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Bapna, Akanksha. "Drug and proton translocation by the multidrug transporter LmrP." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613705.
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Khadilkar, Aswad S. "Manipulations of Sucrose/Proton Symporters and Proton-pumping Pyrophosphatase Lead to Enhanced Phloem Transport But Have Contrasting Effects on Plant Biomass." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801879/.
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Delivery of photoassimilate, mainly sucrose (Suc) from photoautotrophic source leaves provides the substrate for the growth and maintenance of sink tissues such as roots, storage tissues, flowers and fruits, juvenile organs, and seeds. Phloem loading is the energized process of accumulating solute in the sieve element/companion cell complex of source leaf phloem to generate the hydrostatic pressure that drives long-distance transport. In many plants this is catalyzed by Suc/Proton (H+) symporters (SUTs) which are energized by the proton motive force (PMF). Overexpression of SUTs was tested as means to enhance phloem transport and plant productivity. Phloem specific overexpression of AtSUC2 in wild type (WT) tobacco resulted in enhanced Suc loading and transport, but against the hypothesis, plants were stunted and accumulated carbohydrates in the leaves, possibly due to lack of sufficient energy to support enhanced phloem transport. The energy for SUT mediated phloem loading is provided from the PMF, which is ultimately supplied by the oxidation of a small proportion of the loaded photoassimilates. It was previously shown that inorganic pyrophosphate (PPi) is necessary for this oxidation and overexpressing a proton-pumping pyrophosphatase (AVP1) enhanced both shoot and root growth, and augmented several energized processes like nutrient acquisition and stress responses. We propose that AVP1 localizes to the PM of phloem cells and uses PMF to synthesize PPi rather than hydrolyze it, and in doing so, maintains PPi levels for efficient Suc oxidation and ATP production. Enhanced ATP production in turn strengthens the PMF via plasma membrane (PM) ATPase, increasing phloem energization and phloem transport. Phloem-specific and constitutive AVP1 overexpressing lines showed increased growth and more efficiently moved carbohydrates to sink organs compared to WT. This suggested changes in metabolic flux but diagnostic metabolites of central metabolism did not show changes in steady state levels. This research focuses on fundamental aspects of carbon utilization and transport, and has a strong applied component, since increased H+-PPase activity enhances plant biomass, nutrient up-take capacities, and stress tolerance for as yet not fully characterized reasons.
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Wege, Stefanie. "Structure, function and regulation of the nitrate/proton transporter AtCLCa in arabidopsis thaliana." Paris 11, 2010. http://www.theses.fr/2010PA112146.
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AtCLCa chez Arabidopsis thaliana appartient à la famille de transporteurs d’anions appelés ‘ChLoride Channel’ (CLC). AtCLCa est plus sélectif pour le nitrate que pour le chlorure. C’est un antiporteur NO3-/H+ à l’origine de l’accumulation du nitrate dans la vacuole. La différence de sélectivité est due à un simple changement d’un acide aminé. Nous avons pu montrer que le changement de cet acide aminé transforme AtCLCa en un transporteur de chlorure et est incapable de réaliser sa fonction dans l’accumulation de nitrate dans la vacuole in planta. De plus, nous avons démontré que AtCLCa est directement régulé par la liaison de l’ATP et que cet effet est influencé par le rapport ATP/AMP, l’AMP supprimant l’effet de l’ATP. Ceci suggère que la régulation de AtCLCa est dépendante du statut énergétique de la cellule. En supplément, nous avons aussi montré que cette protéine est régulée par phosphorylation dans sa partie N-terminale. Nous avons identifié une classe de protéines, les SnRKs, qui sont capables de phosphoryler AtCLCa in vitro et d’interagir avec AtCLCa in vivo. SnRK1. 1 et SnRK2. 6. SnRK1. 1 est exprimée de manière ubiquitaire dans la plante et peut inhiber l’activité de la nitrate réductase. Des études d’expression GUS montrent que AtCLCa est exprimé au travers de la plante (comme SnRK1. 1) mais une forte expression observée dans les cellules de garde comme pour SnRK2. 6. Des analyses phénotypiques des mutants nuls clca démontrent la fonction de AtCLCa non seulement dans l’accumulation du nitrate mais aussi dans les mouvements stomatiques. Ces résultats suggèrent une possible interaction dans les cellules de garde de la kinase SnRK2. 6 et ATCLCa in plantaThe Arabidopsis thaliana CLCa belongs to the ChLoride Channel (CLC) family of anion transport proteins. AtCLCa is most selective for nitrate and not for chloride. It mediates the accumulation of nitrate into the vacuole by a NO3-/H+ exchanger mechanism. The difference in selectivity is accompanied by a single amino acid difference. We could show that an exchange of this amino acid turns AtCLCa into a chloride transporter and abolishes its function of nitrate accumulation in planta. Furthermore, we could show that AtCLCa is directly regulated by ATP and that this effect is influenced by the ATP/AMP ratio, as AMP abolished the effect of ATP, suggesting an energy-state dependent regulation of AtCLCa in the cell. Additionally to the regulation of AtCLCa by nucleotides, we could also show that it is regulated by phosphorylation on its N-terminus. We identified a specific class of kinases, the SnRKs, which are able to phosphorylate AtCLCa in vitro and interact with it in vivo. We focused on two candidate kinases within this family, SnRK1. 1 and SnRK2. 6. SnRK1. 1 can inhibit the nitrate reductase. Therefore, the activity of SnRK1. 1 is connected to nitrate metabolism, like the activity of AtCLCa. SnRK2. 6 is strongly expressed in stomata guard cells and GUS expression studies showed that AtCLCa is expressed throughout the plant (like SnRK1. 1), but shows a particular high expression in stomata guard cells like SnRK2. 6. Subsequent phenotype analyses of clca knock-out mutants demonstrated a role of AtCLCa not only in nitrate accumulation but also in stomata movement, suggesting a possible interaction of the guard cell kinase SnRK2. 6 and AtCLCa in planta
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Martínez, Molledo María [Verfasser], and Christian [Akademischer Betreuer] Löw. "Multispecific substrate recognition in a Proton-Dependent Oligopeptide Transporter / María Martínez Molledo ; Betreuer: Christian Löw." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2019. http://d-nb.info/1175584835/34.
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Li, Dan. "Novel Protein Materials based on Bacterial Efflux Pumps." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1304692634.
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Hodin, Julie. "Le couplage nitrate/proton au sein de l’échangeur AtClCa est essentiel à la physiologie de la plante en réponse aux fluctuations environnementales." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS181/document.
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Chez les plantes, le nitrate est un élément essentiel mais sa disponibilité dans le sol est fluctuante. Il est donc stocké dans la vacuole grâce à un échangeur nitrate/proton appelé AtClCa. La famille de protéines ClCs comporte à la fois des échangeurs mais aussi des canaux suggérés comme issus de l’évolution des échangeurs par une conversion mécanistique. Chez Arabidopsis thaliana, seuls des ClCs échangeurs assurent la gestion du nitrate. Deux glutamates très conservés, E203 et E270 dans AtClCa, sont essentiels pour le transport des protons chez les ClCs échangeurs. La mutation du résidu E203 en une alanine, un acide aminé non protonable (E203A) a permis de produire artificiellement une telle conversion mécanistique. Afin de mieux comprendre l’importance physiologique du mécanisme d’échange, une analyse a été conduite sur des plantes exprimant la forme mutée d’AtClCa pour ce glutamate. Chez ces plantes, le stockage vacuolaire est fortement réduit au profit d’une importante assimilation accroissant la teneur en protéines. En dépit de cela, elles présentent un défaut de production de biomasse résultant en grande partie d’une perturbation de l’homéostasie hydrique. Elles sont également plus sensibles aux stress hydrique et probablement azoté. La conservation d’un échangeur est donc requise pour croitre en dépit des fluctuations environnementales. En parallèle, la mutation E270A a été introduite en plante afin d’étudier son importance sur la physiologie d’Arabidopsis. Une analyse préliminaire de la biomasse et des contenus en nitrate et eau de plantes exprimant la forme mutée de ce glutamate est donc présentée dans la seconde partie de cette thèseNitrate is a major element for plant but its availability is very fluctuant in soils. Then, it is stored in vacuoles thanks to a nitrate/proton exchanger named AtClCa. In ClCs, exchangers but also channels were identified, the latest were suggested to be evolved from exchanger in which a mechanistic switch happened. In Arabidopsis thaliana, only exchangers are involved in nitrate management. Two conserved glutamate, E203 and E270 in AtClCa, are essential for protons transport in ClCs exchangers. The mutation of E203 into an alanine, a non-protonable amino acid (E203A) artificially produces such a mechanistic switch. To better understand the physiological importance of this exchange mechanism, a study was conducted in plants expressing the mutated form of AtClCa for this glutamate. In those plants, the vacuolar storage is highly restricted whereas the assimilation is favoured and the protein content increased. Despite that, the biomass production is decreased mostly because of a hydric homeostasis disruption. Those plants are also more sensitive to hydric and probably nitrogenous stress. The exchanger conservation is then required for plant growth whatever the environmental fluctuations. In parallel, the mutation E270A was introduced in planta to study its physiological importance. A preliminary analysis of plant biomass and nitrate and water contents was then performed in plants expressing the E270A mutated form of AtClCa and the results are presented in the second part of the manuscript
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Peterson, Emily. "Proteoliposome Proton Flux Assays Establish Net Conductance, pH-Sensitivity, and Functional Integrity of a Novel Truncate of the M2 Ion "Channel" of Influenza A." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2420.
