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Littérature scientifique sur le sujet « HERG gating »

Auteur : Grafiati
Publié le 14 mars 2023

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Articles de revues sur le sujet "HERG gating"

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Zhou, QinLian, et Glenna C. L. Bett. « Modeling HERG Gating Transitions ». Biophysical Journal 100, no 3 (février 2011) : 426a. http://dx.doi.org/10.1016/j.bpj.2010.12.2521.

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Bett, Glenna C. L., Qinlian Zhou et Randall L. Rasmusson. « Models of HERG Gating ». Biophysical Journal 101, no 3 (août 2011) : 631–42. http://dx.doi.org/10.1016/j.bpj.2011.06.050.

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Smith, Paula L., et Gary Yellen. « Fast and Slow Voltage Sensor Movements in HERG Potassium Channels ». Journal of General Physiology 119, no 3 (22 février 2002) : 275–93. http://dx.doi.org/10.1085/jgp.20028534.

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HERG encodes an inwardly-rectifying potassium channel that plays an important role in repolarization of the cardiac action potential. Inward rectification of HERG channels results from rapid and voltage-dependent inactivation gating, combined with very slow activation gating. We asked whether the voltage sensor is implicated in the unusual properties of HERG gating: does the voltage sensor move slowly to account for slow activation and deactivation, or could the voltage sensor move rapidly to account for the rapid kinetics and intrinsic voltage dependence of inactivation? To probe voltage sensor movement, we used a fluorescence technique to examine conformational changes near the positively charged S4 region. Fluorescent probes attached to three different residues on the NH2-terminal end of the S4 region (E518C, E519C, and L520C) reported both fast and slow voltage-dependent changes in fluorescence. The slow changes in fluorescence correlated strongly with activation gating, suggesting that the slow activation gating of HERG results from slow voltage sensor movement. The fast changes in fluorescence showed voltage dependence and kinetics similar to inactivation gating, though these fluorescence signals were not affected by external tetraethylammonium blockade or mutations that alter inactivation. A working model with two types of voltage sensor movement is proposed as a framework for understanding HERG channel gating and the fluorescence signals.
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Hardman, Rachael M., Phillip J. Stansfeld, Sarah Dalibalta, Michael J. Sutcliffe et John S. Mitcheson. « Activation Gating of hERG Potassium Channels ». Journal of Biological Chemistry 282, no 44 (6 septembre 2007) : 31972–81. http://dx.doi.org/10.1074/jbc.m705835200.

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Zhou, Qinlian, et Glenna C. L. Bett. « Regulation of the voltage-insensitive step of HERG activation by extracellular pH ». American Journal of Physiology-Heart and Circulatory Physiology 298, no 6 (juin 2010) : H1710—H1718. http://dx.doi.org/10.1152/ajpheart.01246.2009.

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Human ether-à-go-go-related gene (HERG, Kv11.1, KCNH2) voltage-gated K+ channels dominate cardiac action potential repolarization. In addition, HERG channels play a role in neuronal and smooth cell excitability as well as cancer pathology. Extracellular pH (pHo) is modified during myocardial ischemia, inflammation, and respiratory alkalosis, so understanding the response of HERG channels to changes in pH is of clinical significance. The relationship between pHo and HERG channel gating appears complex. Acidification has previously been reported to speed, slow, or have no effect on activation. We therefore undertook comprehensive analysis of the effect of pHo on HERG channel activation. HERG channels have unique and complex activation gating characteristics with both voltage-sensitive and voltage-insensitive steps in the activation pathway. Acidosis decreased the activation rate, suppressed peak current, and altered the sigmoidicity of gating near threshold potentials. At positive voltages, where the voltage-insensitive transition is rate limiting, pHo modified the voltage-insensitive step with a pKa similar to that of histidine. Hill coefficient analysis was incompatible with a coefficient of 1 but was well described by a Hill coefficient of 4. We derived a pHo-sensitive term for a five-state Markov model of HERG channel gating. This model demonstrates the mechanism of pHo sensitivity in HERG channel activation. Our experimental data and mathematical model demonstrate that the pHo sensitivity of HERG channel activation is dominated by the pHo sensitivity of the voltage-insensitive step, in a fashion that is compatible with the presence of at least one proton-binding site on each subunit of the channel tetramer.
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Zhang, Mei, Jie Liu et Gea-Ny Tseng. « Gating Charges in the Activation and Inactivation Processes of the hERG Channel ». Journal of General Physiology 124, no 6 (15 novembre 2004) : 703–18. http://dx.doi.org/10.1085/jgp.200409119.

