadre d’évaluation pour mesurer et surveiller les effets de la mise en œuvre des biosimilaires sur les 5 domaines prioritaires identifiés, ainsi que pour éclairer les futures mises en œuvre des biosimilaires. Ce cadre peut être utilisé comme point de départ pour évaluer la mise en œuvre des biosimilaires dans les systèmes de soins de santé.
10

Julca, Alex. « Can immigrant remittances support development finance ? » Panoeconomicus 60, no 3 (2013) : 365–80. http://dx.doi.org/10.2298/pan1303365j.

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Immigrant remittances are a significant source of income and finance for developing economies, representing about three times? official development assistance and over half of foreign direct investment annually received. Major motivations to send remittances are for improving food, health, and education spending of families at home as well as for investing in entrepreneurial ventures. Economic policies to channel remittances into development finance should translate these motivations into measures to boost social investment and local and regional production, linking remittances policies to broader fiscal, financial and institutional policies. A national development bank can be a catalyser of public and private interests by supporting the scale up of remittances investment programmes and by building partnerships with regional and multilateral development institutions.
11

Liu, Junli, John W. Crawford et Roberto Viola. « A Theoretical Analysis of the Role of Pyrophosphate,Fructose 6-P,1-Phosphotransferase in Energy Dissipation During the Conversion of Fructose 6-Phosphate to Fructose 1,6-Bisphosphate in Plant Cells ». Journal of Biological Systems 05, no 03 (septembre 1997) : 389–401. http://dx.doi.org/10.1142/s0218339097000242.

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A theoretical analysis of the effect of pyrophosphate,fructose 6-P,1-phosphotransferase (PFP) on energy dissipation in the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate is presented. The conclusion depends sensitively on whether PFP is in equilibrium, or catalyses a net flux in the directions of gluconeogenesis or glycolysis. It is shown that the conditions under which PFP is in equilibrium are rather restricted. Furthermore, experimental evidence supports the theoretical prediction that PFP catalyses a net flux in real systems. When PFP catalyses a net glycolytic flux, the system where both PFP and PFK are active always dissipates less energy than the system where only PFK exists. However, when PFP catalyses a net flux in gluconeogenesis, the PFK-PFP system dissipates more energy than the system where only PFK exists. By comparing the theoretical work with experimental results, the evidence suggests that PFP in higher plant cells catalyses a net glycolytic flux, and its presence increases the energetic efficiency of glycolysis.
12

Guerrero Fajardo, Carlos Alberto, Francisco José Sánchez Castellanos, Anne Cécile Roger et Claire Courson. « Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde ». Ingeniería e Investigación 28, no 1 (1 janvier 2008) : 72–80. http://dx.doi.org/10.15446/ing.investig.v28n1.14869.

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Iron materials supported on silica were prepared by the sol-gel method for evaluating catalytic activity in selective oxidation of methane to formaldehyde. Four catalysts were prepared, one corresponding to the silica support (catalyst 1S), another to the titanium support (catalyst 1T) and two more having 0.5% weight iron loads, one for the silica support (catalyst 2FS) and the last one the titanium support (catalyst 2FT). The higher BET areas were 659 and 850 m2/g for catalysts 1S and 2FS, respectively while catalysts 1T and 2FT displayed areas of 65 and 54 m2/g, respectively. Scanning and transmission electronic microscopy displayed an amorphous structure in the silica-supported materials while titanium-supported materials displayed dense materials having defined structure. X-ray diffraction confirmed the silica’s amorphous structure in 1S and 2FS catalysts and displayed the 1T and 2FT catalysts’ anatase structure. The programmed temperature reduction for the 1S and 2FS catalysts did not display reducible species, while displaying hydrogen consumption peaks related to Fe3O4 reduction to α-Fe via FexO route for 1T and 2FT catalysts. The electronic spectroscopy X-ray photo confirmed the Fe(III) specie as having 710.6 e.V binding energy for both 2FS and 2FT catalysts. Catalytic activity was carried out at atmospheric pressure in a quartz reactor, reaction mixture as CH4/O2/N2 =7.5/1/4 at 400-800°C temperature range. The reaction products were analysed by gas chromatography on Hayesep R and T columns using 5Å molecular screening. The best response for selective oxidation of methane to formaldehyde was displayed by the 2FS catalyst with 3.4% mol methane conversion at 650°C, 11.9% mol formaldehyde selectivity and 0.0211 g HCHO/Kg catalyst yield.
13

Suktanarak, Pattira, Sarayut Watchasit, Kantima Chitchak, Nukorn Plainpan, Kittipong Chainok, Parichatr Vanalabhpatana, Prompong Pienpinijtham et al. « Tuning the reactivity of copper complexes supported by tridentate ligands leading to two-electron reduction of dioxygen ». Dalton Transactions 47, no 45 (2018) : 16337–49. http://dx.doi.org/10.1039/c8dt03183e.

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14

Loomes, K. M., et T. M. Kitson. « Aldehyde dehydrogenase catalyses acetaldehyde formation from 4-nitrophenyl acetate and NADH ». Biochemical Journal 238, no 2 (1 septembre 1986) : 617–19. http://dx.doi.org/10.1042/bj2380617.

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Incubation of sheep liver cytoplasmic aldehyde dehydrogenase with the substrate 4-nitrophenyl [14C]acetate in the presence of NADH leads to the formation of 14C-labelled acetaldehyde. This observation strongly supports the idea that the esterase and dehydrogenase activities of the enzyme occur at the same site and involve the intermediacy of a common acyl-enzyme.
15

Yu, Bin, Tuğçe Ayvalı, Zhi-Qiang Wang, Xue-Qing Gong, Abdulaziz A. Bagabas et S. C. Edman Tsang. « Gas phase selective propylene epoxidation over La2O3-supported cubic silver nanoparticles ». Catalysis Science & ; Technology 9, no 13 (2019) : 3435–44. http://dx.doi.org/10.1039/c9cy00567f.

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It is shown that the Ag nanocube/La2O3 interface catalyses gas phase oxidation of propylene to propylene oxide cooperatively with enhanced selectivity and conversion. Dioxygen is preferentially activated and dissociated by La2O3(001) and the active atomic oxygen over the Ag(100) facet leads to selective propylene epoxidation.
16

Mbang, Théophile, Joseph Mbadcam Ketcha et Claudine Geron. « Hydrogénation et isomérisation de r(+) limonène, 2-cyclohexèn-1-one et cyclohexanone par des catalyseurs au palladium supporté monométalliques et bimétalliques ». Annales de Chimie Science des Matériaux 31, no 4 (31 juillet 2006) : 483–98. http://dx.doi.org/10.3166/acsm.31.483-498.

