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Littérature scientifique sur le sujet « Ion transporter »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Ion transporter"

1

Sacher, A., A. Cohen et N. Nelson. « Properties of the mammalian and yeast metal-ion transporters DCT1 and Smf1p expressed in Xenopus laevis oocytes ». Journal of Experimental Biology 204, no 6 (15 mars 2001) : 1053–61. http://dx.doi.org/10.1242/jeb.204.6.1053.

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Transition metals are essential for many metabolic processes, and their homeostasis is crucial for life. Metal-ion transporters play a major role in maintaining the correct concentrations of the various metal ions in living cells. Little is known about the transport mechanism of metal ions by eukaryotic cells. Some insight has been gained from studies of the mammalian transporter DCT1 and the yeast transporter Smf1p by following the uptake of various metal ions and from electrophysiological experiments using Xenopus laevis oocytes injected with RNA copies (c-RNA) of the genes for these transporters. Both transporters catalyze the proton-dependent uptake of divalent cations accompanied by a ‘slippage’ phenomenon of different monovalent cations unique to each transporter. Here, we further characterize the transport activity of DCT1 and Smf1p, their substrate specificity and their transport properties. We observed that Zn(2+) is not transported through the membrane of Xenopus laevis oocytes by either transporter, even though it inhibits the transport of the other metal ions and enables protons to ‘slip’ through the DCT1 transporter. A special construct (Smf1p-s) was made to enhance Smf1p activity in oocytes to enable electrophysiological studies of Smf1p-s-expressing cells. 54Mn(2+) uptake by Smf1p-s was measured at various holding potentials. In the absence of Na(+) and at pH 5.5, metal-ion uptake was not affected by changes in negative holding potentials. Elevating the pH of the medium to 6.5 caused metal-ion uptake to be influenced by the holding potential: ion uptake increased when the potential was lowered. Na(+) inhibited metal-ion uptake in accordance with the elevation of the holding potential. A novel clutch mechanism of ion slippage that operates via continuously variable stoichiometry between the driving-force pathway (H(+)) and the transport pathway (divalent metal ions) is proposed. The possible physiological advantages of proton slippage through DCT1 and of Na(+) slippage through Smf1p are discussed.
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Agboh, Kelvin, Calvin H. F. Lau, Yvonne S. K. Khoo, Himansha Singh, Sagar Raturi, Asha V. Nair, Julie Howard et al. « Powering the ABC multidrug exporter LmrA : How nucleotides embrace the ion-motive force ». Science Advances 4, no 9 (septembre 2018) : eaas9365. http://dx.doi.org/10.1126/sciadv.aas9365.

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LmrA is a bacterial ATP-binding cassette (ABC) multidrug exporter that uses metabolic energy to transport ions, cytotoxic drugs, and lipids. Voltage clamping in a Port-a-Patch was used to monitor electrical currents associated with the transport of monovalent cationic HEPES+by single-LmrA transporters and ensembles of transporters. In these experiments, one proton and one chloride ion are effluxed together with each HEPES+ion out of the inner compartment, whereas two sodium ions are transported into this compartment. Consequently, the sodium-motive force (interior negative and low) can drive this electrogenic ion exchange mechanism in cells under physiological conditions. The same mechanism is also relevant for the efflux of monovalent cationic ethidium, a typical multidrug transporter substrate. Studies in the presence of Mg-ATP (adenosine 5′-triphosphate) show that ion-coupled HEPES+transport is associated with ATP-bound LmrA, whereas ion-coupled ethidium transport requires ATP binding and hydrolysis. HEPES+is highly soluble in a water-based environment, whereas ethidium has a strong preference for residence in the water-repelling plasma membrane. We conclude that the mechanism of the ABC transporter LmrA is fundamentally related to that of an ion antiporter that uses extra steps (ATP binding and hydrolysis) to retrieve and transport membrane-soluble substrates from the phospholipid bilayer.
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Mayer, Maria, Marek Dynowski et Uwe Ludewig. « Ammonium ion transport by the AMT/Rh homologue LeAMT1;1 ». Biochemical Journal 396, no 3 (29 mai 2006) : 431–37. http://dx.doi.org/10.1042/bj20060051.

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AMT (ammonium transporter)/Rh (Rhesus) ammonium transporters/channels are identified in all domains of life and fulfil contrasting functions related either to ammonium acquisition or excretion. Based on functional and crystallographic high-resolution structural data, it was recently proposed that the bacterial AmtB (ammonium transporter B) is a gas channel for NH3 [Khademi, O'Connell, III, Remis, Robles-Colmenares, Miercke and Stroud (2004) Science 305, 1587–1594; Zheng, Kostrewa, Berneche, Winkler and Li (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 17090–17095]. Key residues, proposed to be crucial for NH3 conduction, and the hydrophobic, but obstructed, pore were conserved in a homology model of LeAMT1;1 from tomato. Transport by LeAMT1;1 was affected by mutations of residues that were predicted to constitute the aromatic recruitment site for NH4+ at the external pore entrance. Despite the structural similarities, LeAMT1;1 was shown to transport only the ion; each transported 14C-methylammonium molecule carried a single positive elementary charge. Similarly, NH4+ (or H+/NH3) was transported, but NH3 conduction was excluded. It is concluded that related proteins and a similar molecular architecture can apparently support contrasting transport mechanisms.
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Krom, Bastiaan P., Jessica B. Warner, Wil N. Konings et Juke S. Lolkema. « Complementary Metal Ion Specificity of the Metal-Citrate Transporters CitM and CitH of Bacillus subtilis ». Journal of Bacteriology 182, no 22 (15 novembre 2000) : 6374–81. http://dx.doi.org/10.1128/jb.182.22.6374-6381.2000.

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ABSTRACT Citrate uptake in Bacillus subtilis is stimulated by a wide range of divalent metal ions. The metal ions were separated into two groups based on the expression pattern of the uptake system. The two groups correlated with the metal ion specificity of two homologousB. subtilis secondary citrate transporters, CitM and CitH, upon expression in Escherichia coli. CitM transported citrate in complex with Mg2+, Ni2+, Mn2+, Co2+, and Zn2+ but not in complex with Ca2+, Ba2+, and Sr2+. CitH transported citrate in complex with Ca2+, Ba2+, and Sr2+ but not in complex with Mg2+, Ni2+, Mn2+, Co2+, and Zn2+. Both transporters did not transport free citrate. Nevertheless, free citrate uptake could be demonstrated in B. subtilis, indicating the expression of at least a third citrate transporter, whose identity is not known. For both the CitM and CitH transporters it was demonstrated that the metal ion promoted citrate uptake and, vice versa, that citrate promoted uptake of the metal ion, indicating that the complex is the transported species. The results indicate that CitM and CitH are secondary transporters that transport complexes of divalent metal ions and citrate but with a complementary metal ion specificity. The potential physiological function of the two transporters is discussed.
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Beckstein, Oliver, et Fiona Naughton. « General principles of secondary active transporter function ». Biophysics Reviews 3, no 1 (mars 2022) : 011307. http://dx.doi.org/10.1063/5.0047967.

