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Relevant bibliographies by topics / Enzyme mimics

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Academic literature on the topic 'Enzyme mimics'

Author: Grafiati

Published: 4 June 2021

Last updated: 22 July 2024

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Journal articles on the topic "Enzyme mimics"

1

Sanders, Jeremy K. M. "Enzyme mimics." Proceedings / Indian Academy of Sciences 106, no. 5 (October 1994): 983–88. http://dx.doi.org/10.1007/bf02841912.

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Breslow, Ronald. "Enzyme mimics." Pure and Applied Chemistry 62, no. 10 (January 1, 1990): 1859–66. http://dx.doi.org/10.1351/pac199062101859.

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Kirby, Anthony J. "Enzyme Mimics." Angewandte Chemie International Edition in English 33, no. 5 (March 17, 1994): 551–53. http://dx.doi.org/10.1002/anie.199405511.

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Zhang, Yihong, Faheem Muhammad, and Hui Wei. "Inorganic Enzyme Mimics." ChemBioChem 22, no. 9 (March 4, 2021): 1496–98. http://dx.doi.org/10.1002/cbic.202100049.

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Liu, Lei, and Ronald Breslow. "Dendrimeric Pyridoxamine Enzyme Mimics." Journal of the American Chemical Society 125, no. 40 (October 2003): 12110–11. http://dx.doi.org/10.1021/ja0374473.

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BRESLOW, R. "ChemInform Abstract: Enzyme Mimics." ChemInform 22, no. 7 (August 23, 2010): no. http://dx.doi.org/10.1002/chin.199107314.

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KIRBY, A. J. "ChemInform Abstract: Enzyme Mimics." ChemInform 25, no. 25 (August 19, 2010): no. http://dx.doi.org/10.1002/chin.199425303.

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Yan, Fei, Ying Mu, Ganglin Yan, Junqiu Liu, Jiacong Shen, and Guimin Luo. "Antioxidant Enzyme Mimics with Synergism." Mini-Reviews in Medicinal Chemistry 10, no. 4 (April 1, 2010): 342–56. http://dx.doi.org/10.2174/138955710791330972.

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Szilágyi, I., G. Nagy, K. Hernadi, I. Labádi, and I. Pálinkó. "Modeling copper-containing enzyme mimics." Journal of Molecular Structure: THEOCHEM 666-667 (December 2003): 451–53. http://dx.doi.org/10.1016/j.theochem.2003.08.054.

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Meeuwissen, Jurjen, and Joost N. H. Reek. "Supramolecular catalysis beyond enzyme mimics." Nature Chemistry 2, no. 8 (July 23, 2010): 615–21. http://dx.doi.org/10.1038/nchem.744.

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Dissertations / Theses on the topic "Enzyme mimics"

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Javor, Sacha. "Peptide dendrimers as enzyme mimics /." [S.l.] : [s.n.], 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000277027.

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Kwong, Joey Sum Wing. "Cyclic sulfoximine mimics of ribosides and 2-deoxyribosides as enzyme inhibitors." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760870.

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Leah, Stephen Anthony John. "The synthesis of cyclic hexapeptide host molecules." Thesis, University of York, 1997. http://etheses.whiterose.ac.uk/9811/.

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Savle, Prashant S. "Thiazolium salts as thiamin models." Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/272636.

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Swaidan, Abir. "Preparation of nanostructured materials and their application as enzyme-mimics for sensing and bacterial fighting." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I109.

