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Artykuły w czasopismach na temat "Lipidic model membranes"
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Le Goff, Thomas, Tung B. T. To i Olivier Pierre-Louis. "Shear dynamics of confined membranes". Soft Matter 17, nr 22 (2021): 5467–85. http://dx.doi.org/10.1039/d1sm00322d.
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Inspired by biolubrication, we model the nonlinear dynamics of lipidic membranes sheared between two walls. Several regimes are found with different wrinkle patterns, leading to a non-monotonous contribution of the membrane to the friction force.
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Sejwal, Kushal, Mohamed Chami, Paul Baumgartner, Julia Kowal, Shirley A. Müller i Henning Stahlberg. "Proteoliposomes – a system to study membrane proteins under buffer gradients by cryo-EM". Nanotechnology Reviews 6, nr 1 (1.02.2017): 57–74. http://dx.doi.org/10.1515/ntrev-2016-0081.
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AbstractMembrane proteins are vital to life and major therapeutic targets. Yet, understanding how they function is limited by a lack of structural information. In biological cells, membrane proteins reside in lipidic membranes and typically experience different buffer conditions on both sides of the membrane or even electric potentials and transmembrane gradients across the membranes. Proteoliposomes, which are lipidic vesicles filled with reconstituted membrane proteins, provide an ideal model system for structural and functional studies of membrane proteins under conditions that mimic nature to a certain degree. We discuss methods for the formation of liposomes and proteoliposomes, their imaging by cryo-electron microscopy, and the structural analysis of proteins present in their bilayer. We suggest the formation of ordered arrays akin to weakly ordered two-dimensional (2D) crystals in the bilayer of liposomes as a means to achieve high-resolution, and subsequent buffer modification as a method to capture snapshots of membrane proteins in action.
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Brémaud, Erwan, Cyril Favard i Delphine Muriaux. "Deciphering the Assembly of Enveloped Viruses Using Model Lipid Membranes". Membranes 12, nr 5 (19.04.2022): 441. http://dx.doi.org/10.3390/membranes12050441.
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The cell plasma membrane is mainly composed of phospholipids, cholesterol and embedded proteins, presenting a complex interface with the environment. It maintains a barrier to control matter fluxes between the cell cytosol and its outer environment. Enveloped viruses are also surrounded by a lipidic membrane derived from the host-cell membrane and acquired while exiting the host cell during the assembly and budding steps of their viral cycle. Thus, model membranes composed of selected lipid mixtures mimicking plasma membrane properties are the tools of choice and were used to decipher the first step in the assembly of enveloped viruses. Amongst these viruses, we choose to report the three most frequently studied viruses responsible for lethal human diseases, i.e., Human Immunodeficiency Type 1 (HIV-1), Influenza A Virus (IAV) and Ebola Virus (EBOV), which assemble at the host-cell plasma membrane. Here, we review how model membranes such as Langmuir monolayers, bicelles, large and small unilamellar vesicles (LUVs and SUVs), supported lipid bilayers (SLBs), tethered-bilayer lipid membranes (tBLM) and giant unilamellar vesicles (GUVs) contribute to the understanding of viral assembly mechanisms and dynamics using biophysical approaches.
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Wrobel, Dominika, Dietmar Appelhans, Marco Signorelli, Brigitte Wiesner, Dimitrios Fessas, Ulrich Scheler, Brigitte Voit i Jan Maly. "Interaction study between maltose-modified PPI dendrimers and lipidic model membranes". Biochimica et Biophysica Acta (BBA) - Biomembranes 1848, nr 7 (lipiec 2015): 1490–501. http://dx.doi.org/10.1016/j.bbamem.2015.03.033.
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Castelli, Francesco, Sebastiana Caruso i Nicola Uccella. "Biomimesis of Linolenic Acid Transport through Model Lipidic Membranes by Differential Scanning Calorimetry". Journal of Agricultural and Food Chemistry 51, nr 4 (luty 2003): 851–55. http://dx.doi.org/10.1021/jf020582z.
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Gallová, J., K. Želinská i P. Balgavý. "Partial molecular volumes of cholesterol and phosphatidylcholine in mixed bilayers". European Pharmaceutical Journal 64, nr 2 (27.11.2017): 1–3. http://dx.doi.org/10.1515/afpuc-2017-0012.
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Abstract Dispersion of multilamellar liposomes of dimyristoylphosphatidylcholine (DMPC) and cholesterol (CHOL) were studied by vibrational densitometer for the CHOL mole fractions X = 0−0.54 in the temperature range 18−50 °C, both below and above the main phase transition. DMPC-CHOL bilayers served as a simple model for lipidic part of biological membrane. Volumetric parameters are essential not only to evaluate the data obtained by scattering and diffraction methods on model membranes but can provide valuable information about molecular packing in bilayers and the phase behaviour of lipid-CHOL mixtures. In this paper, preliminary results regarding the changes in the specific volume of lipid bilayer with increasing temperature and CHOL content are presented. Different values of apparent molecular volume of CHOL for different CHOL mole fraction pointed out the non-ideal mixing of DMPC and CHOL.
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Parra, Elisa, Lara H. Moleiro, Ivan López-Montero, Antonio Cruz, Francisco Monroy i Jesús Pérez-Gil. "A combined action of pulmonary surfactant proteins SP-B and SP-C modulates permeability and dynamics of phospholipid membranes". Biochemical Journal 438, nr 3 (26.08.2011): 555–64. http://dx.doi.org/10.1042/bj20110681.
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Proteins SP-B and SP-C are essential to promote formation of surface-active films at the respiratory interface, but their mechanism of action is still under investigation. In the present study we have analysed the effect of the proteins on the accessibility of native, quasi-native and model surfactant membranes to incorporation of the fluorescent probes Nile Red (permeable) and FM 1-43 (impermeable) into membranes. We have also analysed the effect of single or combined proteins on membrane permeation using the soluble fluorescent dye calcein. The fluorescence of FM 1-43 was always higher in membranes containing SP-B and/or SP-C than in protein-depleted membranes, in contrast with Nile Red which was very similar in all of the materials tested. SP-B and SP-C promoted probe partition with markedly different kinetics. On the other hand, physiological proportions of SP-B and SP-C caused giant oligolamellar vesicles to incorporate FM 1-43 from the external medium into apparently most of the membranes instantaneously. In contrast, oligolamellar pure lipid vesicles appeared to be mainly labelled in the outermost membrane layer. Pure lipidic vesicles were impermeable to calcein, whereas it permeated through membranes containing SP-B and/or SP-C. Vesicles containing only SP-B were stable, but prone to vesicle–vesicle interactions, whereas those containing only SP-C were extremely dynamic, undergoing frequent fluctuations and ruptures. Differential structural effects of proteins on vesicles were confirmed by electron microscopy. These results suggest that SP-B and SP-C have different contributions to inter- and intra-membrane lipid dynamics, and that their combined action could provide unique effects to modulate structure and dynamics of pulmonary surfactant membranes and films.
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Trombetta, Domenico, Francesco Castelli, Maria Grazia Sarpietro, Vincenza Venuti, Mariateresa Cristani, Claudia Daniele, Antonella Saija, Gabriela Mazzanti i Giuseppe Bisignano. "Mechanisms of Antibacterial Action of Three Monoterpenes". Antimicrobial Agents and Chemotherapy 49, nr 6 (czerwiec 2005): 2474–78. http://dx.doi.org/10.1128/aac.49.6.2474-2478.2005.
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ABSTRACT In the present paper, we report the antimicrobial efficacy of three monoterpenes [linalyl acetate, (+)menthol, and thymol] against the gram-positive bacterium Staphylococcus aureus and the gram-negative bacterium Escherichia coli. For a better understanding of their mechanisms of action, the capability of these three monoterpenes to damage biomembranes was evaluated by monitoring the release, following exposure to the compounds under study, of the water-soluble fluorescent marker carboxyfluorescein from unilamellar vesicles with different lipidic compositions (phosphatidylcholine, phosphatidylcholine/phosphatidylserine [9:1], phosphatidylcholine/stearylamine [9:1], and phosphatidylglycerol/cardiolipin [9:1]). Furthermore, the interaction of the terpenes tested with dimyristoylphosphatidylcholine multilamellar vesicles as model membranes was monitored by means of differential scanning calorimetry. Finally, the results were related to the relative lipophilicity and water solubility of the compounds examined. Taken together, our findings lead us to speculate that the antimicrobial effect of (+)menthol, thymol, and linalyl acetate may result, at least partially, from a perturbation of the lipid fraction of microorganism plasma membrane, resulting in alterations of membrane permeability and in leakage of intracellular materials. Besides being related to physicochemical characteristics of the drugs (such as lipophilicity and water solubility), this effect seems to be dependent on lipid composition and net surface charge of microbial membranes. Furthermore, the drugs might cross the cell membranes, penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity.
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Castanho, M. A. R. B., S. Lopes i M. Fernandes. "Using UV-Vis. Linear Dichroism to Study the Orientation of Molecular Probes and Biomolecules in Lipidic Membranes". Spectroscopy 17, nr 2-3 (2003): 377–98. http://dx.doi.org/10.1155/2003/801452.
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Linear dichroism methodologies are based on the different interaction of molecules with linearly polarized light depending on their orientation. Theoretical predictions are used to conclude on the orientation of selected molecules relative to their neighbours (usually an organized matrix). In the specific case of linear dichroism methodologies applied to data obtained from UV-Vis. spectroscopic techniques, the orientational distribution function of the chromophores' electronic transition moment can be calculated and converted to the molecular axis distribution function. In this paper, the orientation of molecular probes and biomolecules in model systems of biomembranes (lipidic matrixes) is explored and illustrated using common membrane probes (trans-parinaric acid, a cyanine and laurdan) and polyene antibiotics (Amphotericin B and Nystatin). The emphasis is on the technique and methodologies themselves, rather than the scientific impact of the attained distributions. The main addressed items are: (1) How to adapt a common UV-Vis. spectrophotometer and spectrofluorimeter to perform linear dicrhoism experiments?, (2) Sample preparation, and (3) Data analysis (including artefacts corrections).
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Mori, Kenichi, Yosuke Imai, Tsubasa Takaoka, Koji Iwamoto, Hideyoshi Fuji i Tyuji Hoshino. "2P270 Database of Lipid Membrane Structures : Computational Analyses of Model Membranes(40. Membrane structure,Poster Session,Abstract,Meeting Program of EABS & BSJ 2006)". Seibutsu Butsuri 46, supplement2 (2006): S363. http://dx.doi.org/10.2142/biophys.46.s363_2.