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Jin, Tong-Shou, Jin-Chong Xiao, Zhen-Hua Wang et Tong-Shuang Li. « Silica Gel-Supported Phosphotungstic Acid (PTA) Catalysed Acylation of Alcohols and Phenols with Acetic Anhydride under Mild Reaction Conditions ». Journal of Chemical Research 2003, no 7 (juillet 2003) : 412–14. http://dx.doi.org/10.3184/030823403103174335.

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Phosphotungstic acid, which is commercially available, practically and efficiently catalyses the acylation of a series of alcohols and phenols with acetic anhydride at room temperature or at refluxing temperature.
18

Li, Rui Rui, Pi Wu Li, Dian Lei Liu, Qiong Hao, Qing Yang et Sheng Wang. « Direct Immobilization of Glucose Oxidase on the Hydrophilic Copolymer Support Containing Oxirane ». Advanced Materials Research 852 (janvier 2014) : 17–22. http://dx.doi.org/10.4028/www.scientific.net/amr.852.17.

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Glucose oxidase (GOD) (EC 1.1.3.4) is an oxido-reductase that catalyses the oxidation action of glucose to hydrogen peroxide and D-glucono-δ-lactone [. GOD is widely used in the determination of free glucose in body fluids, in vegetal raw material and in the food industry [. It also has many applications in biotechnologies, typically enzyme assays for biochemistry including biosensors in nanotechnologies. Free GOD will be denatured and inactivated rapidly due to its structural instability under extreme pH or temperature [. Four immobilizing methods, including physical adsorption, covalent binding, crosslinking and embedding methods, were used to improve their economic feasibility. Covalent binding combined active functional group monomers of carriers onto enzymes [4-. Researches showed that oxirane groups can react with-NH2 and-HS of enzymes under mild conditions so that the enzyme molecules were immobilized on the copolymer support containing oxirane [.
19

Donald, William E. « Three Key Ways That Mentorship Can Support Early Career Scholars ». GiLE Journal of Skills Development 3, no 2 (25 octobre 2023) : 3–6. http://dx.doi.org/10.52398/gjsd.2023.v3.i2.pp3-6.

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Navigating the intrinsic landscape of academia can often feel like attempting to manoeuvre through a maze, especially for individuals at the dawn of their scholarly journey. Drawing on my previous experience as an early career scholar, my current role as a global mentor to emerging scholars, and my decade of research on sustainable careers, I shed light on the profound impact of mentorship for early career scholars. This article uncovers three compelling facets illuminating how mentorship can offer robust scaffolding for these intellectuals. Firstly, we unravel the secret to deciphering the unspoken codes of the academic world, ensuring you are not just a player but a master of the game. Secondly, we explore how taking the reins of your academic destiny can be made more attainable with a mentor's steady support and wisdom. Lastly, we delve into the often overlooked link between mentorship and holistic well-being, emphasising the vital role in nurturing careers and personal fulfilment. Through these insights, we see how mentorship catalyses early career scholars towards heightened productivity, career satisfaction, and an increased likelihood of success in their scholarly pursuits.
20

Bensaddik, A., B. Ernst, F. Garin, G. Maire et A. Kiennemann. « Etude in situ par EXAFS de la réductibilité d'un catalyseur Fischer-Tropsch à base de cobalt supporté sur silice ». Le Journal de Physique IV 06, no C4 (juillet 1996) : C4–545—C4–552. http://dx.doi.org/10.1051/jp4:1996451.

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SHIMAZU, Shogo, et Takayoshi UEMATSU. « Preparation of Clay-Supported Metal Complexes and Application to Catalyses for Molecular Recognition Reactions. » Journal of Synthetic Organic Chemistry, Japan 51, no 7 (1993) : 664–70. http://dx.doi.org/10.5059/yukigoseikyokaishi.51.664.

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Racineux, G. « Extrusion de supports de catalyseurs : Le problème de la caractérisation rhéologique des pâtes fortement chargées ». Mécanique & ; Industries 1, no 2 (mars 2000) : 151–64. http://dx.doi.org/10.1016/s1296-2139(00)00124-x.

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Tripathy, Rajat K., Aneeya K. Samantara, Pratap Mane, Brahmananda Chakraborty et J. N. Behera. « Cobalt metal organic framework (Co-MOF) derived CoSe2/C hybrid nanostructures for the electrochemical hydrogen evolution reaction supported by DFT studies ». New Journal of Chemistry 46, no 6 (2022) : 2730–38. http://dx.doi.org/10.1039/d1nj05528c.

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Through a single step and facile approach, CoSe2/C is synthesized from a HER inactive pristine MOF without adding any external carbon source, which efficiently catalyses HER in acidic medium which was also supported by DFT studies.
24

Gervais, Michel, Lucie Gauthier et Lise Gélinas. « La réhabilitation de l’hôpital psychiatrique : Une question d’audace et de synergie ». Santé mentale au Québec 22, no 2 (11 septembre 2007) : 137–53. http://dx.doi.org/10.7202/032419ar.

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RÉSUMÉ Cet article expose, en utilisant un mode d'analyse psycho-dynamique, certaines similitudes entre les facteurs qui entravent le processus de réinsertion sociale du " patient " et les forces socio-politiques qui s'opposent à la " réhabilitation " de l'institution sociale représentée par l'hôpital psychiatrique. En support à cette analogie, le texte esquisse les transformations réalisées depuis quelques années au Centre hospitalier psychiatrique Sainte-Thérèse de Shawinigan et suggère que, pour faire de telles transformations, le développement de services de réadaptation peut servir de catalyseur. Il propose également une analyse perceptuelle des réactions humaines, politiques et sociales suscitées par la métamorphose du rôle traditionnel attribué à l'institution psychiatrique.
25

Guerrero Fajardo, Carlos Alberto, Yvonne N’Guyen, Claire Courson et Anne Cécile Roger. « Fe/SiO2 catalysts for the selective oxidation of methane to formaldehyde ». Ingeniería e Investigación 26, no 2 (1 mai 2006) : 37–44. http://dx.doi.org/10.15446/ing.investig.v26n2.14735.

