Bibliografias temáticas / Acidic patch

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Literatura científica selecionada sobre o tema "Acidic patch"

Autor: Grafiati

Publicado: 21 de dezembro de 2024

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Artigos de revistas sobre o assunto "Acidic patch"

Skrajna, Aleksandra, Dennis Goldfarb, Katarzyna M. Kedziora, Emily M. Cousins, Gavin D. Grant, Cathy J. Spangler, Emily H. Barbour et al. "Comprehensive nucleosome interactome screen establishes fundamental principles of nucleosome binding". Nucleic Acids Research 48, n.º 17 (7 de julho de 2020): 9415–32. http://dx.doi.org/10.1093/nar/gkaa544.

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Abstract Nuclear proteins bind chromatin to execute and regulate genome-templated processes. While studies of individual nucleosome interactions have suggested that an acidic patch on the nucleosome disk may be a common site for recruitment to chromatin, the pervasiveness of acidic patch binding and whether other nucleosome binding hot-spots exist remain unclear. Here, we use nucleosome affinity proteomics with a library of nucleosomes that disrupts all exposed histone surfaces to comprehensively assess how proteins recognize nucleosomes. We find that the acidic patch and two adjacent surfaces are the primary hot-spots for nucleosome disk interactions, whereas nearly half of the nucleosome disk participates only minimally in protein binding. Our screen defines nucleosome surface requirements of nearly 300 nucleosome interacting proteins implicated in diverse nuclear processes including transcription, DNA damage repair, cell cycle regulation and nuclear architecture. Building from our screen, we demonstrate that the Anaphase-Promoting Complex/Cyclosome directly engages the acidic patch, and we elucidate a redundant mechanism of acidic patch binding by nuclear pore protein ELYS. Overall, our interactome screen illuminates a highly competitive nucleosome binding hub and establishes universal principles of nucleosome recognition.

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Cucinotta, Christine E., A. Elizabeth Hildreth, Brendan M. McShane, Margaret K. Shirra e Karen M. Arndt. "The nucleosome acidic patch directly interacts with subunits of the Paf1 and FACT complexes and controls chromatin architecture in vivo". Nucleic Acids Research 47, n.º 16 (21 de junho de 2019): 8410–23. http://dx.doi.org/10.1093/nar/gkz549.

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Abstract The nucleosome core regulates DNA-templated processes through the highly conserved nucleosome acidic patch. While structural and biochemical studies have shown that the acidic patch controls chromatin factor binding and activity, few studies have elucidated its functions in vivo. We employed site-specific crosslinking to identify proteins that directly bind the acidic patch in Saccharomyces cerevisiae and demonstrated crosslinking of histone H2A to Paf1 complex subunit Rtf1 and FACT subunit Spt16. Rtf1 bound to nucleosomes through its histone modification domain, supporting its role as a cofactor in H2B K123 ubiquitylation. An acidic patch mutant showed defects in nucleosome positioning and occupancy genome-wide. Our results provide new information on the chromatin engagement of two central players in transcription elongation and emphasize the importance of the nucleosome core as a hub for proteins that regulate chromatin during transcription.

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Kalashnikova, Anna A., Mary E. Porter-Goff, Uma M. Muthurajan, Karolin Luger e Jeffrey C. Hansen. "The role of the nucleosome acidic patch in modulating higher order chromatin structure". Journal of The Royal Society Interface 10, n.º 82 (6 de maio de 2013): 20121022. http://dx.doi.org/10.1098/rsif.2012.1022.

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Higher order folding of chromatin fibre is mediated by interactions of the histone H4 N-terminal tail domains with neighbouring nucleosomes. Mechanistically, the H4 tails of one nucleosome bind to the acidic patch region on the surface of adjacent nucleosomes, causing fibre compaction. The functionality of the chromatin fibre can be modified by proteins that interact with the nucleosome. The co-structures of five different proteins with the nucleosome (LANA, IL-33, RCC1, Sir3 and HMGN2) recently have been examined by experimental and computational studies. Interestingly, each of these proteins displays steric, ionic and hydrogen bond complementarity with the acidic patch, and therefore will compete with each other for binding to the nucleosome. We first review the molecular details of each interface, focusing on the key non-covalent interactions that stabilize the protein–acidic patch interactions. We then propose a model in which binding of proteins to the nucleosome disrupts interaction of the H4 tail domains with the acidic patch, preventing the intrinsic chromatin folding pathway and leading to assembly of alternative higher order chromatin structures with unique biological functions.

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Oleinikov, Pavel D., Anastasiia S. Fedulova, Grigoriy A. Armeev, Nikita A. Motorin, Lovepreet Singh-Palchevskaia, Anastasiia L. Sivkina, Pavel G. Feskin et al. "Interactions of Nucleosomes with Acidic Patch-Binding Peptides: A Combined Structural Bioinformatics, Molecular Modeling, Fluorescence Polarization, and Single-Molecule FRET Study". International Journal of Molecular Sciences 24, n.º 20 (14 de outubro de 2023): 15194. http://dx.doi.org/10.3390/ijms242015194.

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In eukaryotic organisms, genomic DNA associates with histone proteins to form nucleosomes. Nucleosomes provide a basis for genome compaction, epigenetic markup, and mediate interactions of nuclear proteins with their target DNA loci. A negatively charged (acidic) patch located on the H2A-H2B histone dimer is a characteristic feature of the nucleosomal surface. The acidic patch is a common site in the attachment of various chromatin proteins, including viral ones. Acidic patch-binding peptides present perspective compounds that can be used to modulate chromatin functioning by disrupting interactions of nucleosomes with natural proteins or alternatively targeting artificial moieties to the nucleosomes, which may be beneficial for the development of new therapeutics. In this work, we used several computational and experimental techniques to improve our understanding of how peptides may bind to the acidic patch and what are the consequences of their binding. Through extensive analysis of the PDB database, histone sequence analysis, and molecular dynamic simulations, we elucidated common binding patterns and key interactions that stabilize peptide–nucleosome complexes. Through MD simulations and FRET measurements, we characterized changes in nucleosome dynamics conferred by peptide binding. Using fluorescence polarization and gel electrophoresis, we evaluated the affinity and specificity of the LANA1-22 peptide to DNA and nucleosomes. Taken together, our study provides new insights into the different patterns of intermolecular interactions that can be employed by natural and designed peptides to bind to nucleosomes, and the effects of peptide binding on nucleosome dynamics and stability.

