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Journal articles on the topic "Affinity sensor"
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Qian, Xiang, Xiaowei Niu, and Karl L. Magleby. "Intra- and Intersubunit Cooperativity in Activation of BK Channels by Ca2+." Journal of General Physiology 128, no. 4 (September 25, 2006): 389–404. http://dx.doi.org/10.1085/jgp.200609486.
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The activation of BK channels by Ca2+ is highly cooperative, with small changes in intracellular Ca2+ concentration having large effects on open probability (Po). Here we examine the mechanism of cooperative activation of BK channels by Ca2+. Each of the four subunits of BK channels has a large intracellular COOH terminus with two different high-affinity Ca2+ sensors: an RCK1 sensor (D362/D367) located on the RCK1 (regulator of conductance of K+) domain and a Ca-bowl sensor located on or after the RCK2 domain. To determine interactions among these Ca2+ sensors, we examine channels with eight different configurations of functional high-affinity Ca2+ sensors on the four subunits. We find that the RCK1 sensor and Ca bowl contribute about equally to Ca2+ activation of the channel when there is only one high-affinity Ca2+ sensor per subunit. We also find that an RCK1 sensor and a Ca bowl on the same subunit are much more effective in increasing Po than when they are on different subunits, indicating positive intrasubunit cooperativity. If it is assumed that BK channels have a gating ring similar to MthK channels with alternating RCK1 and RCK2 domains and that the Ca2+ sensors act at the flexible (rather than fixed) interfaces between RCK domains, then a comparison of the distribution of Ca2+ sensors with the observed responses suggest that the interface between RCK1 and RCK2 domains on the same subunit is flexible. On this basis, intrasubunit cooperativity arises because two high-affinity Ca2+ sensors acting across a flexible interface are more effective in opening the channel than when acting at separate interfaces. An allosteric model incorporating intrasubunit cooperativity nested within intersubunit cooperativity could approximate the Po vs. Ca2+ response for eight possible subunit configurations of the high-affinity Ca2+ sensors as well as for three additional configurations from a previous study.
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Tlili, Chaker, Sushmee Badhulika, Thien-Toan Tran, Ilkeun Lee, and Ashok Mulchandani. "Affinity chemiresistor sensor for sugars." Talanta 128 (October 2014): 473–79. http://dx.doi.org/10.1016/j.talanta.2014.05.055.
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Glad, Cristina, Karin Sjödin, and Bo Mattiasson. "Streaming potential—a general affinity sensor." Biosensors 2, no. 2 (January 1986): 89–100. http://dx.doi.org/10.1016/0265-928x(86)80012-8.
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Huang, Xian, Charles Leduc, Yann Ravussin, Siqi Li, Erin Davis, Bing Song, Dachao Li, et al. "A differential dielectric affinity glucose sensor." Lab Chip 14, no. 2 (2014): 294–301. http://dx.doi.org/10.1039/c3lc51026c.
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Labouesse, Marie A., Reto B. Cola, and Tommaso Patriarchi. "GPCR-Based Dopamine Sensors—A Detailed Guide to Inform Sensor Choice for In Vivo Imaging." International Journal of Molecular Sciences 21, no. 21 (October 28, 2020): 8048. http://dx.doi.org/10.3390/ijms21218048.
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Understanding how dopamine (DA) encodes behavior depends on technologies that can reliably monitor DA release in freely-behaving animals. Recently, red and green genetically encoded sensors for DA (dLight, GRAB-DA) were developed and now provide the ability to track release dynamics at a subsecond resolution, with submicromolar affinity and high molecular specificity. Combined with rapid developments in in vivo imaging, these sensors have the potential to transform the field of DA sensing and DA-based drug discovery. When implementing these tools in the laboratory, it is important to consider there is not a ‘one-size-fits-all’ sensor. Sensor properties, most importantly their affinity and dynamic range, must be carefully chosen to match local DA levels. Molecular specificity, sensor kinetics, spectral properties, brightness, sensor scaffold and pharmacology can further influence sensor choice depending on the experimental question. In this review, we use DA as an example; we briefly summarize old and new techniques to monitor DA release, including DA biosensors. We then outline a map of DA heterogeneity across the brain and provide a guide for optimal sensor choice and implementation based on local DA levels and other experimental parameters. Altogether this review should act as a tool to guide DA sensor choice for end-users.
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Efremenko, Yulia, and Vladimir M. Mirsky. "Electrical Control of the Receptor Affinity." Engineering Proceedings 6, no. 1 (May 17, 2021): 3. http://dx.doi.org/10.3390/i3s2021dresden-10084.
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A concept of virtual sensor array based on an electrically controlled variation of affinity properties of the receptor layer was realized on the base of integrated electrochemical chemotransistor containing conducting polymer as the receptor layer. Electrical control of the redox-state of the polymer (polyaniline) was performed in a five-electrode configuration with four electrodes for conductivity measurements and Ag/AgCl reference electrode integrated on the same glass chip. An ionic liquid provided an electrical connection between the reference electrode and chemosensitive material. Conductivity measurements demonstrated potential controlled electrochemical conversions of the receptor material between different redox states. The binding of trimethylamine at three different potentials corresponding to these states was studied. The results demonstrated that both kinetic- and equilibrium-binding properties of the receptor are controlled by the electrical potential, thus providing a possibility to form a virtual sensor array using only a single sensing element. The concept was applied for monitoring fish headspace. Using three characteristics of the sensor response measured at three different redox states of the same sensor material, we obtained signals from a virtual sensor array consisting of nine chemosensitive elements. The sensor displays systematic changes of its nine signals during fish degradation. This approach can be applied also for the electrical control of the affinity of immunoglobulins. Development of new materials with electrically controlled affinity is in progress.
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Yin, Ruixue, Jizhong Xin, Dasheng Yang, Yang Gao, Hongbo Zhang, Zhiqin Qian, and Wenjun Zhang. "High-Linearity Hydrogel-Based Capacitive Sensor Based on Con A–Sugar Affinity and Low-Melting-Point Metal." Polymers 14, no. 20 (October 13, 2022): 4302. http://dx.doi.org/10.3390/polym14204302.
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Continuous glucose monitoring (CGM) plays an important role in the treatment of diabetes. Affinity sensing based on the principle of reversible binding to glucose does not produce intermediates, and the specificity of concanavalin A (Con A) to glucose molecules helps to improve the anti-interference performance and long-term stability of CGM sensors. However, these affinity glucose sensors have some limitations in their linearity with a large detection range, and stable attachment of hydrogels to sensor electrodes is also challenging. In this study, a capacitive glucose sensor with high linearity and a wide detection range was proposed based on a glucose-responsive DexG–Con A hydrogel and a serpentine coplanar electrode made from a low-melting-point metal. The results show that within the glucose concentration range of 0–20 mM, the sensor can achieve high linearity (R2 = 0.94), with a sensitivity of 33.3 pF mM−1, and even with the larger glucose concentration range of 0–30 mM the sensor can achieve good linearity (R2 = 0.84). The sensor also shows resistance to disturbances of small molecules, good reversibility, and long-term stability. Due to its low cost, wide detection range, high linearity, good sensitivity, and biocompatibility, the sensor is expected to be used in the field of continuous monitoring of blood glucose.