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Transport of ions and small molecules across the cell membrane against electrochemical gradients is catalyzed by integral membrane proteins that use a source of free energy to drive the energetically uphill flux of the transported substrate. Secondary active transporters couple the spontaneous influx of a “driving” ion such as Na+ or H+ to the flux of the substrate. The thermodynamics of such cyclical non-equilibrium systems are well understood, and recent work has focused on the molecular mechanism of secondary active transport. The fact that these transporters change their conformation between an inward-facing and outward-facing conformation in a cyclical fashion, called the alternating access model, is broadly recognized as the molecular framework in which to describe transporter function. However, only with the advent of high resolution crystal structures and detailed computer simulations, it has become possible to recognize common molecular-level principles between disparate transporter families. Inverted repeat symmetry in secondary active transporters has shed light onto how protein structures can encode a bi-stable two-state system. Based on structural data, three broad classes of alternating access transitions have been described as rocker-switch, rocking-bundle, and elevator mechanisms. More detailed analysis indicates that transporters can be understood as gated pores with at least two coupled gates. These gates are not just a convenient cartoon element to illustrate a putative mechanism but map to distinct parts of the transporter protein. Enumerating all distinct gate states naturally includes occluded states in the alternating access picture and also suggests what kind of protein conformations might be observable. By connecting the possible conformational states and ion/substrate bound states in a kinetic model, a unified picture emerges in which the symporter, antiporter, and uniporter functions are extremes in a continuum of functionality. As usual with biological systems, few principles and rules are absolute and exceptions are discussed as well as how biological complexity may be integrated in quantitative kinetic models that may provide a bridge from the structure to function.
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Vergara-Jaque, Ariela, Cristina Fenollar-Ferrer, Christopher Mulligan, Joseph A. Mindell et Lucy R. Forrest. « Family resemblances : A common fold for some dimeric ion-coupled secondary transporters ». Journal of General Physiology 146, no 5 (26 octobre 2015) : 423–34. http://dx.doi.org/10.1085/jgp.201511481.

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Membrane transporter proteins catalyze the passage of a broad range of solutes across cell membranes, allowing the uptake and efflux of crucial compounds. Because of the difficulty of expressing, purifying, and crystallizing integral membrane proteins, relatively few transporter structures have been elucidated to date. Although every membrane transporter has unique characteristics, structural and mechanistic similarities between evolutionarily diverse transporters have been identified. Here, we compare two recently reported structures of membrane proteins that act as antimicrobial efflux pumps, namely MtrF from Neisseria gonorrhoeae and YdaH from Alcanivorax borkumensis, both with each other and with the previously published structure of a sodium-dependent dicarboxylate transporter from Vibrio cholerae, VcINDY. MtrF and YdaH belong to the p-aminobenzoyl-glutamate transporter (AbgT) family and have been reported as having architectures distinct from those of all other families of transporters. However, our comparative analysis reveals a similar structural arrangement in all three proteins, with highly conserved secondary structure elements. Despite their differences in biological function, the overall “design principle” of MtrF and YdaH appears to be almost identical to that of VcINDY, with a dimeric quaternary structure, helical hairpins, and clear boundaries between the transport and scaffold domains. This observation demonstrates once more that the same secondary transporter architecture can be exploited for multiple distinct transport modes, including cotransport and antiport. Based on our comparisons, we detected conserved motifs in the substrate-binding region and predict specific residues likely to be involved in cation or substrate binding. These findings should prove useful for the future characterization of the transport mechanisms of these families of secondary active transporters.
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Lolkema, Juke S., et Dirk-Jan Slotboom. « The Hill analysis and co-ion–driven transporter kinetics ». Journal of General Physiology 145, no 6 (25 mai 2015) : 565–74. http://dx.doi.org/10.1085/jgp.201411332.

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Interaction of multiple ligands with a protein or protein complex is a widespread phenomenon that allows for cooperativity. Here, we review the use of the Hill equation, which is commonly used to analyze binding or kinetic data, to analyze the kinetics of ion-coupled transporters and show how the mechanism of transport affects the Hill coefficient. Importantly, the Hill analysis of ion-coupled transporters can provide the exact number of transported co-ions, regardless of the extent of the cooperativity in ion binding.
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Adelman, Joshua L., Chiara Ghezzi, Paola Bisignano, Donald D. F. Loo, Seungho Choe, Jeff Abramson, John M. Rosenberg, Ernest M. Wright et Michael Grabe. « Stochastic steps in secondary active sugar transport ». Proceedings of the National Academy of Sciences 113, no 27 (20 juin 2016) : E3960—E3966. http://dx.doi.org/10.1073/pnas.1525378113.

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Secondary active transporters, such as those that adopt the leucine-transporter fold, are found in all domains of life, and they have the unique capability of harnessing the energy stored in ion gradients to accumulate small molecules essential for life as well as expel toxic and harmful compounds. How these proteins couple ion binding and transport to the concomitant flow of substrates is a fundamental structural and biophysical question that is beginning to be answered at the atomistic level with the advent of high-resolution structures of transporters in different structural states. Nonetheless, the dynamic character of the transporters, such as ion/substrate binding order and how binding triggers conformational change, is not revealed from static structures, yet it is critical to understanding their function. Here, we report a series of molecular simulations carried out on the sugar transporter vSGLT that lend insight into how substrate and ions are released from the inward-facing state of the transporter. Our simulations reveal that the order of release is stochastic. Functional experiments were designed to test this prediction on the human homolog, hSGLT1, and we also found that cytoplasmic release is not ordered, but we confirmed that substrate and ion binding from the extracellular space is ordered. Our findings unify conflicting published results concerning cytoplasmic release of ions and substrate and hint at the possibility that other transporters in the superfamily may lack coordination between ions and substrate in the inward-facing state.
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Lolkema, Juke S., et Dirk J. Slotboom. « Models to determine the kinetic mechanisms of ion-coupled transporters ». Journal of General Physiology 151, no 3 (10 janvier 2019) : 369–80. http://dx.doi.org/10.1085/jgp.201812055.

