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Christou, Charita. "C-type lectin-like receptors and their interactions." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509908.
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Simpson, Jonathan Robert Henry. "SERS-based nanoparticle biodetection using carbohydrate-lectin interactions." Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27026.
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Endogenous biological processes including cellular recognition, motility and differentiation together with infection often result from carbohydrate-based interactions. Investigation into glycobiological interactions using sugar-coated nanoparticles are the basis for the research described herein. Metallic nanoparticles were coated with a variety of thiol-based linker molecules. Heterobifunctional PEG (carboxyl/thiol) molecules were found to be most successful in preventing non-specific aggregation. The carboxylic acid functionality of the PEG molecules used allowed for subsequent coupling of a variety of carbohydrates to the nanoparticle surface. This resulted in the production of glyconanoparticles with unique surface functionality, for example, glucose or galactose. Additionally, functionalising the particles with Raman reporter molecules (RRMs) resulted in the measurement of surface enhanced Raman scattering (SERS) signals. Aggregation of the glyconanoparticles in the presence of a variety of carbohydrate-binding proteins (lectins) was measured via changes in the extinction profile, size and the SERS response of those particles. Nanoparticle aggregation was used for the sensitive detection of plant lectins, including the Concanavalin A and Jacalin lectin and also bacterial lectins including cholera toxin B subunit (CTB). CTB was detected sensitively, selectively and rapidly by using glyconanoparticles coated in a mixture of different carbohydrates (mixed-monolayers of galactose and N-acetylneuraminic acid). Detection was possible in both buffer and synthetic freshwater conditions, demonstrating the use of these glyconanoparticles in detecting a target in complex samples. By exploiting the reversible nature of carbohydrate-lectin interactions, it was possible to use the glyconanoparticles together with the lectin ConA to develop a glucose sensor. This performed effectively across the physiological range and into the hypo/hyperglycaemic regions in buffer conditions. Finally, the glyconanoparticles were used for the detection of plant and bacterial lectins on glass substrates by initially developing a sandwich SERS assay with a view to eventually creating SERS-based carbohydrate microarrays.
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Bhatt, Veer Sandeep. "Non-lectin type Protein-carbohydrate Interactions: A Structural Perspective." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306858684.
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Gou, Yanzi. "Synthesis of glycopolymers for the study of lectin-carbohydrate interactions." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/79688/.
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Saccharides act important roles in many biological processes as recognition molecules, signalling molecules and adhesion molecules. However, due to the complexity and diversity of oligosaccharides the direct synthetic approaches cannot fully meet the demands for all of the pure and well-defined oligosaccharides being studied in glycobiology. The efficient synthesis of glycomimetics, glycopolymers, offers an attractive route to solve this problem. Thus, the synthesis and application of glycopolymers of various architectures has been extensively investigated. Meanwhile, In order to explore the mechanism of the lectin-carbohydrate interactions and to get a better understanding of the structure-function relationship of oligosaccharides, the assays employed in studies of lectin-carbohydrate interactions become much more sophisticated and accurate with fast development of various analytical approaches. In this work, well-defined glycopolymers were prepared by the combination of CCTP and CuAAC click reactions. Alkyne-containing polymer scaffolds were synthesised by CCTP, followed by post-modification of the clickable polymer scaffolds with sugar azides. Moreover, a library of well-defined synthetic glycopolymers featuring the same macromolecular properties (architecture, polydispersity, valency, polarity, etc.) with difference only in the densities of different sugars (mannose, galactose and glucose) were employed to investigate the influence of different pendant epitopes on the interactions with a model lectin Con A by the traditional methods. Additionally, two powerful modem detection techniques QCM-D and SPR were also exploited to investigate the interactions of the lectin Con A, PNA, or DC-SIGN with a series of different glycopolymers. The diversities of binding properties contributed by different clustering parameters can make it possible to define the structures of the multivalent ligands and densities of binding epitopes for specific functions in the lectin-carbohydrate interactions. These conclusions can be employed as the springboard to develop new glycopolymeric drugs and therapeutic agents and to assess the mechanisms by which they work.
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Pourceau, Gwladys. "Mise au point de nouvelles méthodes de conjugaison oligonucléotide/sucre et développement d'un microsystème d'analyse des interactions lectine/sucre." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20224.