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A novel truncate of Influenza A M2 protein (residues 22-62), incorporated into a uniquely tailored proteoliposome proton uptake assay, demonstrated proton flux more characteristic of an ion transporter than a traditional ion "channel." The liposome paradigm was essential for testing the conductance activity of this M2 truncate at a range of extraphysiological pHs appropriate for channel vs. transport function determination. In addition to transporter-typical proton flux, M2(22-62) showed the key characteristics of functional integrity: selective proton uptake into liposomes and block of uptake by amantadine. Two sets of proteoliposome proton flux assays were carried out, Set 1 at pH values of 6.5, 6.0. 5.5, 5.0, and 4.5; Set 2 at pH values of 6.25, 6.0, 5.75, 5.5, 5.25, 5.0, and 4.75. Observed flux rates followed a proton transport saturation curve similar to that observed in mouse erythroleukemia cells1. Proton transport was maximal at pH 5.5 in Set 1 (139 H+/second/tetramer) and at pH 5.75 in Set 2 (43 H+/second/tetramer). Amantadine block was strongest at pH 5.5 in Set 1 and 6.25 in Set 2, and apparent desensitization of the protein severely reduced proton flux and amantadine sensitivity below pH 5.5 in both sets of experiments. Decreased external pH increased proton uptake with an apparent pKa of 6 (Set 1) or 6.5 (Set 2). These data indicate acid activation of M2(22-62) between pH 5.5-6, optimal amantadine block between pH 5.5-6.25, and a loss of peptide functionality between pH 5.9-4.7.
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Forrest, Lucy R. "Simulation studies of proton channels and transporters." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365828.
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Zhang, Lejie. "Fluorescent Visualization of Cellular Proton Fluxes." eScholarship@UMMS, 2018. https://escholarship.umassmed.edu/gsbs_diss/999.
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Proton fluxes through plasma membranes are essential for regulating intracellular and extracellular pH and mediating co-transport of metabolites and ions. Although conventional electrical measurements are highly sensitive and precise for proton current detection, they provide limited specificity and spatial information. My thesis focuses on developing optical approaches to visualize proton fluxes from ion channels and transporters.
It has been demonstrated that channel-mediated acid extrusion causes proton depletion at the inner surface of the plasma membrane. Yet, proton dynamics at the extracellular microenvironment are still unclear. In Chapter II, we developed an optical approach to directly measure pH change in this nanodomain by covalently attaching small-molecule, fluorescent proton sensors to the cell’s glycocalyx using glyco-engineering and copper free ‘click’ chemistry. The extracellularly facing sensors enable real-time detection of proton accumulation and depletion at the plasma membrane, providing an indirect readout of channel and transporter activity that correlated with whole-cell proton current. Moreover, the proton wavefront emanating from one cell was readily visible as it crossed over nearby cells.
The transport of monocarboxylates, such as lactate and pyruvate is critical for energy metabolism and is mainly mediated by proton-coupled monocarboxylate transporters (MCT1-MCT4). Although pH electrodes and intracellular fluorescent pH sensors have been widely used for measuring the transport of proton-coupled MCTs, they are unable to monitor the subcellular activities and may underestimate the transport rate due to cell’s volume and intracellular buffering. In Chapter III, we used the Chapter II approach to visualize proton-coupled transport by MCT1-transfected HEK293T cells and observed proton depletion followed by a recovery upon extracellular perfusion of L-lactate or pyruvate. In addition, we identified a putative MCT, CG11665/Hrm that is essential for autophagy during cell death in Drosophila. The results demonstrate that Hrm is a bona fide proton-coupled monocarboxylate transporter that transports pyruvate faster than lactate.
Although the approach developed in Chapter II enables visualization of proton fluxes from ion channels and transporters, it’s not applicable in some cell types which cannot incorporate unnatural sialic acid precursors into their glycocalyx, such as INS-1 cells and cardiomyocytes. To address this, in Chapter IV we developed a pH-sensitive, fluorescent WGA conjugate, WGA-pHRho that binds to endogenous glycocalyx. Compared to the results in Chapter II and III, cell surface-attached WGA-pHRho has similar fluorescent signals in response to proton fluxes from proton channel Hv1, omega mutant Shaker-IR R362H and MCT1. With WGA-pHRho, we were able to label the plasma membrane of INS-cells and cardiomyocytes and visualized the transport activity of MCT1 in these cells.
Taken together, these findings provide news insights into proton dynamics at the extracellular environment and provide new optical tools to visualize proton fluxes from ion channels and transporters. Moreover, the modularity of the approaches makes them adaptable to study any transport events at the plasma membrane in cells, tissues, and organisms.
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Samsudin, Mohd Firdaus. "Improving oral drug delivery : computational studies of proton dependent oligopeptide transporters : computational studies of peptide transporters." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:ce400815-fd55-49dc-8f43-3f620d3e132e.
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Proton dependent oligopeptide transporters (POTs) play a central role in nitrogen homeostasis by coupling the uptake of dipeptides and tripeptides to the proton electrochemical gradient across the plasma membrane. In human, members of this transporter family, PepT1 and PepT2, are critical modulators of drug pharmacokinetics as they facilitate the uptake and retention of numerous orally administered drugs including the β-lactam antibiotics. Rationally designing drugs to target these transporters is therefore an attractive approach to improving bioavailability. To this end, the binding of peptides to a bacterial homolog, PepTSt, was modelled based on recently determined crystal structures. A range of computational methods to predict the free energy of binding were evaluated and a hybrid approach, where the end-point methods were used to classify peptides into strong and poor binders and a theoretically exact method for refinement, was able to accurately predict ligand affinities. This approach was utilised to investigate the substrate preference of PepTSt and the results were validated using in vitro transport assays. To extend this study to the human peptide transporters, homology models of PepT1 and PepT2 were built using the crystal structures of PepTSo and mouse and rat extracellular domains (ECDs) as the templates. Essential residues as proposed by various mutational studies align well with the binding cavity, suggesting that the models are structurally sound. Applying the free energy methods to predict the affinities of peptides and drugs to the homology model of PepT1, however, resulted in discrepancies with experimental data, highlighting the importance of a high-resolution crystal structure in binding affinity predictions. Based on the results for PepTSt, a binding model for peptide prodrugs and β-lactam antibiotics to the human PepT1 was proposed. Overall, this thesis provides a framework for future computational studies using free energy methods to understand drug interactions with pharmaceutically relevant transporters.
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Jevons, Mark Paul. "Expression and function of proton-coupled transporters in the mammalian intestine." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531738.
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Anderson, Catriona M. H. "Intestinal proton-coupled amino acid and dipeptide transporters : function and regulation." Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398999.
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Solcan, Nicolae Claudiu. "Biochemical and biophysical studies of the prokaryotic proton dependent oligopeptide transporters." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:5ad900fb-a949-4bac-b69a-f585b44a8382.