Pełny tekst źródłaRozprawy doktorskie na temat "Lipidic model membranes"
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Oldham, Alexis Jean. "Modulation of lipid domain formation in mixed model systems by proteins and peptides". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-1/r1/oldhama/alexisoldham.pdf.
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Azouz, Mehdi. "Alzheimer's disease neurotoxic peptides : towards a comprehension of their modes of action on model membranes". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0419.
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La maladie d'Alzheimer (MA) est une neuropathologie complexe qui constitue la principale forme de démence chez l'être humain. Étroitement associée au vieillissement, elle se manifeste par une perte progressive de la mémoire et des fonctions cognitives. Avec 30 millions d’individus concernés au niveau mondial et des estimations voyant ce chiffre quadrupler d'ici 2050, elle constitue aujourd’hui une menace sociétale majeure. L’atrophie cérébrale observée chez les patients atteints de la MA est la conséquence d’un long processus de neurodégénérescence qui intervient au niveau moléculaire et s’amorce bien avant l’apparition des symptômes. Deux marqueurs histopathologiques ont été identifiés comme étant associés à ce processus : les plaques séniles, composées du peptide Abêta et les dégénérescences neurofibrillaires constituées de la protéine Tau. Ces deux molécules, considérées comme les protagonistes décisifs du développement de la MA, concentrent les recherches afin de mieux comprendre leurs rôles dans le processus neurodégénératif et pouvoir mettre en place des solutions thérapeutiques, inexistantes à ce jour.Un des axes de recherche majeurs se focalise sur l’interaction de ces peptides avec la membrane plasmique. L’occurrence d’un tel phénomène pourrait potentiellement être en cause dans la mort neuronale s’il s’avérait délétère. Il est donc capital d’étudier en détail ces processus afin d’identifier les facteurs qui pourraient conduire Abêta et Tau à endommager l’intégrité des membranes. De nombreux travaux ont démontré que certains lipides pouvaient promouvoir ces interactions. Cependant, les conclusions sont parfois divergentes et un consensus commun reste à trouver quant à leurs rôles.Ce travail de thèse s’est consacré à l’étude des modes d’action du peptide Abêta et d’un fragment clé de la protéine Tau, le peptide K18, sur des membranes modèles, en se focalisant principalement sur l’influence de certains lipides. Afin d’élucider les mécanismes qui régissent ces phénomènes, les processus de solubilisation membranaires ont dans un premier temps été étudiés avec des molécules amphiphiles bien caractérisées : les détergents. Cette étude a permis d’établir que les phénomènes de solubilisation membranaires peuvent varier en fonction de la composition membranaire et démontrer de la sélectivité.Le cœur du projet était de visualiser les effets des peptides amyloïdes Abêta et K18 sur des modèles membranaires, les bicouches supportées, avec pour principale technique d’investigation la microscopie à force atomique. Elle nous a permis d’observer ces phénomènes in situ, en conditions physiologiques et à l’échelle sub-micrométrique. Nous avons pu montrer que la composition membranaire était un facteur pouvant moduler l’interaction avec Abêta. L'étude établit que les domaines lipidiques favorisent les perturbations membranaires induites par le peptide. Il est proposé que des défauts d'empilement lipidiques aux interfaces de ces domaines agissent comme des sites d'adsorption du peptide, menant à la destruction des membranes. En utilisant la même approche, avec des compositions lipidiques plus en adéquation avec Tau, nous avons pu établir que K18 induisait également des effets de solubilisation en fonction de la nature des lipides dans la membrane et des propriétés qui leurs sont associées.Dans les deux cas, nous montrons que les effets délétères que peuvent induire ces peptides se manifestent par des effets comparables à ceux des détergents et sont dépendants de la composition des membranes. L’agrégation des peptides, qui peut conduire à leur fibrillation, n’a également été mise en évidence qu’en présence de certains lipides.Ce travail de thèse apporte de nouvelles informations sur le caractère décisif de la membrane à pouvoir moduler les interactions avec les peptides Abêta; et K18. Par extension aux membranes cellulaires, ces phénomènes pourraient potentiellement être associés aux processus neurodégénératifs impliqués dans la MAAlzheimer’s disease is a complex neuropathological disorder that constitutes the prime form of dementia. Intimately related to ageing, it is associated to the gradual loss of memory and cognitive functions in individual suffering from the pathology. With nearly 30 million people concerned today, and the alarming trends predicting this figure to increase fourfold by 2050, Alzheimer’s disease will constitute a major burden for our societies in the upcoming decades. The cerebral atrophy occurring within the brain results from slow and progressive neurodegenerative mechanisms triggered many years before the appearance of the first symptoms. Two histopathological markers have been identified as strongly associated to the neurodegeneration: the senile plaques, majorly composed of the amyloid peptide Abeta, and the neurofibrillary tangles, constituted of the abnormally phosphorylated form of Tau protein. These two molecules, hence considered as the main culprits of the disease, are therefore under the spotlight of researchers who try to better understand the respective roles in the neurodegeneration process and uncover therapeutic solutions to a still uncurable disease.One of the promising research axis is focusing on the interplay between these molecules and the plasma membrane as potential interactions could convincingly rationalize the neural cell deaths if they happened to be deleterious. Therefore, investigate these interactions in detail is of primary importance to identify the factors that might drive Abeta and Tau to cause damages on membranes. A strong body of evidences has demonstrated that certain lipids could promote these interactions and are then suspected to be involved into detrimental phenomena. However, numerous results appear to be contradicting and consensual conclusions are still lacking.This PhD was dedicated to the investigation of the effects of Abeta and K18, a key peptide fragment of Tau protein, on membranes with a particular focus on the influence of lipids. The aim of this work was to elucidate the action mechanisms of these peptides.To first comprehend how membrane damages can be induced, we first focused on the solubilising ability of extensively used amphiphile agents: detergents. As a first study, we revealed that the membrane composition and the physicochemical properties of lipids play an important role in driving the solubilisation of the bilayer, a process that can even lead to a selectivity during the lipid extraction.The core part of the project was to visualize the effects of the amyloid peptides Abeta and K18 on supported lipid bilayers as membrane models, using atomic force microscopy as an investigation technique. With its high spatial resolution and its ability to operate in physiological milieu, this approach has shown that the membrane composition could promote membrane disruption induced by Abeta oligomers in a lipid-dependent manner. More importantly, we propose that packing defects at the interface of membrane domains act as adsorption and nucleation sites leading to membrane damages.Using the same strategy, we observed that K18 could also induce solubilisation phenomenon and demonstrated to be sensitive to the aspect of lipid order in membranes.In both cases, we highlighted that these peptides could be detrimental to supported lipid bilayers and that their disruptive abilities, associated to detergent-like mechanisms, were intimately dependent of lipids. We also show that the aggregation, a phenomenon that can lead to the peptides fibrillation can only be triggered in presence of certain lipids.This work provides important insights about the decisive role of membrane composition in modulating interactions with the Abeta and K18. This interplay could constitute one of the numerous factors that promote neurotoxic phenomena, taking part in the complex neurodegenerative processes associated to Alzheimer’s disease
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Ury-Thiery, Vicky. "Agrégation in vitro de la protéine amyloïde Tau et étude de son impact sur des modèles membranaires par différentes méthodes biophysiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0440.
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Les maladies neurodégénératives, telles que les maladies d'Alzheimer et de Parkinson, affectent les fonctions cognitives et motrices. Elles se caractérisent par une perte progressive de neurones, sans possibilité de régénération. Avec le vieillissement de la population, ces pathologies, principalement liées à l'âge, représentent un enjeu sociétal majeur. L'absence de diagnostic précoce, de traitements efficaces et la méconnaissance des mécanismes en jeu soulignent la nécessité d'en approfondir la compréhension. Les patients atteints de ces maladies présentent des accumulations de protéines anormales sous forme d’agrégats insolubles, dans ou à proximité des cellules cérébrales. Bien que chaque protéinopathie présente des agrégats spécifiques, elles partagent des caractéristiques communes, notamment leur structure appelée amyloïde. Ces amyloïdes, formés par l’auto-assemblage de monomères protéiques mal conformés par empilement, adoptent une structure caractéristique dite en cross-β. Plusieurs protéines amyloïdes pathogènes ont été identifiées et sont associées à diverses maladies neurodégénératives. La protéine Tau, impliquée dans la maladie d'Alzheimer et plus largement dans un groupe de démences appelées tauopathies, est principalement localisée dans les neurones, où elle stabilise les microtubules, éléments structurants du cytosquelette cellulaire. Toutefois, dans des conditions pathologiques, Tau se dissocie des microtubules, devient hyperphosphorylée et forme des agrégats amyloïdes fibrillaires. Les mécanismes exacts de cette agrégation restent mal compris. L'étude de l'agrégation de Tau repose sur la production in vitro de fibres amyloïdes. En raison de sa solubilité élevée liée à sa charge positive, la formation de ces fibres nécessite l’ajout de molécules polyanioniques, appelées cofacteurs, telles que l’héparine (un polysaccharide), des ARN ou des lipides. Cependant, des incertitudes demeurent quant au rôle précis de ces cofacteurs : catalysent-ils simplement l'agrégation ou sont-ils intégrés dans la structure des fibres ? Si tel est le cas, quel impact cela a-t-il sur la morphologie des agrégats ? La capacité de Tau à s'agréger en présence de lipides suscite des interrogations sur son comportement vis à vis des différentes membranes des neurones. L’interaction de Tau avec les membranes plasmiques a été démontrée, et pourrait jouer un rôle autant dans des processus physiologiques que pathologiques. Tau, en présence de lipides anioniques, altère-t-elle l’intégrité membranaire ? Qu'en est-il des lipides non anioniques ? Pour répondre à ces questions, ce projet de thèse combine plusieurs approches biophysiques : spectroscopie infrarouge à réflexion totale atténuée (ATR-FTIR), microscopie à force atomique (AFM), microscopie électronique à transmission (MET) et résonance plasmonique de surface par ondes guidées (PWR). L’étude est structurée autour de deux axes principaux : (i) caractériser l’agrégation de Tau en présence de différents cofacteurs anioniques (héparine, ARN, phospholipides) et étudier l'impact sur la morphologie des fibres ; (ii) évaluer l’effet de l’interaction de Tau avec des membranes lipidiques de différentes compositions sur leur intégrité. Les résultats de cette thèse apportent de nouvelles perspectives sur les mécanismes pathogéniques de Tau et pourraient contribuer à une meilleure compréhension des tauopathies, ainsi qu'au développement de stratégies thérapeutiquesNeurodegenerative diseases, such as Alzheimer’s and Parkinson’s, affect cognitive and motor functions. They are characterized by a progressive loss of neurons, with no possibility of regeneration. With an aging population, these predominantly age-related diseases represent a major societal challenge. The lack of early diagnosis, effective treatments, and understanding of the underlying mechanisms highlights the need for further investigation. Patients suffering from these diseases exhibit abnormal protein accumulations in the form of insoluble aggregates, within or near brain cells. Although each proteinopathy presents specific aggregates, they share common features, notably their amyloid structure. These amyloids, formed by the misfolded protein monomers’ self-assembly through stacking, adopt a characteristic cross-β structure. Several pathogenic amyloid proteins have been identified and are associated with various neurodegenerative diseases. The Tau protein, implicated in Alzheimer’s disease and more broadly in a group of dementias known as tauopathies, is primarily located in neurons, where it stabilizes microtubules, structural elements of the cellular cytoskeleton. However, under pathological conditions, Tau dissociates from the microtubules, becomes hyperphosphorylated, and forms fibrillar amyloid aggregates. The exact mechanisms of this aggregation remain poorly understood. The study of Tau aggregation relies on the in vitro production of amyloid fibers. Due to its high solubility associated with its positive charge, fiber formation requires the addition of polyanionic molecules, called cofactors, such as heparin (a polysaccharide), RNA, or lipids. However, uncertainties remain regarding the exact role of these cofactors: do they simply catalyze aggregation, or are they integrated into the fiber structure? If so, what impact does this have on the morphology of the aggregates? Tau's ability to aggregate in the presence of lipids raises questions about its behavior in relation to the different membranes of neurons. Tau’s interaction with plasma membranes has been demonstrated and may play a role in both physiological and pathological processes. Does Tau, in the presence of anionic lipids, compromise membrane integrity? What about non-anionic lipids? To address these questions, this thesis project combines several biophysical approaches: attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), transmission electron microscopy (TEM), and plasmon waveguide resonance (PWR). The study is structured around two main axes: (i) characterizing Tau aggregation in the presence of different anionic cofactors (heparin, RNA, phospholipids) and studying their impact on fiber morphology; (ii) assessing the effect of Tau's interaction with lipid membranes of varying compositions on membrane integrity. The results of this thesis provide new insights into the pathogenic mechanisms of Tau and may contribute to a better understanding of tauopathies as well as the development of therapeutic strategies
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Polozov, Ivan V. "Interactions of class A and class L amphipathic helical peptides with model membranes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0006/NQ30110.pdf.