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The hERG channel has a relatively slow activation process but an extremely fast and voltage-sensitive inactivation process. Direct measurement of hERG's gating current (Piper, D.R., A. Varghese, M.C. Sanguinetti, and M. Tristani-Firouzi. 2003. PNAS. 100:10534–10539) reveals two kinetic components of gating charge transfer that may originate from two channel domains. This study is designed to address three questions: (1) which of the six positive charges in hERG's major voltage sensor, S4, are responsible for gating charge transfer during activation, (2) whether a negative charge in the cytoplasmic half of S2 (D466) also contributes to gating charge transfer, and (3) whether S4 serves as the sole voltage sensor for hERG inactivation. We individually mutate S4's positive charges and D466 to cysteine, and examine (a) effects of mutations on the number of equivalent gating charges transferred during activation (za) and inactivation (zi), and (b) sidedness and state dependence of accessibility of introduced cysteine side chains to a membrane-impermeable thiol-modifying reagent (MTSET). Neutralizing the outer three positive charges in S4 and D466 in S2 reduces za, and cysteine side chains introduced into these positions experience state-dependent changes in MTSET accessibility. On the other hand, neutralizing the inner three positive charges in S4 does not affect za. None of the charge mutations affect zi. We propose that the scheme of gating charge transfer during hERG's activation process is similar to that described for the Shaker channel, although hERG has less gating charge in its S4 than in Shaker. Furthermore, channel domain other than S4 contributes to gating charge involved in hERG's inactivation process.
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Hill, Adam P., Anthony Varghese, Socrates Dokos, Stefan Mann et Jamie I. Vandenberg. « Developing In Silico Descriptions Of Herg Channel Gating ». Biophysical Journal 96, no 3 (février 2009) : 191a. http://dx.doi.org/10.1016/j.bpj.2008.12.897.

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Robertson, Gail A. « hERG Subunit-Specific Contributions to Gating and Disease ». Biophysical Journal 102, no 3 (janvier 2012) : 212a. http://dx.doi.org/10.1016/j.bpj.2011.11.1157.

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Dou, Ying, Zeineb Es-Salah-Lamoureux, Ping Yu Xiong et David Fedida. « Understanding hERG Channels Gating using Voltage-Clamp Fluorimetry ». Biophysical Journal 102, no 3 (janvier 2012) : 329a—330a. http://dx.doi.org/10.1016/j.bpj.2011.11.1806.

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Kopfer, David A., Ulrike Hahn, Iris Ohmert, Gert Vriend, Olaf Pongs, Bert L. de Groot et Ulrich Zachariae. « Molecular Determinants in K+ Channel hERG Inactivation Gating ». Biophysical Journal 102, no 3 (janvier 2012) : 529a—530a. http://dx.doi.org/10.1016/j.bpj.2011.11.2894.

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Thèses sur le sujet "HERG gating"

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Thomson, Steven James. « Deactivation gating and pharmacology of hERG potassium channel ». Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/11071.

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hERG (Kv11.1) encodes the α-subunit of the potassium (K+) channel that carries IKr, an important current for repolarisation of the cardiac action potential. Alterations of hERG current, either through inherited mutations that alter gating or through drugs that block the pore, are associated with Long QT syndrome, cardiac arrhythmias and sudden death. The N-terminus has an important role in regulating deactivation, a gating process that is important for timing of the hERG current during cardiac action potentials. Removing the entire N-terminus accelerates deactivation. A crystal structure of part of the N-terminus (residues 26-135) was solved in 1998 and showed it contained a PAS domain, but it did not resolve the structure of the functionally important first 26 residues (NT 1-26). Here we present an NMR structure of residues 1-135. The structure reveals that residues 1-10 are unordered and residues 11-24 form an amphipathic helix one face of which is positively charged. Neutralising the positive charge accelerates deactivation to similar rates as if the whole of the N-terminus has been removed. Neutralising negative charge in the C-terminus also accelerates deactivation. We propose a model where the N and C-termini interact to stabilise the open state of the channel and slow deactivation. Exactly how changes in membrane voltage are transduced into movement of the activation gate is not fully understood. In hERG, the mutation V659A dramatically slows deactivation. Val659 is located in a region where hERG’s activation gate is believed to lie. From the structure of Kv2.1 it can be seen the S4-S5 linker forms a cuff around S6 where the activation gate is thought to be. Using cysteine cross-linking experiments we show that V659C interacts with E544C and Y545C in the S4-S5 linker to lock the channel in the open state. Trapping of drugs in the inner cavity of hERG has been an important model used to help explain why hERG is blocked by so many drugs and with high potency. A series of derivatives of E-4031, a well characterised high-affinity hERG blocker, were made that progressively increased the length of the molecule. Results in this thesis showed these compounds had binding kinetics completely different from E-4031 and none were trapped in the inner cavity. An alternative model of strongly state-dependent drug binding rather than drug-trapping is proposed. Together, the results in this thesis present new insights on the structural basis for deactivation gating and drug binding in hERG channels.
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Pettini, Francesco. « Molecular Dynamics simulation of the hERG channel assisting Precision Medicine in Channelopathies ». Doctoral thesis, Università di Siena, 2023. https://hdl.handle.net/11365/1227475.