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Selective oxidation of methane to formaldehyde was analysed with iron catalysts supported on silica prepared by the sol-gel method, leading to obtaining a large support surface area facilitating high dispersion of iron on silica’s amorphous surface. Seven catalysts were prepared; one of them corresponded to the silica support and another five having an iron load 0.1-0.5% in weight. Catalyst 7 (0.5% Fe in weight) was prepared with neutral pH control and had the most homogeneous characteristics since it did not present isolated iron species, corroborated by SEM and TEM analysis. The highest BET areas were 1,757 and 993 m2.g-1 for 0.5% Fe catalysts, having an average 36% microporosity and 43% mesoporosity. X-ray diffraction confirmed the catalyst’s amorphous structure. Catalytic activity was carried out with catalyser 7 at atmospheric pressure in a quartz reactor using a CH4/O2/N2=7.5/1/4 reaction mixture at 400-750°C temperature range. Reaction products were analysed by gas chromatography with TCD. The heterogeneous catalysts displayed greater methane conversion (but with methanol selectivity) whereas homogenous catalyst 7 gave better results regarding formaldehyde. The highest conversion percentage (8.60% mol) for catalyser 7 was presented at 650°C. Formaldehyde selectivity was 50% mol in the 600-650°C range and maximum yield (0.31g HCHO/Kg catalyst) was found in this range; it was thus considered that 650°C for the reaction was thereby the best operating temperature.
26

Harter, T. S., F. S. Zanuzzo, C. T. Supuran, A. K. Gamperl et C. J. Brauner. « Functional support for a novel mechanism that enhances tissue oxygen extraction in a teleost fish ». Proceedings of the Royal Society B : Biological Sciences 286, no 1903 (29 mai 2019) : 20190339. http://dx.doi.org/10.1098/rspb.2019.0339.

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A successful spawning migration in salmon depends on their athletic ability, and thus on efficient cardiovascular oxygen (O 2 ) transport. Most teleost fishes have highly pH-sensitive haemoglobins (Hb) that can release large amounts of O 2 when the blood is acidified at the tissues. We hypothesized that plasma-accessible carbonic anhydrase (paCA; the enzyme that catalyses proton production from CO 2 ) is required to acidify the blood at the tissues and promote tissue O 2 extraction. Previous studies have reported an elevated tissue O 2 extraction in hypoxia-acclimated teleosts that may also be facilitated by paCA. Thus, to create experimental contrasts in tissue O 2 extraction, Atlantic salmon were acclimated to normoxia or hypoxia (40% air saturation for more than six weeks), and the role of paCA in enhancing tissue O 2 extraction was tested by inhibiting paCA at rest and during submaximal exercise. Our results show that: (i) in both acclimation groups, the inhibition of paCA increased cardiac output by one-third, indicating a role of paCA in promoting tissue O 2 extraction during exercise, recovery and at rest; (ii) the recruitment of paCA was plastic and increased following hypoxic acclimation; and (iii) maximal exercise performance in salmon, and thus a successful spawning migration, may not be possible without paCA.
27

Hong, Hui, Yuhui Sun, Yongjun Zhou, Emily Stephens, Markiyan Samborskyy et Peter F. Leadlay. « Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase ». Beilstein Journal of Organic Chemistry 12 (11 octobre 2016) : 2164–72. http://dx.doi.org/10.3762/bjoc.12.206.

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The assembly-line synthases that produce bacterial polyketide natural products follow a modular paradigm in which each round of chain extension is catalysed by a different set or module of enzymes. Examples of deviation from this paradigm, in which a module catalyses either multiple extensions or none are of interest from both a mechanistic and an evolutionary viewpoint. We present evidence that in the biosynthesis of the 36-membered macrocyclic aminopolyol lactones (marginolactones) azalomycin and kanchanamycin, isolated respectively from Streptomyces malaysiensis DSM4137 and Streptomyces olivaceus Tü4018, the first extension module catalyses both the first and second cycles of polyketide chain extension. To confirm the integrity of the azl gene cluster, it was cloned intact on a bacterial artificial chromosome and transplanted into the heterologous host strain Streptomyces lividans, which does not possess the genes for marginolactone production. When furnished with 4-guanidinobutyramide, a specific precursor of the azalomycin starter unit, the recombinant S. lividans produced azalomycin, showing that the polyketide synthase genes in the sequenced cluster are sufficient to accomplish formation of the full-length polyketide chain. This provides strong support for module iteration in the azalomycin and kanchanamycin biosynthetic pathways. In contrast, re-sequencing of the gene cluster for biosynthesis of the polyketide β-lactone ebelactone in Streptomyces aburaviensis has shown that, contrary to a recently-published proposal, the ebelactone polyketide synthase faithfully follows the colinear modular paradigm.
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Bu, Yifan, Tao Zhang, Bo Jiang et Jingjing Chen. « Improved Performance of D-Psicose 3-Epimerase by Immobilisation on Amino-Epoxide Support with Intense Multipoint Attachment ». Foods 10, no 4 (11 avril 2021) : 831. http://dx.doi.org/10.3390/foods10040831.

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D-allulose is an epimer of D-fructose at the C-3 position. With similar sweetness to sucrose and a low-calorie profile, D-allulose has been considered a promising functional sweetener. D-psicose 3-epimerase (DPEase; EC 5.1.3.30) catalyses the synthesis of D-allulose from D-fructose. Immobilised enzymes are becoming increasingly popular because of their better stability and reusability. However, immobilised DPEase generally exhibits less activity or poses difficulty in separation. This study aimed to obtain immobilised DPEase with high catalytic activity, stability, and ease of separation from the reaction solution. In this study, DPEase was immobilised on an amino-epoxide support, ReliZyme HFA403/M (HFA), in four steps (ion exchange, covalent binding, glutaraldehyde crosslinking, and blocking). Glycine-blocked (four-step immobilisation) and unblocked (three-step immobilisation) immobilised DPEase exhibited activities of 103.5 and 138.8 U/g support, respectively, but contained equal amounts of protein. After incubation at 60 °C for 2 h, the residual activity of free enzyme decreased to 12.5%, but the activities of unblocked and blocked DPEase remained at 40.9% and 52.3%, respectively. Immobilisation also altered the substrate specificity of the enzyme, catalysing L-sorbose to L-tagatose and D-tagatose to D-sorbose. Overall, the immobilised DPEase with intense multipoint attachment, especially glycine-blocked DPEase, showed better properties than the free form, providing a superior potential for D-allulose biosynthesis.
29

Guerriero, Gea, Ian Stokes et Christopher Exley. « Is callose required for silicification in plants ? » Biology Letters 14, no 10 (octobre 2018) : 20180338. http://dx.doi.org/10.1098/rsbl.2018.0338.

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The cell wall polymer callose catalyses the formation of silica in vitro and is heavily implicated in biological silicification in Equisetum (horsetail) and Arabidopsis (thale cress) in vivo . Callose, a β-1,3-glucan, is an ideal partner for silicification, because its amorphous structure and ephemeral nature provide suitable microenvironments to support the condensation of silicic acid into silica. Herein, using scanning electron microscopy, immunohistochemistry and fluorescence, we provide further evidence of the cooperative nature of callose and silica in biological silicification in rice, an important crop plant and known silica accumulator. These new data along with recently published research enable us to propose a model to describe the intracellular events that together determine callose-driven biological silicification.
30

Fedulova, Natalia, Françoise Raffalli-Mathieu et Bengt Mannervik. « Porcine glutathione transferase Alpha 2-2 is a human GST A3-3 analogue that catalyses steroid double-bond isomerization ». Biochemical Journal 431, no 1 (14 septembre 2010) : 159–67. http://dx.doi.org/10.1042/bj20100839.