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Navarro Negredo, Paloma, James R. Edgar, Antoni G. Wrobel, Nathan R. Zaccai, Robin Antrobus, David J. Owen e Margaret S. Robinson. "Contribution of the clathrin adaptor AP-1 subunit µ1 to acidic cluster protein sorting". Journal of Cell Biology 216, n.º 9 (25 de julho de 2017): 2927–43. http://dx.doi.org/10.1083/jcb.201602058.

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Acidic clusters act as sorting signals for packaging cargo into clathrin-coated vesicles (CCVs), and also facilitate down-regulation of MHC-I by HIV-1 Nef. To find acidic cluster sorting machinery, we performed a gene-trap screen and identified the medium subunit (µ1) of the clathrin adaptor AP-1 as a top hit. In µ1 knockout cells, intracellular CCVs still form, but acidic cluster proteins are depleted, although several other CCV components were either unaffected or increased, indicating that cells can compensate for long-term loss of AP-1. In vitro experiments showed that the basic patch on µ1 that interacts with the Nef acidic cluster also contributes to the binding of endogenous acidic cluster proteins. Surprisingly, µ1 mutant proteins lacking the basic patch and/or the tyrosine-based motif binding pocket could rescue the µ1 knockout phenotype completely. In contrast, these mutants failed to rescue Nef-induced down-regulation of MHC class I, suggesting a possible mechanism for attacking the virus while sparing the host cell.

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Debelouchina, Galia T., Karola Gerecht e Tom W. Muir. "Ubiquitin utilizes an acidic surface patch to alter chromatin structure". Nature Chemical Biology 13, n.º 1 (21 de novembro de 2016): 105–10. http://dx.doi.org/10.1038/nchembio.2235.

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Birrane, Gabriel, Anne P. Beigneux, Brian Dwyer, Bettina Strack-Logue, Kristian Kølby Kristensen, Omar L. Francone, Loren G. Fong et al. "Structure of the lipoprotein lipase–GPIHBP1 complex that mediates plasma triglyceride hydrolysis". Proceedings of the National Academy of Sciences 116, n.º 5 (17 de dezembro de 2018): 1723–32. http://dx.doi.org/10.1073/pnas.1817984116.

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Lipoprotein lipase (LPL) is responsible for the intravascular processing of triglyceride-rich lipoproteins. The LPL within capillaries is bound to GPIHBP1, an endothelial cell protein with a three-fingered LU domain and an N-terminal intrinsically disordered acidic domain. Loss-of-function mutations in LPL or GPIHBP1 cause severe hypertriglyceridemia (chylomicronemia), but structures for LPL and GPIHBP1 have remained elusive. Inspired by our recent discovery that GPIHBP1’s acidic domain preserves LPL structure and activity, we crystallized an LPL–GPIHBP1 complex and solved its structure. GPIHBP1’s LU domain binds to LPL’s C-terminal domain, largely by hydrophobic interactions. Analysis of electrostatic surfaces revealed that LPL contains a large basic patch spanning its N- and C-terminal domains. GPIHBP1’s acidic domain was not defined in the electron density map but was positioned to interact with LPL’s large basic patch, providing a likely explanation for how GPIHBP1 stabilizes LPL. The LPL–GPIHBP1 structure provides insights into mutations causing chylomicronemia.

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Batchelor, Lucinda K., Louis De Falco, Paul J. Dyson e Curtis A. Davey. "Viral peptide conjugates for metal-warhead delivery to chromatin". RSC Advances 14, n.º 13 (2024): 8718–25. http://dx.doi.org/10.1039/d4ra01617c.

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CROWLEY, Peter B., David M. HUNTER, Katsuko SATO, William McFARLANE e Christopher DENNISON. "The parsley plastocyanin-turnip cytochrome f complex: a structurally distorted but kinetically functional acidic patch". Biochemical Journal 378, n.º 1 (15 de fevereiro de 2004): 45–51. http://dx.doi.org/10.1042/bj20031423.

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In general, inter-protein electron transfer proceeds via the formation of transient complexes. The initial stage of the interaction between plastocyanin (PCu) and cytochrome f (cyt f) from plants is mediated by complementary electrostatics. Given the diffuse nature of its acidic patch, parsley PCu is an atypical example of a plant PCu. The interaction of this PCu with turnip cyt f was investigated by stopped-flow kinetics, NMR spectroscopy and protein-docking simulations. We show that, despite the altered acidic patch, parsley PCu is as efficient as spinach PCu in accepting electrons from cyt f, over the physiological range of ionic strength. At high ionic strength, the rate constant for the reaction of cyt f with parsley PCu is twice that of the spinach protein. This difference in reactivity is attributed to variations in the hydrophobic patch of parsley PCu. The results of NMR studies and protein-docking simulations indicate that parsley PCu and its spinach analogue adopt different orientations in their complexes with cyt f.

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Haneburger, Ina, Andreas Eichinger, Arne Skerra e Kirsten Jung. "New Insights into the Signaling Mechanism of the pH-responsive, Membrane-integrated Transcriptional Activator CadC of Escherichia coli". Journal of Biological Chemistry 286, n.º 12 (6 de janeiro de 2011): 10681–89. http://dx.doi.org/10.1074/jbc.m110.196923.

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The membrane-integrated transcriptional regulator CadC of Escherichia coli activates expression of the cadBA operon at low external pH with concomitantly available lysine, providing adaptation to mild acidic stress. CadC is a representative of the ToxR-like proteins that combine sensory, signal transduction, and DNA-binding activities within a single polypeptide. Although several ToxR-like regulators such as CadC, as well as the main regulator of Vibrio cholerae virulence, ToxR itself, which activate gene expression at acidic pH, have been intensively investigated, their molecular activation mechanism is still unclear. In this study, a structure-guided mutational analysis was performed to elucidate the mechanism by which CadC detects acidification of the external milieu. Thus, a cluster of negatively charged amino acids (Asp-198, Asp-200, Glu-461, Glu-468, and Asp-471) was found to be crucial for pH detection. These amino acids form a negatively charged patch on the surface of the periplasmic domain of CadC that stretches across its two subdomains. The results of different combinations of amino acid replacements within this patch indicated that the N-terminal subdomain integrates and transduces the signals coming from both subdomains to the transmembrane domain. Alterations in the phospholipid composition did not influence pH-dependent cadBA expression, and therefore, interplay of the acidic surface patch with the negatively charged headgroups is unlikely. Models are discussed according to which protonation of these acidic amino acid side chains reduces repulsive forces between the two subdomains and/or between two monomers within a CadC dimer and thereby enables receptor activation upon lowering of the environmental pH.