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The proton dependent oligopeptide transporters (POT family) are members of the Major Facilitator Superfamily of secondary active transporter proteins. They use the transmembrane proton gradient to drive the uptake of di- and tripeptides into the cytoplasm. Members of the family are highly conserved in pro- and eukaryotic genomes, and in humans they are responsible for the oral absorption of many drug families, including -lactam antibiotics. Recently, the crystal structures of PepTSo and PepTSt, two prokaryotic homologues of the human proteins PepT1 and PepT2, captured the proteins in two distinct conformations, providing insight into the structural aspects of the transport mechanism. A protocol was designed for functional liposome reconstitution of POT proteins, and transport assays were conducted to characterise their substrate specificity, pH dependence and kinetic properties. Using site-directed mutagenesis, we identified binding site residues involved in peptide recognition and proton translocation, and distinguished between the two roles by comparing protein activity in proton- and peptide-driven conditions. We also investigated the roles of key residues in the conformational transitions that accompany the transport cycle, using data from biochemical assays, molecular dynamics simulations and modeling, as well as electron paramagnetic resonance measurements. In addition, several bacterial POT members were screened for crystallisation, in order to assess their stability and crystal diffraction quality in different detergents. Further work was performed with bacterial POT homologues YdgR and GkPOT, including binding studies using NMR spectroscopy and assaying drug transport in vivo and in vitro. Together, the data establish bacterial POTs as model systems for studying the mammalian oligopeptide transporters, and a mechanistic model for peptide transport is proposed.
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Pommarel, Loann. "Transport and control of a laser-accelerated proton beam for application to radiobiology." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX001/document.
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L’accélération de particules par interaction laser-plasma est une alternative prometteuse aux accélérateurs conventionnels qui permettrait de rendre plus compactes les machines du futur dédiées à la protonthérapie. Des champs électriques extrêmes de l’ordre du TV/m sont créés en focalisant une impulsion laser ultra-intense sur une cible solide mince de quelques micromètres d’épaisseur, ce qui produit un faisceau de particules de haute énergie. Ce dernier contient des protons ayant une énergie allant jusqu’à la dizaine de mégaélectron-volts, et est caractérisé par une forte divergence angulaire et un spectre en énergie très étendu.Le but de cette thèse est de caractériser parfaitement un accélérateur laser-plasma afin de produire un faisceau de protons stable, satisfaisant les critères d'énergie, de charge et d'homogénéité de surface requis pour son utilisation en radiobiologie. La conception, la réalisation et l’implémentation d’un système magnétique, constitué d'aimants permanents quadripolaires ont été optimisés au préalable avec des simulations numériques. Ce système permet d’obtenir un faisceau de protons ayant un spectre en énergie qui à été mise en forme, et dont le profil est uniforme sur une surface de taille adaptée aux échantillons biologiques.Une dosimétrie absolue et en ligne a également été établie, permettant le contrôle de la dose délivrée en sortie. Pour cela, une chambre d'ionisation à transmission, précédemment calibrée sur un accélérateur à usage médical de type cyclotron, a été mise en place sur le trajet du faisceau de protons. Des simulations Monte Carlo ont ensuite permis de calculer la dose déposée dans les échantillons. Ce système compact autorise maintenant de définir un protocole expérimental rigoureux pour la poursuite d’expériences in vitro de radiobiologie. De premières irradiations de cellules cancéreuses ont été ainsi réalisées in vitro, ouvrant la voie à l’exploration des effets de rayonnements ionisants pulsés à haut débit de dose sur les cellules vivantesParticle acceleration by laser-plasma interaction is a promising alternative to conventional accelerators that could make future devices dedicated to protontherapy more compact. Extreme electric fields in the order of TV/m are created when an ultra-intense laser pulse is focused on a thin solid target with a thickness of a few micrometers, which generates a beam of highly energetic particles. The latter includes protons with energies up to about ten megaelectron-volts and characterised by a wide angular divergence and a broad energy spectrum.The goal of this thesis is to fully characterise a laser-based accelerator in order to produce a stable proton beam meeting the energy, charge and surface homogeneity requirements for radiobiological experiments. The design, realisation and implementation of a magnetic system made of permanent magnet quadrupoles were optimised beforehand through numerical simulations. It enables to obtain a beam with a shaped energy spectrum and with a uniform profile over a surface with a size adapted to the biological samples.Deferred and online dosimetry was setup to monitor the delivered output dose. For that purpose, a transmission ionisation chamber, previously calibrated absolutely on a medical proton accelerator, was used. Monte Carlo simulations enabled to compute the dose deposited into the samples. This compact system allows now to define a rigorous experimental protocol for in vitro radiobiological experiments. First experiments of cancer cell irradiation have been carried out, paving the way for the exploration of the effects of pulsed ionizing radiations at extremely high dose rates on living cells
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Szałata, Kamila. "Development and characterization of bioartificial polysulfone membranes for proton transport applications." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/586088.
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En aquesta tesi, una membrana de polisulfona bioartificial que conté la biomolècula Gramicidina va ser dissenyada i preparada per tres tècniques diferents: dos mètodes físics i un químic. La caracterització dels materials consisteix en l'avaluació de la morfologia, la interacció de l'aigua i les propietats del transport de ions de la membrana. També es va realitzar la prova de l'activitat biològica de la proteïna immobilitzada, així com la caracterització de membranes que contenien micel·les immobilitzades. Els resultats mostren que la immobilització física de la gramicidina amb l'ús de nanopartícules magnètiques i micelles de proteïnes / surfactants, així com la immobilització químic per l'acoblament de glutaraldehid, permet obtenir membranes amb propietats de transport de ions millorades confirmades per experiments de permeabilitat i mesures de voltatge actual. La proteïna manté la seva activitat biològica quan es troba atrapat dins de la micel·la proteica / tensioactiva en ambdós, la solució i després d'immobilitzar-se en la membrana de polisulfona. Les membranes amb gramicidina immobilitzada físicament exhibeixen propietats antibacterianes millorades, confirmades per assaig de bioactivitat, mesuraments de densitat òptica i anàlisi microscòpica. Les membranes obtingudes són fàcils de preparar, químicament i mecànicament estables i presenten un potencial per a la seva aplicació en el transport de protons.En esta tesis, se diseñó y preparó una membrana de polisulfona bioartificial que contiene biomolécula Gramicidina mediante tres técnicas diferentes: dos métodos físicos y uno químico. La caracterización de materiales consiste en la evaluación de la morfología, la interacción con el agua y las propiedades de transporte de iones de membrana. También se realizó actividad biológica de proteína inmovilizada así como caracterización de micelas inmovilizadas que contenían proteína. Los resultados muestran que la inmovilización física de gramicidina con el uso de nanopartículas magnéticas y micelas de proteína / surfactante, así como la inmovilización de proteína por acoplamiento de glutaraldehído, conducen a obtener membranas con propiedades mejoradas de transporte de iones confirmadas por experimentos de permeabilidad y mediciones de voltaje-corriente. La proteína mantiene su actividad biológica cuando queda atrapada dentro de la micela de proteína / surfactante tanto en la solución como después de la inmovilización en la membrana de polisulfona. Las membranas con gramicidina inmovilizada físicamente exhiben propiedades antibacterianas mejoradas, confirmadas por ensayo de bioactividad, mediciones de densidad óptica y análisis microscópico. Las membranas obtenidas son fáciles de preparar, químicamente y mecánicamente estables y presentan un potencial para ser utilizadas en la aplicación de transporte de protones.
In this thesis a bioartificial polysulfone membrane containing biomolecule Gramicidin was designed and prepared by three different techniques: two physical and one chemical method. Materials characterization consists in evaluation of morphology, water interaction and membrane ion transport properties. Also biological activity of immobilized protein as well as characterization of immobilized micelles containing protein was performed. Results show that physical gramicidin immobilization with use of magnetic nanoparticles and protein/surfactant micelles, as well as chemical protein immobilization by glutaraldehyde coupling, lead to obtain membranes with enhanced ion transport properties confirmed by permeability experiments and Current-Voltage measurements. Protein maintains its biological activity when entrapped within protein/surfactant micelle in both, solution and after immobilization on polysulfone membrane. Membranes with physically immobilized gramicidin exhibits improved antibacterial properties, confirmed by bioactivity assay, optical density measurements and microscopic analysis. Obtained membranes are easy to prepare, chemically and mechanically stable and present a potential to be used in proton transport application.