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A primary role of GSTs (glutathione transferases) is detoxication of electrophilic compounds. In addition to this protective function, hGST (human GST) A3-3, a member of the Alpha class of soluble GSTs, has prominent steroid double-bond isomerase activity. The isomerase reaction is an obligatory step in the biosynthesis of steroid hormones, indicating a special role of hGST A3-3 in steroidogenic tissues. An analogous GST with high steroid isomerase activity has so far not been found in any other biological species. In the present study, we characterized a Sus scrofa (pig) enzyme, pGST A2-2, displaying high steroid isomerase activity. High levels of pGST A2-2 expression were found in ovary, testis and liver. In its functional properties, other than steroid isomerization, pGST A2-2 was most similar to hGST A3-3. The properties of the novel porcine enzyme lend support to the notion that particular GSTs play an important role in steroidogenesis.
31

De Rosa, Marcello, Luca Bartoli, Chrysanthi Charatsari et Evagelos Lioutas. « Knowledge transfer and innovation adoption in women farmers ». British Food Journal 123, no 1 (20 août 2020) : 317–36. http://dx.doi.org/10.1108/bfj-02-2020-0159.

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PurposeThe study aims to analyse patterns of innovation adoption among Italian female-owned farms, by evaluating the impact of innovation support services and entrepreneurial orientation on innovation adoption.Design/methodology/approachTo explore both the entrepreneurial identity of women farmers and the role of innovation support services in boosting innovation, a questionnaire was administered to a sample of Italian women farmers. A multivariate analysis lets to classify the farms under the previous two perspectives.FindingsThe analysis reveals various patterns of innovation adoption, heavily depending on both the effectiveness of innovation support services and farmers' entrepreneurial orientation.Research limitations/implicationsThe research analyses a sample of women farmers to excavate worlds of innovation among female-owned farms. Cross-gender comparisons can offer a more complete picture of the ways gender catalyses innovation adoption.Practical implicationsAt a policy level, the results of our empirical analysis point out the need for gendering innovation analysis and for tailoring policy interventions to the different worlds of innovation that exist in rural Italy.Social implicationsThe paper confirms the importance of deepening research on gender issues, with the purpose of fulfilling gender mainstreaming underlined in numerous policy documents at both the European and international levels.Originality/valueThe analysis represents a first attempt to join both the entrepreneurial identity of women farmers and the role of innovation support services in boosting innovation. Therefore, the paper fills a gap in the literature.
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DØSKELAND, Anne P., et Torgeir FLATMARK. « Recombinant human phenylalanine hydroxylase is a substrate for the ubiquitin-conjugating enzyme system ». Biochemical Journal 319, no 3 (1 novembre 1996) : 941–45. http://dx.doi.org/10.1042/bj3190941.

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Mammalian phenylalanine hydroxylase (PAH) catalyses the conversion of L-phenylalanine to L-tyrosine in the presence of dioxygen and tetrahydrobiopterin; it is a highly regulated enzyme. Little is known about the rates of synthesis and degradation of PAH in vivo. The enzyme has been reported to have a half-life of approx. 2 days in rat liver and 7–8 h in rat hepatoma cells, but the mechanism of its degradation is not known. In the present study it is shown that the tetrameric form of the recombinant wild-type human enzyme is a substrate for the ubiquitin-conjugating enzyme system in the cytosolic fraction of rat testis. Our findings support the conclusion that multi-/poly-ubiquitination of human PAH plays a key role in the turnover of this cytosolic liver enzyme and provides a mechanism for the increased turnover observed for a number of recombinant mutant forms of the enzyme related to the metabolic disorder phenylketonuria, when expressed in eukaryotic cells.
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WIAME, Elsa, et Emile VAN SCHAFTINGEN. « Fructoselysine 3-epimerase, an enzyme involved in the metabolism of the unusual Amadori compound psicoselysine in Escherichia coli ». Biochemical Journal 378, no 3 (15 mars 2004) : 1047–52. http://dx.doi.org/10.1042/bj20031527.

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The frl (fructoselysine) operon encodes fructoselysine 6-kinase and fructoselysine 6-phosphate deglycase, allowing the conversion of fructoselysine into glucose 6-phosphate and lysine. We now show that a third enzyme encoded by this operon catalyses the metal-dependent reversible interconversion of fructoselysine with its C-3 epimer, psicoselysine. The enzyme can be easily assayed through the formation of tritiated water from [3-3H]fructoselysine. Psicoselysine supports the growth of Escherichia coli, causing the induction of the three enzymes of the frl operon. No growth on fructoselysine or psicoselysine was observed with Tn5 mutants in which the putative transporter (FrlA) or fructoselysine 6-phosphate deglycase (FrlB) had been inactivated, indicating the importance of the frl operon for the metabolism of both substrates. The ability of E. coli to grow on psicoselysine suggests the occurrence of this unusual Amadori compound in Nature.
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Esser, Julia, Marija Rakonjac, Bettina Hofmann, Lutz Fischer, Patrick Provost, Gisbert Schneider, Dieter Steinhilber, Bengt Samuelsson et Olof Rådmark. « Coactosin-like protein functions as a stabilizing chaperone for 5-lipoxygenase : role of tryptophan 102 ». Biochemical Journal 425, no 1 (14 décembre 2009) : 265–74. http://dx.doi.org/10.1042/bj20090856.

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The activity of 5-LO (5-lipoxygenase), which catalyses two initial steps in the biosynthesis of pro-inflammatory LTs (leukotrienes), is strictly regulated. One recently discovered factor, CLP (coactosin-like protein), binds 5-LO and promotes LT formation. In the present paper we report that CLP also stabilizes 5-LO and prevents non-turnover inactivation of the enzyme in vitro. Mutagenesis of tryptophan residues in the 5-LO β-sandwich showed that 5-LO-Trp102 is essential for binding to CLP, and for CLP to support 5-LO activity. In addition, the stabilizing effect also depended on binding between CLP and 5-LO. After mutations which prevent interaction (5-LO-W102A or CLP-K131A), the protective effect of CLP was absent. A calculated 5-LO–CLP docking model indicates that CLP may bind to additional residues in both domains of 5-LO, thus possibly stabilizing the 5-LO structure. To obtain further support for binding between CLP and 5-LO in a living cell, subcellular localization of CLP and 5-LO in the monocytic cell line Mono Mac 6 was determined. In these cells, 5-LO associates with a nuclear fraction only when differentiated cells are primed with phorbol ester and stimulated with ionophore. The same pattern of redistribution was found for CLP, indicating that the two proteins associate with the nucleus in a co-ordinated fashion. The results of the present study support a role for CLP as a chaperoning scaffold factor, influencing both the stability and the activity of 5-LO.
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Lynch, C. J., H. Fox, S. A. Hazen, B. A. Stanley, S. Dodgson et K. F. Lanoue. « Role of hepatic carbonic anhydrase in de novo lipogenesis ». Biochemical Journal 310, no 1 (15 août 1995) : 197–202. http://dx.doi.org/10.1042/bj3100197.