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With high-resolution structures available for many ion-coupled (secondary active) transporters, a major challenge for the field is to determine how coupling is accomplished. Knowledge of the kinetic mechanism of the transport reaction, which defines the binding order of substrate and co-ions, together with the sequence with which all relevant states are visited by the transporter, will help to reveal this coupling mechanism. Here, we derived general mathematical models that can be used to analyze data from steady-state transport measurements and show how kinetic mechanisms can be derived. The models describe how the apparent maximal rate of substrate transport depends on the co-ion concentration, and vice versa, in different mechanisms. Similarly, they describe how the apparent affinity for the transported substrate is affected by the co-ion concentration and vice versa. Analyses of maximal rates and affinities permit deduction of the number of co-ions that bind before, together with, and after the substrate. Hill analysis is less informative, but in some mechanisms, it can reveal the total number of co-ions transported with the substrate. However, prior knowledge of the number of co-ions from other experimental approaches is preferred when deriving kinetic mechanisms, because the models are generally overparameterized. The models we present have wide applicability for the study of ion-coupled transporters.
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Demirbilek, Huseyin, Sonya Galcheva, Dogus Vuralli, Sara Al-Khawaga et Khalid Hussain. « Ion Transporters, Channelopathies, and Glucose Disorders ». International Journal of Molecular Sciences 20, no 10 (27 mai 2019) : 2590. http://dx.doi.org/10.3390/ijms20102590.

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Ion channels and transporters play essential roles in excitable cells including cardiac, skeletal and smooth muscle cells, neurons, and endocrine cells. In pancreatic beta-cells, for example, potassium KATP channels link the metabolic signals generated inside the cell to changes in the beta-cell membrane potential, and ultimately regulate insulin secretion. Mutations in the genes encoding some ion transporter and channel proteins lead to disorders of glucose homeostasis (hyperinsulinaemic hypoglycaemia and different forms of diabetes mellitus). Pancreatic KATP, Non-KATP, and some calcium channelopathies and MCT1 transporter defects can lead to various forms of hyperinsulinaemic hypoglycaemia (HH). Mutations in the genes encoding the pancreatic KATP channels can also lead to different types of diabetes (including neonatal diabetes mellitus (NDM) and Maturity Onset Diabetes of the Young, MODY), and defects in the solute carrier family 2 member 2 (SLC2A2) leads to diabetes mellitus as part of the Fanconi–Bickel syndrome. Variants or polymorphisms in some ion channel genes and transporters have been reported in association with type 2 diabetes mellitus.
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Thèses sur le sujet "Ion transporter"

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Chen, Zhihong. « Modeling Ion Binding in the Chloride Transporter ». University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310689.

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Niemiec, Moritz Sebastian. « Human copper ion transfer : from metal chaperone to target transporter domain ». Doctoral thesis, Umeå universitet, Kemiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100511.

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Many processes in living systems occur through transient interactions among proteins. Those interactions are often weak and are driven by small changes in free energy. Due to the short-living nature of these interactions, our knowledge about driving forces, dynamics and structures of these types of protein-protein heterocomplexes are though limited. This is especially important for cellular copper (Cu) trafficking: Copper ions are essential for all eukaryotes and most bacteria. As a cofactor in many enzymes, copper is especially vital in respiration or detoxification. Since the same features that make copper useful also make it toxic, it needs to be controlled tightly. Additionally, in the reducing environment of the cytosol, Cu is present as insoluble Cu(I). To circumvent both toxicity and solubility issues, a system has evolved where copper is comforted by certain copper binding proteins, so-called Cu-chaperones. They transiently interact with each other to distribute the Cu atoms in a cell. In humans, one of them is Atox1. It binds copper with a binding site containing two thiol residues and transfers it to other binding sites, mostly those of a copper pump, ATP7B (also known as Wilsons disease protein). My work was aimed at understanding copper-mediated protein-protein interactions on a molecular and mechanistic level. Which amino acids interact with the metal? Which forces drive the transfer from one protein to the other? Using biophysical and biochemical methods such as chromatography and calorimetry on wild type and point-mutated proteins in vitro, we found that the copper is transferred via a dynamic intermediate complex that keeps the system flexible while shielding the copper against other interactions. Although similar transfer interactions can be observed in other organisms, and many conclusions in the copper field are drawn from bacterial and yeast analogs, we believe that it is important to investigate human proteins, too. Not only is their regulation different, but also only in humans we find the diseases linked to the proteins: Copper level regulation diseases are to be named first, but atypical copper levels have also been linked to tumors and amyloid dispositions. In summary, my observations and conclusions are of basic research character and can be of importance for both general copper and human medicinal research.
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Senior, Adam Paul. « GerT, an ion transporter homologue in Bacillus cereus and its role in spore germination ». Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425216.

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Nicolson, Tamara Jane. « Type II diabetes and the pancreatic B cell : molecular characterisation of ion channel and transporter polymorphisms ». Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516549.

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Lau, Calvin Ho-Fung. « Inorganic ion transport and sensing by the bacterial multidrug ATP-binding cassette transporter LmrA of Lactococcus lactis ». Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608774.

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Haering, Claudia [Verfasser], Hanns [Akademischer Betreuer] Hatt et Stefan [Akademischer Betreuer] Wiese. « Characterization of the ion transporter NKCC1 in the field of chemosensation / Claudia Haering. Gutachter : Hanns Hatt ; Stefan Wiese ». Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1089005881/34.

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Shawki, Ali. « The Functional Properties and Intestinal Role of the H+-Coupled Divalent Metal-Ion Transporter 1, DMT1 ». University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037106.

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Rimington, Tracy L. « Expression, purification and characterisation of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) in Saccharomyces cerevisiae ». Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/expression-purification-and-characterisation-of-the-cystic-fibrosis-transmembrane-conductance-regulator-cftr-in-saccharomyces-cerevisiae(5c8c606b-8925-4627-91dc-67a896b9f286).html.