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Ramanavicius, Simonas, Arunas Jagminas, and Arunas Ramanavicius. "Advances in Molecularly Imprinted Polymers Based Affinity Sensors (Review)." Polymers 13, no. 6 (March 22, 2021): 974. http://dx.doi.org/10.3390/polym13060974.
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Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as “stealth coatings” in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.
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Tuccitto, Nunzio, Luca Spitaleri, Giovanni Li Destri, Andrea Pappalardo, Antonino Gulino, and Giuseppe Trusso Sfrazzetto. "Supramolecular Sensing of a Chemical Warfare Agents Simulant by Functionalized Carbon Nanoparticles." Molecules 25, no. 23 (December 4, 2020): 5731. http://dx.doi.org/10.3390/molecules25235731.
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Real-time sensing of chemical warfare agents by optical sensors is today a crucial target to prevent terroristic attacks by chemical weapons. Here the synthesis, characterization and detection properties of a new sensor, based on covalently functionalized carbon nanoparticles, are reported. This nanosensor exploits noncovalent interactions, in particular hydrogen bonds, to detect DMMP, a simulant of nerve agents. The nanostructure of the sensor combined with the supramolecular sensing approach leads to high binding constant affinity, high selectivity and the possibility to reuse the sensor.
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Brown, Victoria, Jessica A. Sexton, and Mark Johnston. "A Glucose Sensor in Candida albicans." Eukaryotic Cell 5, no. 10 (October 2006): 1726–37. http://dx.doi.org/10.1128/ec.00186-06.
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ABSTRACT The Hgt4 protein of Candida albicans (orf19.5962) is orthologous to the Snf3 and Rgt2 glucose sensors of Saccharomyces cerevisiae that govern sugar acquisition by regulating the expression of genes encoding hexose transporters. We found that HGT4 is required for glucose induction of the expression of HGT12, HXT10, and HGT7, which encode apparent hexose transporters in C. albicans. An hgt4Δ mutant is defective for growth on fermentable sugars, which is consistent with the idea that Hgt4 is a sensor of glucose and similar sugars. Hgt4 appears to be sensitive to glucose levels similar to those in human serum (∼5 mM). HGT4 expression is repressed by high levels of glucose, which is consistent with the idea that it encodes a high-affinity sugar sensor. Glucose sensing through Hgt4 affects the yeast-to-hyphal morphological switch of C. albicans cells: hgt4Δ mutants are hypofilamented, and a constitutively signaling form of Hgt4 confers hyperfilamentation of cells. The hgt4Δ mutant is less virulent than wild-type cells in a mouse model of disseminated candidiasis. These results suggest that Hgt4 is a high-affinity glucose sensor that contributes to the virulence of C. albicans.
Dissertations / Theses on the topic "Affinity sensor"
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Heurich, Meike. "Development of an affinity sensor for ochratoxin A." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/2634.
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Ochratoxin A is a contaminant in wine and known to be immunosuppressive and possibly carcinogenic. Therefore, the development of a rapid and sensitive method for field analysis is required for risk assessment and management. The work presented in this thesis reports the construction of a sensor platform capable of fulfilling these requirements. As a sensor platform, screen-printed thick film electrodes and microelectrodes on a silicone support were investigated for sensor development. As biological recognition elements, an antibody specifically binding ochratoxin A and a peptide receptor that was designed using computational modelling were examined. A disposable immunosensor for ochratoxin A was developed based on screen-printing technology. An indirect competitive immunoassay format was used on bare screen printed gold electrode (SPGE). The performance of this sensor was compared to carboxmethylated dextran (CMD) modified SPGE. Detection was performed by chronoamperometry monitoring the reaction of tetramethylbenzidine and hydrogen peroxide catalysed by horseradish peroxidase. The SPGE-based immunosensor achieved a detection limit of 100 ng L-1 and the CMD-modified SPGE immunosensor 10 ng L-1. The latter has been used for ochratoxin A determination in wine samples and was validated against standard HPLC and a commercial immunoassay test kit. Wine sample analysis involved the sample pre-treatment using immunoaffinity chromatography, electrochemical wine component characterisation and interference control. The immunosensor format was transferred to a gold microelectrode array based on a silicone support for the purpose of signal sensitivity enhancement and miniaturisation in the prospect of field analysis. Preliminary data showed the characterisation of the microelectrode array immunosensor construction and characterisation. Further optimisation is needed to establish a calibration curve with the required sensitivity. The second part of the work comprised the design of a peptide receptor for ochratoxin A using computational methods by screening de novo designed peptide libraries. An octapeptide (CSIVEDGL) and a 13-peptide (GPAGIDGPAGIRC) were selected for synthesis and affinity characterised for ochratoxin A recognition using a surface plasmon resonance biosensor (BiacoreTM). The peptide receptors showed good sensitivity for ochratoxin A of 10 μg L-1. Preliminary affinity characterisation resulted in KA = 63 mM-1 for the 13-mer peptide and KA = 84 mM-1 for the octapeptide, which appears to be binding with higher strength to ochratoxin A. The affinity values correspond to the binding score (binding energy) calculated by computational modelling. This work shows the potential of designing peptide receptors for small molecules (e.g. ochratoxin A) and suggests their application in affinity sensors for detecting ochratoxin A contamination.
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Lotierzo, Manuela. "Biological and artificial receptors in affinity sensor for water toxins detection." Thesis, Cranfield University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274040.
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Kröger, Silke. "A disposable electrochemical affinity sensor for 2,4-D in soil extracts." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299055.
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Parker, C. "Development of an affinity sensor for the detection of aflatoxin M1 in milk." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/2854.