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Les interactions entre les sucres et les lectines sont généralement l'étape clé dans de nombreux phénomènes biologiques et pathologiques. Malgré leu r importance cruciale, ces interactions sont paradoxalement caractérisées par des constantes d'affinité faibles et nécessite une multiprésentation des motifs saccharidiques pour être significatives. Cette augmentation est appelée "effet cluster". En outre, les techniques d'analyse actuellement utilisées en laboratoire nécessitent des quantités importantes de produits, ce qui est difficilement compatible avec les méthodes de synthèse actuelle. Pour pallier ces difficultés, une approche originale basée sur l'utilisation conjointe de glycooligonucléotide et de puces à ADN a été proposée. Les glycoconjugués basés sur des squelettes phosphodiesters et couplés à des séquences d'ADN ont été synthétisés en utilisant la chimie des oligonucléotides, couplée à la "click chemistry". La séquence d'ADN quant à elle a permis l'ancrage sur une puce à ADN et donc la mesure de leur affinité vis-à-vis de différentes lectines. Ce manuscrit rapporte le développement des nouvelles méthodologies de synthèse des glycooligonucléotides ainsi que la préparation de nombreux glycoconjugués originaux, dont l'affinité pour différentes lectines a été mesurée via l'utilisation de la puce à ADN. L'influence de plusieurs paramètres a été étudiée: le nombre de résidus, l'arrangement spatial, la lipophilie etc. Il s'avère que l'arrangement spatial semble être l'un des points les plus importants dans la mise au point d'un glycoconjuguéThe interactions between carbohydrates and lectins are generally the "key step" in many biological and pathological phenomena. Despite their importance, these interactions are paradoxically characterized by low affinity constants and requires multipresence of saccharide to be significant. This increase is called "cluster effect". In addition, the analysis techniques currently used in the laboratory requires large quantities of products, which is hardly compatible with the current methods of synthesis. To circumvent these difficulties, a original approach based on the combined use of glycooligonucleotides and DNA microarrays has been proposed. Glycoconjugates based on phosphodiester skeletons linked to DNA sequences have been synthesized using the chemistry of oligonucleotides, coupled with the "click chemistry". The DNA sequence has allowed the anchoring on a DNA chip and therefore the measurement of their affinity versus different lectins.This manuscript reports the development of new synthetic methodologies for the glycooligonucleotides synthesis and the preparation of many original glycoconjugates, whose affinity for various lectins was measured through the use of DNA microarray. The influence of several parameters was studied: the number of residues, the spatial arrangement, etc. lipophilicity. The spatial arrangement appears to be one of the most important parameters in the development of a glycoconjugate
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Miller, A. "Complement-carbohydrate interactions : studies of mannose binding lectin and complement factor H." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1338984/.
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The complement system is a fundamental component of innate immunity that orchestrates complex immunological and inflammatory processes. Complement comprises over 30 proteins that eliminates invading microorganisms while maintaining host cell integrity. Protein-carbohydrate interactions play critical roles in both the activation and regulation of complement. Mannose binding lectin (MBL) activates the lectin pathway of complement via the recognition of sugar arrays on pathogenic surfaces. X-ray scattering and AUC combined with constrained modelling were used to identify a bent structure for the MBL monomer in terms of crystal structures for its carbohydrate-recognition domain and its triple helical region. Near-planar solution structures were determined for the MBL dimer, trimer and tetramer. These solution structures clarified how MBL binds to pathogenic surfaces and provides a template for the binding and autoactivation of the MASP protease to initiate the lectin pathway of complement activation. Factor H (FH) with 20 short complement regulator (SCR) domains regulates the alternative pathway of complement by facilitating the breakdown of the central component C3b. FH binds to heparan sulphate (HS) and to heparin (a HS analogue) on host cell surfaces where it regulates C3b activity and protects these cells from complement attack. A Tyr402His polymorphism in SCR-7 is a major risk factor for the development of age-related macular degeneration (AMD), and is involved in heparin binding. Both the Tyr402 and His402 allotypes of the SCR-6/8 fragment of FH were cloned and expressed in an E. coli system. X-ray scattering, analytical ultracentrifugation and surface plasmon resonance were used to characterise the interactions of FH Tyr402 and His402 with heparin and HS. These polyanions induce the strong self-association of FH SCR-6/8, the extent of which was found to be dependent on the length of the polyanion and the presence of the His402 allotype. The formation of large FH-heparin aggregates may provide a molecular explanation for the link between the Tyr402His polymorphism and the initial formation of drusen deposits in AMD.
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Wing, James Badger. "The effect of mannose-binding lectin on the cellular interactions of Neisseria gonorrhoeae." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444921.
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Wang, Xin. "Synthesis and Characterization of Glyconanomaterials, and Their Applications in Studying Carbohydrate-Lectin Interactions." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/626.