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Les nanomatériaux à base de CuS ont suscité une attention considérable en raison de leurs propriétés intrinsèques exceptionnelles qui ont justifié leur utilisation dans diverses applications. Les nanomatériaux à base de CuS présentent une activité semblable à celle d'une enzyme, appelée «nanozymes». Ils sont considérés comme des alternatives aux enzymes peroxydases naturelles dans leur comportement catalytique vis-à-vis de l'oxydation de la réaction du substrat de 3,3 ', 5,5′-tétraméthylbenzidine (TMB) en présence de H2O2. Ce mérite en fait des candidats idéaux pour le développement de plates-formes de détection colorimétriques extrêmement sensibles et sélectives pour l'identification quantitative et qualitative de différentes espèces chimiques et biologiques.Encouragés par les propriétés optiques prometteuses des nanomatériaux à base de CuS, leurs applications à des fins biomédicales ont également été démontrées dans cette thèse. Ainsi, nous avons étudié leur utilisation en tant que candidats photothermiques et transporteurs de médicaments pour la libération à la demande d'antibiotique du lysozyme en tant que modèle de médicament antibactérien pour l'élimination bactérienne sous un laser à onde NIR à 980 nm
CuS-based nanomaterials have gained enormous attention due to their intrinsic outstanding properties that warranted their use in various applications. CuS-based nanomaterials exhibit enzyme-like activity, referred to as “nanozymes”. They are considered as alternatives to natural peroxidase enzymes in their catalytic behavior toward oxidizing the reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) substrate in the presence of H2O2. This merit makes them ideal candidates for the development of extremely sensitive and selective colorimetric sensing platforms for the quantitative and qualitative identification of various chemical and biological species. Encouraged by the promising optical properties of CuS-based nanomaterials, their applications for biomedical purposes have been also demonstrated in this thesis. Thus, we investigated their use as photothermal candidates and drug carriers for the on-demand release of lysozyme antibiotic as an antibacterial drug model for bacterial elimination under a 980 nm NIR wave laser

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DVORNIKOVS, VADIMS. "Evolution of the artificial enzyme: from simple cyclophanes to sophisticated host-rotaxanes." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1037897753.

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Liu, Xiaoling. "Polymeric Multicompartmentalized Systems Mimicking Artificial Cells for Controllable Multiple Enzymatic Cascade Reactions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230515.

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Engineering artificial cells is currently an emerging area of research that involves constructing mimics of biological cells. These biomimetic cellular systems hold tremendous promise for the different biomedical applications (diagnostics, therapy, tissue engineering, gene transfection, bioactive coatings) as well as aspects of synthetic biology. A key architectural principle of the cell is a multicompartmentalized assembly, which is one of the features of biological cells that enable the performance of multiple complex biochemical reactions within confined environments. For this purpose, this study demonstrates novel artificial cells, not only presenting organelle mimics but also incorporating various stimuli for regulating enzymatic cascade reactions within the artificial cell and for controlled simultaneous and/or subsequent release of the encapsulated (therapeutic) molecules. To successfully fabricate the multifunctional polymeric multicompartmentalized systems as artificial cells aimed for, in the first step a hollow capsule as biomimetic cellular membrane was developed to simulate a key characteristic of functional artificial cells for the selective uptake and release of (bio)molecules and particles for intra- and intercellular signaling processes. Herein using LbL technique which involved alternate deposition of oppositely charged polyelectrolytes on silica template via electrostatic interaction, the pH and temperature dual-responsive and photo-crosslinked hollow capsule was fabricated and they can be used for the subsequent post-encapsulation process of protein-like macromolecules (≤ 11 nm) and their controllable release triggered by external stimuli for mimicking the controllable bio-inspired functions of cell membranes. The reversible temperature and pH dual-response ability of the hollow capsules has been analyzed. The uptake and release properties of the resulting hollow capsules with different degree of photo-crosslinking for cargos have been further investigated at various temperatures (25, 37 or 45°C) and pH (5.5 or 7.4) of the solution. Next, the design of the polymersomal subcompartmens as organelle mimics, which divide the interior of the multicompartmentalized systems into subcompartments and can stably encapsulate fragile hydrophobic and hydrophilic cargo, e.g., enzymes in order to conduct encapsulated catalysis-resembling cell organelles, was also an important subject. The fabrication of these subcompartments was starting with the synthesis of suitably end-group block copolymers to realize the enzyme-loaded, multifunctional, pH-responsive, photo-crosslinked and post-labelled polymersomes decorated with adamantane groups. The pH sensitivity and various enzymatic reactions of the established multifunctional Ada-polymersomes have been investigated. Based on the above concepts, a bottom-up approach was developed to assemble a structural and functional eukaryotic cell mimics, including “membrane-associated” multicompartmentalized system (MS1) and “free-floating” multicompartmentalized system (MS2), by loading pH-sensitive Ada-polymersomes inside the multifunctional cell membrane. The creation of these multicompartmentalized systems was based on the assembly of enzyme-loaded Ada-polymersomes as organelle mimics onto sacrificial particle templates by host-guest interaction, followed by the LbL deposition of temperature-responsive and photo-crosslinkable PMA(β-CD)/[PAH/PNMD]3 multilayers and outer protective capping PAH/PMA(PEG) bilayer as biomimetic cellular membrane. Upon photo-crosslinking the polymer biomimetic membrane and dissolution of the particle templates, multicompartmentalized systems were obtained. Spatial position of the subcompartments can be controlled using non-covalent host-guest concept, which yielded multicompartmentalized systems containing “membrane-associated” and “free-floating” subunits. Moreover, the metabolism mimicry of multicompartmentalized systems by performing multiple successive two-enzyme cascade reactions in the cells and the multiple parallel reactions by using a third enzyme for deactivating the reaction product and interfering the cascade reaction have been investigated. In conclusion, these multicompartmentalized systems, combining the advantages of both pH-responsive Ada-polymersomes as organelle mimics and multifunctional hollow capsule as biomimetic cellular membrane, present new opportunities for the development of functional cell mimics. The presented studies highlight crucial aspects for the successful applications of such cell mimics for diagnostics, tissue engineering, as nanoreactors, as carriers for multiple drug delivery with controlled release profiles, or as therapeutic artificial cells.