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Much research has been done on aflatoxins since their discovery in the 1960’s where it was concluded that aflatoxins have carcinogenic, mutagenic, teratogenic and immunosuppressive properties. Aflatoxin M1 exists in milk and since milk is a major component of the diet of infants, the maximum permissible limit set by the EU is 50 parts per trillion (ng L -1 ). Current methods of analysis for aflatoxin M1 is primarily based around techniques such as HPLC and TLC which require extensively trained operators and equipped laboratories. Using antibodies as receptors in an enzyme linked immunosorbent assay (ELISA), the analysis costs can be reduced and simplified, however, an equipped laboratory is still required. Hence there is a need for a low cost, rapid, portable instrument which is easy to use at the point of source for the detection of aflatoxin M1. This thesis describes the development of affinity sensors to meet these requirements. Firstly the design and optimisation of an ELISA method was carried out, utilising a commercially sourced monoclonal antibody. Once the antibodies suitability for sensing aflatoxin M1 was determined the antibody was successfully employed as the receptor for a screen printed HRP/TMB based immunosensor. Upon the analysis of milk it was observed that milk caused extensive interference and through a series of chemical extractions the interference was attributed to whey proteins in the milk with suspicion towards a- lactalbumin. A simple pre-treatment technique of adding calcium chloride was performed and the interference from the whey proteins was removed. The resulting immunosensor achieved a sensitivity of 39 ng L -1 (Figure 3.26), however, poor reproducibility was observed due to the screen printed electrode production (%CV = 21% variance for screen printed electrode production). Gold cell on a chip microelectrode arrays were used to replace the screen printed electrodes and the successful covalent attachment of the antibody to the microelectrode array through PDITC cross linking compound was monitored using atomic force microscopy and scanning electron microscopy. It was shown that the majority of the antibodies during immobilisation orientate in a ‘side on’ orientation and therefore a cheap capture polyclonal antibody was first immobilised before the addition of the sensing anti-aflatoxin M1 monoclonal antibody. Using the microelectrode array an improvement of the sensitivity as well as a reduction of the milk interference was shown. Sensitivity was improved to 8 ng L -1 in milk (Figure 4.23). Further work was performed to substitute the fragile antibody used in the sensing layer for a robust synthetic peptide receptor. Initially a virtual library of synthetic peptides was created using de novo design techniques in silico. Further computational techniques were performed to determine the best peptide from the library. This peptide had a sequence of PVGPRP. From literature a peptide (LLAR) was reported with affinity for aflatoxin B1. This sequence along with the de novo design peptide was synthesised and tested using a host of techniques and immobilisation chemistries such as optical waveguide lightmode spectroscopy (OWLS), BIAcore and enzymatic techniques using EDC/NHS, glutaraldehyde and BS 3 cross linking methods. The affinity of both peptides to aflatoxin M1 was demonstrated however further work is required to quantify the affinity and to incorporate the peptides into the microelectrode array.
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Florea, Anca Stefana. "Electrochemical affinity sensors for biomedical, food and environmental applications." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10126/document.
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Les capteurs électrochimiques sont des outils pour la détection fiable, peu coûteux, avec une haute sensibilité et sélectivité, pour la détermination des composés biologiques et chimiques dans les domaines du diagnostic clinique, l'environnement et l'industrie alimentaire. Particulièrement, les Immunocapteurs, alliant une très grande spécificité. Également des nouveaux techniques produisent des résultats similaires, par exemple, les capteurs basés sur la technique des Polymères à empreinte moléculaire, la quelle produise des récepteurs artificiels. La technique devient très important dans les sciences bioanalytiques parce qu'il porte des avantages inhérents sur les récepteurs naturels: une grande stabilité dans des diffèrent environnement et conditions, également comptent avec une grande flexibilité dans la conception, une large gamme de molécules peuvent être utilisées. L'objectif du travail présenté ici est de développer des capteurs électrochimiques avec une très grande affinité et spécificité pour une analyte. Les quelles comprennent des applications très divers comme dans la protection de l'environnement, la sécurité alimentaire et le domaine biomédical. La première partie de la thèse présent l'état actuel de la conception et techniques de fabrication des biocapteurs. Ensuite, les aspects généraux des immuno capteurs électrochimiques et capteurs base sur des aptamères sont présentés ici, ainsi que plusieurs exemples rapportés dans la littérature pour la détection de marqueurs biologiques du cancer. Les avantages de l'intégration nanomatériaux dans les dispositifs de détection sont présentés. Ensuite, plusieurs aspects sur la technique des Polymères à empreinte moléculaire sont introduits. La partie personnelle de contribution est structuré en trois chapitres: en premier temps la méthodologie et les résultats obtenus pour le développement de deux essais biologiques pour la détection du marqueur tumoral Mucinl. Le premier chapitre est dédié sur un capteur à base de billes magnétiques, dans le deuxième chapitre une capteur aptamère base sur des nanoparticules d'or sans aucun marquage et finalement un capteur basée sur la technique des Polymères à empreinte moléculaire, cette protocole a été appliqué pour la détection d'explosifs, des médicaments, des hormones et les pesticidesElectrochemical sensors provide reliable and inexpensive tools for the determination of biological and chemical compounds with high sensitivity and selectivity, in the fields of clinical diagnosis, environment protection and food industry. Immunosensors hold particular promise, combining the high specificity of immuno- reactions with the sensitivity of electrochemical methods. Artificial receptors based on molecularly imprinted technique attracted considerable attention in bioanalytical sciences due to inherent advantages over natural receptors, such as high stability in harsh conditions and freedom of molecular design towards a wide range of molecules. The aim of the thesis presented here was to develop electrochemical affinity sensors based on various recognition receptors for environment monitoring, food safety and biomedical field. The first part of the thesis reviews the current state of knowledge in these fields. General aspects of electrochemical immuno- and apta-sensors are presented herein, together with several examples reported in the literature for the detection of cancer biomarkers. The advantages of integrating nanomaterials in sensing devices are then presented. At last, several aspects of the molecularly imprinted polymers are introduced. The personal contribution part is structured in three chapters, that include the methodology and results obtained for the development of biosensors for the detection of Mucinl tumor marker, the first chapter being focused on bioassays based on magnetic beads and second chapter on a label-free aptasensor based on gold nanoparticles, and finally, a third chapter dedicated to the molecularly imprinted-based sensors for the detection of explosives, drugs, hormones and pesticides
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Zuo, Ziwei. "Development of an Optical Fiber Biosensor with Nanoscale Self-Assembled Affinity Layer." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54590.
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Optical sensor systems that integrate Long-Period-Gratings (LPG) as the detection arm have been proven to be highly sensitive and reliable in many applications. With increasing public recognition of threats from bacteria-induced diseases and their potential outbreak among densely populated communities, an intrinsic, low-cost biosensor device that can perform quick and precise identification of the infection type is in high demand to respond to such challenging situations and control the damage those diseases could possibly cause.
This dissertation describes the development of a biosensor platform that utilizes polymer thin films, known as ionic self-assembled multilayer (ISAM) films, to be the sensitivity- enhancing medium between an LPG fiber and specific, recognition layer. With the aid of cross- linking reactions, monoclonal antibodies (IgG) or DNA probes are immobilized onto the surface of the ISAM-coated fiber, which form the core component of the biosensor.
By immersing such biosensor fiber into a sample suspension, the immobilized antibody molecules will bind the specific antigen and capture the target cells or cell fragments onto the surface of the fiber sensor, resulting in increasing the average thickness of the fiber cladding and changing the refractive index of the cladding. This change occurring at the surface of the fiber results in a decrease of optical power emerging from the LPG section of the fiber. By comparing the transmitted optical power before and after applying the sample suspension, we are able to determine whether or not certain bacterial species have attached to the surface of the fiber, and as a consequence, we are able to determine whether or not the solution contains the targeted bacteria.
This platform has the potential for detection of a wide range of bacteria types. In our study, we have primarily investigated the sensitivity and specificity of the biosensor to methicillin- resistant Staphlococcus aureus (MRSA). The data we obtained have shown a sensitive threshold at as low as 102 cfu/ml with pure culture samples. A typical MRSA antibody-based biosensor assay with MRSA sample at this concentration has shown optical power reduction of 21.78%. In a detailed study involving twenty-six bacterial strains possessing the PBP2a protein that enables antibiotic resistance and sixteen strains that do not, the biosensor system was able to correctly identify every sample in pure culture samples at concentration of 104 cfu/ml. Further studies have also been conducted on infected mouse tissues and clinical swab samples from human ears, noses, and skin, and in each case, the system was in full agreement with the results of standard culture tests. However, the system is not yet able to correctly distinguish MRSA and non-MRSA infections in clinical swab samples taken from infected patient wounds. It is proposed that nonspecific binding due to insufficient blocking methods is the key issue.