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In the last two decades, a revolution in biology has shifted the traditional reductive approach to a bottom-up study of virtual models. This discipline, known as System Biology, integrates information coming from individual components, in order to predict the functioning of biological systems, with the idea that complex systems are made up of many independent components that can interact within well-structured networks changing over time, and that the functional properties of biological systems emerge as a consequence of interactions among their components. This paradigm shift is enabled by rapid advancements in technologies providing high-throughput instruments able to analyse in detail biological processes at the single molecule and single cell scale. The vast amount of data produced by these experimental techniques asks for adequate methods of analyses. The present dissertation focues on structural based methods for simulating the functioning of biological molecules, and in particular on the role of Molecular Dynamics simulations. The advantage of Molecular Dynamics simulations is that it is based on physical description of the systems, and consequently it might offer an atomistic description of the process under investigation. The first chapter of this thesis will provide an introduction on the role of Molecular Genetics and Biology in Medicine, also considering new challenges for the prediction of protein interactions and for development of Precision Medicine. In the Second Chapters, Molecular Dynamics simulations will be discussed, with an emphasis on the methods for data analysis adopted in the research projects presented in the second part of the thesis. The third Chapter will be present the main research project produced during my PhD: the study of inactivation and drug binding in the hERG potassium channel. Side project and parallel collaborations are briefly discussed in the fourth Chapter, followed by concluding remarks.
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Dalibalta, Sarah. « Human ether-a-go-go related gene (hERG) potassium channel gating and drug block ». Thesis, University of Leicester, 2008. http://hdl.handle.net/2381/29964.

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hERG encodes the a-subunit of the rapid delayed rectifier potassium current, a crucial current for normal repolarisation of the cardiac action potential. Pharmacological block of hERG is associated with arrhythmias and sudden death. Given its physiological importance, aspects of both the gating and pharmacology of this channel were investigated.;hERG has unusual gating properties characterised by slow activation and deactivation gating. The roles of conserved S6 glycines (Gly648 and Gly657) in hERG as hinges for activation gating were studied. Glycine residues impart flexibility that is thought to be conducive for channel opening. However, mutations at positions 648 and 657 altered gating in a manner consistent with a role in protein packing rather than flexibility. Deactivation gating in hERG is slow due to interactions between the amino-terminus, the voltage sensor, and the pore that stabilise the open state. The pore mutation V659A dramatically slowed channel deactivation and reduced drug block. Replacing Val659 with larger hydrophobic residues resulted in faster deactivation kinetics, but in contrast, V659G hERG was constitutively open. It was concluded that Val659 mutations influence deactivation through hydrophobic interactions with the S4-S5 linker that couples S6 to the voltage sensor. Effects on drug binding correlated with deactivation rates, indicating that Val659 mutations have allosteric rather than direct effects on drug binding.;Tyr652 is thought to be a critical residue for high affinity drug binding. However, this study showed that the contribution of Tyr652 to drug binding varied considerably among 24 compounds tested, with the majority of low affinity blockers being relatively insensitive to the Y652A mutation. Pharmacophore models generated from the results suggest that higher affinity compounds are longer than lower affinity compounds and simultaneously interact with multiple inner cavity residues. The compact structure of low affinity, Y652A-insensitive drugs permits multiple binding modes, making the compounds less reliant on interactions with Tyr652.
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Macdonald, Logan Campbell Alexander. « Gating and pore block of the human ether-à-go-go related gene (hERG) voltage-gated potassium channel (Kv11.1) ». Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62066.