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Tye, Jesse Wayne. "Explorations of iron-iron hydrogenase active site models by experiment and theory." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1014.

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Sage, Matthew Arthur. "Synthesis of peptide mimetics." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261380.

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Longhurst, Steven. "Metal-sulfur complexes : functional mimics of the active sites of some metalloproteins." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323292.

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Books on the topic "Enzyme mimics"

1

Rioux, Robert M. Model systems in catalysis: Single crystals to supported enzyme mimics. New York: Springer, 2010.

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Rioux, Robert M. Model systems in catalysis: Single crystals to supported enzyme mimics. New York: Springer, 2010.

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Rioux, Robert. Model Systems in Catalysis: Single Crystals to Supported Enzyme Mimics. Springer, 2010.

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Rioux, Robert. Model Systems in Catalysis: Single Crystals to Supported Enzyme Mimics. Springer, 2014.

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(Editor), John N. Abelson, Melvin I. Simon (Editor), and John J. Langone (Editor), eds. Antibodies, Antigens, and Molecular Mimicry, Volume 178: Volume 178: Antibodies, Antigens and Molecular Mimicry (Methods in Enzymology). Academic Press, 1989.

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Lilleker, James B., and Mark E. Roberts. Metabolic myopathies. Edited by Hector Chinoy and Robert Cooper. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198754121.003.0005.

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Metabolic myopathies are caused by defects in the metabolic processes of energy storage and utilization, and can present with exercise intolerance, fatigue, muscle pain, and weakness. Metabolic myopathies are rare and can be difficult to diagnose. However, the clinical presentation can be similar to, and thus mimic, both the idiopathic inflammatory myopathies and other genetic muscle disorders including the muscular dystrophies. Careful enquiry about the nature and timing of muscle pain, as well as identification of other clinical ‘red-flags’, can highlight the possibility of a metabolic myopathy. The possibility of metabolic myopathy or muscular dystrophy mimicking myositis should be considered early in ‘treatment-resistant myositis’ or ‘seronegative myositis’. The diagnosis of metabolic myopathies depends on a multidisciplinary team, an awareness of the increasing availability of enzyme activity testing and the utility of expanding genetic technologies. In some cases, dietary manipulation and enzyme replacement therapies are useful treatments.

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Schussel, Leonard J. Synthesis and oxidation of metal-thiolate compounds which mimic the active site function of thiolate dioxygenase enzymes. 1987.

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Book chapters on the topic "Enzyme mimics"

1

Kirby, Anthony J. "Enzyme Mimics." In Stimulating Concepts in Chemistry, 339–53. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527605746.ch22.

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Breslow, Ronald. "Enzyme Mimics." In Novartis Foundation Symposia, 115–27. Chichester, UK: John Wiley & Sons, Ltd., 2007. http://dx.doi.org/10.1002/9780470514085.ch8.

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Cragg, Peter J. "Supramolecular Enzyme Mimics." In Supramolecular Chemistry, 113–51. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-2582-1_4.

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Wang, Cheng, Gang-lin Yan, and Gui-min Luo. "Synthetic Antioxidant Polymers: Enzyme Mimics." In Antioxidant Polymers, 259–332. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118445440.ch10.