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Teses / dissertações sobre o assunto "Acidic patch"

Martin, Franck. "Structural and functional studies of chromatin remodeling complex mamalian SWI / SNF". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAJ044.

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La chromatine est une structure dynamique régulée par différents mécanismes épigénétiques parmi lesquels le remodelage de la chromatine dépendant de l’ATP comme le SWI/SNF. Leur importance est telle que les mutations des protéines de remodelage de la chromatine sont fortement associées à plusieurs maladies dont le cancer. Par exemple les protéines BCL7, qui sont de nouvelles sous unité centrales récemment identifié du complexe SWI/SNF des mammifère, sont associées à différents types de cancers comme dans le Diffuse Large B-cell Lymphoma (DLBCL). Les informations sur les protéines BCL7 sont à ce jour très limitées. En utilisant des approches biochimiques et structurelles, ce projet vise à mieux comprendre la structure et la fonction de ces sous unités auxiliaires. Nous rapportons ici que les protéines se lient à l’acidique patch du nucleosome avec sa regions N-terminal qui comprend un motif d’ancrage arginines et que la mutation de l’une de ces arginines impacte directement la liaison au nucleosome. Nous apportons aussi une hypothèse sur la position au sein du complexe SWI/SNF de BCL7 qui interagit avec le module ARP et plus particulièrement avec ACTB par l'intermédiaire d'un motif 2W, et qu’elles sont directement des partenaires de liaisons avec BAF47. Nous avons aussi pu identifier qu’une fois sur les nucléosomes c’est BAF47 qui prend place sur l’acidique patch et l’hélice de BCL7A est déplacé
Chromatin is a dynamic structure regulated by various epigenetic mechanisms, including ATP-dependent chromatin remodeling such as SWI/SNF. Their importance is such that mutations in chromatin remodeling proteins are strongly associated with several diseases, including cancer. For example, BCL7 proteins, which are newly identified core subunits of the mammalian SWI/SNF complex, are associated with different types of cancer, such as Diffuse Large B-cell Lymphoma (DLBCL). To date, information on BCL7 proteins is very limited. Using biochemical and structural approaches, this project aims to better understand the structure and function of these auxiliary subunits. We report here that the proteins bind to the nucleosome with its N-terminal regions, which include an arginine anchoring motif, and that mutation of one of these arginines directly impacts binding to the nucleosome. We also hypothesize that the position within the SWI/SNF complex of BCL7, which interacts with the ARP module and more specifically with ACTB via a 2W motif, is directly linked to BAF47. We were also able to identify that once on the nucleosomes, BAF47 takes its place on the acidic patch and the BCL7A helix is displaced

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Malieieva, Galyna. "Les acides gynkgolique et niflumique sont les nouveaux modulateurs de récepteur à la glycine". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0030/document.

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Le récepteur à la glycine est un récepteur neuronal qui appartient à la famille des canaux ligand-dépendants «cys-loop». Avec le récepteur ionotrope GABA ils fournissent la neurotransmission inhibitrice rapide dans le SNC des vertébrés grâce à leur perméabilité sélective au Cl-. Les récepteurs à la glycine participent à différents processus physiologiques comprenant le contrôle de l'activité motrice, la respiration, la sensation de douleur inflammatoire, la perception des stimuli visuels et auditifs. Le développement de modulateurs efficaces des récepteurs à la glycine permettra un contrôle précis de leur activité, ce qui est particulièrement important dans le cas des pathologies des récepteurs à la glycine, comme l'hyperekplexie. En utilisant l'analyse électrophysiologique, la mutagenèse dirigée et l'expression de protéines spécifiques dans un système hétérologue, nous avons identifié les acides ginkgoliques et niflumiques comme nouveaux modulateurs de récepteurs de la glycine, caractérisé leur action sur différentes sous-unités du récepteur et déterminé les sites importants pour la potentialisation ou l'inhibition des récepteurs à la glycine par ces composés. Cette approche est très prometteuse et ouvre de nouvelles voies vers des futures actions thérapeutiques
Glycine receptor is a ligand-gated neuronal receptor that possesses an ion pore permeable for Cl- and represents an important component of inhibitory neurotransmission in CNS of vertebrates. Glycine receptors participate in the control of motor activity, respiration, inflammatory pain sensation, perception of visual and auditory stimuli. Development of efficient modulators of glycine receptors will allow a precise control of their activity, which is especially important in the case of glycine receptor pathologies, such as hyperekplexia. In the present work we have identified ginkgolic and niflumic acids as novel modulators of glycine receptors, characterized their action on different subunits of the receptor and determined the most probable sites of interaction of the compounds with glycine receptors

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Peverini, Laurie. "Conception et application de nouveaux outils photochimiques pour l’étude des récepteurs canaux P2X". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF061/document.

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Les récepteurs P2X (P2XR), activés par l’ATP, sont impliqués dans des rôles physiopathologiques. Leur fonctionnement est associé à différents états conformationnels. Le projet de thèse a mené à associer la synthèse organique et l’application de molécules photo-activables avec des techniques d’électrophysiologie patch-clamp, pour décortiquer les mouvements moléculaires de ces récepteurs et effectuer des relations structure-fonction, via trois stratégies : - La synthèse et application d’agrafes photo-isomérisables qui permet le photo-contrôle des P2XR et l’étude de mouvements - La synthèse et caractérisation d’un acide aminé (aa) photo-clivable pour étudier les implications de zones sur la fonction des P2XR via une photolyse - L’incorporation d’un aa non naturel dans les P2XR pour étudier des interactions et mouvements via un « photo-pontage ». Nous avons élucidé les mécanismes moléculaires responsables de la perméabilité des P2XR, récusé l’existence de l'état dilaté et identifié un cation organique physiologique pouvant les traverser. Nous avons aussi conçu un acide aminé photo-clivable pouvant mener à des études structure-fonction des P2XR
P2X receptors are cationic ligand-gated ion channels, activated by extracellular ATP, involved in many physio-pathological roles. Their function is associated with different allosteric states. During this PhD, we have designed three new strategies, spanning photochemical organic synthesis and patch-clamp electrophysiology to elucidate the molecular mechanisms involved in these conformational states and to collect data in order to study structure-function relationships. - Synthesis and application of molecular tweezers, which allows the photo-control of P2X Rand the study of molecular motions - Synthesis and characterization of a photo-cleavable amino acid with the aim of incorporating it into P2XR and doing structure-function relationships - Incorporation of an unnatural amino acid for photo-crosslinking studies. We have been able to probe the molecular mechanism involved in large organic cations permeation of P2XR, to bring into question the dilated state and to identify a physiological cation that can flow through P2XR. We have also designed a photo-cleavable amino acid which could serve in the study of structure-function relationships

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Chatelier, Aurélien. "Modulation des performances cardio-respiratoires du bar européen (Dicentrarchus labrax) par l'apport d'acides gras alimentaires : une étude intégrée des effets cardiaques in vivo au courant calcique de type L des myocytes ventriculaires". La Rochelle, 2005. http://www.theses.fr/2005LAROS148.