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Ion channels are integral membrane proteins that form an aqueous pore through the cell lipid bilayer, and allow ions to traverse the membrane at rates approaching limits set by diffusion. Selectivity and gating differences amongst members of this protein family enable complex physiological processes such as action potentials. The diversity in ion channel selectivity and gating is endowed through structural permutations of protein structure that slightly alter factors such as the rate at which a channel activates or the width of the pore region and thus the type of ions it interacts with. This thesis investigates structural bases for the anomalous gating and drug interaction behaviour exhibited by the human ether-à-go-go related gene (hERG) voltage-gated potassium channel (VGKC). The unique gating kinetics of hERG allow it to fulfill its role as the rapid delayed rectifier potassium current of the cardiac action potential and the unique susceptibility to drug block can compromise this function. Chapter 2 describes how slow deactivation of hERG can be largely attributed to cytosolic domain interaction with channel gating, an interaction that serves to establish a mode shift of the channel gating charge, shifting the deactivation gating pathway to more hyperpolarized potentials. Chapter 3 demonstrates that an interaction between an acidic residue at the bottom of the S1 and a basic residue at the bottom of the S4 stabilizes the closed state of the channel and slows activation. Through gating currents and fluorescence experiments, we propose a model of hERG gating in which this unique interaction stabilizes an early closed state of the channel. Chapter 4 investigates the role of cation-π interactions in hERG drug block, testing the importance of the two most significant residues for drug interaction, Y652 and F656. Using unnatural amino acid mutagenesis, this final study shows that cation-π interactions do not appear to play a major role in drug interaction with the hERG pore.
Medicine, Faculty of
Anesthesiology, Pharmacology and Therapeutics, Department of
Graduate
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Ncuti, Nobera Alain-Klaus. « Evaluation of Data-Driven Gating for 68Ga-ABY-025 PET/CT in Breast Cancer Patients ». Thesis, Umeå universitet, Institutionen för fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-172663.

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Respiratory motion during PET acquisition degrades image quality. It is mainly the area around the thorax and abdomen which is affected. External devices do provide respiratory gating solutions but are time-consuming to set up on patients and may not always be available. A data-driven gating (DDG) method based on principal component analysis (PCA) was found to provide a reliable respiratory gating signal, discriminating the need for external gating systems with FDG, but it remains to be investigated how well it performs with other PET tracers. The HER2-targeting radiotracer 68Ga-ABY-025 is currently in phase 3 development and is aimed to develop methods to select breast cancer patients that benefit from HER2-targeted treatment. Hence, absolute quantification is important. Respiratory motion correction will be important for improved quantitative accuracy since many patients have metastases in the lower part of the lungs or the liver.  DDG was applied to PET/CT list mode data retrospectively using quiescent period gating. Gated images were then compared to reconstructions without gating with a matched number of coincidences. Two iterative reconstructions were evaluated, TOF OSEM (3 iterations, 16 subsets, and a 5 mm gaussian postprocessing filter) and TOF BSREM β 400. Images were evaluated for standardized uptake value (SUV) changes for well-defined lesions in thorax and abdomen where respiratory motion is prevalent. Respiratory motion was detected in a mean 2.1 bed positions per examination. DDG application resulted in a mean increase of 12.7% in SUVmax for TOF OSEM reconstruction (p=0.0156).
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Hofreiter, Anton. « Die infragenerische Gliederung der Gattung Bomarea Mirb. und die Revision der Untergattungen Sphaerine (Herb.) Baker und Wichuraea (M. Roemer) Baker (Alstroemeriaceae) ». Diss., lmu, 2003. http://nbn-resolving.de/urn:nbn:de:bvb:19-17074.

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Trudeau, Matthew. « Molecular mechanisms of gating in Herg potassium channels ». 1998. http://catalog.hathitrust.org/api/volumes/oclc/40825838.html.

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Wang, Jinling. « Amino-terminal regulations of gating in HERG potassium channels ». 2001. http://www.library.wisc.edu/databases/connect/dissertations.html.

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COSTA, FLAVIO. « Fluid behaviour in biological confinement : gating of the hERG potassium channel via molecular dynamics simulations and network analysis ». Doctoral thesis, 2023. https://hdl.handle.net/11573/1666680.

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The boundary between biological cells and the external environment is represented by a lipid membrane that does not allow the passage of polar molecules such as ions and water. However, their orchestrated movements are fundamental for the function of vital organs. For this reason, there are transmembrane proteins called as “ion channels” that forming pores on the cells allow the ion to flow through these impermeable membranes. Normally, an ion channel has three functional states: the open state that is permeable to ions, the closed state where they can not pass, and the inactivated state that is structurally similar to the open state but functionally closed. The mechanisms by which an ion channel switches from the open to the closed state and vice versa are defined as “activation” and “deactivation” respectively, while the transition from the open to the inactivated state is defined as “inactivation”. All these transitions define the so-called “gating” mechanism. The main features of the biological channels are the selectivity, the sensing and the regulation of their gating mechanism. The characterization of these properties gives the possibility to extract the basic principles to design bioinspired artificial channels that can be used, for example, to study various molecules in confined spaces and in real time by current measurements. The biomimetic channels are becoming the focus of attention for bionanotechnology because they offer greater flexibility in terms of shape and size, robustness and surface properties boosting, in this way, their fields of application. In this context, we studied the human ether-à-go-go–related gene channel (hERG, KCNH2, or Kv11.1) that is a voltage-gated potassium channel involved in the heart contraction. hERG malfunctions are associated with severe pathologies such as long QT syndrome type 2 (LQTS2) that can be due to loss-of-function mutations (congenital LQTS2) or channel blockage induced by unspecific interactions with medications (acquired LQTS2). These conditions have been described to promote arrhythmia and sudden cardiac death. Based on the protein architecture, hERG is a member of the non-domain-swapped channel family where the sensor of the channel is always connected covalently to the pore of the same subunit. The gating mechanism of these channels is still not completely characterized. Due to its importance in human health, we decided to focus on hERG gating addressing the problem with a theoretical approach based on Molecular Dynamics simulations. Using a network analysis, we microscopically identified the kinematic chain of residues that couple the sensor of the channel to the pore. In general, our results could provide the basis for studying the coupling mechanisms between sensors and pores in ion channels to explain the origin of inherited and induced channelopathies such as LQTS2.
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Hofreiter, Anton [Verfasser]. « Die infragenerische Gliederung der Gattung Bomarea Mirb. und die Revision der Untergattungen Sphaerine (Herb.) Baker und Wichuraea (M. Roemer) Baker (Alstroemeriaceae) / vorgelegt von Anton Hofreiter ». 2003. http://d-nb.info/970156103/34.