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Dannehl, Claudia. "Fragments of the human antimicrobial LL-37 and their interaction with model membranes". Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6814/.
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A detailed description of the characteristics of antimicrobial peptides (AMPs) is highly demanded, since the resistance against traditional antibiotics is an emerging problem in medicine. They are part of the innate immune system in every organism, and they are very efficient in the protection against bacteria, viruses, fungi and even cancer cells. Their advantage is that their target is the cell membrane, in contrast to antibiotics which disturb the metabolism of the respective cell type. This allows AMPs to be more active and faster. The lack of an efficient therapy for some cancer types and the evolvement of resistance against existing antitumor agents make AMPs promising in cancer therapy besides being an alternative to traditional antibiotics.
The aim of this work was the physical-chemical characterization of two fragments of LL-37, a human antimicrobial peptide from the cathelicidin family. The fragments LL-32 and LL-20 exhibited contrary behavior in biological experiments concerning their activity against bacterial cells, human cells and human cancer cells. LL-32 had even a higher activity than LL-37, while LL-20 had almost no effect. The interaction of the two fragments with model membranes was systematically studied in this work to understand their mode of action. Planar lipid films were mainly applied as model systems in combination with IR-spectroscopy and X-ray scattering methods. Circular Dichroism spectroscopy in bulk systems completed the results.
In the first approach, the structure of the peptides was determined in aqueous solution and compared to the structure of the peptides at the air/water interface. In bulk, both peptides are in an unstructured conformation. Adsorbed and confined to at the air-water interface, the peptides differ drastically in their surface activity as well as in the secondary structure. While LL-32 transforms into an α-helix lying flat at the water surface, LL-20 stays partly unstructured. This is in good agreement with the high antimicrobial activity of LL-32.
In the second approach, experiments with lipid monolayers as biomimetic models for the cell membrane were performed. It could be shown that the peptides fluidize condensed monolayers of negatively charged DPPG which can be related to the thinning of a bacterial cell membrane. An interaction of the peptides with zwitterionic PCs, as models for mammalian cells, was not clearly observed, even though LL-32 is haemolytic.
In the third approach, the lipid monolayers were more adapted to the composition of human erythrocyte membranes by incorporating sphingomyelin (SM) into the PC monolayers. Physical-chemical properties of the lipid films were determined and the influence of the peptides on them was studied. It could be shown that the interaction of the more active LL-32 is strongly increased for heterogeneous lipid films containing both gel and fluid phases, while the interaction of LL-20 with the monolayers was unaffected. The results indicate an interaction of LL-32 with the membrane in a detergent-like way.
Additionally, the modelling of the peptide interaction with cancer cells was performed by incorporating some negatively charged lipids into the PC/SM monolayers, but the increased charge had no effect on the interaction of LL-32. It was concluded, that the high anti-cancer activity of the peptide originates from the changed fluidity of cell membrane rather than from the increased surface charge. Furthermore, similarities to the physical-chemical properties of melittin, an AMP from the bee venom, were demonstrated.Aufgrund der steigenden Resistenzen von Zellstämmen gegen traditionelle Therapeutika sind alternative medizinische Behandlungsmöglichkeiten für bakterielle Infektionen und Krebs stark gefragt. Antimikrobielle Peptide (AMPs) sind Bestandteil der unspezifischen Immunabwehr und kommen in jedem Organismus vor. AMPs lagern sich von außen an die Zellmembran an und zerstören ihre Integrität. Das macht sie effizient und vor allem schnell in der Wirkung gegen Bakterien, Viren, Pilzen und sogar Krebszellen. Das Ziel dieser Arbeit lag in der physikalisch-chemischen Charakterisierung zweier Peptidfragmente die unterschiedliche biologische Aktivität aufweisen. Die Peptide LL-32 und LL-20 waren Teile des humanen LL-37 aus der Kathelizidin-Familie. LL-32 wies eine stärke Aktivität als das Mutterpeptid auf, während LL-20 kaum aktiv gegen die verschiedenen Zelltypen war. In dieser Arbeit wurde die Wechselwirkung der Peptide mit Zellmembranen systematisch anhand von zweidimensionalen Modellmembranen in dieser Arbeit untersucht. Dafür wurden Filmwaagenmessungen mit IR-spektroskopischen und Röntgenstreumethoden gekoppelt. Circulardichroismus-Spektroskopie im Volumen komplementierte die Ergebnisse. In der ersten Näherung wurde die Struktur der Peptide in Lösung mit der Struktur an der Wasser/Luft-Grenzfläche verglichen. In wässriger Lösung sind beide Peptidfragmente unstrukturiert, nehmen jedoch eine α-helikale Sekundärstruktur an, wenn sie an die Wasser/Luft-Grenzfläche adsorbiert sind. Das biologisch unwirksamere LL-20 bleibt dabei teilweise ungeordnet. Das steht im Zusammenhang mit einer geringeren Grenzflächenaktivität des Peptids. In der Zweiten Näherung wurden Versuche mit Lipidmonoschichten als biomimetisches Modell für die Wechselwirkung mit der Zellmembran durchgeführt. Es konnte gezeigt werden, dass sich die Peptide fluidisierend auf negativ geladene Dipalmitylphosphatidylglycerol (DPPG) Monoschichten auswirken, was einer Membranverdünnung an Bakterienzellen entspricht. Eine Interaktion der Peptide mit zwitterionischem Phosphatidylcholin (PC), das als Modell für Säugetierzellen verwendet wurde, konnte nicht klar beobachtet werden, obwohl biologische Experimente das hämolytische Verhalten zumindest von LL-32 zeigten. In der dritten Näherung wurde das Membranmodell näher an die Membran von humanen Erythrozyten angepasst, indem gemischte Monoschichten aus Sphingomyelin (SM) und PC hergestellt wurden. Die physikalisch-chemischen Eigenschaften der Lipidfilme wurden zunächst ausgearbeitet und anschließend der Einfluss der Peptide untersucht. Es konnte anhand verschiedener Versuche gezeigt werden, dass die Wechselwirkung von LL-32 mit der Modellmembran verstärkt ist, wenn eine Koexistenz von fluiden und Gelphasen auftritt. Zusätzlich wurde die Wechselwirkung der Peptide mit der Membran von Krebszellen imitiert, indem ein geringer Anteil negativ geladener Lipide in die Monoschicht eingebaut wurde. Das hatte allerdings keinen nachweislichen Effekt, so dass geschlussfolgert werden konnte, dass die hohe Aktivität von LL-32 gegen Krebszellen ihren Grund in der veränderten Fluidität der Membran hat und nicht in der veränderten Oberflächenladung. Darüber hinaus wurden Ähnlichkeiten zu Melittin, einem AMP aus dem Bienengift, dargelegt. Die Ergebnisse dieser Arbeit sprechen für einen Detergenzien-artigen Wirkmechanismus des Peptids LL-32 an der Zellmembran.
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Lambert, Eléonore. "Apports de la Microscopie à Force Atomique à l’étude de phénomènes dynamiques en biologie et développement instrumental associé". Thesis, Reims, 2018. http://www.theses.fr/2018REIMS014/document.