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The role of carbonic anhydrase in de novo lipid synthesis was examined by measuring [1-14C]acetate incorporation into total lipids, fatty acids and non-saponifiable lipids in freshly isolated rat hepatocytes. Two carbonic anhydrase inhibitors, trifluoromethylsulphonamide (TFMS) and ethoxozolamide (ETZ) decreased incorporation of 14C into total lipids. Both fatty acid and non-saponifiable lipid components of the total lipid were inhibited to approximately the same extent by 100 microM TFMS (29 +/- 0.3% and 35 +/- 0.3% of control respectively in replicate studies). However, neither drug significantly affected ATP concentrations or the transport activity of Na+/K(+)-ATPase, two measures of cell viability. To establish the site of this inhibition, water-soluble 14C-labelled metabolites from perchloric acid extracts of the radiolabelled cells were separated by ion-exchange chromatography. TFMS inhibited 14C incorporation into citrate, malate, alpha-oxoglutarate and fumarate, but had no effect on incorporation of 14C into acetoacetate. Since ATP citrate-lyase, the cytosolic enzyme that catalyses the conversion of citrate into acetyl-CoA, catalyses an early rate-limiting step in fatty acid synthesis, levels of cytosolic citrate may be rate controlling for de novo fatty acid and sterol synthesis. Indeed citrate concentrations were significantly reduced to 37 +/- 6% of control in hepatocytes incubated with 100 microM TFMS for 30 min. TFMS also inhibited the incorporation of 14C from [1-14C]pyruvate into malate, citrate and glutamate, but not into lactate. This supports the hypothesis that TFMS inhibits pyruvate carboxylation, i.e. since all of the 14C from [1-14C]pyruvate converted into citric acid cycle intermediates must come via pyruvate carboxylase (i.e. rather than pyruvate dehydrogenase). Our findings indicate a role for carbonic anhydrase in hepatic de novo lipogenesis at the level of pyruvate carboxylation.
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Venco, Paola, Sabrina Dusi, Lorella Valletta et Valeria Tiranti. « Alteration of the coenzyme A biosynthetic pathway in neurodegeneration with brain iron accumulation syndromes ». Biochemical Society Transactions 42, no 4 (1 août 2014) : 1069–74. http://dx.doi.org/10.1042/bst20140106.

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NBIA (neurodegeneration with brain iron accumulation) comprises a heterogeneous group of neurodegenerative diseases having as a common denominator, iron overload in specific brain areas, mainly basal ganglia and globus pallidus. In the past decade a bunch of disease genes have been identified, but NBIA pathomechanisms are still not completely clear. PKAN (pantothenate kinase-associated neurodegeneration), an autosomal recessive disorder with progressive impairment of movement, vision and cognition, is the most common form of NBIA. It is caused by mutations in the PANK2 (pantothenate kinase 2) gene, coding for a mitochondrial enzyme that phosphorylates vitamin B5 in the first reaction of the CoA (coenzyme A) biosynthetic pathway. A distinct form of NBIA, denominated CoPAN (CoA synthase protein-associated neurodegeneration), is caused by mutations in the CoASY (CoA synthase) gene coding for a bifunctional mitochondrial enzyme, which catalyses the final steps of CoA biosynthesis. These two inborn errors of CoA metabolism further support the concept that dysfunctions in CoA synthesis may play a crucial role in the pathogenesis of NBIA.
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Cannon, Sheila M., et Karin Kreutzer. « Mission accomplished ? Organizational identity work in response to mission success ». Human Relations 71, no 9 (13 février 2018) : 1234–63. http://dx.doi.org/10.1177/0018726717741677.

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How do nonprofit organizations reinvent their identities after they have accomplished all or part of their missions? This comparative case study of two Irish peacebuilding organizations explores what happens when their raison d’etre is fundamentally challenged. A successful peace process in Northern Ireland resulted in reduced support for peacebuilding organizations and a perception of mission accomplished. Conventional literature on nonprofit organizations portrays mission success as positive. We show that mission success paradoxically threatens the very existence of the organization as it may lead to member and donor dissociation. We find that mission success leads to identity ambiguity, which catalyses organizational identity work including different rhetorical strategies of self–other talk. We develop a process model illustrating competitive versus integrative approaches to organizational identity work to understand nonprofits adapting to mission success. We draw out lessons for practitioners. Focusing on a renewed mission that is consistent with the organization’s history is more important than finding a quick financial fix. Social purpose organizations can efficiently and effectively be redeployed to address new challenges, rather than recreating new organizations each time.
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Rahmani, Talia Putri, Yahdiana Harahap et Denni Joko Purwanto. « A review of the relationship between Doxorubicin and Doxorubicinol, CBR1 polymorphism, and cardiotoxicity ». Pharmacy Education 24, no 6 (14 juin 2024) : 105–15. http://dx.doi.org/10.46542/pe.2024.246.105115.

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Background: Doxorubicin is a chemotherapy drug given to breast cancer patients. However, its administration is limited by its cardiotoxicity. The CBR1 enzyme in the liver catalyses doxorubicin to doxorubicinol, which also contributes to its cardiotoxicity. The polymorphism of the CBR1 enzyme affects doxorubicin and doxorubicinol levels in the body. Objective: To review the effect of CBR1 polymorphisms on the levels of doxorubicin and doxorubicinol after administration of doxorubicin. Methods: Relevant studies from selected databases were examined; Three main studies with 20 support studies were reviewed. Results: The recommended methods were the analysis of doxorubicin and doxorubicinol levels using the Dried Blood Spot biosampling technique, which uses the ultra-high-performance liquid chromatography-tandem mass spectrometry (LCMS/MS), and the evaluation of the genetic profile of CBR1 using Polymerase Chain Reaction. Conclusion: Four CBR1 genetic polymorphisms have been shown to reduce doxorubicinol levels in the body, which is associated with decreased CBR1 activity and expression. Thus, the conversion of doxorubicin to doxorubicinol is reduced. Therefore, individuals who experience CBR1 polymorphisms have a lower risk of cardiotoxicity after the administration of doxorubicin.
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LI, YONGDONG, PAN LI, YUN PENG, QUNFENG WU, FUYAN HUANG, XIANG LIU, XUN LI et al. « Expression, characterization and crystal structure of thioredoxin from Schistosoma japonicum ». Parasitology 142, no 8 (26 mars 2015) : 1044–52. http://dx.doi.org/10.1017/s0031182015000244.