Other bacterial strains, such as Brucella and Francisella tularensis have also been studied using a similar biosensor platform with DNA probes and antibodies, respectively, and the outcomes are also promising. The Brucella DNA biosensor is able to reflect the existence of 3 Brucella strains at 100 cfu/ml with an average of 12.2% signal reduction, while negative control samples at 106cfu/ml generate an average signal reduction of -2.1%. Similarly, the F. tularensis antibodies biosensor has shown a 25.6% signal reduction to LVS strain samples at 100 cfu/ml, while for negative control samples at the same concentration, it only produces a signal reduction of 0.05%. In general, this biosensor platform has demonstrated the potential of detecting a wide range of bacteria in a rapid and relatively inexpensive manner.Ph. D.
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Gandar, Aude. "Échantillonnage et détection des filtres solaires, nouveaux polluants des eaux du littoral méditerranéen." Electronic Thesis or Diss., Perpignan, 2023. http://www.theses.fr/2023PERP0008.
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Les filtres UV font partie des contaminants émergents portant un risque pour les environnements aquatiques. La quantification de ces molécules utilise généralement des techniques chromatographiques. Une méthode utilisant la spectroélectrochimie a été développée, celle-ci se base sur l’utilisation combinée d’une méthode électrochimique, la chronoampérométrie et la spectrophotométrie UV. Suite à l’application d’un potentiel oxydant, certains filtres UV voient leur spectre d’absorption modifié. La méthode développée permet l’enregistrement des spectres d’absorption UV de la solution étudiée avant et après application d’un potentiel, fixé à +1,8 V vs Ag durant 30 min. Un calcul de déconvolution utilisant le jeu de spectres obtenus permet l’identification et la quantification simultanée de quatre filtres UV. Cette méthode a été mise au point pour l’analyse d’avobenzone, d’octinoxate, d’octocrylène et d’oxybenzone. En plus de la mise au point de la méthode analytique, une campagne d’échantillonnage passif a été réalisée dans les eaux du littoral méditerranéen. Parmi les filtres UV étudiés, le bis-ethylhexyloxyphenol methoxyphenyl triazine, l’ethylhexyl triazone, l’octocrylène et le diethylamino hydroxybenzoyl hexyl benzoate ont été quantifiés à des concentrations de l’ordre du µg/L. Une étude de risque menée sur des organismes méditerranéen et tropicaux a montré l’existence d’un risque moyen à fort pour de nombreuses espècesUV filters are part of the emerging contaminants causing a risk to aquatic environments. Quantification of those molecules usually uses chromatographic technics. A method based on spectroelectrochemistry was developed, it is based on the combined use of an electrochemical experiment, chronoamperometry, and UV spectrophotometry. Some UV filters’ spectrum are modified following oxidation. The developed method enable the recording of UV spectra before and after potential application, set at +1,8 V vs Ag during 30 min. Deconvolution using both spectra is then performed to simultaneously identify and quantify four UV filters. This method was developed for the analysis of avobenzone, octinoxate, octocrylene and oxybenzone. In addition to the analytical method, a passive sampling experiment was performed in Mediterranean waters. Among the studied UV filters, bis-ethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazone, octocrylene and diethylamino hydroxybenzoyl hexyl benzoate were measured at concentration in the µg/L range. A risk assessment on Mediterranean and tropical species showed a medium to high risk for many species
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Brooks, Simon James. "From linear to cyclic anion receptors : high affinity receptors and sensors for oxo-anions." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438694.
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Chianella, Iva. "Development of affinity sensors for Microcystin-LR based on a computationally designed molecularly imprinted polymer." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/10744.
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In this work the development of affinity sensors for the detection of microcystin-LR
based on a computationally designed artificial receptor is presented. Microcystin-LR is
a cyclic heptapeptide hepatotoxin produced by Cyanobacteria (aquatic organisms also
known as blue-green algae), which during blooms period can release toxins in water.
Clinical signs of hepatotoxicosis have been observed in domestic animals and livestock
and recently also in humans. At present, analysis of these toxins is achieved largely
using conventional, time consuming and expensive techniques such as chromatographic
methods (HPLC, TLC) and immunoassay. Therefore, the necessity of an easy and
inexpensive method of analysis such a biosensor is becoming urgent. In this work an
artificial receptor for microcystin-LR was synthesised using a combined approach of
molecular imprinting and computer modelling. A computer-aided rational design was
applied to study microcystin-LRlmonomers interactions in order to find an optimal
composition for the synthesis of the receptor. The optimised composition, suggested by
computer modelling, consisted in 1 mol of2-acrylamido-2-methyl-propanesulfonic acid
and 6 mol ofurocanic acid ethyl ester for 1 mol of template. This monomer composition
was then used to synthesise a molecularly imprinted polymer (MIP) and an enzyme-
linked competitive assay was developed to characterise the computational receptor. In
the assay, computational MIP was able both to detect 0.1 ~g rl of microcystin-LR and
to distinguish the analyte among analogues such as microcystin-YR, microcystin-RR
and nodularin.
The computationally designed receptor was then used as a sensing element for the
construction of sensor devices. A MIP-based piezoelectric sensor, capable of detecting
35 ~g rl of toxin in water, was developed. In order to improve the system sensitivity,
the computational polymer was also used as a material in solid-phase extraction (SPE)
for samples pre-concentration. The receptor was able to pre-concentrate up to 1,000 fold
tap water samples spiked with only 1 J.1g rl of toxin. By combining MIP-based SPE and
piezoelectric sensor an improved system with a minimum detectable concentration of
toxin of 0.35 ~g rl was achieved.
Encouraging preliminary results were also obtained in developing a MIP-based
electrochemical sensor.
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Pellizzaro, Anthoni. "Caractérisation du transporteur de nitrate à double affinité, MtNPF6.8 (MtNRT1.3), de Medicago truncatula : rôles dans le transport et la perception du signal nitrate." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0011/document.