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Le Laboratoire de Recherche en Nanosciences EA 4682 s’est récemment équipé de la microscopie à force atomique haute-vitesse (HS-AFM) permettant la visualisation en temps réel des dynamiques d’interactions d’un panel infini d’échantillons biologiques à l’échelle nanométrique. De nombreux champ de recherche nécessite la mise au point de techniques permettant à la fois une imagerie dynamique (vidéomicroscopie) mais également de plus en plus une imagerie haute résolution (microscopie champ proche). Ce couplage a été récemment obtenu grâce au développement de la microscopie à force atomique ultra-rapide. La limitation actuelle de ce microscope ultra-rapide, à savoir l’acquisition d’informations en relation uniquement avec la surface de l’objet biologique étudié, crée un rempart à l’obtention de connaissances nouvelles sur les dynamiques sous-jacentes que renferment certains systèmes biomoléculaires. Pour s’affranchir de cette contrainte, nous nous proposons dans ce projet de faire évoluer notre outil de nanocaractérisation en lui ajoutant des fonctionnalités optiques et des fonctionnalités permettant de faire de la spectroscopie de force. La conduite de ce projet se fera selon un travail de développement instrumental scindé en deux grandes étapes : - l’apport d’outils de microscopie optique conventionnels : FRAP – FRET – FLIM – Fluorescence – TIRFM. Nous couplons ainsi la nanocaractérisation hautement résolue spatialement et temporellement avec des informations intrinsèques de nos échantillons. Cette complémentarité apparaît de plus en plus comme fondamentale dans les demandes des biologistes. - la mise au point de protocoles de fonctionnalisation de leviers AFM afin de réaliser de la spectroscopie de force et ainsi obtenir des informations sur les propriétés mécaniques des échantillons biologiques. Ce projet de recherche sera réalisé au Laboratoire de Recherche en Nanosciences EA 4682, Université de Reims Champagne Ardenne sous la direction du Pr. Michael Molinari et du Dr. Maxime Ewald récemment recruté en tant que maître de conférences (sept. 2013) et qui pu démarrer la thématique de la microscopie AFM haute-vitesse au sein de l’équipe. Il s’effectuera en collaboration avec le Pr. T. Ando du Biophysics Lab’ de l’Université de Kanazawa (Japon) pour la partie instrumentation, et avec le Dr. Gabriel Paës pour l’étude des échantillons biologiques. Les objets étudiés lors de cette thèse seront liés au projet ANR Lignoprog qui vient de démarrer au 1er novembre 2014 porté par Dr. Gabriel Paës (INRA UMR FARE, Reims). Dans ce projet, des échantillons biologiques se doivent d’être caractériser en dynamique. Ils concernent la biomasse lignocellulosique (BL), réseau complexe de polymères constituant les parois végétales (PV). La complexité architecturale et chimique de la BL est un frein à sa conversion industrielle. Pour atteindre ce but, non seulement la fraction cellulosique mais aussi les fractions hémicellulosiques et ligneuses doivent être valorisées, sinon les bio-raffineries ne seront pas compétitives. Le principal challenge à relever est celui du coût élevé et de la relative faible efficacité de l’étape de déconstruction enzymatique de la BL. Avec les fonctionnalités d’imagerie développées dans ce projet, nous espérons apporter des éléments de réponses sur la déconstruction enzymatique. Par ailleurs, même si les objets étudiés seront principalement ceux du projet Lignoprog, une validation du dispositif pourra être réalisée en parallèle sur d’autres échantillons biologiques tels que des cellules vivantes seront envisagées : caractérisation, mise en évidence leur réactivité vis-à-vis des divers paramètres physiologiques du milieu (pH, concentration, composition), corrélation de ces résultats avec leurs propriétés mécaniquesOur laboratory recently acquired a high-speed atomic force microscope (HS-AFM) which enables us to visualize in real time a wide range of biological samples and their dynamics of interaction at nanoscale. Several research fields require the development of new techniques in order to get high resolution imaging and dynamic imaging at the same time. This is why HS-AFM was developed. Its current limitation is that the only data it provides are about the surface which means we can’t get access to what occurs beneath. This is limiting the knowledge we could get about the underlying dynamics of some biomolecular system. In order to overcome this issue, we propose to upgrade this nanocharacterization tool by combining optical microscopy and force spectroscopy. This project of instrumental development will be in two major steps: - the adding of conventional optical microscopy : fluorescence, TIRFM, FRAP, FRET, FLIM. The aim is to nanocharacterize sample with highly spatiotemporal data combined in combination with integral data (fundamental to respond to biological issues) - the development of tip functionalization protocols in order to achieve force spectroscopy and get mechanical properties of biological samples This project will take place at the Laboratory of Research in Nanosciences, EA 4682, University of Reims Champagne Ardennes, under the supervision of Pr. Michael Molinari and Dr. Maxime Ewald who started HS-AFM among our team. We will collaborate with Pr. T. Ando from the Biophysics Lab of Kanazawa University (Japan) for the instrumental part and with Dr. Gabriel Paës for the biological samples. The samples used during this thesis will be linked to an ANR project called Lignoprog directed by Dr. Gabriel Paës (INRA, UMR FARE, Reims) and started on the first of November, 2014. In the project, the dynamical aspect of the biological samples is essential. Indeed, lignocellulosic biomass is a complex network of polymers composing plant cell wall. Its architectural and chemical complexity prevents its industrial conversion. In order to be cost-effective, bio refineries need to valorize all the fractions: cellulose, hemicelluloses and lignins. The major challenge is the high cost and low efficiency of the enzymatic hydrolysis of the lignocellulosic biomass. Our aim is to bring some answer to understand better and improve enzymatic hydrolysis thanks to the HS-AFM and the combination of new functionalities. By the way, the disposal might be validated on other biological samples in parallel, such as live cells in order to characterize them, enlighten their reactivity in response to physiological parameters of the medium (pH, concentration, composition) and correlate the results with mechanical properties
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Bechtella, Leïla. "Molecular analysis of the interactions of the cell-penetrating peptide Penetratin and lipid membranes. Contributions of the lipid PIP2, biophysical approaches and benzophenone photoreactivity in model membranes". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS045.
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Les peptides vecteurs (CPP) peuvent entrer dans les cellules et y transporter des molécules biologiquement actives. De précédents travaux ont montré que les CPP pouvaient remodeler le cytosquelette d'actine, interagissaient fortement avec les lipides chargés négativement et que le PIP2 pourrait jouer un rôle dans l'internalisation de la Pénétratine. Nos expériences en DSC ont montré que la Pénétratine interagit avec les têtes polaires et influence la fluidité de la membrane de vésicules contenant du PIP2. La présence de PIP2 favorise l’interaction Pénétratine-lipide. De plus, l’estimation de l'affinité de liaison par fluorescence du tryptophane a montré que la Pénétratine a une affinité plus élevée pour le PIP2 que pour la PS. Le photomarquage par affinité couplé à la spectrométrie de masse, à l'aide de peptides fonctionnalisés par une benzophénone (Bzp), a permis d’étudier les interactions non covalentes des CPP et des membranes lipidiques à un niveau moléculaire. Le PIP2 s'est avéré être un partenaire d'interaction de la Pénétratine et a été marqué préférentiellement dans les liposomes contenant du PC, de la PS et du PIP2. Nous avons mis en évidence des réactions secondaires très informatives qui peuvent se produire simultanément lors de l'irradiation UV, dans un unique système biologique : un CPP inséré dans une bicouche lipidique. Ce travail montre comment exploiter de manière originale les différentes réactivités de la Bzp dans le contexte d'une membrane lipidique, informant sur l'interaction CPP/lipide au niveau moléculaire comme la profondeur d'insertion ou la fluidité membranaire au voisinage du CPPCell-penetrating peptides (CPP) can cross cell membranes and deliver biologically active molecules into cells. Previous work showed that CPPs could remodel the actin cytoskeleton, interacted strongly with negatively charged lipids and PIP2 could play a role in Penetratin internalization. Our DSC experiments showed that Penetratin interacts with polar head groups and impacts the lipid bilayer fluidity of PIP2-containing liposomes. It indicated that presence of PIP2 in liposomes triggers Penetratin-lipid interaction. Moreover, Penetratin binding affinity for PIP2-containing lipid vesicles, estimated by tryptophan fluorescence, pointed out that Penetratin has a higher affinity for PIP2 than for PS. Affinity photocrosslinking coupled to mass spectrometry, using benzophenone (Bzp)-functionalized peptides, was used to study the non-covalent interactions of CPPs and lipid membranes at a molecular level. PIP2 was found to be a good interaction partner for Penetratin and was preferably labelled in liposomes containing PC, PS and PIP2. We revealed highly informative secondary reactions occurring during UV irradiation that can occur concomitantly in a single biological system: a membrane-active peptide inserted within a phospholipid bilayer. This work shows how to exploit in an original way the different reactivities of Bzp in the context of a lipid membrane, giving access to information on the CPP/lipid interaction at a molecular level such as depth of insertion or membrane fluidity in the CPP vicinity
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Veatch, Sarah Louise. "Liquid immiscibility in model bilayer lipid membranes /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9772.
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Nomura, Daniela Akiko. "Caracterização estrutural de dispersões aquosas de lipídios aniônicos". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-08052018-005348/.