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This dissertation focuses on the synthesis and characterization of glyconanomaterials, as well as their applications in studying carbohydrate-protein interactions. A new and versatile method for coupling underivatized carbohydrates to nanomaterials including gold and silica nanoparticles was developed via the photochemically induced coupling reaction of perfluorophenylazide (PFPA). A wide range of carbohydrates including mono-, oligo- and poly-saccharides were conjugated to the nanoparticles with high yields and efficiency. New analytical methods were developed to determine the binding affinities of glyconanoparticles (GNPs) with lectins; these include fluorescence-based competition assay, dynamic light scattering (DLS) and isothermal titration calorimetry (ITC). Results showed that the multivalent presentation of carbohydrate ligands significantly enhanced the binding affinity of GNPs by several orders of magnitude compared to the free ligands. Systematic studies were carried out to investigate the impact of ligand presentation, i.e., the type and length of spacer linkage, the ligand density and the nanoparticle size on the binding affinity of the resulting glyconanoparticles. We used gold GNPs to study interactions with anti-HIV lectin cyanovirin-N (CV-N), and dye-doped silica nanoparticles for labeling glyans and developing high-throughput screening technique.
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Ligeour, Caroline. "Synthèse de nouveaux glycooligonucléotides et glycoclusters : étude de leurs affinités avec les lectines I et II de Pseudomonas aeruginosa et la lectine de Burkholderia ambifaria." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20211/document.
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Les interactions sucre-lectine jouent un rôle très important dans de nombreux processus biologiques comme les infections par des virus ou des bactéries. Toutefois, ces interactions étant faibles, la présentation de manière multivalente des résidus saccharidiques est nécessaire pour obtenir une augmentation significative des constantes d'association. Une technique basée sur l'utilisation de glycooligonucléotides et d'une puce à ADN utilisée comme plateforme d'ancrage a permis d'étudier l'affinité d'un grand nombre de composés envers les lectines PA-IL et PA-IIL de Pseudomonas aeruginosa et la lectine BambL de Burkholderia ambifaria. Les glycooligonucléotides ont été synthétisés, à partir de blocs de construction synthétisés en aval, en utilisant la chimie des acides nucléiques supportée et automatisée (phosphoramidites et H-phosphonate) ainsi que des réactions de « click chemistry » (la cycloaddition 1,3-dipolaire catalysée par le cuivre (I) ou le couplage thiol par addition de type Michael ou par substitution nucléophile d'un dérivé bromoacetamide).Les glycoclusters ayant montrés une bonne affinité envers les lectines cibles ont été sélectionnés et resynthétisés en solution sans l'étiquette ADN à l'échelle de la centaine de milligrammes. Les glycoclusters ainsi synthétisés en deux ou trois étapes avec une seule purification ont pu être évalués par quatre techniques d'analyse des interactions (HIA, ELLA, SPR et ITC) en présence des lectines PA-IL, PA-IIL et BambL. Nous avons trouvé un tétragalactocluster et un tétrafucocluster possédant une forte affinité envers la lectine PA-IL et BambL respectivement avec des valeurs de Kd de 157 nM et 43 nMCarbohydrate-lectin interactions play a key role in various biological processes such as infection by viruses or bacteria. As these interactions are weak, the multivalent association of carbohydrate is necessary to increase the binding constant. We used glycooligonucleotide and DNA chip to study the affinity of diverse compounds to PA-IL and PA-IIL lectins of Pseudomonas aeruginosa and Bambl lectin of Burkholderia ambifaria. Glycooligonucleotides were synthesized with previously prepared building blocks, using automated supported nucleic acid chemistry (phosphoramidites and H-phosphonate) and “Click chemistry” (copper (I) catalyzed 1,3-dipolar cycloaddition, thiol coupling by Michael addition and nucleophilic substitution of bromoacetamide derivative).Glycoclusters showing the better affinities toward the lectins have been synthesized to a hundred milligrams scale in solution without the DNA tag. The synthesis processes in two or three steps and only one final purification. Their interactions with the lectins PA-IL, PA-IIL and BambL were studied by several assays (HIA, ELLA, SPR and ITC). A tetragalactocluster and a tetrafucocluster showed high affinity toward respectively the lectin PA-IL (Kd = 157 nM) and the lectin BambL (Kd = 43 nM)
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Roussel, Francis. "Interactions cellulaires et couples lectine-sucre." Rouen, 1994. http://www.theses.fr/1994ROUE5071.