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Le nitrate, source majeur d’azote pour la plupart des plantes,n’est pas seulement un élément nutritif mais est aussi une molécule signale. Il existe cependant des réponses au nitrate contrastées entre les différentes plantes supérieures. Chez Medicago truncatula, espèce modèle de la famille des légumineuses, le nitrate a un effet inhibiteur sur la croissance de la racine primaire en phase post-germinative. Une étude de génétique quantitative a montré qu’un transporteur de nitrate se situe au pic d’un QTL impliqué dans la croissance de la racine primaire. La caractérisation fonctionnelle de ce transporteur, nommé MtNRT1.3 et renommé MtNPF6.8, a montré que celui-ci est à double affinité pour le nitrate. Ce transporteur est alors susceptible de participer à l’influx de nitrate dans la plante. Après l’obtention de trois génotypes mutants RNAi stables, les expérimentations utilisant duK15NO3 ont montré que ce transporteur participe effectivement à l’influx de nitrate lié au système de transport à faible affinité inductible dans la plante (iLATS). En revanche,la mutation de MtNPF6.8 ne semble pas avoir de conséquence sur le métabolisme azoté. Par ailleurs, les études sur la croissance de la racine primaire ont permis de confirmer l’implication du transporteur sur ce caractère phénotypique. L’inhibition de croissance de la racine primaire observée sur nitrate chez le génotype sauvage est alors imputée, à l’échelle cellulaire, à une modulation de l'élongation cellulaire. La possibilité que l’ABA, hormone végétale, joue un rôle dans la médiation de cette réponse dépendant du nitrate, est fortement favorisée. L’ensemble de résultats, conforté par une étude de mutants exprimant ce transporteur chez A. thaliana, indique donc que MtNPF6.8 est un senseur de nitrate pour la plante en phase post germinative,ceci indépendamment de sa fonction de transport de nitrateNitrate, a major nitrogen source for most plants, is not only anutrient but also a signaling molecule. However, there arecontrasting responses to nitrate between different higherplants. In the model legume Medicago truncatula, nitrate hasan inhibitory effect on the primary root growth in postgerminationphase. A quantitative genetic study has shownthat a nitrate transporter is localized at the peak of a QTLinvolved in the primary root growth. Functionalcharacterization of the transporter, named MtNRT1.3 andrenamed MtNPF6.8, showed that it encodes a dual affinitynitrate transporter. MtNPF6.8 is likely to participate in thenitrate influx in the plant. After obtaining three knockdownlines by RNA interference, experiments using K15NO3 showedthat this transporter is effect involved in nitrate influx relatedto the inducible low affinity transport system (iLATS).However, mutation in MtNPF6.8 does not any effect onnitrogen metabolism. In addition, studies on the primary rootgrowth have confirmed the involvement of the transporteron phenotypic trait. In wild-type plants, cortical cell sizedecreased after nitrate treatment, showing that primary rootgrowth was due to this reduced cell elongation. Thepossibility that ABA also plays a role in mediating this nitratedependent response is heavily favored. All these results,reinforced by a study of mutants expressing this transporterin A. thaliana, indicate that MtNPF6.8 is a nitrate sensor forMedicago in the post-germination phase, independently ofits nitrate transport activity
Books on the topic "Affinity sensor"
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Sauceda, Jimena Celia. Peptide-derived sensors with tuned affinity for heparin. 2006.
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Peretti, Daniel. Superman in Myth and Folklore. University Press of Mississippi, 2017. http://dx.doi.org/10.14325/mississippi/9781496814586.001.0001.
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Many artists draw upon folklore to craft films, music, literature, and other elements of popular culture. This book examines how the opposite phenomenon occurs: the use of popular culture in the expressive culture called folklore. Superman is an ideal focus for such as study because of his ubiquity. Though Superman is under the control of a corporation, fans nonetheless have developed a sense of ownership of him, often because of an affinity they feel toward him. Early chapters of this book explore the varieties of this affinity as experienced by individuals and as understood through interviews. Later chapters delve into specific events, such as the Superman Celebration in Illinois, and other modes of expression such as humor, personal narrative, and myth. Superman in Myth and Folklore explores the idea that a fictional character can be foundationally important in morality through fieldwork and interviews. In other words, fans use Superman to think through complex issues in their personal lives, and this book explores how. Despite the focus on fieldwork, there is some attention to the extant literature on Superman, ranging from educational works on science to psychology and history. There is also attention to the mythical aspects of Superman, with analyses of the character through several theories such as structuralism and functionalism. By examining jokes, festival, costuming, and narrative, this book explores the impact a fictional character can have.
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Bosse, Joanna. Introduction. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252039010.003.0001.
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This book examines the transformative potential of ballroom dance, and especially how it can make anyone become beautiful. Drawing on ethnographic fieldwork with a local community of amateur ballroom dancers from the Regent Ballroom and Banquet Center in Savoy, Illinois, the book explores the intersection of notions of beauty and experience—the act of becoming beautiful through performance. It considers the ethnographic trope of becoming beautiful as an “expression” in the sense suggested by Victor Turner and Edward Bruner in their anthropological work on experience. It demonstrates how the contemporary performance of ballroom dance among amateurs generates feelings of positive personal transformation, of becoming beautiful. The book also discusses the dance hall as a social space where disparate groups come together to move in synchrony, along with the ways in which race, class, and gender converge in ballroom dancing. Finally, it provides detailed ethnographic data on the formation of affinity groups.
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Raposa, Michael L. Theosemiotic. Fordham University Press, 2020. http://dx.doi.org/10.5422/fordham/9780823289516.001.0001.
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This book is an attempt to adapt some of Peirce’s ideas, particularly his theory of semiotic, for the purpose of re-thinking certain issues in contemporary philosophical theology and the philosophy of religion. It begins with an historical sketch that links Peirce’s thought to that of earlier figures, certain contemporaries, and later thinkers and developments. Drawing on Peirce’s thought, the book then develops a semiotic conception of persons/selves and of community. It analyzes in some detail the role that acts of attention play in shaping human inferences and perception, while also exploring the relationship between attention, volition, and love. Its central Peircean presuppositions are that all human experience takes the form of semiosis and that the universe is “pefused” with signs. Theology is portrayed here in its manifestations as inquiry, therapy, and praxis. The book dramatically closes the gap between what would typically be recognized as the nature and purpose of a philosophical theology and a theology of the spiritual life. It draws on both Peirce’s logic of vagueness and his logic of relations to make sense out of how we talk about the nature and reality of God, and also about the relationship between different religious communities. Theosemiotic is portrayed here as a form of religious naturalism, broadly conceived. The book also argues that there is a natural affinity between a theosemiotic inspired by Peirce’s pragmatism and liberation theology.
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Jagger, Jasmine. Rhythms of Feeling in Edward Lear, T. S. Eliot, and Stevie Smith. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198868804.001.0001.
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What does it mean to write or visualize a feeling rhythmically? Where does feeling sit within rhythm, and rhythm within feeling? This book looks into the heart of rhythm and the poetic imagination through the works of three of the most celebrated poets of all time. Through close studies of poetic and visual process, Rhythms of Feeling interprets the manuscripts, letters, diaries, drawings, and poetry of Edward Lear, T. S. Eliot, and Stevie Smith. Tracing exciting lines of interplay, affinity, and influence between these writers for the first time, the book shifts the terms of critical debate on Lear, Eliot, and Smith and subtly reorients the traditional account of the genealogies of modernism. Going beyond a biographically framed close reading or a more general analysis framed by affect theory, Rhythms of Feeling traces out these poets’ ‘affective rhythms’ (tears, nerves, rage) to consider the way that poetics, the mental and physical process of writing and reading, and the ebbs and flows of their emotional weather, might be in dialogue. Attentive, acute, and often forensic, the book broadens its reach beyond these three poets to contemporary writers and medical accounts of creativity and cognition. Alongside deep critical study, Rhythms of Feeling seeks to bring emotional intelligence to criticism, finding ways of speaking lucidly and humanely about emotional and physical states that defy lucidity and stretch our sense of the human.