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É conhecido que a força iônica do meio desempenha um papel fundamental na estrutura de vesículas aniônicas de DMPG (dimiristoil fosfatidilglicerol) em dispersões aquosas. A baixa força iônica (~ 6 mM), as dispersões de DMPG exibem várias características anômalas, que foram interpretadas como a abertura de poros na bicamada ao longo da larga região de transição de fase gel-fluida (de ~ 18°C a 30°C). Aqui, revisitamos o sistema de DMPG em tampão a baixa força iônica, mas com dispersões obtidas após a extrusão por filtros de 100 nm, portanto menos polidispersas. Para enfatizar as interações eletrostáticas entre as cabeças polares dos lipídios, que não estarão blindadas pela presença de sais na solução, estudamos dispersões de DMPG em água pura, de modo a monitorar os agregados presentes na dispersão, e suas interações. As dispersões em água foram caracterizadas antes e depois da extrusão. Para tal, utilizamos diversas técnicas experimentais, em diferentes temperaturas: espalhamento de luz estático (SLS) e dinâmico (DLS), calorimetria diferencial de varredura (DSC), Ressonância Paramagnética Eletrônica (RPE) de marcadores de spin incorporados aos agregados, espalhamento de raios-X a altos e baixos ângulos (WAXS e SAXS), e medidas de viscosidade, turbidez, mobilidade eletroforética e condutividade elétrica. Resultados das várias técnicas com dispersões extrusadas de DMPG em tampão mostraram que o comportamento anômalo é observado de forma similar ao de dispersões não extrusadas. Entretanto, o pico de SAXS em muito baixo ângulo é visto de 5 a 45°C, e não apenas na região de transição de fase, portanto não deve ser modelado como a distância entre poros na bicamada lipídica que se abririam nesta região. A distância de repetição relacionada a este pico diminui na região de transição de fase, e com o aumento da concentração lipídica. Medidas de DSC indicaram que, em água, a região de transição de fase da vesícula de DMPG é ainda mais ampla, começando em torno de 10°C, mas ainda terminando em ~ 30oC. No entanto, a alta condutividade elétrica, viscosidade, mobilidade eletroforética, raio efetivo, e a baixa turbidez, vistas apenas na região de transição de fase do DMPG em tampão, são encontradas até altas temperaturas em água, quando a bicamada lipídica já se encontra na fase fluida. Medidas de RPE e WAXS mostraram a transição da membrana de uma fase mais rígida/imóvel/organizada para uma fase mais frouxa/móvel. Dados de espalhamento de luz, RPE e SAXS mostram que, similar ao DMPG em tampão, em água, o DMPG organiza-se como vesículas esféricas, unilamelares, mas possivelmente menores e mais carregadas, exibindo fortes interações vesícula-vesícula. Nas medidas de SAXS, o pico de Bragg na região de muito baixo ângulo foi visto em todas as temperaturas (de 5 a 60°C), sendo que a distância de repetição diminui para temperaturas maiores do que 10oC. Os resultados obtidos para dispersões em água, reforçam o comportamento anômalo observado anteriormente para dispersões em tampão em baixa força iônica. De acordo com eles, propomos a existência de vesículas altamente deformadas e ionizadas a partir de uma certa temperatura, T1 para o DMPG em água e Tmon em tampão baixa força iônica, sendo que em água a forte repulsão eletrostática PG--PG- levaria a fortes deformações e interações vesícula-vesícula, em uma ampla extensão de temperaturas.It is known that the ionic strength plays a fundamental role in the structure of DMPG (dimyristoyl phosphatidylglycerol) anionic vesicles in water medium. At low ionic strength (~ 6 mM), DMPG dispersions display several anomalous characteristics, which were interpreted as the opening of bilayer pores along the wide bilayer gel-fluid transition region (from ~ 18°C to 30°C). Here, we revisit DMPG in buffer at low ionic strength, but with dispersions obtained after the extrusion by 100 nm filters, thus less polydisperse. To emphasize electrostatic interactions between the polar head-groups, which will not be shielded by ions in solution, we studied DMPG dispersions in pure water to monitor the aggregates in the dispersion and their interactions. Water dispersions were characterized before and after extrusion. For such, we used several experimental techniques, at different temperatures: light scattering, both static (SLS) and dynamic (DLS); differential scanning calorimetry (DSC); electron spin resonance (ESR) of spin labels incorporated into the aggregates, Small and Wide Angle X-Ray Scattering (SAXS and WAXS); and viscosity, turbidity, electrophoretic mobility and electrical conductivity measurements. Several techniques with extruded dispersions of DMPG in buffer showed that the anomalous behavior is also observed. However, the SAXS peak at very low angles is seen from 5 to 45°C, and not only in the phase transition region, therefore it should not be modeled as the distance of correlated pores in the lipid bilayer that would open in this region. The repeating distance related to this peak decreases in the phase transition region, and with increasing lipid concentration. DSC indicates that, in water, the bilayer gel-fluid transition is even wider, starting around 10oC but still ending ~ 30oC. However, high electric conductivity, viscosity, electrophoretic mobility, effective radius and low turbidity found only in the gel-fluid transition region for DMPG in buffer, are found at higher temperatures in water, when lipid bilayers are already in the fluid state. ESR and WAXS measurements evidenced the transition of the membrane from a more rigid/immobile/organized phase to a more soft/mobile phase. Light scattering, ESR and SAXS data showed that, similar to DMPG in buffer, in water, DMPG is organized as spherical unillamelar vesicles, but possibly smaller, highly charged, displaying strong vesicle-vesicle interactions. With SAXS the Bragg peak at very low angles was seen at all temperatures (from 5 to 60°C) with the repetition distance decreasing at temperatures higher than 10 ° C. The results obtained for water dispersions reinforce the anomalous behavior previously observed for buffer at low ionic strength dispersions. According to them, we propose the existence of highly deformed and ionized vesicles from a certain temperature, T1 for DMPG in water and Tmon in buffer at low ionic strength. In water the strong PG- - PG- electrostatic repulsion would lead to strong deformations and vesicle-vesicle interactions, over a wide range of temperatures.
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De, Ghellinck D'Elseghem Alexis. "Natural and model membranes: structure and interaction with bio-active molecules via neutron reflection". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209550.
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Dans cette thèse de doctorat, la structure de membranes naturelles et modèles et leurs interactions avec des molécules biologiquement actives ont été étudiées au moyen de la réflectométrie de neutrons. Les lipides naturels ont été extraits de la levure Pichia pastoris, poussée en milieux deutéré et hydrogéné. L’analyse a montré que la quantité relative de phospholipides n’est pas affectée par le changement en composition isotopique du milieu de croissance. Cependant, les cellules de levures deutérées contiennent principalement des acides gras C18 :1 alors que le degré d’insaturation est plus élevé chez les levures hydrogénés. Diminuer la température du milieu de croissance permet d’augmenter le degré d’insaturation des acides gras chez les levures deutérées. Une analyse qualitative des sphingolipides a été réalisée et un protocole pour séparer les fractions phosphocholines et phosphoethanolamine a été établi.La structure de bicouches composées des lipides de levures a été étudiée par réflectivité de neutrons. La bicouche composée de lipides deutérés polaires a une épaisseur similaire aux bicouches faites de phosphocholines C18:1 synthétiques. En présence de stérols, la rugosité aux interfaces entre les têtes polaires et les chaînes augmente. La bicouche composée de lipides polaires hydrogénés est plus mince que celle deutérée. Ceci est dû à la composition en acides gras beaucoup plus variée et du plus grand nombre d’insaturations. En présence de stérols, l’épaisseur de la bicouche hydrogénée augmente.
L’interaction de ces bicouches avec l’amphotéricine B (AmB) a été étudiée. L’AmB est un antifongique qui interagit fortement avec les membranes contenant de l’ergostérol et moins fortement avec des membranes contenant du cholestérol. Dans tous les cas, les molécules d’AmB forment une couche épaisse et diluée au dessus de la bicouche lipidique. En présence de stérols, les molécules d’AmB pénètrent dans la bicouche et change sa structure selon la composition en acide gras.
La structure de bicouches lipidiques de plante et leurs interactions avec des intermédiaires de synthèse ont aussi été étudiées par réflectivité de neutrons. Des mélanges ternaires de plantes étaient déposés sur silicium et des mélanges quaternaires sur saphir. L’épaisseur de la bicouche composée de mélange ternaire est de 38 Å, tandis que celle du mélange ternaire est de 28 Å, la différence venant probablement d’un effet de substrat. La présence de diacylglycérol (DAG) a comme conséquence d’augmenter l’aire par lipide, et ainsi de changer la conformation des têtes polaires. L’interaction des bicouches de lipide de plante avec l’acide phosphatidique (PA) dans le but d’observer un flip-flop possible a aussi été étudiée mais le PA a tendance à désorbé les bicouches du substrat et aucun mécanisme de flip flop n’a été détecté.
Finalement, la localisation d’une petite molécule, le resvératrol, dans des bicouches modèles a été étudiée. Le resvératrol est connu pour être responsable du « paradoxe français » qui est une corrélation inverse entre la consommation d’aliment gras et un faible taux de maladie cardiaque. Quand le resvératrol est adsorbé à partir de la phase liquide, il induit une réorganisation des têtes polaires. Quand il est déposé sur le substrat en présence des lipides, il est présent à l’interface entre les têtes polaires et les chaines.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Książki na temat "Lipidic model membranes"
1
Derek, Marsh, red. Phospholipid bilayers: Physical principles and models. New York: Wiley, 1987.
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L, Longo Marjorie, Risbud Subhash H, Jue Thomas i SpringerLink (Online service), red. Biomembrane Frontiers: Nanostructures, Models, and the Design of Life. Totowa, NJ: Humana Press, 2009.
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Cholesterol in membrane models. Boca Raton, Fla: CRC Press, 1992.
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Katsaras, John, Georg Pabst, Norbert Kucerka i Mu-Ping Nieh. Liposomes, Lipid Bilayers and Model Membranes: From Basic Research to Application. Taylor & Francis Group, 2014.
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Pabst, Georg. Liposomes, Lipid Bilayers and Model Membranes: From Basic Research to Application. Taylor & Francis Group, 2014.
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Katsaras, J., Georg Pabst, Norbert Kucerka i Mu-Ping Nieh. Liposomes, Lipid Bilayers and Model Membranes: From Basic Research to Application. Taylor & Francis Group, 2016.
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Katsaras, John, Georg Pabst, Norbert Kucerka i Mu-Ping Nieh. Liposomes, Lipid Bilayers and Model Membranes: From Basic Research to Application. Taylor & Francis Group, 2014.
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Liposomes, Lipid Bilayers and Model Membranes: From Basic Research to Application. Taylor & Francis Group, 2014.
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Electrical Properties of Model Lipid Membranes. MDPI, 2022. http://dx.doi.org/10.3390/books978-3-0365-4057-3.
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Naumowicz, Monika. Electrical Properties of Model Lipid Membranes. Mdpi AG, 2022.
Znajdź pełny tekst źródłaCzęści książek na temat "Lipidic model membranes"
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Grancelli, A., J. Cladera, J. Villaverde, J. Trias i A. Morros. "Interactions of Fluoroquinolone Antibiotics with Model Lipidic Membranes: An FT-IR Study". W Spectroscopy of Biological Molecules: Modern Trends, 321–22. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5622-6_143.
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Bienvenüe, A., J. Sainte-Marie i L. Maurin. "Protein-Lipid and Lipid-Lipid interactions in model systems and in biological membranes". W Trafficking of Intracellular Membranes:, 1–10. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79547-3_1.
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Prosser, R. Scott, i Charles R. Sanders. "Solid State NMR Approaches to the Study of Membrane Proteins in Magnetically Aligned Model Membranes". W Lipid Bilayers, 207–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-662-04496-4_10.
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Stegmann, Toon, Justin Teissie i Mathias Winterhalter. "Fusion and Rupture of Lipid Model Membranes". W Lipid Bilayers, 265–87. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-662-04496-4_12.
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Raleigh, J. A. "Radiation Peroxidation in Model Membranes". W Prostaglandin and Lipid Metabolism in Radiation Injury, 3–27. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-5457-4_1.
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Tilcock, C., S. Eastman i D. Fisher. "Determination of Lipid Asymmetry and Exchange in Model Membrane Systems". W Cell and Model Membrane Interactions, 1–14. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3854-7_1.