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Livres sur le sujet "HERG gating"

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Mora, Pat. Here, kitty, kitty ! = : Ven, gatita, ven ! New York : Rayo, 2008.

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Here, kitty, kitty!/ven, gatita, ven ! New York : Rayo, 2008.

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Mora, Pat. Here, kitty, kitty ! = : Ven, gatita, ven ! New York : Rayo, 2008.

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Mora, Pat. Here, kitty, kitty ! = : Ven, gatita, ven ! New York : Rayo, 2008.

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Haupt, Carl F. Gary Gatlin : Reluctant Hero. Dudley Court Press, 2019.

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Haupt, Carl. Gary Gatlin Reluctant Hero : World War 2 Trilogy-Book 1. Three Knolls Publishing, 2020.

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Haupt, Carl. Gary Gatlin Reluctant Hero : World War 2 Trilogy-Book 1. Three Knolls Publishing, 2020.

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Sabharwal, Nikant, Chee Yee Loong et Andrew Kelion. Introduction to nuclear cardiology. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199206445.003.0001.

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Introduction 2Important milestones 4Relation to other imaging modalities 6The cardiologist of the early twenty-first century takes for granted the wide range of imaging modalities at his/her disposal, but it was not always so. At the beginning of the 1970s, invasive cardiac catheterization was the only reliable cardiac imaging technique. Subsequently, nuclear cardiology investigations led the way in the non-invasive assessment of cardiac disease. Some of the principles underlying these investigations [e.g. electrocardiogram (ECG)-triggered gating] have also been of great importance in the development of other imaging modalities....
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Pedrasa, Maria. I Am a Hero and My Name Is Gavin : Writing and Drawing Journal Notebook for Boys,sketch Book for Kids, Gavin's Personalized Birthday Gift, Taccuino Gatlin for 4-12 ... Son or Nephew Happy Birthday in Your Own Way ! Independently Published, 2021.

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Chapitres de livres sur le sujet "HERG gating"

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Robertson, Gail A., Eugenia M. C. Jones et Jinling Wang. « Gating and Assembly of Heteromeric hERG1a/1b Channels Underlying I Kr in the Heart ». Dans The hERG Cardiac Potassium Channel : Structure, Function and Long QT Syndrome, 4–18. Chichester, UK : John Wiley & Sons, Ltd, 2008. http://dx.doi.org/10.1002/047002142x.ch2.

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Sanguinetti, Michael C., et Frank B. Sachse. « Structural Determinants and Biophysical Properties of hERG1 Channel Gating ». Dans Cardiac Electrophysiology : From Cell to Bedside, 113–21. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-323-44733-1.00012-2.

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C. Sanguinetti, Michael, Martin Tristani-Firouzi et Frank B. Sachse. « Structural Determinants and Biophysical Properties of hERG1 Channel Gating ». Dans Cardiac Electrophysiology : From Cell to Bedside, 121–28. Elsevier, 2014. http://dx.doi.org/10.1016/b978-1-4557-2856-5.00012-1.

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N., Manjunatha K., Raghu N. et Kiran B. « Evalutation of Turbo Decoder Performance Through Software Reference Model ». Dans Advances in Wireless Technologies and Telecommunication, 179–97. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-6988-7.ch011.