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Uzdavinys, Povilas. "Establishing the molecular mechanism of sodium/proton exchangers." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147333.
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Sodium/proton exchangers are ubiquitous secondary active transporters that can be found in all kingdoms of life. These proteins facilitate the transport of protons in exchange for sodium ions to help regulate internal pH, sodium levels, and cell volume. Na+/H+ exchangers belong to the SLC9 family and are involved in many physiological processes including cell proliferation, cell migration and vesicle trafficking. Dysfunction of these proteins has been linked to physiological disorders, such as hypertension, heart failure, epilepsy and diabetes. The goal of my thesis is to establish the molecular basis of ion exchange in Na+/H+ exchangers. By establishing how they bind and catalyse the movement of ions across the membrane, we hope we can better understand their role in human physiology. In my thesis, I will first present an overview of Na+/H+ exchangers and their molecular mechanism of ion translocation as was currently understood by structural and functional studies when I started my PhD studies. I will outline our important contributions to this field, which were to (i) obtain the first atomic structures of the same Na+/H+ exchanger (NapA) in two major alternating conformations, (ii) show how a transmembrane embedded lysine residue is essential for carrying out electrogenic transport, and (iii) isolate and recorde the first kinetic data of a mammalian Na+/H+ exchanger (NHA2) in an isolated liposome reconstitution system.
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El, Aiba Farah. "Propriétés complexantes d'une macromolécule naturelle, un acide fulvique, vis à vis du proton et du plomb en eau douce." Paris 5, 1988. http://www.theses.fr/1988PA05P628.
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Miao, Meng, Yingchun Liu, Tao Wu, Qi Wang, and Keith E. Gubbins. "Does a hydrogen atom/proton diffuse through graphene?" Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185536.
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Hu, Sheng. "Proton transport through two dimensional materials." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/proton-transport-through-two-dimensional-materials(c7d5491e-5ddb-475c-9d6c-40fa6f0e2d88).html.
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Two-dimensional (2D) materials, referring to materials being just one atom thick, prove to be attractive not only in fundamental research but also in applications. Graphene, a single layer of carbon atoms arranged in hexagonal rings, is just the first among other materials (including hexagonal boron nitride and molybdenum disulfide) that could be isolated into mono-atomic layers. The presented thesis investigates proton transport through atomically thin two-dimensional materials. While the electronic, optical and mechanical properties of graphene and other 2D materials have been intensely researched over the past decade, much less is known on the interaction of these crystals with protons. It has been reported that most of the defect free two dimensional materials are impermeable to nearly all gases, molecules and ions. Whether proton, the smallest positively charged ion, could transport through two dimensional materials at a low energy level remains unknown. This work investigates proton transport through 2D materials, including graphene, hexagonal boron nitride and molybdenum disulfide, in two different systems: Nafion/Pd solid system and liquid/liquid interface system, both of which provided consistent results. Our results suggest that proton can transport through the interatomic spacings in the lattice of single layer BN and graphene, while single layer MoS2 is impermeable to protons. Single layer BN is the most conductive to protons among the 2D materials investigated in this thesis. Lower proton conductance of graphene is due to its delocalized π electrons while proton impermeability of MoS2 is due to the three atomic layers structure. Moreover, proton transfer is greatly facilitated by the deposition of platinum nanoparticles on the proton conductive 2D membranes to such a degree that platinum decorated BN seems to present negligible resistance to the transfer of protons through its lattice.
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Lechner, Ruep Ekkehard, Goetz Schuck, and Klaus Langer. "Mechanism of proton conduction in solid-state protonic conductors." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186538.
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Maiden, M. C. J. M. "Arabinose-proton symport in Escherichia coli." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383815.
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Ohkubo, Takahiro, Koh Kidena, and Akihiro Ohira. "Time-dependent diffusion coefficient of proton in polymer electrolyte membrane." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192269.
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We investigated the time-dependent self-diffusion coefficients of water, D(T eff), in polymer electrolyte membranes at 278 K. TheD(T eff) was measured from T eff=0.7 to 100 ms by field gradient NMR techniques. The results showed that the self-diffusion coefficients of water were dependent on T eff less than 2 ms due to restricted diffusion, and were constant beyond 3 ms. The tortuosity and surface-to-volume ratio related to water diffusion were also estimated from D(T eff). The obtained values revealed the existence of large-scale restricted geometry compared with well-known nanometer-sized domain in polymer electrolyte membranes.
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Miao, Meng, Yingchun Liu, Tao Wu, Qi Wang, and Keith E. Gubbins. "Does a hydrogen atom/proton diffuse through graphene?" Diffusion fundamentals 16 (2011) 66, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A12757.
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Zwarycz, Bailey. "Tissue- and Development-specific Expression of Proton-mediated Peptide Transporters in the Developing Chicken." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43761.
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PepT1, PepT2 and PHT1 are all members of the proton-coupled oligopeptide transporter family, which are important in the transport of amino acids in peptide form. PepT1 acts as a low affinity/high capacity transporter and PepT2 as a high affinity/low capacity transporter for di- and tri-peptides. PHT1 transports di- and tri-peptides as well as histidine. The objective of this study was to profile PepT1, PepT2 and PHT1 mRNA expression in the proventriculus, duodenum, jejunum, ileum, ceca, large intestine, brain, heart, bursa of Fabricius, lung, kidney, and liver in layer chicks on embryonic days 18 and 20 and days 1, 3, 7, 10, and 14 post-hatch. Absolute quantification real-time PCR was used to measure gene expression. PepT1 expression was greatest in the duodenum, jejunum and ileum. Over time, PepT1 expression increased in the duodenum, jejunum, ileum and large intestine and decreased in the ceca. PepT2 expression was greatest in the brain, aiding in neuropeptide homeostasis, and the kidney, aiding in the reabsorption of substrates. Over time, PepT2 expression increased in the bursa of Fabricius and decreased in the proventriculus, duodenum, jejunum and liver. In the small intestine during embryogenesis, PepT2 may function to transport di- and tri-peptides prior to the induction of PepT1. PHT1 expression was expressed in all tissues analyzed. Over time, PHT1 expression increased in the jejunum, large intestine, brain and liver and decreased in the proventriculus. The uptake of peptides in the developing chick is regulated by peptide transporters that are expressed in a tissue- and development-specific manner.Master of Science
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Wark, Michael, Monir Sharifi, Roland Marschall, Martin Wilkening, Pia Tölle, Christof Köhler, Thomas Frauenheim, and Dirk Wallacher. "Proton conductivity of aluminium or sulfonic acid functionalized ordered mesoporous silica materials." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186778.
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Foltz, Martin. "Molecular and functional characterisation of a new mammalian family of proton-coupled amino acid transporters." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974170380.
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Silva, Marco Aurelio Pedron e. "Caracteristicas do transporte de calcio, fosfato e protons em mitocondrias de plantas." [s.n.], 1991. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314852.
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Orientador : Anibal Eugenio VercesiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-07-14T00:25:26Z (GMT). No. of bitstreams: 1 Silva_MarcoAurelioPedrone_D.pdf: 10964647 bytes, checksum: 4c2f2a52f92774ecf5130af723c937e0 (MD5) Previous issue date: 1991
Resumo: Com o objetivo de acrescentar dados que pudessem ajudar a esclarecer algumas particularidades da fisiologia de mitocôndrias de plantas, foram investigadas algumas das características do funcionamento de mitocôndrias isoladas de milho, batata e beterraba. Numa primeira parte de deste trabalho foram estudados alguns aspectos relacionados ao transporte de 'Ca IND. 2+¿, em mitocôndrias isoladas de coleóptiles de milho. Foi possível observar que o fosfato é estequiometricamente acumulado com o 'Ca IND. 2+¿, mantendo uma razão 'Ca IND. 2+¿/Pi próxima a 1,5 e que a atividade do transportador é independente da idade dos coleóptiles utilizados ... Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: The first part of this work was dedicated to some aspects related to 'Ca IND. 2+¿ transport by corn coleoptile mitochondria. It was observed that the activity of the 'Ca IND. 2+¿ carrier is independent of the coleoptile age and that phosphate is accumulated together with 'Ca IND. 2+¿ keeping a 'Ca IND. 2+¿/Pi ratio near to 1.5 ... Note: The complete abstract is available with the full electronic digital thesis or dissertations
Doutorado
Doutor em Ciências Biológicas
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Ohkubo, Takahiro, Koh Kidena, and Akihiro Ohira. "Time-dependent diffusion coefficient of proton in polymer electrolyte membrane." Diffusion fundamentals 10 (2009) 21, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14112.