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McIntosh, Thomas J., Alan D. Magid i Sidney A. Simon. "Short-Range Repulsive Interactions between the Surfaces of Lipid Membranes". W Cell and Model Membrane Interactions, 249–65. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3854-7_15.
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Skolnick, Jeffrey, i Mariusz Milik. "Monte Carlo Models of Spontaneous Insertion of Peptides into Lipid Membranes". W Biological Membranes, 535–54. Boston, MA: Birkhäuser Boston, 1996. http://dx.doi.org/10.1007/978-1-4684-8580-6_16.
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Verkleij, A. J., R. Van Venetië, J. Leunissen-Bijvelt, B. de Kruijff, M. Hope i P. R. Cullis. "Membrane Fusion and Lipid Polymorphism". W Physical Methods on Biological Membranes and Their Model Systems, 179–92. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-7538-8_13.
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Kimelberg, H. K. "Membrane Fluidity and Lipid Composition". W Physical Methods on Biological Membranes and Their Model Systems, 261–76. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-7538-8_19.
Pełny tekst źródłaStreszczenia konferencji na temat "Lipidic model membranes"
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Kononova, P. A., O. Yu Selyutina, V. V. Fomenko i N. E. Polyakov. "INTERACTION OF ANTIVIRAL TRITERPENOIDS WITH THE TRANSMEMBRANE DOMAIN OF THE SARS-COV-2 E-PROTEIN IN A MODEL MEMBRANE". W X Международная конференция молодых ученых: биоинформатиков, биотехнологов, биофизиков, вирусологов и молекулярных биологов — 2023. Novosibirsk State University, 2023. http://dx.doi.org/10.25205/978-5-4437-1526-1-186.
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The interaction of glycyrrhizic acid (GA) and glycivir with the transmembrane domain of the SARS-CoV-2 E-protein in model lipid membranes was studied by nuclear magnetic resonance methods. The interaction of GA, glycivir, and the peptide with bilayer lipids was shown, the effect of GA on the mobility of both lipids and peptide molecules and the mutual influence of the peptide and antiviral agents on localization in the membrane was found.
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Lykotrafitis, George, i He Li. "Two-Component Coarse-Grain Model for Erythrocyte Membrane". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62133.
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Biological membranes are vital components of living cells as they function to maintain the structural integrity of the cells. Red blood cell (RBC) membrane comprises the lipid bilayer and the cytoskeleton network. The lipid bilayer consists of phospholipids, integral membrane proteins, peripheral proteins and cholesterol. It behaves as a 2D fluid. The cytoskeleton is a network of spectrin tetramers linked at the actin junctions. It is connected to the lipid bilayer primarily via Band-3 and ankyrin proteins. In this paper, we introduce a coarse-grained model with high computational efficiency for simulating a variety of dynamic and topological problems involving erythrocyte membranes. Coarse-grained agents are used to represent a cluster of lipid molecules and proteins with a diameter on the order of lipid bilayer thickness and carry both translational and rotational freedom. The membrane cytoskeleton is modeled as a canonical exagonal network of entropic springs that behave as Worm-Like-Chains (WLC). By simultaneously invoking these characteristics, the proposed model facilitates simulations that span large length-scales (∼ μm) and time-scales (∼ ms). The behavior of the model under shearing at different rates is studied. At low strain rates, the resulted shear stress is mainly due to the spectrin network and it shows the characteristic non-linear behavior of entropic networks, while the viscosity of the fluid-like lipid bilayer contributes to the resulting shear stress at higher strain rates. The apparent ease of this model in combining the spectrin network with the lipid bilayer presents a major advantage over conventional continuum methods such as finite element or finite difference methods for cell membranes.
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El-Beyrouthy, Joyce, i Eric C. Freeman. "Rapid and Real-Time Measurement of Membrane Potential Through Intramembrane Field Compensation". W ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/smasis2020-2352.
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Abstract Synthetic lipid membranes are self-assembled biomolecular double layers designed to approximate the properties of living cell membranes. These membranes are employed as model systems for studying the interactions of cellular envelopes with the surrounding environment in a controlled platform. They are constructed by dispersing amphiphilic lipids into a combination of immiscible fluids enabling the biomolecules to self-assemble into ordered sheets, or monolayers at the oil-water interface. The adhesion of two opposing monolayer sheets forms the membrane, or the double layer. The mechanical properties of these synthetic membranes often differ from biological ones mainly due to the presence of residual solvent in between the leaflets. In fact, the double layer compresses in response to externally applied electrical field with an intensity that varies depending on the solvent present. While typically viewed as a drawback associated with their assembly, in this work the elasticity of the double layer is utilized to further quantify complex biophysical phenomena. The adsorption of charged molecules on the surface of a lipid bilayer is a key property to decipher biomolecule interactions at the interface of the cell membrane, as well as to develop effective antimicrobial peptides and similar membrane-active molecules. This adsorption generates a difference in the boundary potentials on either side of the membrane which may be tracked through electrophysiology. The soft synthetic membranes produced in the laboratory compress when exposed to an electric field. Tracking the minimum membrane capacitance allows for quantifying when the intrinsic electric field produced by the asymmetry is properly compensated by the supplied transmembrane voltage. The technique adopted in this work is the intramembrane field compensation (IFC). This technique focuses on the current generated by the bilayer in response to a sinusoidal voltage with a DC component, VDC. Briefly, the output sinusoidal current is divided into its harmonics and the second harmonic equals zero when VDC compensates the internal electric field. In this work, we apply the IFC technique to droplet interface bilayers (DIB) enabling the development of a biological sensor. A certain membrane elasticity is needed for accurate measurements and is tuned through the solvent selection. The asymmetric DIBs are formed, and an automated PID-controlled IFC design is implemented to rapidly track and compensate the membrane asymmetry. The closed loop system continuously reads the current and generates the corresponding voltage until the second harmonic is abated. This research describes the development and optimization of a biological sensor and examines how varying the structure of the synthetic membrane influences its capabilities for detecting membrane-environment interactions. This platform may be applied towards studying the interactions of membrane-active molecules and developing models for the associated phenomena to enhance their design.
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Zhelev, Doncho V., i David Needham. "Pore Formation and Pore Dynamics in Bilayer Membranes". W ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0750.
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Abstract Pore formation in cell membranes is widely used to deliver hydrophilic substances to the cell interior, such as DNA, drugs etc. Among the methods used for pore formation are electroporation and exposure of the membrane to mild surfactants, such as digitonin or lysolipid. Pore formation in the first case is a result of the apparent electrocompression generated across the membrane, while in the second case, it is a result of the preferential partitioning of the surfactant molecules at the edge of spontaneously formed membrane defects. Both in electroporation and when surfactants are used, pores form mainly in lipid membrane domains. Thus, the use of model membranes allows us to access important characteristics of pore formation and dynamics, such as their dependence on membrane composition and far field membrane tension. The role of these characteristics in pore formation is studied by using single lipid vesicles, which are manipulated by glass micropipets.
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Zakharova, A. A., S. S. Efimova i O. S. Ostroumova. "RESEARCH OF THE ABILITY OF ANIDULAFUNGIN TO FORM PORES IN MODEL MEMBRANES OF VARIOUS COMPOSITION". W X Международная конференция молодых ученых: биоинформатиков, биотехнологов, биофизиков, вирусологов и молекулярных биологов — 2023. Novosibirsk State University, 2023. http://dx.doi.org/10.25205/978-5-4437-1526-1-176.
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It was for the first time showed that anidulafungin is able to form ion-permeable pores in model membranes formed by inverted cone-shaped lipids. It might indicate a significant contribution of changes in the distribution of the lateral pressure in the bilayer in the regulation of the membrane activity of the antibiotic.
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Freeman, Eric C., Michael K. Philen i Donald J. Leo. "Combined Modeling of Bilayer Networks for Sensing Applications". W ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8115.
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The bilayer lipid membrane (BLM) is a naturally occurring thin layer of phospholipid molecules that surrounds cellular systems. The membrane operates as a near-impermeable barrier allowing for the generation of membrane potentials across the layer through changes in ionic concentrations. This membrane is required for regular cell function ranging from storing energy to passing signals. Engineering advancements have allowed for the rapid creation of artificial bilayer membranes, and these membranes are currently considered for many biomimetic applications. The application of interest for this paper is the further development of these cellular systems for sensing applications. This will be accomplished through a combined fluid-bilayer model, allowing for study of the bilayer transduction properties at both high and low frequencies. Several approaches are discussed and applied to multiple cell systems with or without embedded voltage-dependent ion pores. Finally the results are studied and evidence is presented for the development of a new molecular model for cellular systems combining chemical, electrical, and mechanical stimuli.
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Karlsson, Jens O. M., i Mehmet Toner. "Thermally-Induced Pore Formation in Cell Membranes". W ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0745.
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Abstract A statistical mechanical model of pore formation in lipid bilayer membranes due to thermal fluctuations is coupled with a model of diffusion in pores to obtain predictions of cell membrane permeabilities to a variety of molecules. Predictions of pore size distributions in the cell membrane, as well as activation energies for transmembrane transport, are obtained for water, glycerol, and electrolytes, in a wide range of cell types. A good correlation between theoretical predictions and experimental data from the literature indicates that diffusion through transient bilayer pores may be an important cause of increased membrane permeability in thermally stressed cells.
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Alapati, Raghava, Dorel Moldovan i Ram V. Devireddy. "Asymmetry of Structural Characteristics of Lipid Bilayers Induced by Dimethylsulfoxide: An Atomistic Simulation Study". W ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192813.
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In a typical cryopreservation protocol, the system to be preserved is first equilibrated with chemicals known as cryoprotective agents (CPAs). CPAs have been shown to alleviate cell damage from either the solute effects or the formation of intracellular ice during the subsequent freezing process. Thus, an extensive body of literature reporting the effects of CPAs on cellular systems has been accumulated over the last 50 years; detailing largely experimental interactions between cell systems and chemicals. Recent advances in computational methodology now offer an additional dimension in our ability to understand the molecular interactions between cell membranes, idealized as lipid bilayers and CPAs at atomistic scales. Computer simulations provide unique capabilities for analyzing biomembrane properties from atomistic perspective with a degree of detail that is hard to reach by other techniques. The excellent agreement with the experiment obtained in various molecular dynamics (MD) studies [1] on simple model membranes has raised the confidence in applying the molecular dynamics simulations to even more complex systems. Dimethylsulfoxide (DMSO) is one of the most widely used solvents in cell biology and cryopreservation. During a typical cryopreservation protocol the DMSO composition of aqueous buffers inside and outside of the cell is known to differ considerably. To model and understand the structural changes in cell membranes in such a situation we performed MD simulations of an idealized lipid bilayer membrane which separates two aqueous reservoirs with and without DMSO. Zwitterionic dimyritoylphosphatidylcholine (DMPC) lipid bilayers was chosen as the model membrane.