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La qualité du régime alimentaire, et en particulier sa composition en acides gras, est un facteur environnemental émergeant en tant que source de diversité physiologique. En effet, de nombreux travaux montrent que la composition en acides gras de l'alimentation influence les performances cardiaques et métaboliques des organismes. Le cœur joue un rôle central dans l'adaptation des poissons à leur environnement en assurant et en régulant, les flux internes d'énergie et de matière. Dans le contexte de l'adaptation environnementale des individus et de l'évolution des espèces, la compréhension des origines de la variabilité interindividuelle et notamment de l'influence exercée par les acides gras sur le fonctionnement du système cardio-respiratoire est un élément important. L'objectif de ce travail réalisé sur le bar européen (Dicentrarchus labrax) a été d'étudier, à deux niveaux organisationnels (organe, cellule), les effets de la composition en acides gras de l'alimentation et des tissus sur les performances cardio-respiratoires mesurées au cours d'un effort musculaire et d'une épreuve d'hypoxie, l'activité des canaux calciques de type L des myocytes ventriculaires. Les bars ont été nourris avec trois alimentations enrichies soit huile de poissons (riche en acides gras n-3 poly-insaturés), soit en huile de colza (riche en acide oléique et linoléique) ou encore en huile de palme (riche en acides gras saturés). L'étude à l'échelle de l'animal entier, réalisée au moyen d'un respiromètre de type Brett, a permis de mettre en évidence une modification significative des performances cardio-respiratoires des bars en fonction de la composition en acides gras de l'alimentation. Une forte teneur en acide oléique dans l'alimentation et donc dans les tissus cardiaques est toujours associée à de meilleures performances cardiaques et métaboliques. Au cours de l'épreuve d'hypoxie, aucune différence ne fut mise en évidence entre les différentes alimentations. L'étude électrophysiologique du canal calcique de type L a été réalisée grâce à la technique du patch clamp en configuration " whole-cell ". Nos résultats ont révélé que la perfusion d'acide oléique, ainsi qu'une teneur élevée de cet acide gras dans les membranes, pouvait induire une inhibition de l'influx des ions calcium via le courant calcique de type L. Cette baisse n'est accompagnée d'aucune modification majeure des paramètres d'activation et d'inactivation du canal. De par ses caractéristiques morphofonctionnelles, le cœur est responsable de la limitation des performances métaboliques et natatoire des poissons. Au cours d'un effort musculaire intense, la diminution du niveau d'oxygénation du sang veineux (source principale d'oxygène du tissus myocardique) va conduire à une hypoxie à l'échelle des cardiomyocytes. Cette baisse de l'oxygénation du myocarde conduit à des dérèglements de l'homéostasie calcique responsables d'une élévation du calcium cellulaire et de l'apparition d'arythmies. Les résultats expérimentaux obtenus suggèrent que l'acide oléique, par son action inhibitrice sur le courant calcique de type L, permet de limiter les risques d'apparition de ces arythmies. Cet effet protecteur de l'acide oléique serait responsable des performances cardio-respiratoires et natatoires observées chez les animaux nourris avec le régime enrichi en huile de colza
Diet fatty acid composition is an environmental factor that is emerging as a significant source of physiological diversity. Heart plays a central role in fish adaptability to their environment. The objective of the study on the sea bass (Dicentrarchus labrax) was to investigate the effects of fatty acids on: cardio-respiratory performances during a swim test and a hypoxic test, L-type calcium channel activity of ventricular myocytes. Sea bass were fed with three different diets enriched in fish oil (n-3 poly-unsaturated fatty acid), canola oil (oleic acid) and palm oil (saturated fatty acid). The study carried out on the whole animal shows that diet and cardiac high level of oleic acid is associated with best cardiac and metabolic performances. The hypoxic test revealed no significant difference between the diets. Studies on L-type calcium channel revealed that both oleic acid perfusion and high membrane content of oleic acid induce a reduction in ventricular myocyte calcium influx. The heart may limit metabolic and swimming performance of fishes. During an intensive muscular challenge, this restriction is due to cardiac hypoxia which leads to a rise in intracellular calcium and to the appearance or cardiac arrhythmias. Results suggest that oleic acid, by decreasing cell calcium entry, limit cardiac arrhythmia occurrence. This protective effect could be responsible of differences observed during the swim test

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Mistry, Dineshkumar. "The vertebrate neuronal gamma-aminobutyric acid (GABAa) receptor and its modulation : a patch clamp study". Thesis, University of St Andrews, 1988. http://hdl.handle.net/10023/14452.

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Pressure application of gamma-aminobutyric acid (GABA) to mouse spinal and rat DBG neurones maintained in culture evoked transient membrane currents. Using the whole-cell patch clamp technique, these currents were shown to primarily involve the flow of Cl-. The GABA-evoked whole-cell currents in both types of neurones were reversibly suppressed by the GABAA antagonist bicuculline. The barbiturate phenobarbitone reversibly potentiated GABA-evoked whole-cell currents in mouse spinal neurones. Attempts to look at the unitary currents activated by GABA in outside-out patches, revealed spontaneous unitary currents. The I-V relationships of the spontaneous currents were linear and had a reversal potential of OmV in symmetrically distributed Cl solutions. Changing the monovalent cation concentrations on one or both sides of the membrane patch had no effect on the amplitude or the reversal potential of the spontaneous currents. Replacing some of the Cl- in the patch pipette with the impermeant anion SO42- shifted the reversal potential to more negative values. These spontaneous currents in both types of neurones were blocked by bath perfusion of bicuculline. GABA-activated unitary currents in outside-out patches, the main conductance state in both types of neurones was 30pS. However, GABA could occasionally also activate other conductance levels. Spontaneous Cl- currents did not occur in cell-attached patches from mouse spinal and rat DRG neurones, suggesting that the spontaneous events in the outside-out patches did not represent the activity of voltage dependent Cl- channels. Alphaxalone, a steroid anaesthetic, potentiated GABA-evoked whole cell currents in both spinal and DRG neurones. At high (muM) concentrations, pressure application of alphaxalone evoked a membrane Cl- current; this current was reversibly suppressed by blcuculline and potentiated by phenobarbitone. Pregnanolone (5beta-pregnane-3x-ol-20-one) a progesterone metabolite at low (nM) concentrations reversibly enhanced GABA currents in spinal neurones. Pregnanolone at higher concentrations pressure applied to spinal neurones had a weak direct agonist action on the GABAA receptor. Pregnanolone prolonged the burst duration of GABA-activated unitary currents in outside-out patches from spinal neurones. Some of the actions of the steroids on the GABAA receptor were very similar to the barbiturates, bemegride, a respiratory stimulant was formerly used clinically to counteract barbiturate poisoning in man. Experiments were conducted to see whether bemegride could be used as a specific barbiturate antagonist. Bemegride reduced phenobarbitone enhanced GABA currents in mouse spinal neurones. However, bemegride alone also reduced GABA and pentobarbitone evoked currants to a similar extent. This is suggestive of a noncompetitive action on the GABAA receptor, therefore it was not used to elucidate the site of action of steroids.