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L'expression de sucres de membrane (insolubles) par certaines cellules peut aller de pair avec l'expression de lectines endogènes (insolubles) par d'autres cellules. La complémentarité des deux réactifs solubles utilisés pour les mettre en évidence (lectines végétales, néoglycoprotéines) définit un couple lectine-sucre. L'interaction fonctionnelle ou plus banalement la complémentarité anatomique de ces deux cellules porteuses pose le problème de l'implication du couple lectine-sucre dans leur mise en place spécifique. Cette problématique a été explorée 1) au niveau de la voie sensitive douloureuse où un couple lactose et/ou galactose est impliqué. 2) Au niveau des interactions hôte parasite Trichomonas vaginalis-cellule MacCoy qui sont modulables in vitro, et donc régulables in vivo, par des inhibiteurs solubles, révélant un couple mannose/N Acétyl Glucosamine. 3) Au niveau des cellules cancéreuses qui représentent un exemple typique de désorganisation des relations intercellulaires et qui ont montré des déséquilibres dans le couple fucose. Elles ont perdu la notion d'organe en devenant aptes à former des métastases grâce aux interactions qu'elles contractent avec les cellules endothéliales qui expriment beaucoup de fucose et qui constituent leur porte d'entrée dans le reste de l'organisme. Ces anomalies des couples lectine-sucre qui atteignent au plus profond la spécificité d'organe apparaissent liées à la dissémination métastatique. Les couples lectine-sucre définiraient la notion d'organe et seraient indispensables au maintien de la cohérence de l'organisme. L'utilisation de réactifs complémentaires, lectines et néoglycoprotéines, de spécificité de plus en plus fine, de pouvoir discriminant équilibré entre eux, la détection systématique d'éventuels compétiteurs solubles, en particulier dans le domaine du fucose, devraient permettre de progresser dans l'analyse du processus métastatique qui fait la gravité du cancer
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Pei, Zhichao. "Carbohydrate Synthesis and Study of Carbohydrate-Lectin Interactions Using QCM Biosensors and Microarray Technologies." Doctoral thesis, Stockholm : Chemical Science and Engineering, KTH, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4177.
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Fraser, Stuart Tallis. "Lectin - carbohydrate interactions in lympho-haemopoiesis: a study of L-selectin, ligands of L-selectin and CD24 inthe rat." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31236844.
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Dunstan, Kerrie Women's & Children's Health Faculty of Medicine UNSW. "Understanding the early interactions between vaccinia virus and dendritic cells - towards an enhanced vaccine vector." Awarded by:University of New South Wales. Women's and Children's Health, 2007. http://handle.unsw.edu.au/1959.4/32456.
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In the post smallpox era, vaccinia virus (VACV) has emerged as an important candidate vaccine vector. As yet, the binding receptors and entry mechanisms utilised by the two infectious forms, IMV and EEV, in dendritic cells (DCs) are unknown. We have investigated the interactions between VACV and C-type lectin receptors (CLRs) that are known to be utilised by many other viruses for binding and entry in DCs. Using a variety of CLR ligands and inhibitors we were unable to inhibit IMV or EEV binding to MDDCs and we conclude that they do not bind to CLRs. We have also investigated VACV entry in MDDCs and show that both IMV and EEV enter MDDCs via an endocytic pathway. Using a variety of drugs that inhibit cellular processes we found IMV and EEV entry to be actin- and calcium-dependent. EEV entry was also cholesterol- and energy-dependent, whereas IMV entry was only partially dependent on these factors. Both IMV and EEV colocalised with endolysosomal markers. This data suggests that EEV may enter DCs via caveolin-mediated endocytosis whereas IMV entry can occur via multiple complementary mechanisms, including endocytosis and fusion. Macropinocytosis may also constitute a minor route of entry for IMV as entry was partially inhibited by dimethyl amiloride and the virus colocalised with dextran. Finally we have provided a comprehensive flow cytometric analysis of Toll-like receptor (TLR) expression at the protein level in MDDCs and monocyte-derived Langerhans cells (MDLCs) as models for different myeloid DC subsets. We found TLR expression to be cell type-specific and MDDCs expressed the full repertoire of TLRs 1-9, including small amounts of TLR8 and TLR9 on the cell surface. The expression of these TLRs that recognise nucleic acids on the surface of cells may constitute an early warning system for signalling the presence of viral invaders that would normally subvert the function of DCs. We also found TLR expression in mature cells to be dependent on the nature of the maturation stimulus (lipopolysaccharide versus cytokine/prostaglandin cocktail) and VACV infection induced profound down-regulation of all TLRs. These findings will have important implications for the rational design of VACV-vectored vaccines.
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Okolo, C. J. "Studies on lectin binding sites of Glossina in relation to host parasite interactions with particular reference to Glossina trypanosome systems." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293804.