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Nelson, Chad E. Revolutionary Contagion and International Politics. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197601921.001.0001.
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Abstract When do leaders fear that a revolution elsewhere will spread to their own polities, and what are the international effects of this fear? This book develops and tests the domestic contagion effects theory. According to the theory, fear of contagion is driven more by the characteristics of the host rather than by the activities of the infecting agents. In other words, leaders will fear revolutionary contagion when they have significant revolutionary opposition movements that share the same ideological affinity of the revolution. Whether the revolutionary state merely serves as a model for revolution or whether it also acts as a platform, attempting to spread revolution abroad, is not the crucial distinction. When leaders have a fear of contagion, it will have a profound effect on international politics, prompting hostility toward the revolutionary state and cooperation with states that have similar fears, sometimes in contrast to geopolitical pressures. Cases spanning the reaction to the democratic American Revolution and the Dutch Patriot Revolt, the wave of liberal revolutions in Europe in 1820–21, the Russian communist and Italian fascist revolutions, and the Iranian Islamist revolution in the Middle East largely, though not uniformly, support the theory. This book advances our understanding of when, why, and how much states with different domestic ideologies affect international relations. In certain periods in international relations, one simply cannot make sense of international politics—patterns of alliances and wars—without considering the fear of contagion.
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Santiago Iglesias, José Andrés, and Ana Soler Baena, eds. Anime Studies: Media-Specific Approaches to Neon Genesis Evangelion. Stockholm University Press, 2021. http://dx.doi.org/10.16993/bbp.
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Anime Studies: Media-Specific Approaches to Neon Genesis Evangelion aims at advancing the study of anime, understood as largely TV-based genre fiction rendered in cel, or cel-look, animation with a strong affinity to participatory cultures and media convergence. Taking Neon Genesis Evangelion (Shin Seiki Evangerion) as a case study, this volume acknowledges anime as a media form with clearly recognizable aesthetic properties, (sub)cultural affordances and situated discourses. First broadcast in Japan in 1995-96, Neon Genesis Evangelion became an epoch-making anime, and later franchise. The initial series used already available conventions, visual resources and narrative tropes typical of anime in general and the mecha (or giant-robot) genre in particular, but at the same time it subverted and reinterpreted them in a highly innovative and as such standard-setting way. Investigating anime through Neon Genesis Evangelion this volume takes a broadly understood media-aesthetic and media-cultural perspective, which pertains to medium in the narrow sense of technology, techniques, materials, and semiotics, but also mediality and mediations related to practices and institutions of production, circulation, and consumption. In no way intended to be exhaustive, this volume attests to the emergence of anime studies as a field in its own right, including but not prioritizing expertise in film studies and Japanese studies, and with due regard to the most widely shared critical publications in Japanese and English language. Thus, the volume provides an introduction to studies of anime, a field that necessarily interrelates media-specific and transmedial aspects. In Anime Studies: Media-Specific Approaches to Neon Genesis Evangelion, anime is addressed from a transnational and transdisciplinary stance. The disciplinary and methodological perspectives taken by the individual chapters range from audio-visual culture, narratology, performance and genre theory to fandom studies and gender studies. In its first part, the book focuses on textual analysis and media form in the narrow sense with regard to filmic media, bank footage, voice acting and musical score, and then it broadens the scope to consider subcultural discourse, franchising, manga and video game adaptations, as well as critical and affective user engagement.
Book chapters on the topic "Affinity sensor"
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Komives, C. F. "A Novel Concept for a Competitive Affinity Optical Sensor." In Recent Advances in Biotechnology, 525–26. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2468-3_54.
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Li, Jiming, and Xiaogang Jin. "Modeling Wireless Sensor Network with Spatial Constrained Affinity Propagation." In Advances in Intelligent and Soft Computing, 615–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-25658-5_73.
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Yatsimirsky, Anatoly K., and Vladimir M. Mirsky. "Quantitative Affinity Data on Selected Artificial Receptors." In Artificial Receptors for Chemical Sensors, 439–60. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527632480.ch14.
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Mirsky, Vladimir M. "Quantitative Characterization of Affinity Properties of Immobilized Receptors." In Artificial Receptors for Chemical Sensors, 1–15. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527632480.ch1.
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Xu, Hongwu, Miriam M. Masila, and Omowunmi A. Sadik. "Affinity Biosensors for Characterization of Environmental Endocrine Disruptors." In Chemical and Biological Sensors for Environmental Monitoring, 207–22. Washington, DC: American Chemical Society, 2000. http://dx.doi.org/10.1021/bk-2000-0762.ch015.
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Linman, Matthew J., and Quan Jason Cheng. "Surface Plasmon Resonance: New Biointerface Designs and High-Throughput Affinity Screening." In Springer Series on Chemical Sensors and Biosensors, 133–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-88242-8_5.
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Ramanaviciene, A., and A. Ramanavicius. "Affinity Sensors Based on Nano-Structured ∏-∏ Conjugated Polymer Polypyrrole." In Advanced Biomaterials for Medical Applications, 111–25. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2908-0_9.
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Milán-Rois, Paula, Ciro Rodriguez-Diaz, Milagros Castellanos, and Álvaro Somoza. "Conjugation of Nucleic Acids and Drugs to Gold Nanoparticles." In Methods in Molecular Biology, 103–16. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2010-6_6.
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AbstractGold nanoparticles (AuNPs) can be used as carriers for biomolecules or drugs in cell culture and animal models. Particularly, AuNPs ease their internalization into the cell and prevent their degradation. In addition, engineered AuNPs can be employed as sensors of a variety of biomarkers, where the electronic and optical properties of the AuNPs are exploited for a convenient, easy, and fast read out. However, in all these applications, a key step requires the conjugation of the different molecules to the nanoparticles. The most common approach exploits the great affinity of sulfur for gold. Herein, we summarize the methods used by our group for the conjugation of different molecules with AuNPs. The procedure is easy and takes around 2 days, where the reagents are slowly added, following an incubation at room temperature to ensure the complete conjugation. Finally, the unbound material is removed by centrifugation.
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"Metal Nanoparticles-Based Affinity Biosensors." In Smart Nanomaterials for Sensor Application, edited by Giovanna Marrazza, 42–59. BENTHAM SCIENCE PUBLISHERS, 2012. http://dx.doi.org/10.2174/978160805241711201010042.
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Isabel Pividori, Maria, and Salvador Alegret. "Chapter 22 Electrochemical immunosensing of food residues by affinity biosensors and magneto sensors." In Electrochemical Sensor Analysis, 467–93. Elsevier, 2007. http://dx.doi.org/10.1016/s0166-526x(06)49022-x.
Full textConference papers on the topic "Affinity sensor"
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Hilton, John P., ThaiHuu Nguyen, Renjun Pei, Milan Stojanovic, and Qiao Lin. "A Microfluidic Affinity Cocaine Sensor." In 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems (MEMS). IEEE, 2009. http://dx.doi.org/10.1109/memsys.2009.4805389.