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Turbo encoder and decoder are two important blocks of long-term evolution (LTE) systems, as they address the data encoding and decoding in a communication system. In recent years, the wireless communication has advanced to suit the user needs. The power optimization can be achieved by proposing early termination of decoding iteration where the number of iterations is made adjustable which stops the decoding as it finishes the process. Clock gating technique is used at the RTL level to avoid the unnecessary clock given to sequential circuits; here clock supplies are a major source of power dissipation. The performance of a system is affected due to the numbers of parameters, including channel noise, type of decoding and encoding techniques, type of interleaver, number of iterations, and frame length on the Matlab Simulink platform. A software reference model for turbo encoder and decoder are modeled using MATLAB Simulink. Performance of the proposed model is estimated and analyzed on various parameters like frame length, number of iterations, and channel noise.
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Dyb, Evelyn. « Bostedsløse, uteliggere og tiggere – konstruksjon av «verdige trengende» og «de andre» ». Dans Presse, profesjon og politikk : Festskrift til Paul Bjerke, 237–58. Cappelen Damm Akademisk/NOASP, 2022. http://dx.doi.org/10.23865/noasp.169.ch10.

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I løpet av to tiår er betegnelser som løsgjenger, hjemløs og uteligger erstattet av begrepet bostedsløs i forskning, offentlige dokumenter og til dels i mer uformelle sammenhenger. Begrepet bostedsløs markerer at problemet dreier seg om fravær av bolig, selv om andre merkelapper for sosiale avvik, som historisk har fulgt denne gruppa, fremdeles henger ved. Begrepsendringen, sammen med en sosial vending i boligpolitikken fra generell til sosial boligpolitikk, bidro til at bostedsløse har fått, eller har nærmet seg, en posisjon som «verdige trengende», de som moralsk sett har rett til hjelp. I løpet av denne perioden ble en nye gruppe, betegnet som fattige tilreisende og «rumenske tiggere», synlige i gatene. Denne gruppa fattige tilreisende lever som bostedsløse, men de er ikke regnet som del av populasjonen av bostedsløse her i landet. Kapittelet undersøker om og eventuelt hvordan massemediene representert ved riks- og regionavisene er med på å forme ideen om våre egne bostedsløse som verdige trengende versus ideen om fattige tilreisende, som «de andre» utenforstående. Pressa er i hovedsak positiv eller nøytral i dekningen av bostedsløshet og tigging, men gjennom innrammingen (framing) bidrar avisene til å forme og opprettholde dikotomien mellom «våre bostedsløse» og «de andre».
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Actes de conférences sur le sujet "HERG gating"

1

Fittinghoff, David N., Kenneth W. DeLong, Rick Trebino et Celso L. Ladera. « Noise in Frequency-Resolved-Optical-Gating Measurements of Ultrashort Laser Pulses ». Dans Signal Recovery and Synthesis. Washington, D.C. : Optica Publishing Group, 1995. http://dx.doi.org/10.1364/srs.1995.rtud1.

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Frequency-resolved optical gating[1, 2] (FROG) is a technique that uses a phase-retrieval algorithm to obtain the intensity, I(t), and phase, ϕ(t), from a measured spectrogram of the pulse. Previous simulations have shown that, for noise-free data, the algorithm retrieves the correct intensity and phase for all pulses attempted, including those with complex intensity and phase structure. In practice, however, noise is present in actual FROG traces, and here we discuss the effects of noise on FROG and image-processing techniques to improve the retrieval.
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Fittinghoff, David N., Marco A. Krumbügel, John N. Sweetser, Rick Trebino et Thomas Tsang. « Measuring Weak Laser Pulses Using Frequency-Resolved Optical Gating ». Dans Nonlinear Optics : Materials, Fundamentals and Applications. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/nlo.1996.nthd.2.

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Frequency-Resolved Optical Gating [1] (FROG) measurements based on polarization gating [2] (PG FROG), self diffraction [3] (SD FROG), and second-harmonic generation [4] (SHG FROG) have been used successfully to measure ultrashort laser pulses with spatially uniform temporal pulse shape and phase with durations from 9 fs to 2 ps and with wavelengths from the ultraviolet to the near infrared. Temporal Analysis by Dispersing a Pair of Light E-fields [5] (TADPOLE), a combination of FROG and spectral interferometry, has been used to measure pulse trains with average pulse energies of 42 zeptojoules (42 × 10-21 J). None of these techniques, however, has proved capable of measuring the pulses from a Ti:sapphire laser without a temporal ambiguity or an amplified reference pulse. The difficulty lies in the fact that the pulses from such oscillators are too weak for PG or SD FROG, and SHG FROG has a time-reversal ambiguity due to the symmetry of the second-harmonic signal in time. TADPOLE, while capable of measuring extremely weak pulses, uses FROG to measure a reference pulse and thus has the same restrictions Here we use surface third-harmonic generation (THG) to make an unambiguous measurement of the intensity and phase of pulses from a Ti:sapphire oscillator. In addition, we describe a new method for using TADPOLE for measuring ultrashort laser pulse fields that vary arbitrarily in time and in space.
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Zhang, Wei, Qun He, Benjamin Lopez, Jianfang Hu, Anirban Kundu, Michelle C. Andraza, Alissa R. Kerner, Gregory H. Schreiber, H. Michael Shepard et Gregory I. Frost. « Abstract PO074 : Logic-gating HER2 CAR-T to the tumor microenvironment mitigates on-target, off-tumor toxicity without compromising cytotoxicity against HER2-over-expressing tumors ». Dans Abstracts : AACR Virtual Special Conference : Tumor Immunology and Immunotherapy ; October 19-20, 2020. American Association for Cancer Research, 2021. http://dx.doi.org/10.1158/2326-6074.tumimm20-po074.