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SUMMARYSchistosoma japonicum, a human blood fluke, causes a parasitic disease affecting millions of people in Asia. Thioredoxin–glutathione system of S. japonicum plays a critical role in maintaining the redox balance in parasite, which is a potential target for development of novel antischistosomal agents. Here we cloned the gene of S. japonicum thioredoxin (SjTrx), expressed and purified the recombinant SjTrx in Escherichia coli. Functional assay shows that SjTrx catalyses the dithiothreitol (DTT) reduction of insulin disulphide bonds. The coupling assay of SjTrx with its endogenous reductase, thioredoxin glutathione reductase from S. japonicum (SjTGR), supports its biological function to maintain the redox homeostasis in the cell. Furthermore, the crystal structure of SjTrx in the oxidized state was determined at 2·0 Å resolution, revealing a typical architecture of thioredoxin fold. The structural information of SjTrx provides us important clues for understanding the maintenance function of redox homeostasis in S. japonicum and pathogenesis of this chronic disease.
40

Hamran, Nurshahira Hazwani, Fauziah Marpani, Nur Hidayati Othman, Nik Raikhan Nik Him, Nur Hashimah Alias et Junaidah Jai. « Effect of pH on membrane fouling during alcohol dehydrogenase immobilization in PES membrane ». Malaysian Journal of Chemical Engineering and Technology (MJCET) 3, no 2 (31 décembre 2020) : 30. http://dx.doi.org/10.24191/mjcet.v3i2.11232.

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Fouling-induced enzyme immobilization is a technique to immobilize enzyme by positively manipulating the knowledge of membrane fouling. In this study, Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was immobilized in the support layer of ultrafiltration PES membrane at different solution pH (acid, neutral and alkaline). ADH catalyses formaldehyde (CHOH) to methanol (CH3OH) and simultaneously oxidised nicotinamide adenine dinucleotide (NADH) to NAD+. The initial feed amount of enzyme is 3.0 mg. The objective of the study aims at the effect of different pH of feed solution during enzyme immobilization, in terms of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that, pH 5 holds the highest enzyme loading which is 65% while pH 7 holds the lowest at 52% out of 3.0 mg as the initial enzyme feed. The permeate flux for each pH decreased with increasing cumulative permeate volume. The observed rejection is inversely correlated with the pH where increase in pH will cause a lower observed rejection. The fouling model predicted that irreversible fouling occurs during enzyme immobilization at pH 7 with standard blocking mechanism while reversible fouling occurs at pH 5 and 9 with intermediate and complete blocking, respectively.
41

Chen, Yang, Joakim Näsvall, Shiying Wu, Dan I. Andersson et Maria Selmer. « Structure of AadA fromSalmonella enterica : a monomeric aminoglycoside (3′′)(9) adenyltransferase ». Acta Crystallographica Section D Biological Crystallography 71, no 11 (31 octobre 2015) : 2267–77. http://dx.doi.org/10.1107/s1399004715016429.

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Aminoglycoside resistance is commonly conferred by enzymatic modification of drugs by aminoglycoside-modifying enzymes such as aminoglycoside nucleotidyltransferases (ANTs). Here, the first crystal structure of an ANT(3′′)(9) adenyltransferase, AadA fromSalmonella enterica, is presented. AadA catalyses the magnesium-dependent transfer of adenosine monophosphate from ATP to the two chemically dissimilar drugs streptomycin and spectinomycin. The structure was solved using selenium SAD phasing and refined to 2.5 Å resolution. AadA consists of a nucleotidyltransferase domain and an α-helical bundle domain. AadA crystallizes as a monomer and is a monomer in solution as confirmed by small-angle X-ray scattering, in contrast to structurally similar homodimeric adenylating enzymes such as kanamycin nucleotidyltransferase. Isothermal titration calorimetry experiments show that ATP binding has to occur before binding of the aminoglycoside substrate, and structure analysis suggests that ATP binding repositions the two domains for aminoglycoside binding in the interdomain cleft. Candidate residues for ligand binding and catalysis were subjected to site-directed mutagenesis.In vivoresistance andin vitrobinding assays support the role of Glu87 as the catalytic base in adenylation, while Arg192 and Lys205 are shown to be critical for ATP binding.
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Por, Elaine D., Bret K. Samelson, Sergei Belugin, Armen N. Akopian, John D. Scott et Nathaniel A. Jeske. « PP2B/calcineurin-mediated desensitization of TRPV1 does not require AKAP150 ». Biochemical Journal 432, no 3 (25 novembre 2010) : 549–56. http://dx.doi.org/10.1042/bj20100936.

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Activation of protein kinases and phosphatases at the plasma membrane often initiates agonist-dependent signalling events. In sensory neurons, AKAP150 (A-kinase-anchoring protein 150) orientates PKA (protein kinase A), PKC (protein kinase C) and the Ca2+/calmodulin-dependent PP2B (protein phosphatase 2B, also known as calcineurin) towards membrane-associated substrates. Recent evidence indicates that AKAP150-anchored PKA and PKC phosphorylate and sensitize the TRPV1 (transient receptor potential subfamily V type 1 channel, also known as the capsaicin receptor). In the present study, we explore the hypothesis that an AKAP150-associated pool of PP2B catalyses the dephosphorylation and desensitization of TRPV1. Biochemical, electrophysiological and cell-based experiments indicate that PP2B associates with AKAP150 and TRPV1 in cultured TG (trigeminal ganglia) neurons. Gene silencing of AKAP150 reduces basal phosphorylation of TRPV1. However, functional studies in neurons isolated from AKAP150−/− mice indicate that the anchoring protein is not required for pharmacological desensitization of TRPV1. Behavioural analysis of AKAP150−/− mice further support this notion, demonstrating that agonist-stimulated desensitization of TRPV1 is sensitive to PP2B inhibition and does not rely on AKAP150. These findings allow us to conclude that pharmacological desensitization of TRPV1 by PP2B may involve additional regulatory components.
43

Alshehri, Fahad S. M., Claire S. Whyte et Nicola J. Mutch. « Factor XIII-A : An Indispensable “Factor” in Haemostasis and Wound Healing ». International Journal of Molecular Sciences 22, no 6 (17 mars 2021) : 3055. http://dx.doi.org/10.3390/ijms22063055.