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Mutations in the eukaryotic integral membrane protein Cystic Fibrosis Transmembrane conductance Regulator (CFTR) cause the hereditary disease cystic fibrosis (CF). CFTR functions as an ion channel at the surface of epithelial cells and regulates the movement of chloride ions and water across the plasma membrane. CFTR is difficult to express and purify in heterologous systems due to its propensity to form insoluble aggregates and its susceptibility to degradation. Obtaining good yields of highly purified CFTR has proven problematic and contributes to our limited understanding of the structure and function of the protein. The most prevalent disease causing mutation, F508del, results in misfolded CFTR which is particularly unstable and is quickly targeted for degradation by the host system and is prevented from being trafficked to the plasma membrane. There are limited treatment options for patients with the F508del mutation and it is therefore of significant interest within CF research. New methods and assays are required to identify potential compounds which could correct the F508del mutation. This thesis investigates the use of Saccharomyces cerevisiae to express and purify codon optimised recombinant CFTR. The use of a green fluorescent protein (GFP) tag enabled quick and simple detection of CFTR in whole cells and after extraction from the plasma membrane. By optimising the culture conditions for CFTR expression and detergent solubilisation conditions, relatively high yields of full-length protein were obtained. When used as a chemical chaperone at the time of inducing CFTR expression, glycerol increased yields of full-length protein. Degradation of CFTR could be limited by inducing expression at an optimal cell density and by harvesting cells within a specific time window. CFTR was extracted by solubilisation in the mild detergent dodecyl-β-D-maltopyranoside (DDM) in the presence of up to 1 M NaCl with up to ~87% efficiency in some cases. Using a gene optimisation strategy in which additional purification tags and a yeast Kozak-like sequence were added, the human CFTR (hCFTR) protein was expressed and purified. Fluorescence microscopy revealed CFTR localisation at the periphery of yeast cells. Immunoaffinity chromatography facilitated by the GFP tag at the C terminus of CFTR produced protein of up to 95% purity. An assessment of the thermal stability of this highly purified CFTR using a fluorescent probe binding assay revealed a denaturation midpoint (Tm) of ~43 degC. The ability of this assay to determine the stability of CFTR is encouraging and there is the potential to further develop it in a high-throughput manner to identify compounds which stabilise the F508del protein and which may hold the key to developing new treatments for CF.
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Murphy-Royal, Ciaran. « Surface diffusion of the astrocytic glutamate transporter glt-1 shapes synaptic transmission ». Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0113/document.

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Le glutamate est le principal neurotransmetteur excitateur du système nerveux central des vertébrés, et le codage de l’information cérébrale repose en partie sur des modulations de l’amplitude et de la fréquence des transmissions synaptiques glutamatergiques. De ce fait, la résolution spatiale et temporelle de ces transmissions nécessite un contrôle fin de la présence de glutamate dans la fente synaptique. Cette durée de vie du glutamate dans les synapses dépend directement de l’action de transporteurs spécifiques exprimés à la surface des astrocytes, en particulier les transporteurs de type GLT-1, qui retirent le neurotransmetteur et permettent ainsi de « nettoyer » la fente synaptique avant la survenue d’un nouvel épisode de neurotransmission
A classic understanding of neurotransmitter clearance at glutamatergic synapses is that, in order to ensure sufficient glutamate uptake on a fast timescale, it is necessary to have high numbers of glutamate transporters in the vicinity of release sites to compensate for their slow transport kinetics. Using a combination of single molecule imaging and electrophysiological approaches, we now challenge this view by first demonstrating that GLT-1 transporters are not static but highly mobile at the surface of astrocytes, and that their surface diffusion is dependent upon both neuronal and glial cell activities. In the vicinity of glutamate synapses, GLT-1 dynamics are strongly reduced favoring their retention within this strategic location. Remarkably, glutamate uncaging at synaptic sites instantaneously increases GLT-1 diffusion, displacing the glutamate-bound transporter away from this compartment. Functionally, impairment of the transporter lateral diffusion through an antibody-based surface cross linking, both in vitro and in vivo, significantly slows the kinetics of excitatory postsynaptic currents. Taken together, these data reveal the unexpected and major role of the astrocytic surface GLT-1 fast dynamics in shaping glutamatergic synaptic transmission.Keywords:
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Lee, Shernita. « Ironing Out the Host-fungal Interaction in Airway Epithelial Cells ». Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/56689.

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Aspergillus fumigatus is a ubiquitous fungus associated with several airway complications and diseases including asthma, allergies, cystic fibrosis, and most commonly invasive aspergillosis. The airway epithelium, a protective barrier, is the first anatomical site to interact with A. fumigatus. Although this host-fungal interaction is often asymptomatic for immunocompetent individuals, for immunocompromised persons, due to a weakened competence of the immune system, they have an increased likelihood of fungal infection. This dissertation aims to investigate the effect of A. fumigatus on the transcriptional response of human airway epithelial cells, focusing on the relationship between innate immunity and iron regulation from the host perspective. The trace element iron is needed by both the fungus and the host for cellular maintenance and survival, but tightly controlled iron regulation in the host is required to prevent oxidative stress and cell death. The research methods in this dissertation employ a systems biology approach, by incorporating mathematical modeling, RNA-seq analysis, and experimental biology techniques to assess the role of airway epithelial cells in the host-fungal interaction. Both the quantitative and qualitative research design allows for characterization of airway epithelial cells and the downstream changes in iron importer genes. This study addresses literature gaps through analysis of the host transcriptome using multiple time points, by performing an extensive evaluation of the effect of cytokines on iron importer genes, and conceptualization of a comprehensive mathematical model of the airway epithelial cell. The major findings suggest the following: 1) airway epithelial cells avidly respond to A. fumigatus through modification of the expression of immune response related genes at different infection stages, 2) during A. fumigatus co-incubation with airway epithelial cells, the iron importers genes respond in strikingly different ways, and 3) cytokines have a significant effect on the increase in expression of an iron importer gene. We illuminated the role of airway epithelial cells in fungal recognition and activation of the immune response in signaling cascades that consequently modify iron importer genes and hope to use this information as a platform to discover potential therapeutic targets.
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Livres sur le sujet "Ion transporter"

1

Sepúlveda, Francisco V., et Francisco Bezanilla, dir. Pumps, Transporters, and Ion Channels. New York : Kluwer Academic Publishers-Plenum Publishers, 2005. http://dx.doi.org/10.1007/b139057.

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E, Clapham David, et Ehrlich Barbara E, dir. Organellar ion channels and transporters. New York : Rockefeller University Press, 1996.

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3

Hamilton, Kirk L., et Daniel C. Devor, dir. Studies of Epithelial Transporters and Ion Channels. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-55454-5.

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4

Electrogenic ion pumps. Sunderland, Mass., U.S.A : Sinauer Associates, 1991.

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5

Morad, Martin, Setsuro Ebashi, Wolfgang Trautwein et Yoshihisa Kurachi, dir. Molecular Physiology and Pharmacology of Cardiac Ion Channels and Transporters. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-3990-8.

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Hamilton, Kirk L., et Daniel C. Devor, dir. Ion Channels and Transporters of Epithelia in Health and Disease. New York, NY : Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-3366-2.

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7

Martin, Morad, dir. Molecular physiology and pharmacology of cardiac ion channels and transporters. Dordrecht : Kluwer Academic Publishers, 1996.

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8

P, Rosen Barry, et Silver S, dir. Ion transport in prokaryotes. San Diego : Academic Press, 1987.

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Gupta, Satya Prakash. Ion Channels and Their Inhibitors. Berlin, Heidelberg : Springer-Verlag Berlin Heidelberg, 2011.