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Mansouri, Sohrab, Cheryl Jones, Roy Martin, and Ron Heil. "Absorbance-Based Affinity Glucose Sensor." In 1988 Los Angeles Symposium--O-E/LASE '88, edited by Abraham Katzir. SPIE, 1988. http://dx.doi.org/10.1117/12.945255.
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Huang, Xian, Siqi Li, Jerome Schultz, Qian Wang, and Qiao Lin. "A capacitively based MEMS affinity glucose sensor." In TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference. IEEE, 2009. http://dx.doi.org/10.1109/sensor.2009.5285818.
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Alam, M. Z., J. S. Aitchison, and M. Mojahedi. "Vertical Wall Affinity Sensor with Polarization Diversity." In Optical Sensors. Washington, D.C.: OSA, 2011. http://dx.doi.org/10.1364/sensors.2011.smb3.
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Gandhi, Kalgi, and Minal Bhise. "Affinity-based Fragmentation for Sensor Data." In 2019 IEEE 16th India Council International Conference (INDICON). IEEE, 2019. http://dx.doi.org/10.1109/indicon47234.2019.9030273.
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Ott, Lionel, and Fabio Ramos. "Multi-sensor clustering using Layered Affinity Propagation." In 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2013). IEEE, 2013. http://dx.doi.org/10.1109/iros.2013.6696755.
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Shang, J., Z. Zhang, J. Yan, Q. Wang, and Q. Lin. "A hydrogel-based MEMS dielectric affinity glucose sensor." In TRANSDUCERS 2015 - 2015 18th International Solid-State Sensors, Actuators and Microsystems Conference. IEEE, 2015. http://dx.doi.org/10.1109/transducers.2015.7180983.
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Shang, Junyi, Hao Sun, and Qiao Lin. "Modeling of a viscometric MEMS affinity glucose sensor." In 2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS). IEEE, 2017. http://dx.doi.org/10.1109/transducers.2017.7994486.
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Wang, Yushun, Peng Lei, and Hong Xu. "Affinity propagation algorithm in WLAN network deployment." In 2013 2nd International Symposium on Instrumentation & Measurement, Sensor Network and Automation (IMSNA). IEEE, 2013. http://dx.doi.org/10.1109/imsna.2013.6743430.
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Huang, X., J. Oxsher, C. LeDuc, Y. Ravussin, Q. Wang, D. Accili, R. Leibel, and Q. Lin. "A MEMS differential affinity sensor for continuous glucose detection." In TRANSDUCERS 2011 - 2011 16th International Solid-State Sensors, Actuators and Microsystems Conference. IEEE, 2011. http://dx.doi.org/10.1109/transducers.2011.5969384.
Full textReports on the topic "Affinity sensor"
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Banta, Scott, and Jennifer Haghpanah. Engineering of an Extremely Thermostable Alpha/Beta Barrel Scaffold to Serve as a High Affinity Molecular Recognition Element for Use in Sensor Applications. Fort Belvoir, VA: Defense Technical Information Center, November 2015. http://dx.doi.org/10.21236/ad1007471.
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Glasscott, Matthew, Johanna Jernberg, Erik Alberts, and Lee Moores. Toward the electrochemical detection of 2,4-dinitroanisole (DNAN) and pentaerythritol tetranitrate (PETN). Engineer Research and Development Center (U.S.), March 2022. http://dx.doi.org/10.21079/11681/43826.
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Analytical methods to rapidly detect explosive compounds with high precision are paramount for applications ranging from national security to environmental remediation. This report demonstrates two proof-of-concept electroanalytical methods for the quantification of 2,4-dinitroanisol (DNAN) and pentaerythritol tetranitrate (PETN). For the first time, DNAN reduction was analyzed and compared at a bare graphitic carbon electrode, a polyaniline-modified (PANI) electrode, and a molecularly imprinted polymer (MIP) electrode utilizing PANI to explore the effect of surface-area and preconcentration affinity on the analytical response. Since some explosive compounds such as PETN are not appreciably soluble in water (<10 μg/L), necessitating a different solvent system to permit direct detection via electrochemical reduction. A 1,2-dichloroethane system was explored as a possibility by generating a liquid-liquid extraction-based sensor exploiting the immiscibility of 1,2-dichloroethane and water. The reduction process was explored using a scan rate analysis to extract a diffusion coefficient of 6.67 x 10⁻⁶ cm/s, in agreement with literature values for similarly structured nitrate esters. Once further refined, these techniques may be extended to other explosives and combined with portable electrochemical hardware to bring real-time chemical information to soldiers and citizens alike.
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Wisniewski, Michael, Samir Droby, John Norelli, Dov Prusky, and Vera Hershkovitz. Genetic and transcriptomic analysis of postharvest decay resistance in Malus sieversii and the identification of pathogenicity effectors in Penicillium expansum. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597928.bard.
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Use of Lqh2 mutants (produced at TAU) and rNav1.2a mutants (produced at the US side) for identifying receptor site-3: Based on the fact that binding of scorpion alpha-toxins is voltage-dependent, which suggests toxin binding at the mobile voltage-sensing region, we analyzed which of the toxin bioactive domains (Core-domain or NC-domain) interacts with the DIV Gating-module of rNav1.2a. This analysis was based on the assumption that the dissociation of toxin mutants upon depolarization would vary from that of the unmodified toxin should the substitutions affect a site of interaction with the channel Gating-module. Using a series of toxin mutants (mutations at both domains) and two channel mutants that were shown to reduce the sensitivity to scorpion alpha-toxins, and by comparison of depolarization-driven dissociation of Lqh2 derivatives off their binding site at rNav1.2a mutant channels we found that the toxin Core-domain interacts with the Gating-module of DIV. Details of the experiments and results appear in Guret al (2011). Mapping receptor site 3 at Nav1.2a by extensive channel mutagenesis (Seattle): Since previous studies with photoaffinity labeling and antibody mapping implicated domains I and IV in scorpion alpha-toxin binding, Nav1.2 channel mutants containing substitutions at these extracellular regions were expressed and tested for receptor function by whole-cell voltage clamp. Of a large number of channel mutants, T1560A, F1610A, and E1613A in domain IV had ~5.9-, ~10.7-, and ~3.9-fold lower affinities for the scorpion toxin Lqh2, respectively, and mutant E1613R had 73-fold lower affinity. Toxin dissociation was accelerated by depolarization for both wild-type and mutants, and the rates of dissociation were also increased by mutations T1560A, F1610A and E1613A. In contrast, association rates for these three mutant channels at negative membrane potentials were not significantly changed and were not voltage-dependent. These results indicated that Thr1560 in the S1-S2 loop, Phe1610 in the S3 segment, and Glu1613 in the S3-S4 loop in domain IV participate in toxin binding. T393A in the SS2-S6 loop in domain I also showed a ~3.4-fold lower affinity for Lqh2, indicating that this extracellular loop may form a secondary component of the toxin binding site. Analysis with the Rosetta-Membrane algorithm revealed a three-dimensional model of Lqh2 binding to the voltage sensor in a resting state. In this model, amino acid residues in an extracellular cleft formed by the S1-S2 and S3-S4 loops in domain IV that are important for toxin binding interact with amino acid residues on two faces of the wedge-shaped Lqh2 molecule that are important for toxin action. The conserved gating charges in the S4 transmembrane segment are in an inward position and likely form ion pairs with negatively charged amino acid residues in the S2 and S3 segments (Wang et al 2011; Gurevitz 2012; Gurevitzet al 2013).