Full textAbstract:
We investigated the time-dependent self-diffusion coefficients of water, D(T eff), in polymer electrolyte membranes at 278 K. TheD(T eff) was measured from T eff=0.7 to 100 ms by field gradient NMR techniques. The results showed that the self-diffusion coefficients of water were dependent on T eff less than 2 ms due to restricted diffusion, and were constant beyond 3 ms. The tortuosity and surface-to-volume ratio related to water diffusion were also estimated from D(T eff). The obtained values revealed the existence of large-scale restricted geometry compared with well-known nanometer-sized domain in polymer electrolyte membranes.
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Rouhet, Marlene. "Etude de l'influence des protons sur la réduction de l'oxygène dans des couches catalytiques ordonnées en vue d'une application en pile à combustible." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF031/document.
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Les couches catalytiques avec une structure ordonnée à base de nanoparticules de Pt supportées sur des nanofilaments de carbone verticalement alignés ont montré des performances intéressantes grâce à l’amélioration des propriétés du transport de matière et à une meilleure utilisation du Pt. Des études électrochimiques combinées à une modélisation mathématique ont mis en évidence l’influence du transport de protons sur les processus d’oxydo-réduction, la cinétique et le mécanisme de réduction de l’O2 (ORR), et sur H2O2 qui s’échappe des couches pendant l’ORR. Nous avons montré que (i) les protons sont impliqués dans l’étape limitante de la réaction, (ii) pour un pH ≥ 3, un plateau de courant limité par la diffusion des protons est observé et, (iii) pour un pH ≥ 3, le mécanisme de l’ORR implique non seulement les ions hydroniums mais aussi les molécules d’eau. L’intégration de ces couches catalytiques dans des PEMFCs haute température a ensuite été étudiée. Les performances obtenues sont légèrement plus basses que celles des couches conventionnelles. Un travail d’optimisation reste donc à accomplir pour améliorer les performancesOrdered catalytic layers based on vertically aligned carbon nanofilaments with Pt nanoparticles demonstrate high efficiency for oxygen transport and Pt utilization in the catalytic layer. Electrochemical studies combined with mathematical modeling confirm the influence of the proton transport on surface red-ox processes, the kinetics and the mechanism of the O2 reduction (ORR), and on the H2O2 escape. We show that (i) protons are involved in the rate-determining step of the O2 reduction, (ii) for pH ≥ 3, a plateau corresponding to the diffusion-limited current of protons is observed and, (iii) for pH ≥ 3, the mechanism of the ORR involves not only the hydronium ions but also water molecules. The integration of these catalytic layers in high temperature PEMFCs was then studied. The performance is slightly lower than that for conventional layers. An optimization work is required to improve the performance
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Choi, Pyoungho. "Investigation of thermodynamic and transport properties of proton-exchange membranes in fuel cell applications." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0430104-094215/.
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Roy, Abhishek. "Structure Property Relationships of Proton Exchange Membranes." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26365.
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The major challenge of the research was to characterize and develop concepts for establishing structure/property relationships between the functionality of the polymer backbone, the states of water and the membrane transport properties. Most of the hydrocarbon based random copolymers reported in the literature show reduced proton conductivity at low water content. This was attributed to the formation of an isolated morphology. Over the last few years our group has synthesized thermally stable multiblock copolymers with varying chemical structures and compositions. Block copolymers consist of two or more incompatible polymers (i.e. blocks) that are chemically conjoined in the same chain. The transport properties of the multiblock copolymers showed a strong dependence on the morphology in contrast to the random copolymers. Irrespective of the nature of the backbone, the transport properties scaled with the block lengths of the copolymers. An increase in block length for a given series of block copolymer was associated with improved proton conduction, particularly under partially hydrated conditions compared to the random copolymers. The structure-property relationship of the proton conductivity and self-diffusion coefficient of water was obtained as a function of the volume fraction of water for all the random and block copolymers. At a given volume fraction, the block copolymers displayed both higher self-diffusion coefficients of water and proton conductivities relative to the random copolymers. This improvement in transport properties indicates the presence of desired and favorable morphology for the blocks. For DMFC applications, the block copolymers also showed low methanol permeability and high selectivity. The states of water in the copolymers were characterized using DSC and NMR relaxation techniques. At similar ionic contents, the free water concentration increased with increasing block lengths. The distribution of the states of water in the copolymers correlates to transport properties. This knowledge, coupled with the state of water experiments, transport measurements, and chemical structure of the copolymers provided a fundamental picture of how the chemical nature of a phase separated copolymer influences its transport properties. The experimental procedure involved impedance spectroscopy, DSC, TGA, FTIR, DMA, pulse gradient stimulated echo (PGSE) NMR, NMR relaxation experiments and various electrochemical fuel cell performance experiments.Ph. D.
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Darley, Catherine P. "The physiological roles of the vacuolar proton-pumping pyrophosphatase." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337633.
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Freiman, Gabriel, Jean-Pierre Korb, Benjamin Nicot, and Patrice Ligneul. "Microscopic wettability of carbonate rocks: a proton field cycling NMR approach." Diffusion fundamentals 10 (2009) 25, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14116.
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Nuclear Magnetic Relaxation Dispersion (NMRD) is strongly sensitive to the microscopic wettability of oil and brine bearing carbonate rocks. Exploring a very large range of low frequency enables isolating the typical NMRD dispersion features, 1/T1Surf, associated to
the different processes of molecular surface dynamics. This allows a separation of the surface and bulk microdynamics of oil and water even for a biphasic saturation of petroleum rocks. Several surface dynamical parameters were determined and related to the concept of microscopic wettability of oil and water in porous media.
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Wark, Michael, Monir Sharifi, Roland Marschall, Martin Wilkening, Pia Tölle, Christof Köhler, Thomas Frauenheim, and Dirk Wallacher. "Proton conductivity of aluminium or sulfonic acid functionalized ordered mesoporous silica materials." Diffusion fundamentals 12 (2010) 43, 2010. https://ul.qucosa.de/id/qucosa%3A13884.
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Armstrong, Gillian. "Solute transport and intracellular pH in intestinal epithelial cells." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320390.
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Bray, Christina L., Robert G. Bryant, M. J. Cox, Gianni Ferrante, Y. Goddard, Sandip Sur, and Joseph P. Hornack. "The proton Nuclear Magnetic Resonance spin-lattice relaxation rate of some hydrated synthetic and natural sands." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192008.
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The proton nuclear magnetic resonance (NMR) spin-lattice relaxation rate (R1) of hydrated sands is often used to determine porosity characteristics of near-surface aquifers using magnetic resonance sounding. Large variations in R1 have been reported in laboratory measurements on hydrated sands. To understand these variations, the R1 values of several fully hydrated sands were studied as a function of grain diameter (d) and magnetic field strength (BB0).
We conclude the variations are a consequence of trace paramagnetic metals in the sand grains. R1 values from magnetic resonance sounding data should not be used to predict void size in aquifers unless the exact chemical composition of the grains is known.
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Ogmundsdottir, Margret Helga. "Regulation of TORC1-mediated growth by intracellular proton-assisted amino acid transporters : a genetic and cell biological approach." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547486.
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Handley, Stephen Michael. "Monte Carlo simulations using MCNPX of proton and anti-proton beam profiles for radiation therapy." Oklahoma City : [s.n.], 2010.
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Ädelroth, Pia. "Mechanisms and pathways for proton transfer in cytochrome-c oxidase." Göteborg : Göteborg University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945135.html.
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Bray, Christina L., Robert G. Bryant, M. J. Cox, Gianni Ferrante, Y. Goddard, Sandip Sur, and Joseph P. Hornack. "The proton Nuclear Magnetic Resonance spin-lattice relaxation rate of some hydrated synthetic and natural sands." Diffusion fundamentals 10 (2009) 8, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14098.