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G, Kamkin A., et Kiseleva Irina, dir. Mechanosensitive ion channels. [Berlin : Springer Verlag, 2008.

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Chapitres de livres sur le sujet "Ion transporter"

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Vergani, Paola, David C. Gadsby et László Csanády. « CFTR, an Ion Channel Evolved from ABC Transporter ». Dans Encyclopedia of Biophysics, 254–65. Berlin, Heidelberg : Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-16712-6_364.

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Keep, Richard F., J. Xiang, L. J. Ulanski, F. C. Brosius et A. Lorris Betz. « Choroid Plexus Ion Transporter Expression and Cerebrospinal Fluid Secretion ». Dans Brain Edema X, 279–81. Vienna : Springer Vienna, 1997. http://dx.doi.org/10.1007/978-3-7091-6837-0_86.

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Ravna, Aina Westrheim, et Ingebrigt Sylte. « Homology Modeling of Transporter Proteins (Carriers and Ion Channels) ». Dans Methods in Molecular Biology, 281–99. Totowa, NJ : Humana Press, 2011. http://dx.doi.org/10.1007/978-1-61779-588-6_12.

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Ashrafuzzaman, Mohammad, et Jack Tuszynski. « The Membrane as a Transporter, Ion Channels and Membrane Pumps ». Dans Biological and Medical Physics, Biomedical Engineering, 51–74. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-16105-6_4.

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Booth, Ian R., Michelle D. Edwards, Banuri Gunasekera, Chan Li et Samantha Miller. « The Ktn Domain and Its Role as a Channel and Transporter Regulator ». Dans Bacterial Ion Channels and Their Eukaryotic Homologs, 21–40. Washington, DC, USA : ASM Press, 2014. http://dx.doi.org/10.1128/9781555816452.ch2.

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Fyles, Thomas M. « Biomimetic Ion Transport with Synthetic Transporters ». Dans Bioorganic Chemistry Frontiers, 71–113. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75256-8_2.

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Sarkar, Buddhadev, et Swarnendu Roy. « Ion Transporter Genes from Wild Relatives of Cereals Hold the Key for the Development of Salinity Tolerance ». Dans Sustainable Agriculture in the Era of Climate Change, 187–209. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45669-6_8.

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Johnsen, Rainer. « Electron-Ion, Ion-Ion, and Ion-Neutral Interactions ». Dans Nonequilibrium Effects in Ion and Electron Transport, 261–74. Boston, MA : Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-0661-0_16.

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Sachs, George, John Cuppoletti, Robert D. Gunther, Jonathan Kaunitz, John Mendlein, Edwin C. Rabon et Bjorn Wallmark. « Ion Pumps, Ion Pathways, Ion Sites ». Dans New Insights into Cell and Membrane Transport Processes, 75–95. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5062-0_5.

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Becchetti, Andrea, et Patrizia Aracri. « Ion Channels and Transporters ». Dans Molecular Life Sciences, 1–22. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-6436-5_190-2.

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Actes de conférences sur le sujet "Ion transporter"

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Fedorova, E. E., et N. A. Trifonova. « Ion transporters in the root nodule of Medicago truncatula : potassium transporters ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.071.

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The transporter proteins were mistargeted and partly depleted from plasma membrane of mature infected cells, this phenomenon may contribute to the potassium loss by symbiosomes during their development and senescence.
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Sundaresan, Vishnu Baba, et Donald J. Leo. « Modeling and Characterization of a Chemomechanical Actuator Based on Protein Transporters ». Dans ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43712.

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Plants and animal cells are naturally occurring actuators that exhibit force and motion driven by fluid transport through the cell membrane. The protein transporters embedded in the cell membrane serve as the selective gateway for ion and fluid transport. The actuator presented in this work generates force and deformation from mass transport through an artificial membrane with protein transporters extracted from plant cell membranes. The artificial membrane is formed from purified 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoethanolamine (POPE) lipids and supported on a porous substrate. The protein transporter used in the actuator membrane is a proton-sucrose cotransporter, SUT4, extracted from yeast cells that genetically modified to grow the cotransporter in their cell membranes. The SUT4 transporter conducts proton and sucrose from the side of the membrane with higher concentration and carries water molecules across the membrane. It is observed from transport characterization experiments that fluid flux through the membrane varies with the applied sucrose concentration and hence is chosen as the control stimulus in the actuator. A modified four-state facilitated diffusion model is applied to the transport characterization data to compute the two characteristic parameters for fluid transport, saturation concentration and translocation rate, through the membrane. The flux rate through the membrane is observed to increase with the concentration till a particular value and saturates at a higher concentration. The concentration at which the flux rate through the membrane saturates is referred to as the saturation concentration. The saturation concentration for the actuator is experimentally found to be 6±0.6mM sucrose on the side with lower pH. The corresponding maximum translocation rate is found to be 9.6±1.2 nl/μ.cm2.min. The maximum steady state deformation produced by the actuator is observed at 30 mM sucrose that corresponds to a force of 0.89 mN.
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Nara, Matsunori. « Invention Using a Liposome of a Bio-Micromachine ». Dans ASME 4th Integrated Nanosystems Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/nano2005-87031.

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It is thought that a minus hydrogen ion is useful to the apotosis of a mitochondria and prevention of a necrosis, or prevention of the illness resulting from the oxygen radical in a human body. So, in this research, examination about the possibility and its practical use method of production of the hydrogen ion by which it was minus electrified was performed. First, the lipid bilayer as a medicine transporter of DDS (Drug Delivery System) was produced using the supercritical fluid. Next, experimental examination was performed for the purpose of enclosing the substance for hydrogen ion generating, and the substance for electronic accumulation with the inside of a lipid bilayer. Furthermore, fundamental examination was performed in order to use the enclosed minus hydrogen ion. In order to check what the electron of oxygen ion was taken into the hydrogen ion, and the minus hydrogen ion generated, electrical conductivity measurement was performed. By mixing and heating, 12CaO · 7Al2O3 and metal calcium, the electron was accumulated in the inside of the reaction object of 12CaO7Al2O3. The check of accumulation of the electron (anion) inside a reaction object was judged by measurement of the electrical conductivity before and behind processing. That is, when the electron was accumulated, I thought that the electrical conductivity of a reaction object increased. Moreover, this reaction object was used as an electronic transporter. In the range of the temperature set up in the liposome production experiment, and pressure, it could not say that the influence temperature and pressure affect the determination of the particle diameter of a liposome was large, but average particle diameter was about 10 micrometers. The following conclusions were obtained as a result of conducting a fundamental experiment for the purpose of production of a medicine which made the minus hydrogen ion include inside a lipid bilayer (liposome), and a confirmation of the validity as DDS in the living body. (1) The liposome suitable for DDS was able to be obtained. (2) By using metal magnesium and metal calcium, the minus hydrogen ion was able to be accumulated in the reaction inside of the body of alumina cement.
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Borbor, M., P. Nguemgo-Kouam, T. Hero, IA Adamietz et H. Bühler. « The ion transporter Na-K-ATPase plays a decisive role in the selective inhibition of breast cancer stem-like cells by the ionophore salinomycin ». Dans 62. Kongress der Deutschen Gesellschaft für Gynäkologie und Geburtshilfe – DGGG'18. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1671212.