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Horwitz, Benjamin A., and Barbara Gillian Turgeon. Fungal Iron Acquisition, Oxidative Stress and Virulence in the Cochliobolus-maize Interaction. United States Department of Agriculture, March 2012. http://dx.doi.org/10.32747/2012.7709885.bard.
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Our project focused on genes for high affinity iron acquisition in Cochliobolus heterostrophus, a necrotrophic pathogen of maize, and their intertwined relationship to oxidative stress status and virulence of the fungus on the host. An intriguing question was why mutants lacking the nonribosomal peptide synthetase (NRPS) gene (NPS6) responsible for synthesis of the extracellular siderophore, coprogen, are sensitive to oxidative stress. Our overall objective was to understand the mechanistic connection between iron stress and oxidative stress as related to virulence of a plant pathogen to its host. The first objective was to examine the interface where small molecule peptide and reactive oxygen species (ROS) mechanisms overlap. The second objective was to determine if the molecular explanation for common function is common signal transduction pathways. These pathways, built around sensor kinases, response regulators, and transcription factors may link sequestering of iron, production of antioxidants, resistance to oxidative stress, and virulence. We tested these hypotheses by genetic manipulation of the pathogen, virulence assays on the host plant, and by following the expression of key fungal genes. An addition to the original program, made in the first year, was to develop, for fungi, a genetically encoded indicator of redox state based on the commercially available Gfp-based probe pHyper, designed for animal cell biology. We implemented several tools including a genetically encoded indicator of redox state, a procedure to grow iron-depleted plants, and constructed a number of new mutants in regulatory genes. Lack of the major Fe acquisition pathways results in an almost completely avirulent phenotype, showing how critical Fe acquisition is for the pathogen to cause disease. Mutants in conserved signaling pathways have normal ability to regulate NPS6 in response to Fe levels, as do mutants in Lae1 and Vel1, two master regulators of gene expression. Vel1 mutants are sensitive to oxidative stress, and the reason may be underexpression of a catalase gene. In nps6 mutants, CAT3 is also underexpressed, perhaps explaining the sensitivity to oxidative stress. We constructed a deletion mutant for the Fe sensor-regulator SreA and found that it is required for down regulation of NPS6 under Fe-replete conditions. Lack of SreA, though, did not make the fungus over-sensitive to ROS, though the mutant had a slow growth rate. This suggests that overproduction of siderophore under Fe-replete conditions is not very damaging. On the other hand, increasing Fe levels protected nps6 mutants from inhibition by ROS, implying that Fe-catalyzed Fenton reactions are not the main factor in its sensitivity to ROS. We have made some progress in understanding why siderophore mutants are sensitive to oxidative stress, and in doing so, defined some novel regulatory relationships. Catalase genes, which are not directly related to siderophore biosynthesis, are underexpressed in nps6 mutants, suggesting that the siderophore product (with or without bound Fe) may act as a signal. Siderophores, therefore, could be a target for intervention in the field, either by supplying an incorrect signal or blocking a signal normally provided during infection. We already know that nps6 mutants cause smaller lesions and have difficulty establishing invasive growth in the host. Lae1 and Vel1 are the first factors shown to regulate both super virulence conferred by T-toxin, and basic pathogenicity, due to unknown factors. The mutants are also altered in oxidative stress responses, key to success in the infection court, asexual and sexual development, essential for fungal dissemination in the field, aerial hyphal growth, and pigment biosynthesis, essential for survival in the field. Mutants in genes encoding NADPH oxidase (Nox) are compromised in development and virulence. Indeed the triple mutant, which should lack all Nox activity, was nearly avirulent. Again, gene expression experiments provided us with initial evidence that superoxide produced by the fungus may be most important as a signal. Blocking oxidant production by the pathogen may be a way to protect the plant host, in interactions with necrotrophs such as C. heterostrophus which seem to thrive in an oxidant environment.
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Cox, Jeremy. The unheard voice and the unseen shadow. Norges Musikkhøgskole, August 2018. http://dx.doi.org/10.22501/nmh-ar.621671.
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The French composer Francis Poulenc had a profound admiration and empathy for the writings of the Spanish poet Federico García Lorca. That empathy was rooted in shared aspects of the artistic temperament of the two figures but was also undoubtedly reinforced by Poulenc’s fellow-feeling on a human level. As someone who wrestled with his own homosexuality and who kept his orientation and his relationships apart from his public persona, Poulenc would have felt an instinctive affinity for a figure who endured similar internal conflicts but who, especially in his later life and poetry, was more open about his sexuality. Lorca paid a heavy price for this refusal to dissimulate; his arrest in August 1936 and his assassination the following day, probably by Nationalist militia, was accompanied by taunts from his killers about his sexuality. Everything about the Spanish poet’s life, his artistic affinities, his personal predilections and even the relationship between these and his death made him someone to whom Poulenc would be naturally drawn and whose untimely demise he would feel keenly and might wish to commemorate musically. Starting with the death of both his parents while he was still in his teens, reinforced by the sudden loss in 1930 of an especially close friend, confidante and kindred spirit, and continuing throughout the remainder of his life with the periodic loss of close friends, companions and fellow-artists, Poulenc’s life was marked by a succession of bereavements. Significantly, many of the dedications that head up his compositions are ‘to the memory of’ the individual named. As Poulenc grew older, and the list of those whom he had outlived lengthened inexorably, his natural tendency towards the nostalgic and the elegiac fused with a growing sense of what might be termed a ‘survivor’s anguish’, part of which he sublimated into his musical works. It should therefore come as no surprise that, during the 1940s, and in fulfilment of a desire that he had felt since the poet’s death, he should turn to Lorca for inspiration and, in the process, attempt his own act of homage in two separate works: the Violin Sonata and the ‘Trois Chansons de Federico García Lorca’. This exposition attempts to unfold aspects of the two men’s aesthetic pre-occupations and to show how the parallels uncovered cast reciprocal light upon their respective approaches to the creative process. It also examines the network of enfolded associations, musical and autobiographical, which link Poulenc’s two compositions commemorating Lorca, not only to one another but also to a wider circle of the composer’s works, especially his cycle setting poems of Guillaume Apollinaire: ‘Calligrammes’. Composed a year after the ‘Trois Chansons de Federico García Lorca’, this intricately wrought collection of seven mélodies, which Poulenc saw as the culmination of an intensive phase in his activity in this genre, revisits some of ‘unheard voices’ and ‘unseen shadows’ enfolded in its predecessor. It may be viewed, in part, as an attempt to bring to fuller resolution the veiled but keenly-felt anguish invoked by these paradoxical properties.