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Factor XIII (FXIII) is a transglutaminase enzyme that catalyses the formation of ε-(γ-glutamyl)lysyl isopeptide bonds into protein substrates. The plasma form, FXIIIA2B2, has an established function in haemostasis, with fibrin being its principal substrate. A deficiency in FXIII manifests as a severe bleeding diathesis emphasising its crucial role in this pathway. The FXIII-A gene (F13A1) is expressed in cells of bone marrow and mesenchymal lineage. The cellular form, a homodimer of the A subunits denoted FXIII-A, was perceived to remain intracellular, due to the lack of a classical signal peptide for its release. It is now apparent that FXIII-A can be externalised from cells, by an as yet unknown mechanism. Thus, three pools of FXIII-A exist within the circulation: plasma where it circulates in complex with the inhibitory FXIII-B subunits, and the cellular form encased within platelets and monocytes/macrophages. The abundance of this transglutaminase in different forms and locations in the vasculature reflect the complex and crucial roles of this enzyme in physiological processes. Herein, we examine the significance of these pools of FXIII-A in different settings and the evidence to date to support their function in haemostasis and wound healing.
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Fernández-Irigoyen, Joaquín, Mónica Santamaría, Virginia Sánchez-Quiles, Maria U. Latasa, Enrique Santamaría, Javier Muñoz, Manuel M. Sánchez Del Pino et al. « Redox regulation of methylthioadenosine phosphorylase in liver cells : molecular mechanism and functional implications ». Biochemical Journal 411, no 2 (27 mars 2008) : 457–65. http://dx.doi.org/10.1042/bj20071569.

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MTAP (5′-methylthioadenosine phosphorylase) catalyses the reversible phosphorolytic cleavage of methylthioadenosine leading to the production of methylthioribose-1-phosphate and adenine. Deficient MTAP activity has been correlated with human diseases including cirrhosis and hepatocellular carcinoma. In the present study we have investigated the regulation of MTAP by ROS (reactive oxygen species). The results of the present study support the inactivation of MTAP in the liver of bacterial LPS (lipopolysaccharide)-challenged mice as well as in HepG2 cells after exposure to t-butyl hydroperoxide. Reversible inactivation of purified MTAP by hydrogen peroxide results from a reduction of Vmax and involves the specific oxidation of Cys136 and Cys223 thiols to sulfenic acid that may be further stabilized to sulfenyl amide intermediates. Additionally, we found that Cys145 and Cys211 were disulfide bonded upon hydrogen peroxide exposure. However, this modification is not relevant to the mediation of the loss of MTAP activity as assessed by site-directed mutagenesis. Regulation of MTAP by ROS might participate in the redox regulation of the methionine catabolic pathway in the liver. Reduced MTA (5′-deoxy-5′-methylthioadenosine)-degrading activity may compensate for the deficient production of the precursor S-adenosylmethionine, allowing maintenance of intracellular MTA levels that may be critical to ensure cellular adaptation to physiopathological conditions such as inflammation.
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Mäkelä, Miia R., Kristiina Hildén, Annele Hatakka et Taina K. Lundell. « Oxalate decarboxylase of the white-rot fungus Dichomitus squalens demonstrates a novel enzyme primary structure and non-induced expression on wood and in liquid cultures ». Microbiology 155, no 8 (1 août 2009) : 2726–38. http://dx.doi.org/10.1099/mic.0.028860-0.

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Oxalate decarboxylase (ODC) catalyses the conversion of oxalic acid to formic acid and CO2 in bacteria and fungi. In wood-decaying fungi the enzyme has been linked to the regulation of intra- and extracellular quantities of oxalic acid, which is one of the key components in biological decomposition of wood. ODC enzymes are biotechnologically interesting for their potential in diagnostics, agriculture and environmental applications, e.g. removal of oxalic acid from industrial wastewaters. We identified a novel ODC in mycelial extracts of two wild-type isolates of Dichomitus squalens, and cloned the corresponding Ds-odc gene. The primary structure of the Ds-ODC protein contains two conserved Mn-binding cupin motifs, but at the N-terminus, a unique, approximately 60 aa alanine-serine-rich region is found. Real-time quantitative RT-PCR analysis confirmed gene expression when the fungus was cultivated on wood and in liquid medium. However, addition of oxalic acid in liquid cultures caused no increase in transcript amounts, thereby indicating a constitutive rather than inducible expression of Ds-odc. The detected stimulation of ODC activity by oxalic acid is more likely due to enzyme activation than to transcriptional upregulation of the Ds-odc gene. Our results support involvement of ODC in primary rather than secondary metabolism in fungi.
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Shepherd, Mark, Tamara A. Dailey et Harry A. Dailey. « A new class of [2Fe-2S]-cluster-containing protoporphyrin (IX) ferrochelatases ». Biochemical Journal 397, no 1 (14 juin 2006) : 47–52. http://dx.doi.org/10.1042/bj20051967.

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Protoporphyrin (IX) ferrochelatase catalyses the insertion of ferrous iron into protoporphyrin IX to form haem. These ferrochelatases exist as monomers and dimers, both with and without [2Fe-2S] clusters. The motifs for [2Fe-2S] cluster co-ordination are varied, but in all cases previously reported, three of the four cysteine ligands are present in the 30 C-terminal residues and the fourth ligand is internal. In the present study, we demonstrate that a group of micro-organisms exist which possess protoporphyrin (IX) ferrochelatases containing [2Fe-2S] clusters that are co-ordinated by a group of four cysteine residues contained in an internal amino acid segment of approx. 20 residues in length. This suggests that these ferrochelatases have evolved along a different lineage than other bacterial protoporphyrin (IX) ferrochelatases. For example, Myxococcus xanthus protoporphyrin (IX) ferrochelatase ligates a [2Fe-2S] cluster via cysteine residues present in an internal segment. Site-directed mutagenesis of this ferrochelatase demonstrates that changing one cysteine ligand into serine results in loss of the cluster, but unlike eukaryotic protoporphyrin (IX) ferrochelatases, this enzyme retains its activity. These data support a role for the [2Fe-2S] cluster in iron affinity, and strongly suggest convergent evolution of this feature in prokaryotes.
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Rowland, Rhianna J., Liang Wu, Feng Liu et Gideon J. Davies. « A baculoviral system for the production of human β-glucocerebrosidase enables atomic resolution analysis ». Acta Crystallographica Section D Structural Biology 76, no 6 (29 mai 2020) : 565–80. http://dx.doi.org/10.1107/s205979832000501x.