Full textAbstract:
The proton nuclear magnetic resonance (NMR) spin-lattice relaxation rate (R1) of hydrated sands is often used to determine porosity characteristics of near-surface aquifers using magnetic resonance sounding. Large variations in R1 have been reported in laboratory measurements on hydrated sands. To understand these variations, the R1 values of several fully hydrated sands were studied as a function of grain diameter (d) and magnetic field strength (BB0).
We conclude the variations are a consequence of trace paramagnetic metals in the sand grains. R1 values from magnetic resonance sounding data should not be used to predict void size in aquifers unless the exact chemical composition of the grains is known.
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Celis, Salazar Paula Juliana. "Investigations of Electron, Ion, and Proton Transport in Zirconium-based Metal-Organic Frameworks." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96312.
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Metal-Organic Frameworks (MOFs) are porous materials consisting of organic ligands connected by inorganic nodes. Their structural uniformity, high surface area, and synthetic tunability, position these frameworks as suitable active materials to achieve efficient and clean electrochemical energy storage. In spite of recent demonstrations of MOFs undergoing diverse electrochemical processes, a fundamental understanding of the mechanism of electron, proton, and ion transport in these porous structures is needed for their application in electronic devices. The current work focuses on contributing to such understanding by investigating proton-coupled electron transfer, capacitance performance, and the relative contribution of electron and ionic transport in the voltammetry of zirconium-based MOFs.
First, we investigated the effects that the quinone ligand orientation inside two new UiO-type metal-organic frameworks (2,6-Zr-AQ-MOF and 1,4-Zr-AQ-MOF) have on the ability of the MOFs to achieve proton and electron conduction. The number of electrons and protons transferred by the frameworks was tailored in a Nernstian manner by the pH of the media, revealing different electrochemical processes separated by distinct pKa values. In particular, the position of the quinone moiety with respect to the zirconium node, the effect of hydrogen bonding, and the amount of defects in the MOFs, lead to different PCET processes. The ability of the MOFs to transport discrete numbers of protons and electrons, suggested their application as charge carriers in electronic devices.
With that purpose in mind, we assembled 2,6-Zr-AQ-MOF and 1,4-Zr-AQ-MOF into two different types of working electrodes: a slurry-modified glassy carbon electrode, and as solvothermally-grown MOF thin films. The specific capacitance and the percentage of quinone accessed in the two frameworks were calculated for the two types of electrodes using cyclic voltammetry in aqueous buffered media as a function of pH. Both frameworks showed an enhanced capacitance and quinone accessibility in the thin films as compared to the powder-based electrodes, while revealing that the structural differences between 2,6-Zr-AQ-MOF and 1,4-Zr-AQ-MOF in terms of defectivity and the number of electrons and protons transferred were directly influencing the percentage of active quinones and the ability of the materials to store charge.
Additionally, we investigated in detail the redox-hopping electron transport mechanism previously proposed for MOFs, by utilizing the chronoamperometric response (I vs. t) of three metallocene-doped metal-organic frameworks (MOFs) thin films (M-NU-1000, M= Fe, Ru, Os) in two different electrolytes (TBAPF6 and TBATFAB). We were able to elucidate, for the first time, the diffusion coefficients of electrons and ions (De and Di, respectively) through the structure in response to an oxidizing applied bias. The application of a theoretical model for solid state-voltammetry to the experimental data revealed that the diffusion of ions is the rate-determining step at the three different time stages of the electrochemical transformation. Remarkably, the trends observed in the diffusion coefficients (De and Di) of these systems obtained in PF61- and TFAB1- based electrolytes at the different stages of the electrochemical reaction, demonstrated that the redox hopping rates inside frameworks can be controlled through the modifications of the self-exchange rates of redox centers, the use of large MOF channels, and the utilization of smaller counter anions. These structure-function relationships provide a foundation for the future design, control, and optimization of electronic and ionic transport properties in MOF thin films.PHD
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Hickner, Michael Anthony. "Transport and Structure in Fuel Cell Proton Exchange Membranes." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28895.
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Transport properties of novel sulfonated wholly aromatic copolymers and the state-of-the-art poly(perfluorosulfonic acid) copolymer membrane for fuel cells, Nafion, were compared. Species transport (protons, methanol, water) in hydrated membranes was found to correspond with the water-self diffusion coefficient as measured by pulsed field gradient nuclear magnetic resonance (PFG NMR), which was used as a measure of the state of absorbed water in the membrane. Generally, transport properties decreased in the order Nafion > sulfonated poly(arylene ether sulfone) > sulfonated poly(imide). The water diffusion coefficients as measured by PFG NMR decreased in a similar fashion indicating that more tightly bound water existed in the sulfonated poly(arylene ether sulfone) (BPSH) and sulfonated poly(imide) (sPI) copolymers than in Nafion.
Electro-osmotic drag coefficient (ED number of water molecules conducted through the membrane per proton) studies confirmed that the water in sulfonated wholly aromatic systems is more tightly bound within the copolymer morphology. Nafion, with a water uptake of 19 wt % (λ = 12, where λ = N H2O/SO3H) had an electro-osmotic drag coefficient of 3.6 at 60°C, while BPSH 35 had an electro-osmotic drag coefficient of 1.2 and a water uptake of 40 wt % (λ = 15) under the same conditions.
Addition of phosphotungstic acid decreased the total amount of water uptake in BPSH/inorganic composite membranes, but increased the fraction of loosely bound water. Zirconium hydrogen phosphate/BPSH hybrids also showed decreased bulk water uptake, but contrary to the results with phosphotungstic acid, the fraction of loosely bound water was decreased. This dissimilar behavior is attributed to the interaction of phosphotungstic acid with the sulfonic acid groups of the copolymer thereby creating loosely bound water. No such interaction exists in the zirconium hydrogen phosphate materials. The transport properties in these materials were found to correspond with the water-self diffusion coefficients.
Proton exchange membrane (PEM) transport properties were also found to be a function of the molecular weight of sulfonated poly(arylene thioether sulfone) (PATS). Low molecular weight (IV ~ 0.69) copolymers absorbed more water on the same ion exchange capacity basis than the high molecular weight copolymers (IV ~ 1.16). Surprisingly, protonic conductivity of the two series was similar. Moreover, the methanol permeability of the low molecular weight copolymers was increased, resulting in lower membrane selectivity and decreased mechanical properties.
The feasibility of converting the novel sulfonated wholly aromatic systems to membrane electrode assemblies (MEAs) for use in fuel cells was studied by comparing free-standing membrane properties to those of MEAs assembled with standard Nafion electrodes. Significantly higher interfacial resistance was measured for BPSH samples. Fluorine was introduced into the copolymer backbone by utilizing bisphenol-AF in the copolymer synthesis (6F copolymers). These 6F copolymers showed a markedly lower interfacial resistance with Nafion electrodes and correspondingly greater direct methanol fuel cell performance. It was proposed that the addition of the hexafluoro groups increased the compatibility of the PEM with the highly fluorinated Nafion electrode.Ph. D.
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Lozada, Hidalgo Marcelo. "One-atom-thick crystals as a novel class of proton conducting materials." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/oneatomthick-crystals-as-a-novel-class-of-proton-conducting-materials(398d313b-4e8f-4341-817d-1612be3374bb).html.
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Graphene, a one-atom-thick sheet of carbon atoms, is impermeable to all atoms and molecules; the same can be expected for other 2D crystals like hexagonal boron nitride (hBN). In this work we show that monolayers of graphene and hBN are highly permeable to thermal protons. As a reference, we show that monolayers of molybdenum disulphide as well as bilayers of graphene and tetralayers of hBN are not. Moreover, we show that water plays a crucial role in the transport mechanism. Because of the zero point energy of vibration in the oxygen-hydrogen bonds in water, protons face energy barriers smaller than previously predicted by theory. The effect, revealed by substituting hydrogen for deuterium, also shows that protons and deuterons transport at different rates across the membranes; establishing them as membranes with subatomic selectivity. Beyond the purely scientific implications, our results establish monolayers of graphene and hBN as a promising new class of proton conducting materials with potential applications in fuel cells, hydrogen purification and isotope enrichment technologies.