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4

Boone, C., M. Fuest, K. Wellmerling et S. Prakash. « Effect of Time Dependent Excitation Signals on Gating in Nanofluidic Channels ». Dans ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53038.

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Nanofluidic field effect devices feature a gate electrode embedded in the nanochannel wall. The gate electrode creates local variation in the electric field allowing active, tunable control of ionic transport. Tunable control over ionic transport through nanofluidic networks is essential for applications including artificial ion channels, ion pumps, ion separation, and biosensing. Using DC excitation at the gate, experiments have demonstrated multiple current states in the nanochannel, including the ability to switch off the measured current; however, experimental evaluation of transient signals at the gate electrode has not been explored. Modeling results have shown ion transport at the nanoscale has known time scales for diffusion, electromigration, and convection. This supports the evidence detailed here that use of a time-dependent signal to create local perturbation in the electric field can be used for systematic manipulation of ionic transport in nanochannels. In this report, sinusoidal waveforms of various frequencies were compared against DC excitation on the gate electrode. The ionic transport was quantified by measuring the current through the nanochannels as a function of applied axial and gate potentials. It was found that time varying signals have a higher degree of modulation than a VRMS matched DC signal.
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Kane, Daniel J., A. J. Taylor et Rick Trebino. « Measurement of the intensity and phase of a femtosecond UV laser pulse in a single shot ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.fz2.

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We report and demonstrate what is to our knowledge the first measurement of the intensity and phase of a single femtosecond UV pulse. The technique, which we call frequency resolved optical gating (FROG), is inexpensive, easy to implement, and provides an output that graphically displays the instantaneous frequency vs. time of the pulse. It uses the well-known polarization-spectroscopy optical-gate arrangement with an instantaneously responding χ(3) sample medium such as quartz. Here, however, the pulse gates itself. The signal spectrum is then measured as a function of delay between the two input pulses. Because the gate is shorter than the input pulse, it reveals, for a given delay, the frequency of a particular temporal component of the ultrashort pulse. For reasonably well-behaved pulses, the output plot of intensity vs. frequency and delay graphically displays the pulse instantaneous frequency vs. time.
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Fittinghoff, David N., Jason L. Bowie, John N. Sweetser, Richard T. Jennings, Marco A. Krumbügel, Kenneth W. DeLong, Rick Trebino et Ian A. Walmsley. « Recent Developments in Frequency-Resolved Optical Gating : Measurement of Ultraweak Ultrashort Pulses ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.fe.15.

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Frequency-Resolved Optical Gating (FROG) [1] has been used to fully characterize ultrashort laser pulses over a wide range of wavelengths, pulse lengths, pulse energies, time-bandwidth products, and pulse repetition rates. There are, however, many situations in which the sensitivity of FROG is inadequate. For example, ultrafast spectroscopy experiments that generate signal pulses of sub-picojoule energies offer much additional information about the medium if the weak signal pulse could be better characterized. [2] In this work, we combine FROG with Spectral Interferometry (SI) [3] to yield a simple method for measuring nearly arbitrarily weak pulses. Here, FROG is used to characterize a reference pulse, and SI sensitively measures the phase difference between the reference pulse and an unknown pulse, thus yielding the full intensity and phase of the unknown, potentially ultraweak, pulse. We demonstrate this method on a pulse train containing 40 zeptojoules (zJ) of energy, or about 1/5 of a photon per pulse (See Figs. 1-3). This method is quite general because ultraweak ultrashort pulses do not exist by themselves; an optical nonlinearity is required to make ultrashort pulses, which are then strong enough to be measured with FROG and hence act as reference pulses. Because this method uses FROG, and because ST involves simply measuring the spectrum of a pair of pulses, we call it Temporal Analysis by Dispersing a Pair Of Light E-fields (TADPOLE).
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Snow, P. A., I. E. Day, R. V. Penty, Z. Jiang, I. H. White, D. A. O. Davies, M. A. Fisher et M. J. Adams. « Low power all-optical switch in a passive InGaAsP multiple quantum well waveguide ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cfg2.