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Zlochevskiy, I. I., i D. V. Zav’yalov. "INVESTIGATION OF THE RESPONSE OF A DPPC MEMBRANE IN AN AQUEOUS SOLUTION OF NACL TO AN ALTERNATING ELECTRIC FIELD USING THE METHOD OF CLASSICAL MOLECULAR DYNAMICS". W Actual problems of physical and functional electronics. Ulyanovsk State Technical University, 2023. http://dx.doi.org/10.61527/appfe-2023.218-220.
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The results of a theoretical study of the impact of an alternating electric field on the biological structure of a coarse-grained model of a lipid membrane consisting of DPPC-lipids by the method of classical molecular dynamics are presented.
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Zhu, Qiang, Zhangli Peng i Robert J. Asaro. "Investigation of RBC Remodeling With a Multiscale Model". W ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13121.
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Erythrocyte (red blood cell, or RBC) possesses one of the simplest and best characterized molecular architectures among all cells. It contains cytosol enclosed inside a composite membrane consisting of a fluidic lipid bilayer reinforced by a single layer of protein skeleton pinned to it. In its normal state, this system demonstrates tremendous structural stability, manifested in its ability to sustain large dynamic deformations during circulation. On the other hand, it has been illustrated in experiments that triggered by mechanical loads structural remodeling may occur. A canonical example of this remodeling is vesiculation, referring to the partial separation of the lipid bilayer from the protein skeleton and the formation of vesicles that contain lipids only.
Raporty organizacyjne na temat "Lipidic model membranes"
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Wang, X. F., i M. Schuldiner. Systems biology approaches to dissect virus-host interactions to develop crops with broad-spectrum virus resistance. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2020. http://dx.doi.org/10.32747/2020.8134163.bard.
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More than 60% of plant viruses are positive-strand RNA viruses that cause billion-dollar losses annually and pose a major threat to stable agricultural production, including cucumber mosaic virus (CMV) that infects numerous vegetables and ornamental trees. A highly conserved feature among these viruses is that they form viral replication complexes (VRCs) to multiply their genomes by hijacking host proteins and remodeling host intracellular membranes. As a conserved and indispensable process, VRC assembly also represents an excellent target for the development of antiviral strategies that can be used to control a wide-range of viruses. Using CMV and a model virus, brome mosaic virus (BMV), and relying on genomic tools and tailor-made large-scale resources specific for the project, our original objectives were to: 1) Identify host proteins that are required for viral replication complex assembly. 2) Dissect host requirements that determine viral host range. 3) Provide proof-of-concept evidence of a viral control strategy by blocking the viral replication complex-localized phospholipid synthesis. We expect to provide new ways and new concepts to control multiple viruses by targeting a conserved feature among positive-strand RNA viruses based on our results. Our work is going according to the expected timeline and we are progressing well on all aims. For Objective 1, among ~6,000 yeast genes, we have identified 96 hits that were possibly play critical roles in viral replication. These hits are involved in cellular pathways of 1) Phospholipid synthesis; 2) Membrane-shaping; 3) Sterol synthesis and transport; 4) Protein transport; 5) Protein modification, among many others. We are pursuing several genes involved in lipid metabolism and transport because cellular membranes are primarily composed of lipids and lipid compositional changes affect VRC formation and functions. For Objective 2, we have found that CPR5 proteins from monocotyledon plants promoted BMV replication while those from dicotyledon plants inhibited it, providing direct evidence that CPR5 protein determines the host range of BMV. We are currently examining the mechanisms by which dicot CPR5 genes inhibit BMV replication and expressing the dicot CPR5 genes in monocot plants to control BMV infection. For Objective 3, we have demonstrated that substitutions in a host gene involved in lipid synthesis, CHO2, prevented the VRC formation by directing BMV replication protein 1a (BMV 1a), which remodels the nuclear membrane to form VRCs, away from the nuclear membrane, and thus, no VRCs were formed. This has been reported in Journal of Biological Chemistry. Based on the results from Objective 3, we have extended our plan to demonstrate that an amphipathic alpha-helix in BMV 1a is necessary and sufficient to target BMV 1a to the nuclear membrane. We further found that the counterparts of the BMV 1a helix from a group of viruses in the alphavirus-like superfamily, such as CMV, hepatitis E virus, and Rubella virus, are sufficient to target VRCs to the designated membranes, revealing a conserved feature among the superfamily. A joint manuscript describing these exciting results and authored by the two labs will be submitted shortly. We have also successfully set up systems in tomato plants: 1) to efficiently knock down gene expression via virus-induced gene silencing so we could test effects of lacking a host gene(s) on CMV replication; 2) to overexpress any gene transiently from a mild virus (potato virus X) so we could test effects of the overexpressed gene(s) on CMV replication. In summary, we have made promising progress in all three Objectives. We have identified multiple new host proteins that are involved in VRC formation and may serve as good targets to develop antiviral strategies; have confirmed that CPR5 from dicot plants inhibited viral infection and are generating BMV-resistance rice and wheat crops by overexpressing dicot CPR5 genes; have demonstrated to block viral replication by preventing viral replication protein from targeting to the designated organelle membranes for the VRC formation and this concept can be further employed for virus control. We are grateful to BARD funding and are excited to carry on this project in collaboration.
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Epel, Bernard, i Roger Beachy. Mechanisms of intra- and intercellular targeting and movement of tobacco mosaic virus. United States Department of Agriculture, listopad 2005. http://dx.doi.org/10.32747/2005.7695874.bard.
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To cause disease, plant viruses must replicate and spread locally and systemically within the host. Cell-to-cell virus spread is mediated by virus-encoded movement proteins (MPs), which modify the structure and function of plasmodesmata (Pd), trans-wall co-axial membranous tunnels that interconnect the cytoplasm of neighboring cells. Tobacco mosaic virus (TMV) employ a single MP for cell- cell spread and for which CP is not required. The PIs, Beachy (USA) and Epel (Israel) and co-workers, developed new tools and approaches for study of the mechanism of spread of TMV that lead to a partial identification and molecular characterization of the cellular machinery involved in the trafficking process. Original research objectives: Based on our data and those of others, we proposed a working model of plant viral spread. Our model stated that MPᵀᴹⱽ, an integral ER membrane protein with its C-terminus exposed to the cytoplasm (Reichel and Beachy, 1998), alters the Pd SEL, causes the Pd cytoplasmic annulus to dilate (Wolf et al., 1989), allowing ER to glide through Pd and that this gliding is cytoskeleton mediated. The model claimed that in absence of MP, the ER in Pd (the desmotubule) is stationary, i.e. does not move through the Pd. Based on this model we designed a series of experiments to test the following questions: -Does MP potentiate ER movement through the Pd? - In the presence of MP, is there communication between adjacent cells via ER lumen? -Does MP potentiate the movement of cytoskeletal elements cell to cell? -Is MP required for cell-to-cell movement of ER membranes between cells in sink tissue? -Is the binding in situ of MP to RNA specific to vRNA sequences or is it nonspecific as measured in vitro? And if specific: -What sequences of RNA are involved in binding to MP? And finally, what host proteins are associated with MP during intracellular targeting to various subcellular targets and what if any post-translational modifications occur to MP, other than phosphorylation (Kawakami et al., 1999)? Major conclusions, solutions and achievements. A new quantitative tool was developed to measure the "coefficient of conductivity" of Pd to cytoplasmic soluble proteins. Employing this tool, we measured changes in Pd conductivity in epidermal cells of sink and source leaves of wild-type and transgenic Nicotiana benthamiana (N. benthamiana) plants expressing MPᵀᴹⱽ incubated both in dark and light and at 16 and 25 ᵒC (Liarzi and Epel, 2005 (appendix 1). To test our model we measured the effect of the presence of MP on cell-to-cell spread of a cytoplasmic fluorescent probe, of two ER intrinsic membrane protein-probes and two ER lumen protein-probes fused to GFP. The effect of a mutant virus that is incapable of cell-to-cell spread on the spread of these probes was also determined. Our data shows that MP reduces SEL for cytoplasmic molecules, dilates the desmotubule allowing cell-cell diffusion of proteins via the desmotubule lumen and reduces the rate of spread of the ER membrane probes. Replicase was shown to enhance cell-cell spread. The data are not in support of the proposed model and have led us to propose a new model for virus cell-cell spread: this model proposes that MP, an integral ER membrane protein, forms a MP:vRNAER complex and that this ER-membrane complex diffuses in the lipid milieu of the ER into the desmotubule (the ER within the Pd), and spreads cell to cell by simple diffusion in the ER/desmotubule membrane; the driving force for spread is the chemical potential gradient between an infected cell and contingent non-infected neighbors. Our data also suggests that the virus replicase has a function in altering the Pd conductivity. Transgenic plant lines that express the MP gene of the Cg tobamovirus fused to YFP under the control the ecdysone receptor and methoxyfenocide ligand were generated by the Beachy group and the expression pattern and the timing and targeting patterns were determined. A vector expressing this MPs was also developed for use by the Epel lab . The transgenic lines are being used to identify and isolate host genes that are required for cell-to-cell movement of TMV/tobamoviruses. This line is now being grown and to be employed in proteomic studies which will commence November 2005. T-DNA insertion mutagenesis is being developed to identify and isolate host genes required for cell-to-cell movement of TMV.
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Kanner, Joseph, Edwin Frankel, Stella Harel i Bruce German. Grapes, Wines and By-products as Potential Sources of Antioxidants. United States Department of Agriculture, styczeń 1995. http://dx.doi.org/10.32747/1995.7568767.bard.