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Lechner, Ruep Ekkehard, Goetz Schuck, and Klaus Langer. "Mechanism of proton conduction in solid-state protonic conductors: method and results from investigations by QENS techniques." Diffusion fundamentals 12 (2010) 3, 2010. https://ul.qucosa.de/id/qucosa%3A13865.
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Wang, Caijuan. "Involvement of the modulation of proton motive force in the regulation of photosynthesis." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215348.
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Chapter 1: “Role of cyclic electron transport around photosystem I in the regulation of proton motive force” is based on the following paper. Caijuan Wang, Hiroshi Yamamoto, Toshiharu Shikanai, Role of cyclic electron transport around photosystem I in regulating proton motive force, Biochimica et Biophysica Acta (BBA) - Bioenergetics, Volume 1847, Issue 9, September 2015, Pages 931-938, ISSN 0005-2728, http://dx.doi.org/10.1016/j.bbabio.2014.11.013.(http://www.sciencedirect.com/science/article/pii/S0005272814006586)Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第19535号
理博第4195号
新制||理||1602(附属図書館)
32571
京都大学大学院理学研究科生物科学専攻
(主査)教授 鹿内 利治, 教授 西村 いくこ, 教授 長谷 あきら
学位規則第4条第1項該当
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Zhang, Zuman. "Open heavy-flavour measurements via muons in proton-proton and nucleus-nucleus collisions with the ALICE detector at the CERN-LHC." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC077/document.
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Les collisions d'ions lourds ultra-relativistes ont pour objectif l'étude d'un état de matière en interaction forte dans des conditions extrêmes de densité d'énergie et température, le plasma de quarks et gluons (QGP). Les saveurs lourdes (charme et beauté) sont produites principalement lors de processus durs aux premiers instants de la collision et participent aux différentes étapes de la collision. Par conséquent, la mesure des saveurs lourdes ouvertes devrait permettre d'extraire des informations importantes concernant le système créé aux premiers instants de la collision. L'étude des collisions proton-proton (pp) fournit la référence indispensable pour la mesure des saveurs lourdes dans les systèmes lourds. Cette thèse est dédiée à l'étude de la production des muons de décroissance des hadrons charmés et beaux aux rapidités avant (2.5 < y < 4) dans les collisions pp sqrt (s) = 5.02 TeV, Pb-Pb à sqrt (sNN) = 2.76 et 5.02 TeV et Xe-Xe à sqrt (sNN) = 5.44 TeV enregistrées avec le détecteur ALICE au CERN-LHC. La mesure des sections efficaces différentielles de production des muons de décroissance des hadrons charmés et beaux dans les collisions pp à sqrt (s) = 5.02 TeV couvre un grand domaine en impulsion transverse de 2 à 20 GeV/c et ont une meilleure précision par rapport aux résultats publiés à sqrt (s) = 2.76 et 7 TeV. Les résultats sont en bon accord avec les calculs perturbatifs de QCD. Une importante suppression de la production des muons de décroissance des hadrons charmés et beaux est observée dans les collisions centrales (0-10%) Pb-Pb à sqrt (sNN) = 2.76 et 5.02 TeV. Cette suppression est attribuée au milieu dense et chaud formé dans ces collisions. L'influence de la taille du système est étudiée avec le système Xe-Xe à sqrt (sNN) = 5.44 TeV. La suppression est similaire à celle mesurée dans les collisions Pb-Pb. Les résultats obtenus dans les collisions Pb-Pb et Xe-Xe apportent des contraintes fortes aux paramètres des modèlesThe study of ultra-relativistic heavy-ion collisions aims at investigating a state of strongly-interacting matter at high energy density and temperature, the Quark-Gluon Plasma (QGP). Heavy quarks (charm and beauty) are predominantly produced in initial hard scattering processes during the early stage of the collisions and experience the full evolution of the medium. Therefore, the measurement of open heavy flavours should provide essential information on the QGP properties. Similar measurements in small systems are also essential for a comprehensible understanding of the QGP properties. The study of open heavy flavours in proton-proton (pp) collisions provides the mandatory reference for measurements in heavy-ion collisions. This thesis presents measurements of the production of muons from heavy-flavour hadron decays at forward rapidity (2.5 < y < 4) in pp collisions at sqrt (s) = 5.02 TeV, Pb-Pb collisions at sqrt (sNN) = 2.76 and 5.02 TeV and Xe-Xe collisions at sqrt (sNN) = 5.44 TeV collected with the ALICE detector at the CERN-LHC. The differential production cross sections of muons from heavy-flavour hadron decays in pp collisions at sqrt (s) = 5.02 TeV are obtained in a wide transverse momentum interval, 2 < pT < 20 GeV/c, and with an improved precision compared to the previously published measurements at sqrt (s) = 2.76 and 7 TeV. The measurements are described within uncertainties by predictions based on perturbative QCD. A strong suppression of the yield of muons from heavy-flavour decays is observed in the 10% most central Pb-Pb collisions at both sqrt (sNN) = 2.76 and 5.02 TeV. This suppression is due to final-state effects induced by the hot and dense medium. The suppression in Xe-Xe collisions is similar to that observed with Pb-Pb collisions. The comparison in the two colliding systems provides insight in the path-length dependence of medium-induced parton energy loss. The results constrain model calculations
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Castan, Anaïs. "Propagation laser en plasma sous-dense et modélisation de déflectométrie protonique." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX002/document.
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Dans le cadre de la Fusion par Confinement Inertiel, la maîtrise de la propagation des faisceaux laser intenses, qui se propagent dans le plasma sous-dense d'une cavité d'ignition, reste un enjeu majeur. En effet, durant leur propagation, les faisceaux vont modifier les paramètres du plasma, ces paramètres contrôlant eux-mêmes la propagation. Cette rétroaction entre le plasma et le laser est potentiellement instable et produit de l'autofocalisation, de la filamentation, etc. Ces mécanismes peuvent alors dégrader fortement la propagation et in fine l'uniformité du dépôt d'énergie recherché.Dans cette étude, expérimentale et numérique, nous nous intéressons à la propagation d'un filament laser (tache focale d'une dizaine de micromètres, impulsion de 1,5 ns et d'intensité variant de 1014 W.cm-2 à 1016 W.cm-2) dans un milieu très sous dense (quelques pour-cents de la densité électronique critique). Deux expériences ont été réalisées sur l'installation de puissance LULI2000 et ont permis à la fois d'observer la transmission laser et de caractériser les gradients de température. Ces gradients sont produits par le transport électronique et influencent la réponse du plasma au laser. Afin de modéliser le rôle des gradients de température dans les instabilités d'auto-focalisation et de filamentation, nous avons associé un code d'hydrodynamique-radiative (FCI2) à un code détaillé de propagation (Héra). Pour compléter les observables précédentes, nous avons aussi mis en œuvre un diagnostic de déflectométrie protonique. Ce diagnostic permet de mesurer les champs électriques présents dans le plasma, ces champs étant issus du chauffage et de l'interaction laser. Un nouvel outil, associant le code de propagation laser et un code Monte-Carlo de transport de protons, a donc été mis en place pour modéliser les déflexions des protons. Cet outil ouvre en plus de nouvelles perspectives pour discuter de l'influence des effets 3D dans l'exploitation de ce diagnostic. Les résultats obtenus confirment l'intérêt à sonder les champs électriques au cœur même du plasma pendant la propagation laserThe understanding and the control of high-power laser propagation into under-dense plasma is important to achieve inertial confinement fusion. During this process, the interaction of the laser with the plasma filling the hohlraum can lead to significant losses of laser energy which prevent ignition. Self-focusing or filamentation of the laser light is one of these phenomena which are desired to be mitigated since they also affect the uniformity of the laser illumination on the hohlraum wall.In order to improve our understanding of the laser-plasma interaction phenomena at play, we describe an experimental and numerical study involving an intense laser pulse between 1014 W.cm-2 and 1016 W.cm-2 , and which interacts with millimetric and under-dense plasma (having density of few % of the critical density). This work presents two experiments fielding a series of diagnostics aimed at well characterizing the laser propagation (Hisac camera) together with heat deposition in plasmas using Thomson scattering. Experimental results will be presented and discussed in the light of detailed simulations performed with the 3D laser propagation code Hera. In order to take into account the temperature gradients within the plasma during the laser propagation, Hera (laser propagation code) and FCI2 (radiation-hydrodynamic code) have been coupled. Besides, proton radiography has been used in order to access to electric fields. The measurements led to the implementation of a new and promising numerical tool using the Hera and Diane codes (Diane is a Monte Carlo particle tracing code). 3D proton radiography modelling opens new possibilities for users of this temporally and spatially resolved diagnostic
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Lacoste, Isabelle. "Mecanismes de transports ioniques et d'eau a travers la peau de rana esculenta : role des protons." Nice, 1993. http://www.theses.fr/1993NICE4645.