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Syme, C. A. "Patch-clamp studies on endothelial cell and chromaffin cell K'+ channels : effects of shear stress, membrane stretch and fatty acids". Thesis, University of Strathclyde, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298575.

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Tatu, Rigwed R. "Development and Characterization of aPoly (l-lactic acid)/ Poly (e-caprolactone) Self-Expanding Patch forFetoscopic Repair of Myelomeningocele". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635832679162.

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Zieren, Jürgen. "Hernienreparationen mit Netzprothesen klinische und experimentelle Untersuchungen". Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2001. http://dx.doi.org/10.18452/13702.

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In einer prospektiv-randomisierten klinischen Studie zur Leistenhernienreparation wurde die konventionelle Shouldice Operation mit den spannungsfreien Verfahren durch Netzimplantation in endoskopischer (transabdominelle praeperitoneale Netzplastik, TAPP) und offener Technik (Plug und Patch Reparation; PP) verglichen. Bezogen auf das Hauptzielkriterium postoperative Schmerzen ergaben beide spannungsfreie Verfahren (TAPP, PP) signifikant guenstigere Ergebnisse als die Shouldice Operation. Bei vergleichbarer Komplikationsrate war die Dauer postoperativer Einschraenkungen bei den spannungsfreien Verfahren ebenfalls signifikant kuerzer als nach Shouldice Operation. Zur Verbesserung der fuer die spannungsfreie Reparation erforderlichen Netzimplantate wurde in einer Tierstudie versucht, die bislang durch Resorption ungenuegende mechanische Stabilitaet eines resorbierbaren Polyglycolsaeure-Netzes durch Zugabe von Fibrinkleber bzw. humanen thrombozytaeren Wachstumsfaktoren zu verbessern. Hierdurch gelang ein signifikanter Anstieg der mechanischen Stabilitaet, so daß in dem verwendeten Tiermodell keine Herniationen auftraten.
In a prospective-randomized study conventional Shouldice operation was compared with tension-free procedures using mesh implantation in endoscopic (transabdominal preperitoneal mesh repair, TAPP) and open technique (Plug and patch repair; PP) for inguinal hernia repair. Regarding the mean end point postoperative pain both tension-free procedures (TAPP, PP) revealed significantly better results than Shouldice operation. Complications were comparable between the groups but duration of postoperative restrictions was significantly shorter after both tension-free procedures. To improve mesh quality for tension-free hernia repair an animal experiment was performed using a resorbable polyglycolic acid mesh. Despite good incorporation this mesh shows insufficient tensile strength due to absorption. Application of fibrin glue or platelet releasates significantly improve the mechanical stability of the repair protecting against herniation in this animal model.

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Facchin, Andrea. "New path for thermochemical-biological conversion with a power-to-material approach". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23117/.

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I sistemi termochimico-biologici si basano su due proprietà: la capacità dei processi termochimici di dissociare le macromolecole della biomassa producendo composti a basso peso molecolare, e l’abilità dei batteri di convertire substrati anche complessi in sostanze chimiche di valore. Questa tesi ha sviluppato un nuovo approccio metodologico per approfondire la possibilità di un accoppiamento diretto tra pirolisi e digestione anaerobica, allo scopo di produrre acidi grassi volatili (VFA), sinergicamente con l’utilizzo di idrogeno come fonte rinnovabile per aumentare il valore del prodotto finale. In primo luogo, è stata fatta un'ampia caratterizzazione del rendimento di COD e della composizione chimica dei prodotti di pirolisi che ha rivelato come più del 50% del COD della biomassa di partenza sia convogliato in sostanze chimiche biodisponibili. In secondo luogo, sono stati sviluppati tre reattori anaerobici a gocciolamento con diversi materiali di riempimento, incluso il biochar. I prodotti di pirolisi sono stati successivamente fermentati con e senza idrogeno, per valutarne, in via preliminare, la possibile conversione in VFA. I risultati suggeriscono che il biochar ha agito come promotore per la biotrasformazione dei prodotti di pirolisi in VFA, producendo una conversione del 35% rispetto al COD in input, mentre l'idrogeno ha dimostrato la capacità di stabilizzare le rese di VFA a catena lunga.

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Kacem, Hanana Houda. "Établissement de primocultures de cellules cardiaques de palourdes Ruditapes decussatus : étude des courants ioniques et des MAP Kinases après exposition des cellules à des xénoobiotiques". Brest, 2011. http://www.theses.fr/2011BRES2011.

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La nécessité d’évaluer l’impact des xénobiotiques du milieu aquatique sur les organismes, justifie la mise en place de nouveaux bioessais et de biomarqueurs afin d’identifier les risques sanitaires et mieux les prévenir. L’utilisation de méthodes alternatives à l’expérimentation animale, telles que les cultures de cellules, est préconisée en toxicologie. C’est dans ce contexte que des cultures primaires de cellules cardiaques de palourde Ruditapes decussatus ont été mises en place afin d’évaluer les effets de trois types de polluants du milieu marin un biocide, une phycotoxine et un herbicide. Les primocultures sont obtenues en routine et restent fonctionnelles in vitro pendant au moins un mois. Parmi les cellules, les cardiomyocytes, dont un certain nombre de caractéristiques électrophysiologiques ont pu être précisées par patch clamp, présentent un intérêt comme bioessai pour des applications en toxicologie. Les réponses cellulaires évaluées in vitro varient selon le polluant testé et de manière dose-dépendante. En particulier, l’étude des voies de signalisation MAP kinases (P38, JNK et ERK) se révèle intéressante
The necessity to evaluate impact of xenobiotics from aquatic environment in marine organisms justifies the implementation of new bioassays and biomarkers to identify health risks for better prevention. The use of alternative methods to animal experiment, such as cell cultures, is recommended in toxicology. In this context, primary cultures of heart cells from clam Ruditapes decussatus was established and used to evaluate the effects of three types of pollutants from marine environment: a biocide, a phycotoxine and an herbicide. Primary cultures were routinely obtained and maintained functional in vitro for at least one month. Among cells, cardiomyocytes identified by electrophysiological properties after study by patch clamp presents an interest as bioassay for applications in toxicology. Cellular responses evaluated in vitro varie with the pollutant and are time and dose dependent. In particular, study of MAPK signaling pathways (P38, JNK and ERK) are of major interest