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The lysosomal glycoside hydrolase β-glucocerebrosidase (GBA; sometimes called GBA1 or GCase) catalyses the hydrolysis of glycosphingolipids. Inherited deficiencies in GBA cause the lysosomal storage disorder Gaucher disease (GD). Consequently, GBA is of considerable medical interest, with continuous advances in the development of inhibitors, chaperones and activity-based probes. The development of new GBA inhibitors requires a source of active protein; however, the majority of structural and mechanistic studies of GBA today rely on clinical enzyme-replacement therapy (ERT) formulations, which are incredibly costly and are often difficult to obtain in adequate supply. Here, the production of active crystallizable GBA in insect cells using a baculovirus expression system is reported, providing a nonclinical source of recombinant GBA with comparable activity and biophysical properties to ERT preparations. Furthermore, a novel crystal form of GBA is described which diffracts to give a 0.98 Å resolution unliganded structure. A structure in complex with the inactivator 2,4-dinitrophenyl-2-deoxy-2-fluoro-β-D-glucopyranoside was also obtained, demonstrating the ability of this GBA formulation to be used in ligand-binding studies. In light of its purity, stability and activity, the GBA production protocol described here should circumvent the need for ERT formulations for structural and biochemical studies and serve to support GD research.
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Hatzimichael, Eleftheria, Aggeliki Dasoula, Nelofer Syed, Peter Wojciech Szlosarek, George Dranitsaris, Tim Crook et Evangelos C. Briasoulis. « Epigenetic inactivation to target the arginine biosynthetic pathway in multiple myeloma. » Journal of Clinical Oncology 30, no 15_suppl (20 mai 2012) : e18567-e18567. http://dx.doi.org/10.1200/jco.2012.30.15_suppl.e18567.

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e18567 Background: Argininoosuccinate synthetase-1 (ASS1) catalyses the rate-limiting step in arginine biosynthesis, the conversion of citruline to arginine. Argininosuccinate lyase (ASL) is an enzyme that catalyses the reversible breakdown of arginosuccinate producing arginine and fumerate. Arginine deprivation using arginine deiminase (ADI-PEG20) is currently considered as a novel therapeutic intervention for cancer. In this perspective, we investigated the methylation status of the ASS1 and ASL CpG islands in multiple myeloma (MM) and analyzed for clinical relevance. Methods: Genomic DNA was extracted from bone marrow aspirate samples from 46 MM patients (28 male, 18 female, median age 64 years) obtained at diagnosis. Methylation-specific PCR was employed to study the methylation in the ASS1 and ASL CpG islands. DNA was isolated and bisulphite modified using commercially available kits. Logistic regression analyses were used to measure the association between gene methylation and sex, age>65, ISS stage, presence of extramedullary disease, renal failure and bone disease. Kaplan-Meier curves were used to estimate the probabilities of survival and the Log-rank test to assess the statistical significance of differences in event rates. Results: Methylation in the CpG island of ASS1 was detected in 71.7% patients and of ASL in 37% patients, while simultaneous methylation in both genes was present in 10 patients. None of the two genes was detectably methylated in the control group. Patients with ASS1 methylation were less likely to have bone disease (p=0.04, OR=0.22) and extramedullary disease (p=0.05, OR=0.22) and a trend was also noted that these patients were less likely to be >65 years of age (p=0.2, OR=0.37). We did not detect any statistically significant difference in overall survival by methylation status of the studied genes in this small study size. Conclusions: We demonstrate for the first time that arginine biosynthesis genes ASS1 and ASL are methylated in MM.Methylation of ASS1 was found to be more frequent and negatively associated with bone or extramedullary disease. Further evaluation of ASS1 and ASL is warranted in MM and supports the expansion of arginine deprivation trials in these patients
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Nomikos, Michail, Junaid Kashir et F. Anthony Lai. « The role and mechanism of action of sperm PLC-zeta in mammalian fertilisation ». Biochemical Journal 474, no 21 (23 octobre 2017) : 3659–73. http://dx.doi.org/10.1042/bcj20160521.

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At mammalian fertilisation, the fundamental stimulus that triggers oocyte (egg) activation and initiation of early embryonic development is an acute rise of the intracellular-free calcium (Ca2+) concentration inside the egg cytoplasm. This essential Ca2+ increase comprises a characteristic series of repetitive Ca2+ oscillations, starting soon after sperm–egg fusion. Over the last 15 years, accumulating scientific and clinical evidence supports the notion that the physiological stimulus that precedes the cytosolic Ca2+ oscillations is a novel, testis-specific phospholipase C (PLC) isoform, known as PLC-zeta (PLCζ). Sperm PLCζ catalyses the hydrolysis of phosphatidylinositol 4,5-bisphosphate triggering cytosolic Ca2+ oscillations through the inositol 1,4,5-trisphosphate signalling pathway. PLCζ is the smallest known mammalian PLC isoform with the most elementary domain organisation. However, relative to somatic PLCs, the PLCζ isoform possesses a unique potency in stimulating Ca2+ oscillations in eggs that is attributed to its novel biochemical characteristics. In this review, we discuss the latest developments that have begun to unravel the vital role of PLCζ at mammalian fertilisation and decipher its unique mechanism of action within the fertilising egg. We also postulate the significant potential diagnostic and therapeutic capacity of PLCζ in alleviating certain types of male infertility.
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Benavente, Rocío, María Esteban-Torres, Gert-Wieland Kohring, Álvaro Cortés-Cabrera, Pedro A. Sánchez-Murcia, Federico Gago, Iván Acebrón, Blanca de las Rivas, Rosario Muñoz et José M. Mancheño. « Enantioselective oxidation of galactitol 1-phosphate by galactitol-1-phosphate 5-dehydrogenase fromEscherichia coli ». Acta Crystallographica Section D Biological Crystallography 71, no 7 (30 juin 2015) : 1540–54. http://dx.doi.org/10.1107/s1399004715009281.

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Galactitol-1-phosphate 5-dehydrogenase (GPDH) is a polyol dehydrogenase that belongs to the medium-chain dehydrogenase/reductase (MDR) superfamily. It catalyses the Zn2+- and NAD+-dependent stereoselective dehydrogenation of L-galactitol 1-phosphate to D-tagatose 6-phosphate. Here, three crystal structures of GPDH fromEscherichia coliare reported: that of the open state of GPDH with Zn2+in the catalytic site and those of the closed state in complex with the polyols Tris and glycerol, respectively. The closed state of GPDH reveals no bound cofactor, which is at variance with the conformational transition of the prototypical mammalian liver alcohol dehydrogenase. The main intersubunit-contacting interface within the GPDH homodimer presents a large internal cavity that probably facilitates the relative movement between the subunits. The substrate analogue glycerol bound within the active site partially mimics the catalytically relevant backbone of galactitol 1-phosphate. The glycerol binding mode reveals, for the first time in the polyol dehydrogenases, a pentacoordinated zinc ion in complex with a polyol and also a strong hydrogen bond between the primary hydroxyl group and the conserved Glu144, an interaction originally proposed more than thirty years ago that supports a catalytic role for this acidic residue.
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