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In recent years there has been much interest in all-optical switching in nonlinear semi-conductor waveguides, because of their potential for high-speed switching. To date much of the published work on all optical switching at wavelengths around 1.55 μm has concentrated on utilising the nonresonant Kerr nonlinearity in GaAs/AlGaAs structures.1 Whilst these devices exhibit switching times of approximately 100 fs, they require peak optical powers of the order of a hundred watts to operate. This makes them unattractive for telecommunications applications due to the high powers required. We demonstrate here the use of the resonant bandfilling nonlinearity in an InGaAsP/InGaAsP Multiple Quantum Well (MQW) waveguide due to photo generated carriers to obtain switching at pulse powers, which can readily be obtained from an erbium amplified diode laser source. In order to produce gating a polarisation rotation gate was used, which relies on an asymmetry in the nonlinear refraction on the principle axes of the waveguide.2 It has recently been shown that this nonlinearity can have a relaxation time as low as 18 ps.3
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Nelson, L. E., S. B. Fleischer, E. P. Ippen et H. A. Haus. « High-power and Frequency-doubled Stretched-Pulse Fiber Laser ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.tua.4.

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Stretched-pulse additive-pulse mode-locked (SP-APM) fiber lasers generate ultra-short pulses (100 fsec) with energies comparable to those of color-center lasers [1]. By using the APM rejection port as the output port, pulse energies of over 2 nJ have been achieved with average powers of > 90 mW [2]. Here we report that frequency-doubling of these pulses results in high conversion efficiencies and transform-limited pulses of up to 200 pJ at 775 nm. When operating the SP-APM laser to optimize the frequency-doubled power, the fundamental pulses tend to have excess energy in the pulse wings and larger time-bandwidth products than when the SP-APM laser is optimized for fundamental pulse width. In order to better characterize both the fundamental and frequency-doubled pulses, we used frequency-resolved optical gating (FROG) which allows the direct determination of the intensity and phase of an ultrashort pulse [3,4]. Results indicate that the frequency-doubled SP-APM laser is a possible, inexpensive and compact, replacement for the argon-pumped Ti:Sapphire laser as a seeding source for regenerative amplifiers.
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9

Najem, Joseph S., Sergei Sukharev et Donald J. Leo. « The Effect of Transmembrane Potential on the Gating of MscL Channels in Droplet Interface Bilayers ». Dans ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9150.

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The ability to functionalize droplet interface bilayers (DIBs) with the MscL channel and its mutants has been demonstrated. In previous work, the V23T gain of function mutant of MscL produced consistent activation when harmonic axial compressions were applied to the aqueous droplets supporting the lipid bilayer, where the channels settle. The deformation of the droplets results, at maximum compression, in an increase in surface area, and thus an increase in tension at the water-lipid-oil interface. This increase in monolayer tension was found to be the product of the relative change in surface area of each of the droplets and the compressibility modulus of the DPhPC monolayer (∼120 mN/m). The tension increase at the water-lipid-oil interface almost doubles to make up the increase in tension in the bilayer interface, resulting in activation of the incorporated MscL channels. However, it was found that the application of a relatively high transmembrane potential (∼100 mV), from an external power source, is a requirement for the activation of the V23T-MscL channels. Here, we investigate and analyze the impact of transmembrane potential on the activity of MscL channels in both a droplet interface bilayer system and E. coli spheroplast via patch-clamp. We demonstrate that the channels became more susceptible to gating upon the application of a negative potential, compared to when a positive potential is applied, proving their sensitivity to voltage polarity.
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Pare, C., et W. J. Firth. « Instabilities of counterpropagating waves in a Kerrlike medium ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.wl49.

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Over the last few years, different types of instability associated with counterpropa- gating waves in a bulk Kerrlike medium have been discovered.1−3 Considering a finite response time for the nonlinearity, Silberberg and Bar-Joseph1 first predicted temporal oscillations and chaos at high intensity. Taking into account the extra degree of freedom due to the polarization state of the fields, Gaeta et al.2 have then shown that this polarization state is actually unstable above some intensity threshold. Finally, we have recently shown, using a linear stability analysis, that transverse instabilities also occur above another intensity threshold and an analytical expression has been given for this threshold.3 Here, we present a simple explicit analytical expression (in terms of the length of the medium and the tensor components of the susceptibility) for the polarization instability threshold in the case of equal beam intensities, considering only the first bifurcation. This instability can then be interpreted as a four-wave mixing self-oscillation. This result allows us to compare the different instability thresholds associated with contra- directional waves. It is shown that the transverse instability should dominate, not excluding however the possible onset of polarization instability at higher intensity.
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