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Livros sobre o assunto "Acidic patch"

Kostyukov, Viktor. Molecular mechanics of biopolymers. ru: INFRA-M Academic Publishing LLC., 2020. http://dx.doi.org/10.12737/1010677.

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The monograph is devoted to molecular mechanics simulations of biologically important polymers like proteins and nucleic acids. It is shown that the algorithms based on the classical laws of motion of Newton, with high-quality parameterization and sufficient computing resources is able to correctly reproduce and predict the structure and dynamics of macromolecules in aqueous solution. Summarized the development path of biopolymers molecular mechanics, its theoretical basis, current status and prospects for further progress. It may be useful to researchers specializing in molecular Biophysics and molecular biology, as well as students of senior courses of higher educational institutions, studying the biophysical and related areas of training.

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Nolte, David D. The Measure of Life. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805847.003.0011.

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This final topic of the book extends the ideas of dynamics in abstract spaces of high dimension to encompass the idea of a trajectory of life. Health and disease become dynamical systems defined by all the proteins and nucleic acids that comprise the physical self. Concepts from network theory, autonomous oscillators and synchronization contribute to this viewpoint. Healthy trajectories are like stable limit cycles in phase space, but disease can knock the system trajectory into dangerous regions of health space, as doctors turn to new developments in personalized medicine try to return the individual to a healthy path. This is the ultimate generalization of Galileo’s simple parabolic trajectory.

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Capítulos de livros sobre o assunto "Acidic patch"

Bosch, Thomas C. G. "The Path Less Explored: Innate Immune Reactions in Cnidarians". In Nucleic Acids and Molecular Biology, 27–42. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-73930-2_2.

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Ascher, P., e L. Nowak. "A Patch-Clamp Study of Excitatory Amino Acid Activated Channels". In Advances in Experimental Medicine and Biology, 507–11. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-7971-3_39.

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Dalafu, Haydee, Modesto T. Chua e Soma Chakraborty. "Development of κ-Carrageenan Poly(acrylic acid) Interpenetrating Network Hydrogel as Wound Dressing Patch". In ACS Symposium Series, 125–35. Washington, DC: American Chemical Society, 2010. http://dx.doi.org/10.1021/bk-2010-1054.ch006.

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Paul, Rajesh, Emily Ostermann e Qingshan Wei. "Rapid Extraction of Plant Nucleic Acids by Microneedle Patch for In-Field Detection of Plant Pathogens". In Plant Pathology, 77–90. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2517-0_4.

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Hollander, Jay B., Ananias C. Diokno e Bruce Steinert. "Mapping of the Extended Focus (“Blast Path”) Using Uric Acid Calculi". In Shock Wave Lithotripsy 2, 99–102. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-2052-5_19.

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Zaman, M., K. Kleineidam, L. Bakken, J. Berendt, C. Bracken, K. Butterbach-Bahl, Z. Cai et al. "Methane Production in Ruminant Animals". In Measuring Emission of Agricultural Greenhouse Gases and Developing Mitigation Options using Nuclear and Related Techniques, 177–211. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-55396-8_6.

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AbstractAgriculture is a significant source of GHGsglobally and ruminant livestock animals are one of the largest contributors to these emissions, responsible for an estimated 14% of GHGs (CH4and N2O combined) worldwide. A large portion of GHG fluxes from agricultural activities is related to CH4 emissions from ruminants. Both direct and indirect methods are available. Direct methods include enclosure techniques, artificial (e.g. SF6) or natural (e.g. CO2) tracer techniques, and micrometeorological methods using open-path lasers. Under the indirect methods, emission mechanisms are understood, where the CH4 emission potential is estimated based on the substrate characteristics and the digestibility (i.e. from volatile fatty acids). These approximate methods are useful if no direct measurement is possible. The different systems used to quantify these emission potentials are presented in this chapter. Also, CH4 from animal waste (slurry, urine, dung) is an important source: methods pertaining to measuring GHG potential from these sources are included.

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Salleh, W. S., S. Nurulain, M. A. S. Aspar, M. R. Salim e H. Manap. "Free Fatty Acid Detection in Heated Palm Cooking Oil Using an Open Path Optical Method". In Lecture Notes in Electrical Engineering, 213–21. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-3847-2_19.

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Weligama, Chandrakumara, Caixian Tang, Peter W. G. Sale, Mark K. Conyers e Liu De Li. "Extra Supply of Calcium Is Not Required for Maximal Root Growth in the Nitrate and Phosphorus-rich Patch in an Acid Soil". In Molecular Environmental Soil Science at the Interfaces in the Earth’s Critical Zone, 167–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-05297-2_51.

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Pathak, Prasad, e Stephen Whalen. "Using Geospatial Techniques to Analyze Landscape Factors Controlling Ionic Composition of Arctic Lakes, Toolik Lake Region, Alaska". In Geographic Information Systems, 130–50. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-2038-4.ch012.

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The impacts of climate change on landscapes in arctic Alaska are evident in terms of permafrost melting, frequent thermokarst activity, and the occurrence of more broadleaf vegetation. These changes may alter natural biogeochemical cycles of ions along with major nutrients and affect ionic compositions of lakes, as they are connected with the landscapes. However, the nature of the connectivity between lakes and landscapes in this region is not yet explored. The authors propose that geospatial analysis of landscape properties along with observed lake ion concentrations will enable an understanding of the currently existing landscape controls over ion inputs into the lakes. For the watersheds of 41 lakes in the Arctic Foothills region of Alaska, spatial properties of natural vegetation communities expressed in terms of percentage, shape complexity, and patch density metrics were derived using satellite data. Regression analyses were performed for concentration of ions as well as conductivity in lake water where the spatial metrics along with lake physical properties, lake order, and glacial till age categories were used as predicting variables in the regression. Landscape metrics for major land covers i.e., Percentage of Moist Acidic Tundra (MAT) and Moist Non-acidic Tundra (MNT) were the major predicting variables for concentration of several ions.