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Several grape varieties and red wines were found to contain large concentration of phenolic compounds which work as antioxidant in-vitro and in-vivo. Wastes from wine production contain antioxidants in large amounts, between 2-6% on dry material basis. Red wines but also white wines were found to prevent lipid peroxidation of turkey muscle tissues stored at 5oC. The antioxidant reaction of flavonoids found in red wines against lipid peroxidation were found to depend on the structure of the molecule. Red wine flavonoids containing an orthodihydroxy structure around the B ring were found highly active against LDL and membrane lipid peroxidation. The antioxidant activity of red wine polyphenols were also found to be dependent on the catalyzer used. In the presence of H2O2-activated myoglobin, the inhibition efficiency was malvidin 3-glucoside>catechin>malvidin>resveratol. However, in the presence of an iron redox cycle catalyzer, the order of effectiveness was resveratol>malvidin 3-glucoside = malvidin>catechin. Differences in protein binding were found to affect antioxidant activity in inhibiting LDL oxidation. A model protein such as BSA, was investigated on the antioxidant activity of phenolic compounds, grape extracts, and red wines in a lecithin-liposome model system. Ferulic acid followed by malvidin and rutin were the most efficient in inhibiting both lipid and protein oxidation. Catechin, a flavonal found in red-wines in relatively high concentration was found to inhibit myoglobin catalyzed linoleate membrane lipid peroxidation at a relatively very low concentration. This effect was studied by the determination of the by-products generated from linoleate during oxidation. The study showed that hydroperoxides are catalytically broken down, not to an alcohol but most probably to a non-radical adduct. The ability of wine-phenolics to reduce iron and from complexes with metals were also demonstrated. Low concentration of wine phenolics were found to inhibit lipoxygenase type II activity. An attempt to understand the bioavailability in humans of antocyanins from red wine showed that two antocyanins from red wine were found unchanged in human urine. Other antocyanins seems to undergo molecular modification. In hypercholesterolemic hamsters, aortic lipid deposition was significantly less in animals fed diets supplemented with either catechin or vitamin E. The rate of LDL accumulation in the carotid arteries was also significantly lower in the catechin and vitamin E animal groups. These results suggested a novel mechanism by which wine phenolics are associated with decreased risk of coronary heart diseases. This study proves in part our hypothesis that the "French Paradox" could be explained by the action of the antioxidant effects of phenolic compounds found at high concentration in red wines. The results of this study argue that it is in the interest of public health to increase the consumption of dietary plant falvonoids. Our results and these from others, show that the consumption of red wine or plant derived polyphenolics can change the antioxidant tone of animal and human plasma and its isolated components towards oxidative reactions. However, we need more research to better understand bioavailability and the mechanism of how polyphenolics affect health and disease.
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Fallik, Elazar, Robert Joly, Ilan Paran i Matthew A. Jenks. Study of the Physiological, Molecular and Genetic Factors Associated with Postharvest Water Loss in Pepper Fruit. United States Department of Agriculture, grudzień 2012. http://dx.doi.org/10.32747/2012.7593392.bard.
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The fruit of pepper (Capsicum annuum) commonly wilts (or shrivels) during postharvest storage due to rapid water loss, a condition that greatly reduces its shelf life and market value. The fact that pepper fruit are hollow, and thus have limited water content, only exacerbates this problem in pepper. The collaborators on this project completed research whose findings provided new insight into the genetic, physiological, and biochemical basis for water loss from the fruits of pepper (Capsicum annuum and related Capsicum species). Well-defined genetic populations of pepper were used in this study, the first being a series of backcross F₁ and segregating F₂, F₃, and F₄ populations derived from two original parents selected for having dramatic differences in fruit water loss rate (very high and very low water loss). The secondly population utilized in these studies was a collection of 50 accessions representing world diversity in both species and cultivar types. We found that an unexpectedly large amount of variation was present in both fruit wax and cutin composition in these collections. In addition, our studies revealed significant correlations between the chemical composition of both the fruit cuticular waxes and cutin monomers with fruit water loss rate. Among the most significant were that high alkane content in fruit waxes conferred low fruit water loss rates and low permeability in fruit cuticles. In contrast, high amounts of terpenoids (plus steroidal compounds) were associated with very high fruit water loss and cuticle permeability. These results are consistent with our models that the simple straight chain alkanes pack closely together in the cuticle membrane and obstruct water diffusion, whereas lipids with more complex 3-dimensional structure (such as terpenoids) do not pack so closely, and thus increase the diffusion pathways. The backcross segregating populations were used to map quantitative trait loci (QTLs) associated with water loss (using DART markers, Diversity Arrays Technology LTD). These studies resulted in identification of two linked QTLs on pepper’s chromosome 10. Although the exact genetic or physiological basis for these QTLs function in water loss is unknown, the genotypic contribution in studies of near-isogenic lines selected from these backcross populations reveals a strong association between certain wax compounds, the free fatty acids and iso-alkanes. There was also a lesser association between the water loss QTLs with both fruit firmness and total soluble sugars. Results of these analyses have revealed especially strong genetic linkages between fruit water loss, cuticle composition, and two QTLs on chromosome 10. These findings lead us to further speculate that genes located at or near these QTLs have a strong influence on cuticle lipids that impact water loss rate (and possibly, whether directly or indirectly, other traits like fruit firmness and sugar content). The QTL markers identified in these studies will be valuable in the breeding programs of scientists seeking to select for low water loss, long lasting fruits, of pepper, and likely the fruits of related commodities. Further work with these newly developed genetic resources should ultimately lead to the discovery of the genes controlling these fruit characteristics, allowing for the use of transgenic breeding approaches toward the improvement of fruit postharvest shelf life.
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O'Neill, Sharman, Abraham Halevy i Amihud Borochov. Molecular Genetic Analysis of Pollination-Induced Senescence in Phalaenopsis Orchids. United States Department of Agriculture, 1991. http://dx.doi.org/10.32747/1991.7612837.bard.
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The project investigated the molecular genetic and biochemical basis of pollination-induced senescence of Phalaenopsis flowers. This experimental system offered unique advantages in that senescence is strictly regulated by pollination, providing the basis to experimentally initiate and synchronize senescence in populations of flowers. The postpollination syndrome in the Phalaenopsis orchid system was dissected by investigating the temporal and spatial regulation of ACC synthase gene expression. In the stigma, pollen-borne auxin induces the expression of the auxin-regulated ACC synthase (PS-ACS2) gene, resulting in ACC synthesis within 1 h following pollination. Newly formed ACC is oxidized by basal constitutive ACC oxidase to ethylene, which then induces the expression of the ethylene-regulated ACC synthase(PS-ACS1) and oxidase (ACO1) genes for further autocatalytic production of ethylene. It is speculated that during the 6-h period following pollination, emasculation leads to the production or release of a sensitivity factor that sensitizes the cells of the stigma to ethylene. ACC and ethylene molecules are translocated from the stigma to the labellum and perianth where ethylene induces the expression of PS-ACS1 and ACO1 resulting in an increased production of ACC and ethylene. Organ-localized ethylene is responsible for inrolling and senescence of the labellum and perianth. The regulation of ethylene sensitivity and signal transduction events in pollinated flowers was also investigated. The increase in ethylene sensitivity appeared in both the flower column and the perianth, and was detected as early as 4 h after pollination. The increase in ethylene sensitivity following pollination was not dependent on endogenous ethylene production. Application of linoleic and linoleic acids to Phalaenopsis and Dendrobium flowers enhanced their senescence and promoted ethylene production. Several major lipoxygenase pathway products including JA-ME, traumatic acid, trans-2-hexenal and cis-3-hexenol, also enhanced flower senescence. However, lipoxygenase appears to not be directly involved in the endogenous regulation of pollination-induced Phalaenopsis and Dendrobium flower senescence. The data suggest that short-chain saturated fatty acids may be the ethylene "sensitivity factors" produced following pollination, and that their mode of action involves a decrease in the order of specific regions i the membrane lipid bilayer, consequently altering ethylene action. Examination of potential signal transduction intermediates indicate a direct involvement of GTP-binding proteins, calcium ions and protein phosphorylation in the cellular signal transduction response to ethylene following pollination. Modulations of cytosolic calcium levels allowed us to modify the flowers responsiveness to ethylene.
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Grumet, R., J. Burger, Y. Tadmor, A. Gur, C. Barry, A. Schäffer i M. Petreikov. Cucumis fruit surface biology: Genetic analysis of fruit exocarp features in melon (C. melo) and cucumber (C. sativus). Israel: United States-Israel Binational Agricultural Research and Development Fund, 2020. http://dx.doi.org/10.32747/2020.8134155.bard.
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The fruit surface (exocarp) is a unique tissue with multiple roles influencing fruit growth and development, disease susceptibility, crop yield, post-harvest treatments, shipping and storage quality, and food safety. Furthermore, highly visible exocarp traits are the consumer's first exposure to the fruit, serving to identify fruit type, variety, attractiveness, and market value. Cucurbit fruit, including the closely related Cucumis species, melon (C. melo) and cucumber (C. sativus), exhibit tremendous diversity for fruit surface properties that are not present in model species. In this project, we identified genetic factors influencing Cucumis fruit surface morphology with respect to important quality determinants such as exocarp and flesh color, cuticle deposition, and surface netting. We employed a combination of approaches including: genome-wide association studies (GWAS) utilizing an extensive melon population and the U.S. Plant Introduction (PI) collection for cucumber to identify genomic regions associated with natural variation in fruit surface traits; bulked segregant RNA-seq (BSR-seq) analysis of bi-parental F2:3 or RIL (recombinant inbred line) populations to genomic regions and candidate genes segregating for fruit surface traits; and comparison of syntenic genomic regions and identification of homologous candidate genes. Candidate genes were examined for sequence and/or expression differences during fruit development that correspond with phenotypic differences. Primary outcomes of the work included identification of candidate genes influencing cuticle deposition, epidermal cell structure, surface netting, and intensity of rind and flesh color. Parallel studies identified mutations within the cucumber and melon homologs of the transcription factor WIN1 (WAX INDUCER1) as a significant factor influencing these surface properties. Additional QTL (quantitative trait loci) were identified in both species, and candidate genes in melon include a novel beta-glucosidase involved in lignin production and an integral membrane protein potentially involved in cuticle metabolism. Genetic resources and biochemical approaches have been developed to study cuticle and wax deposition in both species: segregating populations of melon were developed and sequenced for bulked segregant analysis and samples collected for metabolic analysis; an isolation procedure was developed for lipid droplets from cucumber peel and metabolomic analyses have been initiated. Genetic studies in melon identified mutations in a candidate gene (APRR2), associated with light immature rind, and further indicated that this gene is also associated with color intensity of both mature rinds and flesh, making it a good target for breeding. GWAS studies utilizing the cucumber core diversity population are being performed to identify additional sources of variation for fruit surface properties, map QTL, and examine for synteny with melon. Collectively these studies identified genetic regions associated with important quality traits and contributed to our understanding of underlying biological processes associated with fruit surface development. Knowledge of genetic control of these characteristics can facilitate more efficient breeding for important fruit surface traits.