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Kang, Byeongdong, Moojoong Kim, Hyungmin Joo, Hyun Jung Kim et Dong-Kwon Kim. « Experimental Study on Energy Harvesting From Salinity Gradient by Reverse Electrodialysis in Ag/AgCl Deposited AAO Nanochannel Array ». Dans ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64364.

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Reverse electrodialysis (RED) is energy conversion phenomena which generates electricity from concentration gradient energy by mixing the ions in sea water with fresh water through ion-selective nanochannel. When nanochannels are filled with an aqueous solution, the surface of nanochannels is charged by ionization, ion adsorption, and ion dissolution. Therefore, co-ions are repelled from the nanochannels and only counter-ions can be transported through the nanochannels. As a result, the electric current can be generated by selective ion transport through the nanochannels from sea water to fresh water. Recently, solid-state nanochannels or nanopores have received attention because they have potential to replace polymer ion-selective membranes. Especially, anodic aluminum oxide (AAO) nanochannel array has advantage of easiness of pore size control and high pore density. In the present study, to collect electric current generated by the nanochannels, we deposited the porous silver layer on both front and rear surface of the AAO nanochannel array by using e-beam evaporation and changed the silver layer to the silver/silver chloride layer by chemical oxidation with aqueous FeCl3. Finally, we conduct an experimental investigation for the power generation from the AAO nanochannel arrays placed between two potassium chloride solutions with various combinations of concentrations.
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Hery, Travis M., et Vishnu-Baba Sundaresan. « Pore-Spanning PPy(DBS) as a Voltage-Gated Synthetic Membrane Ion Channel ». Dans ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9193.

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The transport of monovalent cations across a suspended PPy(DBS) polymer membrane in an aqueous solution as a function of its redox state is investigated. Maximum ion transport is found to occur when PPy(DBS) is in the reduced state, and minimum transport in the oxidized state. No deviation in the dynamics of ion transport based on the direction of the applied electrical field is observed. Additionally, it is found that ion transport rates linearly increased proportional to the state of reduction until a steady state is reached when the polymer is fully reduced. Therefore controlled, bidirectional ion transport is for the first time demonstrated. The effect of aqueous Li+ concentration on ion transport in the fully reduced state of the polymer is studied. It is found that ion transport concentration dependence follows Michaelis-Menten kinetics (which models protein reaction rates, such as those forming ion channels in a cell membrane) with an r2 value of 0.99. For the given PPy(DBS) polymer charge density and applied potential across the membrane, the maximum possible ion transport rate per channel is found to be 738 ions per second and the Michaelis constant, representing the concentration at which half the maximum ion transport rate occurs, is 619.5mM.
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Tawfik, Mena E., Shashwat Gupta, Aaron Stern et F. J. Diez. « Transient Effects in High Power Electroosmotic Pumps ». Dans ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icnmm2016-8077.

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On generating high electroosmotic flows in microfluidic pumps under applied DC voltage, the flow rate and the drawn current drop with time. When generating high electroosmotic flows using microfluidic pumps under applied DC voltage, the flow rate and current draw decrease with time. The electroosmotic (EO) pump efficiency decreases with time due to flow rate deterioration. In order to study the transient effect in EO pumps, the mass transport of ions in the membrane is investigated. Ions mass transport are affected by the membrane surface charge, ion diffusion, ion migration and flow convection. Many studies investigate the mass transport in ion selective membranes, micro-channels, and nano-channels without focus on the transient effects at high electric fields. In most of these studies, the Poisson-Nernst-Plank and the Naiver stokes equations are used to model the ion transport in electrokinetic devices. Without applying simplifying assumptions, these system of equations can be only solved numerically. A theoretical model, based on diffusion and ion migration, is developed to predict the current drop and experiments are conducted to verify this model. EO flow can be neglected when there is no membrane installed between the pump electrodes (electrochemical cell). The current drop is predicted under no flow conditions using the advection diffusion equation and it solved analytically using the Ogata and Banks solution. In order to predict the current drop in the EO pump under flow conditions, the Helmholtz-Smoluchowski equation is used to calculate the EO flow velocity. This equation holds under thin electrical double layer assumption and small zeta potential. The current drop has been calculated theoretically and compared with the experimental data. The ion screening and depletion at the electrodes result in increasing the EO pump total resistance and decrease the total current. The calculated current drop time scale has been found to be in the order of 100 seconds under no flow conditions. As flow rate increases, the flow rate contributes to the mass transport of ions (convection current) and screens the ions faster, leading to a decrease in the current drop time scale. On the other hand, by increasing the fluid molar concentration, the current drop is much slower as more ions are available and need more time to be depleted. The current drop time scale decreases rapidly as higher DC voltages are applied, leading to low efficiency. The ion transport can be limited by applying a pulse voltage waveform instead of DC voltage, leading to more stable flow rate, current and hence constant EO efficiency. The pulse voltage waveform allows the ions to diffuse back from high to low concentration regions during the off-time, preventing ion depletion and current drop.
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Cuppoletti, John. « Composite Synthetic Membranes Containing Native and Engineered Transport Proteins ». Dans ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-449.