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Davenport, William G., e Matthew J. King. "2nd Catalyst Bed Heatup Path". In Sulfuric Acid Manufacture, 165–75. Elsevier, 2006. http://dx.doi.org/10.1016/b978-008044428-4/50014-2.

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Trabalhos de conferências sobre o assunto "Acidic patch"

K, Santhanalakshmi, Neelakandeswari N, Gomathi Thandapani, Mohanapriya N e Vinoth M. "Synthesis and characterization of Nickel Aluminate-innovative a green path with solid acid catalyst for solvent free acylation reaction". In 2024 Third International Conference on Smart Technologies and Systems for Next Generation Computing (ICSTSN), 1–6. IEEE, 2024. http://dx.doi.org/10.1109/icstsn61422.2024.10670850.

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Skrajna, Aleksandra, Holly Simmons, Charlotte Smith, Jeanne-Marie E. Mcpherson, Dennis Goldfarb e Robert K. McGinty. "Abstract 2082: Deciphering the nucleosome acidic patch binding at amino acid resolution". In Proceedings: AACR Annual Meeting 2021; April 10-15, 2021 and May 17-21, 2021; Philadelphia, PA. American Association for Cancer Research, 2021. http://dx.doi.org/10.1158/1538-7445.am2021-2082.

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Xu, Ting-Hai, Minmin Liu, Edward Zhou, Gangning Liang, Eric H. Xu, Karsten Melcher e Peter A. Jones. "Abstract 1078: The nucleosomal acidic patch helps anchor ofde novoDNA methyltransferase DNMT3A2/3B3 complex". In Proceedings: AACR Annual Meeting 2020; April 27-28, 2020 and June 22-24, 2020; Philadelphia, PA. American Association for Cancer Research, 2020. http://dx.doi.org/10.1158/1538-7445.am2020-1078.

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Japir, Abd Al-Wali, Jumat Salimon, Darfizzi Derawi, Murad Bahadi e Muhammad Rahimi Yusop. "Separation of free fatty acids from high free fatty acid crude palm oil using short-path distillation". In THE 2016 UKM FST POSTGRADUATE COLLOQUIUM: Proceedings of the Universiti Kebangsaan Malaysia, Faculty of Science and Technology 2016 Postgraduate Colloquium. Author(s), 2016. http://dx.doi.org/10.1063/1.4966739.

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Nurdin, Muhammad, Haznan Abimanyu, Retno Cahyaningrum, Zul Arham, Muhammad Natsir e Maulidiyah Maulidiyah. "Bioethanol production based on OPEFB biomass by sulfuric acid followed by saccharification and co-fermentation simultaneously". In THE 3RD INTERNATIONAL SEMINAR ON SCIENCE AND TECHNOLOGY 2021: The Path of Sustainable Development for a Better Life. AIP Publishing, 2023. http://dx.doi.org/10.1063/5.0133285.

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Zahniser, M. S., P. L. Kebabian, S. Anderson, A. Freedman e C. E. Kolb. "Infrared laser absorption eddy correlation measurement devices for trace atmospheric gases". In International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.thl53.

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We discuss the development of two open path IR absorption instruments for eddy correlation measurements of fluxes of atmospheric trace gases which impact greenhouse and acidic dry deposition problems. One instrument, designed for CH4 measurements, uses a tunable IR He-Ne laser operating at 3.39/µm. The second, based on a tunable diode laser system, will be used to detect a variety of molecules including N2O, O3, and HNO3. Since these measurements are made in the free atmosphere, the instrument must discriminate against spectral features of the atmospheric background, especially water vapor. The chosen approaches to this problem are described, including the use of a frequency-modulated source and detection at both the first and second harmonic of the modulation frequency. The multipass cell must exhibit minimal sensitivity to the expected vibration of its supporting structure; methodsof achieving this are described.

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Marsetyo, Marsetyo, Ninda Wahyuni, Tarsono Tarsono, I. Wayan Sulendre e Mulyati Pamulu. "The effect of scarification with different level of sulphuric acid on seed germination and seedling growth of Indigofera zollingeriana Miq". In THE 3RD INTERNATIONAL SEMINAR ON SCIENCE AND TECHNOLOGY 2021: The Path of Sustainable Development for a Better Life. AIP Publishing, 2023. http://dx.doi.org/10.1063/5.0133403.

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Hernandez, Ernesto, e Rob Reintjes. "Recent developments on thin film and short path evaporation technologies for edible oils processing". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/zlex8082.

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Short path distillation and thin film evaporation are generally associated with processing of heat-sensitive oils that require short residence times, high heat and mass transfer coefficients and shorter contact times. Thin film evaporation and short path distillation processes that normally operate at lower temperatures and higher vacuums are commonly used in the processing heat-sensitive oils like omega 3 oils and concentration of omega 3 ethyl esters. These technologies are now also being considered for the removal of processing and environmental contaminants from oils like palm, soybean and other marine oils.Artisan's thin evaporation and the new short path stripping (SPS) technology, with internal multistage-condensing capabilities, take advantage of both principles, namely short path distillation and thin film evaporation. Artisan-SPS system, with no internal moving parts and higher processing capacity, offers several advantages over commercial molecular distillation and deodorizer systems including applications in the removal of contaminants, physical refining and recovery and concentration of omega 3 ethyl esters.This presentation will include results on applications of the new thin evaporation and short path evaporation Artisan systems for the removal of environmental and processing-generated contaminants such as polychlorinated biphenyl (PCBs), dioxins, furans, 3-chloropropane-1,2-diol (3-MCPD), glycidyl esters (GE) from oils such as palm, soybean and marine fats. The oils were also analyzed for free fatty acids, mono and diglycerides, peroxide value, anisidine value, color and flavor. The resulting oils met commercial quality specifications for refined edible oils, with the added advantage of reducing free fatty acids from 3.87 % (for palm oil) to < 0.1 % and removal of over 90 percent of mono and diglycerides, confirming the additional application of Artisan's SPS as a physical refining system and fractionation and recovery of mono and diglycerides. Regulatory specs for PCBs, dioxins and furans, MCPDs, GEs for edible oils were also successfully met.