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Herron, Norman. "Zeolite Catalysts as Enzyme Mimics." In ACS Symposium Series, 141–54. Washington, DC: American Chemical Society, 1989. http://dx.doi.org/10.1021/bk-1989-0392.ch011.

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Walter, Christopher J., Lindsey G. Mackay, and Jeremy K. M. Sanders. "Can Enzyme Mimics Compete with Catalytic Antibodies?" In Chemical Synthesis, 419–28. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0255-8_18.

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Seltzman, Herbert H., and Zdzislaw M. Szulc. "Chemically Modified Cyclodextrins as Catalytic Enzyme Mimics." In Proceedings of the Eighth International Symposium on Cyclodextrins, 267–72. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-5448-2_58.

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Anderson, Sally, and Jeremy K. M. Sanders. "Templated Synthesis of Enzyme Mimics: How Far can We Go?" In Chemical Synthesis, 277–91. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0255-8_12.

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Herget, Karoline, Hajo Frerichs, Felix Pfitzner, Muhammad Nawaz Tahir, and Wolfgang Tremel. "Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation." In Nanozymology, 195–278. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-1490-6_8.

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Verma, Vibha, Manpreet Kaur, Sucheta Sharma, and Divya Utreja. "Nanoarchitectured Ferrites, Graphene Oxide, and Their Composites as Enzyme Mimics and Photocatalysts." In Advances in Catalysts Research, 61–98. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-49108-5_3.

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Conference papers on the topic "Enzyme mimics"

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Kasyanova, V. V., I. N. Bazhukova, A. V. Myshkina, E. O. Baksheev, and M. A. Mashkovtsev. "The enzyme-mimic activity of maltodextrin stabilized cerium dioxide nanoparticles." In PHYSICS, TECHNOLOGIES AND INNOVATION (PTI-2019): Proceedings of the VI International Young Researchers’ Conference. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5134373.

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De Oliveira Pinto, Lidiane, Italo Odone Mazali, LARISSA HELENA DE OLIVEIRA, and Fernando Aparecido Sigoli. "Development of semiconductor catalysts for enzyme mimic based on cerium oxide nanoparticles system." In XXIV Congresso de Iniciação Científica da UNICAMP - 2016. Campinas - SP, Brazil: Galoa, 2016. http://dx.doi.org/10.19146/pibic-2016-51300.

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Liz, Daiane Gobbatto de, Gustavo P. silveira, and Antonio Luiz Braga. "Synthesis of Hidroxamic acid and Proline derivatives of Diselenide as Mimetics Enzyme to GPx." In 14th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-14bmos-r0359-2.

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Gonza´lez, Camille, Anai´s Va´zquez, Angel Morales, Liz Di´az, Carlos R. Cabrera, and Kai Griebenow. "Development of a Peroxidase Biosensor for the Detection of Endocrine Disrupting Chemicals (EDCs)." In ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13059.

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Endocrine disruptor compounds are able to mimic or antagonize the effects of endogenous hormones. Phenolic compounds are one of the most abundant classes of endocrine disruptors due to their presence in a broad range of chemical manufacturing processes. The detection of such compounds in food, medicine, and the environment (i.e., water) is crucial to ensure their quality. To prevent the noxious effects of endocrine disruptors an efficient monitoring system is required in order for immediate remediation to be activated. The long-term goal of the project is to develop a robust and stable amperometric enzyme based biosensor able to determine the concentration of phenolic endocrine disruptors. This type of biosensor can be useful to monitor endocrine distruptors in biological fluids and environmental samples as for example the spacecraft drinking water, to ensure the health of the astronauts in space.

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Vermeer, C., BA M. Soute, and MM W. Ulrich. "IN VITRO CARBOXYLATION OF EXOGENOUS PROTEIN SUBSTRATES BY VITAMIN K-DEPENDENT CARBOXYLASE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643994.