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Our membrane transport protein laboratory has worked with material scientists, computational chemists and electrical and mechanical engineers to design bioactuators and sensing devices. The group has demonstrated that it is possible to produce materials composed native and engineered biological transport proteins in a variety of synthetic porous and solid materials. Biological transport proteins found in nature include pumps, which use energy to produce gradients of solutes, ion channels, which dissipate ion gradients, and a variety of carriers which can either transport substances down gradients or couple the uphill movement of substances to the dissipation of gradients. More than one type of protein can be reconstituted into the membranes to allow coupling of processes such as forming concentration gradients with ion pumps and dissipating them with an ion channel. Similarly, ion pumps can provide ion gradients to allow the co-transport of another substance. These systems are relevant to bioactuation. An example of a bioactuator that has recently been developed in the laboratory was based on a sucrose-proton exchanger coupled to a proton pump driven by ATP. When coupled together, the net reaction across the synthetic membrane was ATP driven sucrose transport across a flexible membrane across a closed space. As sucrose was transported, net flow of water occurred, causing pressure and deformation of the membrane. Transporters are regulated in nature. These proteins are sensitive to voltage, pH, sensitivity to a large variety of ligands and they can be modified to gain or lose these responses. Examples of sensors include ligand gated ion channels reconstituted on solid and permeable supports. Such sensors have value as high throughput screening devices for drug screening. Other sensors that have been developed in the laboratory include sensors for membrane active bacterial products such as the anthrax pore protein. These materials can be self assembled or manufactured by simple techniques, allowing the components to be stored in a stable form for years before (self) assembly on demand. The components can be modified at the atomic level, and are composed of nanostructures. Ranges of sizes of structures using these components range from the microscopic to macroscopic scale. The transport proteins can be obtained from natural sources or can be produced by recombinant methods from the genomes of all kingdoms including archea, bacteria and eukaryotes. For example, the laboratory is currently studying an ion channel from a thermophile from deep sea vents which has a growth optimum of 90 degrees centigrade, and has membrane transport proteins with very high temperature stability. The transport proteins can also be genetically modified to produce new properties such as activation by different ligands or transport of new substances such as therapeutic agents. The structures of many of these proteins are known, allowing computational chemists to help understand and predict the transport processes and to guide the engineering of new properties for the transport proteins and the composite membranes. Supported by DARPA and USARMY MURI Award and AFOSR.
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Sundaresan, Vishnu Baba, et Donald J. Leo. « Experimental Investigation for Chemo-Mechanical Actuation Using Biological Transport Mechanisms ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81366.

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Plants have the ability to develop large mechanical force from chemical energy available with bio-fuels. The energy released by the cleavage of a terminal phosphate ion during the hydrolysis of bio-fuel assists the transport of ions and fluids in cellular homeostasis. Materials that develop pressure and hence strain similar to the response of plants to an external stimuli are classified as nastic materials. Calculations for controlled actuation of an active material inspired by biological transport mechanism demonstrated the feasibility of developing such a material with actuation energy densities on the order of 100kJ/m3 by Sundaresan et. al [2004]. The mathematical model for a simplified proof of concept actuator referred to as micro hydraulic actuator uses ion transporters extracted from plants reconstituted on a synthetic bilayer lipid membrane (BLM). Thermodynamic model of the concept actuator discussed in Sundaresan et. al [2005] predicted the ability to develop 5% normalized deformation in thickness of the micro-hydraulic actuator. Our experimental demonstration of controlled fluid transport through AtSUT4 reconstituted on a 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoethanolamine (POPE) BLM on lead silicate glass plate having an array of 50 μm holes driven by proton gradient is discussed here.
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Bollinger, L. D., et C. B. Zarowin. « Control of Plasma Etch Rates, Selectivity and Anisotropy with Plasma Parameters ». Dans Optical Fabrication and Testing. Washington, D.C. : Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oft.1987.pdp1.

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We discuss the experimental verification of relations derived earlier (1) between observable plasma etch rate, selectivity and anisotropy and reactor parameters for a variety of etch gases. Since the hetergeneous etch reaction is a superposition of neutral and ionic components, it can be shown that such etch chemistry exhibits enhancement and is made anisotropic by the energy transport of ions to the etch surface only when the process is ion dominated. The ion energy transport is controlled by the plasma sheath electric field-electrode area/gas pressure-collision cross section ratio, E.A./pQ, similarly controlling chemical anisotropy for ion dominated etch reactions. Under such circumstances, we show that many etch gases can yield identical ion transport, etch rate and anisotropy for a given rf current, gas pressure, ion-neutral collision cross section & electrode area, Irf/pQA.
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Rapports d'organisations sur le sujet "Ion transporter"

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Wong, Eric A., et Zehava Uni. Nutrition of the Developing Chick Embryo : Nutrient Uptake Systems of the Yolk Sac Membrane and Embryonic Intestine. United States Department of Agriculture, juin 2012. http://dx.doi.org/10.32747/2012.7697119.bard.

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We have examined the developmental changes in composition, amount, and uptake of yolk nutrients (fat, protein, water and carbohydrates) and the expression ofnutrient transporters in the yolk sac membrane (YSM) from embryonic day 11 (Ell) to 21 (E21) and small intestine from embryonic day 15 (E15) to E21 in embryos from young (22-25 wk) and old (45-50 wk) Cobb and Leghorn breeder flocks. The developmental expression profiles for the peptide transporter 1 (PepTl), the amino acid transporters, EAAT3, CAT-1 and BOAT, the sodium glucose transporter (SGLTl), the fructose transporter (GLUT5), the digestive enzymes aminopeptidase N (APN) and sucraseisomaltase (SI) were assayed by the absolute quantification real time PCR method in the YSM and embryonic intestine. Different temporal patterns of expression were observed for these genes. The effect of in ovo injection of peptides (the dipeptide Gly-Sar, purified peptides, trypsin hydrolysate) on transporter gene expression has been examined in the embryonic intestine. Injection of a partial protein hydrolysate resulted in an increase in expression of the peptide transporter PepT2. We have initiated a transcriptome analysis of genes expressed in the YSM at different developmental ages to better understand the function of the YSM.
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Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion et Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, octobre 2007. http://dx.doi.org/10.32747/2007.7592119.bard.

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Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.
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Raghothama, Kashchandra G., Avner Silber et Avraham Levy. Biotechnology approaches to enhance phosphorus acquisition of tomato plants. United States Department of Agriculture, janvier 2006. http://dx.doi.org/10.32747/2006.7586546.bard.