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La peau de grenouille est impliquee dans l'equilibre acido-basique et hydromineral de l'animal, elle est soumise a des transports vectoriels de h#+ et de na#+ de directions opposees. Le role des h#+ intracellulaires et extracellulaires dans ces differents mecanismes de transport a ete etudie. Les permeabilites protoniques passives ont ete suivies: si la membrane basolaterale (m#b) est spontanement permeable aux h#+, la permeabilite de la membrane apicale (m#a) est faible, mais peut etre augmentee par l'ocytocine. Les etudes cinetiques et pharmacologiques indiquent que cette voie de transport est un canal, commun aux protons et a l'eau, mais de nature differente au niveau des deux membranes opposees. L'existence d'une permeabilite protonique apicale n'est pas le moteur d'un cotransport proton-uree. Aucune relation entre les h#+ et le transport d'uree n'a pu etre mise en evidence. Le transport d'uree est un mecanisme actif, sensible aux agents mercuriels, a l'amiloride (et derives) ainsi qu'aux acidifications intracellulaires, mais sa nature reste a preciser, comme la localisation membranaire de l'etape active. Les h#+ intracellulaires interviennent dans la regulation des transports ioniques transepitheliaux. Ils determinent l'activite de la pompe a h#+ localisee sur m#a des cellules riches en mitochondries (mrc). Cette pompe est determinante pour l'etablissement du gradient electrochimique de na#+ (permettant l'entree cellulaire et le transport transepithelial du na#+) a bas na#+ externe. Dans les cellules granuleuses (grc) et les mrc, le ph intracellulaire est regule grace a deux mecanismes complementaires et independants, localises sur m#b, qui reguleront le ph#i lors d'une acidose ou d'une alcalose intracellulaire (echangeurs na/h et cl/hco#3). Indirectement, par le controle qu'ils exercent sur l'activite intracellulaire du na#+, ces mecanismes regulent egalement l'activite de la na/k atpase. Par contre les h#+ ont une action inhibitrice directe sur les conductances apicale au na#+ et basolaterale au k#+ des grc. Enfin dans des situations ou les capacites de transport (na#+ et h#+) sont accrues, une augmentation des phenomenes d'exocytose liee a une diminution de la quantite de f-actine cellulaire est observee. Les taux de transport pourraient etre modules par la mise en place de transporteurs ou de proteines regulatrices contenues dans des vesicules sous membranaires, qui sous l'action d'un signal (h#+ ou ca#2#+) viendraient s'incorporer aux membranes apicales de l'epithelium
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Siegel, Nathan Phillip. "Development and validation of a computational model for a proton exchange membrane fuel cell." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11105.
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A steady-state computational model for a proton exchange membrane fuel cell (PEMFC) is presented. The model accounts for species transport, electrochemical kinetics, energy transport, current distribution, water uptake and release within the polymer portion of the catalyst layers, and liquid water production and transport. Both two-dimensional and three-dimensional geometries are modeled. For a given geometry, the governing differential equations are solved over a single computational domain. For the two-dimensional model, the solution domain includes a gas channel, gas diffusion layer, and catalyst layer for both the anode and cathode sides of the cell as well as the solid polymer membrane. For the three-dimensional model the current collectors are also modeled on both the anode and cathode sides of the fuel cell.
The model for the catalyst layers is based on an agglomerate geometry, which requires water species to exist in dissolved, gaseous, and liquid forms simultaneously. Data related to catalyst layer morphology that was required by the model was obtained via a physical analysis of both commercially available and in-house membrane electrode assemblies (MEA). Analysis techniques including cyclic voltammetry and electron microscopy were used. The coupled set of partial differential equations is solved sequentially over a single solution domain with the commercial computational fluid dynamics (CFD) solver, CFDesign™ and is readily adaptable with respect to geometry and material property definitions.
A fuel cell test stand was designed and built to facilitate experimental validation of the model. The test stand is capable of testing cells up to 50 cm2 under a variety of controlled conditions. Model results for both two and three-dimensional fuel cell geometries are presented. Parametric studies performed with the model are also presented and illustrate how fuel cell performance varies due to changes in parameters associated with the transport of reactants and liquid water produced in the cell. In particular, the transport of oxygen, water within the polymer portions of the catalyst layers and membrane, and liquid water within the porous regions of the cell are shown to have significant impact on cell performance, especially at low cell voltage. Parametric studies also address the sensitivity of the model results to certain physical properties, which illustrates the importance of accurately determining the physical properties of the fuel cell components on which the model is based. The results from the three-dimensional model illustrate the impact of the collector plate shoulders (for a conventional flowfield) on oxygen transport and the distribution of current production within the cell.Ph. D.
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Oyarce, Alejandro. "Electrode degradation in proton exchange membrane fuel cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133437.
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The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.Denna doktorsavhandling behandlar degraderingen av polymerelektrolytbränslecellselektroder. polymerelektrolytbränslecellselektroder. Den handlar särskilt om nedbrytningen av elektroden kopplad till en degraderingsmekanism som heter ”localized fuel starvation” oftast närvarande vid uppstart och nedstängning av bränslecellen. Vid start och stopp kan syrgas och vätgas förekomma samtidigt i anoden. Detta leder till väldigt höga elektrodpotentialer i katoden. Resultatet av detta är att kolbaserade katalysatorbärare korroderar och att bränslecellens livslängd förkortas. Målet med avhandlingen har varit att utveckla metoder, material och strategier för att både öka förståelsen av denna degraderingsmekanism och för att maximera katalysatorbärarens livslängd.Ett vanligt tillvägagångsätt för att bestämma graden av katalysatorns degradering är genom mätning av den elektrokemiskt aktiva ytan hos bränslecellselektroderna. I denna avhandling har dessutom effekten av temperatur och relativ fukthalt studerats. Låga fukthalter minskar den aktiva ytan hos elektroden, vilket sannolikt orsakas av en omstrukturering av jonomeren och av kontaktförlust mellan jonomer och katalysator.Olika accelererade degraderingstester för kolkorrosion har använts. Potentiostatiska tester vid 1.2 V mot RHE visade sig vara för milda. Potentiostatiska tester vid 1.4 V mot RHE visade sig däremot medföra en hög grad av reversibilitet, som också den tros vara orsakad av en omstrukturering av jonomeren. Cykling av elektrodpotentialen degraderade istället elektroden irreversibelt, inom rimlig tid och kunde väldigt nära simulera förhållandena vid uppstart och nedstängning.Korrosionen av katalysatorbäraren medför degradering av katalysatorn och har också en stor inverkan på elektrodens morfologi. En minskad elektrodporositet, en ökad agglomeratstorlek och en anrikning av jonomeren gör att elektrodens masstransportegenskaper försämras. Grafitiska kolfibrer visade sig vara mer resistenta mot kolkorrosion än konventionella kol, främst p.g.a. deras låga ytarea. Grafitiska kolfibrer visade också en förmåga att bättre bibehålla elektrodens morfologi efter accelererade tester, vilket resulterade i lägre masstransportförluster.Olika systemstrategier för nedstängning jämfördes. Att inte göra något under nedstängning är mycket skadligt för bränslecellen. Förbrukning av syre med en last och spolning av katoden med vätgas visade 100 gånger lägre degraderingshastighet av bränslecellsprestanda jämfört med att inte göra något alls och 10 gånger lägre degraderingshastighet jämfört med spolning av anoden med luft. In-situ kontaktresistansmätningar visade att kontaktresistansen mellan bipolära plattor och GDL är dynamisk och kan ändras beroende på driftförhållandena.
QC 20131104