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In vivo treatment of experimental animals with vitamin K-antagonists induces the accumulation of non-carboxylated coagulation factor precursors in the liver, where they are tightly bound to vitamin K-dependent carboxylase. If hepatic carboxylase is isolated from warfarin-treated animals, it is obtained therefore almost exclusively in the form of an enzyme/substrate complex. If carboxylase is prepared from non-treated animals, on the other hand, the resulting enzyme is predominantly substrate-free. Small substrates like F L E E L or decarboxylated osteocalcinare carboxylated equally well by both types of carboxylase, but protein substrates(Mr > 30 000) are recognized exclusively by substrate-free carboxylase.Initial attempts to purify carboxylasewere performed with livers from warfarin-treated cows as a starting material. Antibodies against the normal blood coagulation factors crossreact with the hepatic precursor proteins so that the enzyme/substrate complexes could be specifically extracted from detergent-solubilized microsomes by the substrate/antibody interaction. This procedure resulted ina substantial purification of carboxylase, but because its endogenous substrate remained firmly bound, even after it had been carboxylated in vitro, the enzyme system was not suitable for the carboxylation of protein substrates.Therefore a second strategy was developed by which substrate-free carboxylase (from normal livers) was partly purified by sequential extraction of the microsomal membranes with detergents, followed by ammonium sulfate precipitation and size exclusion chromatography.This procedure resulted in a soluble carboxylase complex, still consisting of 7 proteins and phosphatidylcholine. Although further dissociation of the complex resulted in a complete loss of activity, it is not sure if all components play a role in the carboxylation reaction. Exogenous substrates which could be carboxylated by substrate-free carboxylase were: the penta-peptide F L E E L, descarboxyprothrombin from bovine plasma, thermally decarboxylated osteocalcin from bovine bone and non-car-boxy lated coagulaton factor precursors which had been produced by recombinant-DNA techniques in various laboratories. The . efficiency of CO^ incorporation was: 1 mole per 100 moles of F L E E L, 1 mole per 240 moles of descarboxy-prothrombin, 1 mole per mole of decarboxylated osteocalcin and 8 moles per mole of a recombinant factor IX precursor. We assume that the high efficiency with which the recombinant coagulation factor precursors were carboxylated is due to the presence of at least part of their leader sequence. The importance of the aminoacid chain preceding the first carboxylatable Glu residue is demonstrated by the fact that descarboxylated osteocalcin of bovine origin is carboxylated with a relatively high efficiency, whereas descarboxylated osteocalcin from monkey bone is not recognized atal.. Yet the only difference between the two substrates is found in their aminoacids 3 and 4, whereas the first carboxylatable Glu occurs at position 17. It seems, therefore, that the aminoacids 1-16 in bovine osteocalcin mimic to some extent part of the leader sequence in the coagulation factor precursors. Chemical or biochemical modification of decarboxylated osteocalcin might reveal which structural features contribute to its recognition by hepatic carboxylase.The optimal conditions for carboxylation include a high concentration of dithiols (e.g. DTT) and under these conditions disulfide bridges are reduced. Obviously this will lead to a complete destruction of the biological activity of various carboxylated products. Therefore we have searched for a more natural reducing system and it was found that the bacterial thioredoxin/thiore-doxin-reductase system in the presence of 40 uM NADFH was able to replace DTT in the reaction mixtures. Since a comparable system also occurs in calf liver it seems not unlikely that this is the physiological counterpart of the dithiols used in vitro.

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Chun, Young Wook, Joey Barnett, and W. David Merryman. "Aortic Valve Interstitial Cell Activation Does Not Occur at Low Tissue Stiffness During Embryogenesis." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80501.

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An estimated 2.5 percent of the American population has heart valve (HV) disease and more than 100,000 US patients require a prosthetic valve replacement each year [1]. However, prosthetic valves can cause accelerated calcification leading to recurrence of HV disease in patients [2]. Thus, the development of a suitable tissue-engineered heart valve (TEHV) would greatly benefit patients with HV disease. Aortic valve interstitial cells (AVICs) play a crucial role in the progression of aortic valve disease as well as the maintenance of normal valve. Therefore, in order to design a suitable TEHV, these specialized cells need to be better understood. AVICs are known to synthesize ECM and express matrix degrading enzymes and their inhibitors that mediate and regulate remodeling of ECM components [3]. Interestingly, it was recently established that AVICs sense the stiffness of their surrounding ECM in vivo and are phenotypically responsive to mechanical cues with AVICs differentiating into myofibroblasts or osteoblasts, which are pathologic markers. Specifically, soft collagen gels (∼34kPa) caused less differentiation of AVICs than stiffer collagen gel (∼100kPa) [4]. However, for these experiments the AVICs were cultured on tissue culture polystyrene (TCPS) for at least one passage, and it is likely that AVICs cultured on TCPS might retain modified characteristics of AVICs in tissue prior to seed them on soft gels because of the memory to rigid substrate stiffness. Therefore, in this study, we examined the phenotype and function of AVICs on substrates that mimic ECM stiffness of adult leaflet as well as of developing embryo. In addition, we examine the effects of transforming growth factor-β1 (TGF-β1) which has been the most extensively studied cytokine initiator of fibrotic response of AVICs.