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Abstract: Phosphorus is one of the least available macronutrient in the soil. The high affinity phosphate transporters are known to be associated with phosphate acquisition under natural conditions. Due to unique interactions of phosphate with soil particles, up to 80% of the applied phosphates may be fixed forcing the farmers to apply 4 to 5 times the fertilizers necessary for crop production. Efficient uptake and utilization of this essential nutrient is essential for sustainability and profitability of agriculture. Many predictions point to utilization/exhaustion of high quality phosphate rocks within this century. This calls for efforts to improve the ability of plants to acquire and utilize limiting sources of phosphate in the rhizosphere. Two important molecular and biochemical components associated with phosphate efficiency are phosphate transporters and phosphatases. This research project is aimed at defining molecular determinants of phosphate acquisition and utilization in addition to generating phosphate uptake efficient plants. The main objectives of the project were; Creation and analysis of transgenic tomato plants over-expressing phosphatases and transporters Characterization of the recently identified members (LePT3 and LePT4) of the Pi transporter family Generate molecular tools to study genetic responses of plants to Pi deficiency During the project period we have successfully identified and characterized a novel phosphate transporter associated with mycorrhizal symbiosis. The expression of this transporter increases with mycorrhizal symbiosis. A thorough characterization of mutant tomato lacking the expression of this gene revealed the biological significance of LePT3 and another novel gene LePT4. In addition we have isolated and characterized several phosphate starvation induced genes from tomato using a combination of differential and subtractive mRNA hybridization techniques. One of the genes, LePS2 belongs to the family of phospho-protein phosphatase. The functionality of the recombinant protein was determined using synthetic phosphor-peptides. Over expression of this gene in tomato resulted in significant changes in growth, delay in flowering and senescence. It is anticipated that phospho-protein phosphatase may have regulatory role in phosphate deficiency responses of plants. In addition a novel phosphate starvation induced glycerol 3-phosphate permease gene family was also characterized. Two doctoral research students are continuing the characterization and functional analysis of these genes. Over expression of high affinity phosphate transporters in tobacco showed increased phosphate content under hydroponic conditions. There is growing evidence suggesting that high affinity phosphate transporters are crucial for phosphate acquisition even under phosphate sufficiency conditions. This project has helped train several postdoctoral fellows and graduate students. Further analysis of transgenic plants expressing phosphatases and transporters will not only reveal the biological function of the targeted genes but also result in phosphate uptake and utilization efficient plants.
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Ho, D. D. M., et R. M. Kulsrud. Ion transport in stellarators. Office of Scientific and Technical Information (OSTI), septembre 1985. http://dx.doi.org/10.2172/5142094.

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Smela, Elisabeth, Benjamin Shapiro et Xuezheng Wang. Understanding Ion Transport in Conjugated Polymers. Fort Belvoir, VA : Defense Technical Information Center, février 2004. http://dx.doi.org/10.21236/ada425255.

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Stern, R. A. Ion Transport in Beam-Plasma Interactions. Fort Belvoir, VA : Defense Technical Information Center, mai 1985. http://dx.doi.org/10.21236/ada169936.

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Fredrickson, E., R. Bell, D. Darrow, N. Gorelenkov, G. Kramer, S. Kubota, F. Levinton et al. Modeling Fast Ion Transport in TAE Avalanches in NSTX. Office of Scientific and Technical Information (OSTI), août 2009. http://dx.doi.org/10.2172/962923.

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Blumwald, Eduardo, et Avi Sadka. Citric acid metabolism and mobilization in citrus fruit. United States Department of Agriculture, octobre 2007. http://dx.doi.org/10.32747/2007.7587732.bard.

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Accumulation of citric acid is a major determinant of maturity and fruit quality in citrus. Many citrus varieties accumulate citric acid in concentrations that exceed market desires, reducing grower income and consumer satisfaction. Citrate is accumulated in the vacuole of the juice sac cell, a process that requires both metabolic changes and transport across cellular membranes, in particular, the mitochondrial and the vacuolar (tonoplast) membranes. Although the accumulation of citrate in the vacuoles of juice cells has been clearly demonstrated, the mechanisms for vacuolar citrate homeostasis and the components controlling citrate metabolism and transport are still unknown. Previous results in the PIs’ laboratories have indicated that the expression of a large number of a large number of proteins is enhanced during fruit development, and that the regulation of sugar and acid content in fruits is correlated with the differential expression of a large number of proteins that could play significant roles in fruit acid accumulation and/or regulation of acid content. The objectives of this proposal are: i) the characterization of transporters that mediate the transport of citrate and determine their role in uptake/retrieval in juice sac cells; ii) the study of citric acid metabolism, in particular the effect of arsenical compounds affecting citric acid levels and mobilization; and iii) the development of a citrus fruit proteomics platform to identify and characterize key processes associated with fruit development in general and sugar and acid accumulation in particular. The understanding of the cellular processes that determine the citrate content in citrus fruits will contribute to the development of tools aimed at the enhancement of citrus fruit quality. Our efforts resulted in the identification, cloning and characterization of CsCit1 (Citrus sinensis citrate transporter 1) from Navel oranges (Citrus sinesins cv Washington). Higher levels of CsCit1 transcripts were detected at later stages of fruit development that coincided with the decrease in the juice cell citrate concentrations (Shimada et al., 2006). Our functional analysis revealed that CsCit1 mediates the vacuolar efflux of citrate and that the CsCit1 operates as an electroneutral 1CitrateH2-/2H+ symporter. Our results supported the notion that it is the low permeable citrateH2 - the anion that establishes the buffer capacity of the fruit and determines its overall acidity. On the other hand, it is the more permeable form, CitrateH2-, which is being exported into the cytosol during maturation and controls the citrate catabolism in the juice cells. Our Mass-Spectrometry-based proteomics efforts (using MALDI-TOF-TOF and LC2- MS-MS) identified a large number of fruit juice sac cell proteins and established comparisons of protein synthesis patterns during fruit development. So far, we have identified over 1,500 fruit specific proteins that play roles in sugar metabolism, citric acid cycle, signaling, transport, processing, etc., and organized these proteins into 84 known biosynthetic pathways (Katz et al. 2007). This data is now being integrated in a public database and will serve as a valuable tool for the scientific community in general and fruit scientists in particular. Using molecular, biochemical and physiological approaches we have identified factors affecting the activity of aconitase, which catalyze the first step of citrate catabolism (Shlizerman et al., 2007). Iron limitation specifically reduced the activity of the cytosolic, but not the mitochondrial, aconitase, increasing the acid level in the fruit. Citramalate (a natural compound in the juice) also inhibits the activity of aconitase, and it plays a major role in acid accumulation during the first half of fruit development. On the other hand, arsenite induced increased levels of aconitase, decreasing fruit acidity. We have initiated studies aimed at the identification of the citramalate biosynthetic pathway and the role(s) of isopropylmalate synthase in this pathway. These studies, especially those involved aconitase inhibition by citramalate, are aimed at the development of tools to control fruit acidity, particularly in those cases where acid level declines below the desired threshold. Our work has significant implications both scientifically and practically and is directly aimed at the improvement of fruit quality through the improvement of existing pre- and post-harvest fruit treatments.
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Podesta, ,. Mario, Marina Gorelenkova et Roscoe White. Reduced Fast Ion Transport Model For The Tokamak Transport Code TRANSP. Office of Scientific and Technical Information (OSTI), février 2014. http://dx.doi.org/10.2172/1128924.

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Tajima, T., W. Horton, J. Q. Dong et Y. Kishimoto. Shear flow effects on ion thermal transport in tokamaks. Office of Scientific and Technical Information (OSTI), mars 1995. http://dx.doi.org/10.2172/42486.

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