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Wahab, Abdul Wahid, Abdul Karim, Nursiah La Nafie, Triana Febrianti e Nuritasari Azis. "Biosynthesis of silver nanoparticles using Lannea coromandelica bark extract: A comparative study with Polyvinyl alcohol (PVA) and Polyacrylic acid (PAA) as stabilizing agents". In THE 3RD INTERNATIONAL SEMINAR ON SCIENCE AND TECHNOLOGY 2021: The Path of Sustainable Development for a Better Life. AIP Publishing, 2023. http://dx.doi.org/10.1063/5.0133380.

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Zhang, Yikai. "Intelligent Balance Vehicle for Medical Nucleic Acid Collection Based on Path Planning". In ICITEE 2022: 5th International Conference on Information Technologies and Electrical Engineering. New York, NY, USA: ACM, 2022. http://dx.doi.org/10.1145/3582935.3582968.

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Relatórios de organizações sobre o assunto "Acidic patch"

Dhandha, Maulik. Dietary survey and patch testing for tannic acid and allyl compound in Pemphigus vulgaris and Bullous pemphigoid patients. ResearchHub Technologies, Inc., fevereiro de 2024. http://dx.doi.org/10.55277/researchhub.8qeynmru.

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Montville, Thomas J., e Roni Shapira. Molecular Engineering of Pediocin A to Establish Structure/Function Relationships for Mechanistic Control of Foodborne Pathogens. United States Department of Agriculture, agosto de 1993. http://dx.doi.org/10.32747/1993.7568088.bard.

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This project relates the structure of the bacteriocin molecule (which is genetically determined) to its antimicrobial function. We have sequenced the 19,542 bp pediocin plasmid pMD136 and developed a genetic transfer system for pediococci. The pediocin A operon is complex, containing putative structural, immunity, processing, and transport genes. The deduced sequence of the pediocin A molecule contains 44 amino acids and has a predicted PI of 9.45. Mechanistic studies compared the interaction of pediocin PA-1 and nisin with Listeria monocytgenes cells and model lipid systems. While significant nisin-induced intracellular ATP depletion is caused by efflux, pediocin-induced depletion is caused exclusively by hydrolysis. Liposomes derived from L. monocytogenes phospholipids were used to study the physical chemistry of pediocin and nisin interactions with lipids. Their different pH optima are the results of different specific ionizable amino acids. We generated a predicted 3-D structural model for pediocin PA-1 and used a variety of mutant pediocins to demonstrate that the "positive patch" at residues 11 and 12 (and not the YGNGV consensus sequence) is responsible for the binding step of pediocin action. This structure/function understanding gained here provides necessary prerequisites to the more efficacious use of bacteriocins to control foodborne pathogens.

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Simandl, G. J., R. J. D'Souza, S. Paradis e J. Spence. Rare-earth element content of carbonate minerals in sediment-hosted Pb-Zn deposits, southern Canadian Rocky Mountains. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328001.

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Paleozoic platform carbonate rocks of the Rocky Mountains host Mississippi Valley-type (MVT), magnesite, barite, and REE-barite-fluorite deposits. Farther west, platform carbonate rocks of the Kootenay Arc host MVT and fracture-controlled replacement (FCR) deposits. This is the first systematic LA-ICP-MS study of carbonates in MVT and FCR deposits. We investigated seven MVT deposits in the Rocky Mountains, and five MVT deposits in the Kootenay Arc. None of the post-Archean Australian shale (PAAS)-normalized REE profiles show light REE (LREE) depletion and strong negative Ce anomalies characteristic of modern seawater: some profiles are nearly flat; others show depletion in LREE similar to seawater but without negative Ce anomalies; others are middle REE enriched. Carbonates with a strong positive Eu anomaly precipitated from or interacted with different fluids than carbonates with flatter profiles without a strong positive Eu anomaly. REE signatures reflect crystallization conditions of primary carbonates, and crystallization and re-equilibration conditions of carbonates with ambient fluids during diagenesis, deep burial, and/or metamorphic recrystallization. Chemical evolution of fluids along their migration path, fluid-to-rock ratio, fluid acidity, redox, and temperature also influence REE profile shape, which helps establish genetic and timing constraints on studied deposits and improves knowledge of the metallogeny of the Kootenay Arc and Rocky Mountains.

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Desbarats, A. J., e J. B. Percival. Hydrogeochemistry of mine tailings from a carbonatite-hosted Nb-REE deposit, Oka, Quebec, Canada. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331256.

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Environmental impacts associated with the mining of carbonatite deposits are an emerging concern due to the demand for critical metals. This study investigates the chemistry of tailings seepage at the former Saint Lawrence Columbium mine near Oka, Québec, Canada, which produced pyrochlore concentrate and ferroniobium from a carbonatite-hosted Nb-REE deposit. Its objectives are to characterize the mineralogy of the tailings and their pore water and effluent chemistries. Geochemical mass balance modeling, constrained by aqueous speciation modeling and mineralogy, is then used to identify reactions controlling the chemical evolution of pore water along its flow path through the tailings impoundment. The tailings are composed mainly of REE-enriched calcite (82 wt. %), biotite (12 wt. %) and fluorapatite (4 wt. %). Minor minerals include chlorite, pyrite, sphalerite, molybdenite and unrecovered pyrochlore. Secondary minerals include gypsum, barite and strontianite. Within the unsaturated zone, pore water chemistry is controlled by sulfide oxidation and calcite dissolution with acid neutralization. With increasing depth below the water table, pore water composition reflects gypsum dissolution followed by sulfate reduction and FeS precipitation driven by the oxidation of organic carbon in the tailings. Concomitantly, incongruent dissolution of biotite and chlorite releases K, Mg, Fe, Mn, Ba and F, forming kaolinite and Ca-smectite. Cation exchange reactions further remove Ca from solution, increasing concentrations of Na and K. Fluoride concentrations reach 23 mg/L and 8 mg/L in tailings pore water and effluent, respectively. At a pH of 8.3, Mo is highly mobile and reaches an average concentration of 83 µg/L in tailings effluent. Although U also forms mobile complexes, concentrations do not exceed 16 µg/L due to the low solubility of its pyrochlore host. Adsorption and the low solubility of pyrochlore limit concentrations of Nb to less than 49 µg/L. Cerium, from calcite dissolution, is strongly adsorbed although it reaches concentrations (unfiltered) in excess of 1 mg/L and 100 µg/L in pore water and effluent, respectively. Mine tailings from carbonatite deposits are enriched in a variety of incompatible elements with mineral hosts of varying reactivity. Some of these elements, such as F and Mo, may represent contaminants of concern because of their mobility in alkaline tailings waters.

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