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Mointire, V. L., A. J. Frangos, G. B. Rhee, G. S. Eskin, and R. E. Hall. "RHEOLOGY AND CELL ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643988.

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The subject of this work is to examine the hypothesis that some sublytic levels of mechanical perturbation of cells can stimulate cell metabolism. As a marker metabolite, we have chosen arachidonic acid. Principal metabolites for platelets include the cyclooxygenase product thromboxane A2(TXA2) and the lipoxygenase product 12-hydroperoxy-eicosatetraenoic acid (12-HPETE). Polymorphonuclear leukocytes (PMNLs) initally produce principally 5-HPETE, somtimes leading to the formation leukotrienes, though many other metabolites of arachidonic acid have been isolated from activated neutrophils. Human umbilical vein endothelial cells utilize arachidonic acid to produce mainly prostaglandin I2(PGI2). All of these metabolites are biologically active and modulate cell function - sometimes in quite contrasting ways. We will show that levels of sublytic mechanical stress exposure can stimulate arachidonic acid metabolism in all three of the cell types mentioned above. The biological implications of this stress/metabolism coupling may be quite far reaching.Human platelets, leukocytes and endothelial cells all appear to be sensitive to mechanical stress induced activation of arachidonic acid metabolism. Sheared PRP exhibited greatly increased synthesis of 12-HETE and surprisingly little thromboxane B2 production. This indicates that shear stress stimulation of platelets may produce quite different arachidonic acid metabolism than that seen with many direct chemical stimuli, such as thrombin or collagen.Our data demonstrate that a substance derived from shear induced platelet activation may activate the C-5 lipoxygenase of human PMNL under stress, leading to the production of LTB4. We hypothesize that this substance maybe 12-HPETE. LTB4 is known to be a very potent chemotactic factor and to induce PMNL aggregation and degranulation. Our studies provide further evidence that lipoxygenase products of one cell type can modulate production of lipoxygenase products in a second cell type, and that shear stress can initiate cell activation. This kind of coupling could have far reaching implications in terms of our understanding of cell/cell interaction in flowing systems, such as acute inflammation, artificial organ implantation and tumor metastasis.The data on PGI2 production by endothelial cells demonstrate that physiological levels of shear stress can dramatically increase arachidonic acid metabolism. Step increases in shear stress lead to a burst in production of PGI2 which decayed to a steady state value in several minutes. This longer term stimulation of prostacyclin production rate increased linearly with shear stress over the range of 0-24 dynes/cm2. In addition, pulsatile flow of physiological frequency and amplitude caused approximately 2.4 times the PGI2 production rate as steady flow with the same mean stress. Although only PGI2 was measured, it is likely that other arachidonic acid metabolites of endothelial cells are also affected by shear stress.The ability of cells to respond to external stimuli involves the transduction of a signal across the plasma membrane. One such external stimulus appears to be fluid shear stress. Steady shear flow induces cell rotation in suspended cells, leading to a periodic membrane loading, with the peak stress proportional to the bulk shear stress. On anchorage-dependent cells, such as endothelial cells, steady shear stress may act by amplifying the natural thermal or Brownian fluttering or rippling of the membrane. There are several possible mechanisms by which shear stress induced membrane perturbation could mimic a hormone/receptor interaction, leading to increased intracellular metabolism. Shear stress may induce increased phospholipase C activity, caused by translocation of the enzyme, increased substrate (arachidonic acid) pool availability to phospholipase C (particularly from that stored in phosphoinositols) due to shear-induced membrane movements or changes in membrane fluidity, direct activation of calcium - activated phospholipase A2 by increased membrane calcium ion permeability, or most probably by a combination of these mechanisms.

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Reports on the topic "Enzyme mimics"

1

Library, Spring. Where Does Current Quorum Sensing Research Stand. Spring Library, December 2020. http://dx.doi.org/10.47496/sl.blog.16.

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Quorum quenching is achieved by inactivating signalling enzymes, by introducing molecules that mimic signalling molecules and block their receptors, by degrading signalling molecules themselves, or by a modification of the quorum sensing signals due to an enzyme activity.

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Meidan, Rina, and Robert Milvae. Regulation of Bovine Corpus Luteum Function. United States Department of Agriculture, March 1995. http://dx.doi.org/10.32747/1995.7604935.bard.

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The main goal of this research plan was to elucidate regulatory mechanisms controlling the development, function of the bovine corpus luteum (CL). The CL contains two different sterodigenic cell types and therefore it was necessary to obtain pure cell population. A system was developed in which granulosa and theca interna cells, isolated from a preovulatory follicle, acquired characteristics typical of large (LL) and small (SL) luteal cells, respectively, as judged by several biochemical and morphological criteria. Experiments were conducted to determine the effects of granulosa cells removal on subsequent CL function, the results obtained support the concept that granulosa cells make a substaintial contribution to the output of progesterone by the cyclic CL but may have a limited role in determining the functional lifespan of the CL. This experimental model was also used to better understand the contribution of follicular granulosa cells to subsequent luteal SCC mRNA expression. The mitochondrial cytochrome side-chain cleavage enzyme (SCC), which converts cholesterol to pregnenolone, is the first and rate-limiting enzyme of the steroidogenic pathway. Experiments were conducted to characterize the gene expression of P450scc in bovine CL. Levels of P450scc mRNA were higher during mid-luteal phase than in either the early or late luteal phases. PGF 2a injection decreased luteal P450scc mRNA in a time-dependent manner; levels were significantly reduced by 2h after treatment. CLs obtained from heifers on day 8 of the estrous cycle which had granulosa cells removed had a 45% reduction in the levels of mRNA for SCC enzymes as well as a 78% reduction in the numbers of LL cells. To characterize SCC expression in each steroidogenic cell type we utilized pure cell populations. Upon luteinization, LL expressed 2-3 fold higher amounts of both SCC enzymes mRNAs than SL. Moreover, eight days after stimulant removal, LL retained their P4 production capacity, expressed P450scc mRNA and contained this protein. In our attempts to establish the in vitro luteinization model, we had to select the prevulatory and pre-gonadotropin surge follicles. The ratio of estradiol:P4 which is often used was unreliable since P4 levels are high in atretic follicles and also in preovulatory post-gonadotropin follicles. We have therefore examined whether oxytocin (OT) levels in follicular fluids could enhance our ability to correctly and easily define follicular status. Based on E2 and OT concentrations in follicular fluids we could more accurately identify follicles that are preovulatory and post gonadotropin surge. Next we studied OT biosynthesis in granulosa cells, cells which were incubated with forskolin contained stores of the precursor indicating that forskolin (which mimics gonadotropin action) is an effective stimulator of OT biosynthesis and release. While studying in vitro luteinization, we noticed that IGF-I induced effects were not identical to those induced by insulin despite the fact that megadoses of insulin were used. This was the first indication that the cells may secrete IGF binding protein(s) which regonize IGFs and not insulin. In a detailed study involving several techniques, we characterized the species of IGF binding proteins secreted by luteal cells. The effects of exogenous polyunsaturated fatty acids and arachidonic acid on the production of P4 and prostanoids by dispersed bovine luteal cells was examined. The addition of eicosapentaenoic acid and arachidonic acid resulted in a dose-dependent reduction in basal and LH-stimulated biosynthesis of P4 and PGI2 and an increase in production of PGF 2a and 5-HETE production. Indomethacin, an inhibitor of arachidonic acid metabolism via the production of 5-HETE was unaffected. Results of these experiments suggest that the inhibitory effect of arachidonic acid on the biosynthesis of luteal P4 is due to either a direct action of arachidonic acid, or its conversion to 5-HETE via the lipoxgenase pathway of metabolism. The detailed and important information gained by the two labs elucidated the mode of action of factors crucially important to the function of the bovine CL. The data indicate that follicular granulosa cells make a major contribution to numbers of large luteal cells, OT and basal P4 production, as well as the content of cytochrome P450 scc. Granulosa-derived large luteal cells have distinct features: when luteinized, the cell no longer possesses LH receptors, its cAMP response is diminished yet P4 synthesis is sustained. This may imply that maintenance of P4 (even in the absence of a Luteotropic signal) during critical periods such as pregnancy recognition, is dependent on the proper luteinization and function of the large luteal cell.

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