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Fraser, Stuart Tallis. "Lectin - carbohydrate interactions in lympho-haemopoiesis : a study of L-selectin, ligands of L-selectin and CD24 in the rat /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20667450.
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DiLillo, Ana M. ""Noncovalent Complexation of Single-Wall Carbon Nanotubes with Biopolymers: Dispersion, Purification, and Protein Interactions"." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1624461866858216.
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Thomas, Celestine J. "Endotoxin Peptide/Protein Interactions: Thermodynamic And Kinetic Analysis." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/213.
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Endotoxin or Lipopolysaccharide (LPS) is the invariant structural component of gram negative bacterial outer membranes and is the chief causative factor of Sepsis or endotoxic shock. Sepsis is a syndrome that has very high mortality rates even in this age of excellent therapeutics and critical patient care. The treatment for sepsis till date remains nonspecific and supportive due to lack of effective anti-endotoxic drugs. Sepsis is initiated when the circulating bacteria shed LPS from their cell envelopes. Shed LPS aggregates are recognized by LPS binding proteins and receptors, which activate the host's immune system. Uncontrolled and excessive stimulation of the host's immune system precipitates endotoxic shock which in advanced cases involving multiple system organ failure inevitably lead to patient's death.
Many strategies have been tested out to combat this deadly affliction. One of the attractive clinical modalities in sepsis treatment is the use of peptides as LPS sequestering anti-endotoxic drugs. A classical peptide antibiotic of this class is Polymyxin B (PMB) a cyclic cationic acylated molecule, that recognizes LPS with a very high affinity.
This thesis describes kinetics and thermodynamics of PMB-LPS interactions and applies these parameters over a framework of different models so as to gain insights into the structure-function relationships that govern the interactions of this peptide with endotoxin(s). Classical biophysical techniques like fluorescence, circular dichroism spectroscopy, stopped flow kinetics, titration calorirnetry (ITC) and the relatively new technique of Surface Plasmon Resonance (SPR) have been employed to dissect out the mechanism of the range of non-covalent forces that are involved in peptide-endotoxin recognition. Certain proteins that exhibit LPS binding activity have also been studied to gains insight about their mode of action. Implications of these studies for designing peptides that have better anti-endotoxic properties are also highlighted.
The first chapter introduces and highlights the clinical features of sepsis. It also attempts to shed light on the LPS mediated signal transduction pathway that leads to endotoxic shock. This chapter also briefly explains the roles of many LPS receptors that are present in the human system and their specific roles in the signal transduction pathways.
The second part of this chapter deals with the role of cationic peptides as anti-endotoxic drugs. Certain key functional aspects of these peptides, which impart in them, the desirable property of LPS recognition have also been discussed
The second chapter describes the kinetic studies undertaken to unravel the exact mechanism of LPS-PMB interaction. The studies reveal that PMB recognizes LPS in a biphasic manner, with the second, unimolecular isomerization step of the reaction being the rate-limiting step. The initial reaction is shown to be influenced by the presence of salt in the reaction medium. The dissociation phase of this interaction also shows a biphasic pattern. These data allow us to speculate upon the exact mechanism by which PMB is able to recognize LPS. The studies also shed light on some structural aspects that govern and confer such high LPS binding activity to PMB. Based on these a model has been proposed to explain this recognition (C.J. Thomas et al, 1998).
The second chapter discuses the mode of action of various PMB analogs. These analogs have been chosen in terms of their mode of action as well as their structural similarly to PMB. The affinities of these analogs to LPS and lipid A were quantified using the Surface plasmon resonance (SPR) method. SPR, a technique that relies on the quantification of change in mass during a binary binding process occurring between an immobilized entity and a flowing ligand, is a rapid and sensitive method to measure biologically relevant interactions.
SPR studies provide us with the binding constants and thermodynamic parameters that allow evaluation of the affinities of these peptides towards LPS (C.J.Thomas and A.Surolia, 1999).
The third chapter discusses a hitherto unknown mode by which PMB acts on a LPS lamellae. The results of this study wherein the binding affinities of PMB and its analogs were performed on monolayers and tethered liposomes, show that PMB is able to remove specifically LPS or lipid A from monolayers or bilayer assemblies such as tethered liposomes. The exact mode of action of PMB is deciphered in the light of these new studies, which allow us to posit on the observed efficacy of PMB in neutralizing the endotoxin as compared to peptides with nearly similar affinities for LPS (C.J Thomas et al 1999).
In the fourth chapter a series of 23 residue peptides, based on the sequence corresponding to the anti-sense strand of magainin gene have been synthesized. Magainin an amphiphilic helical peptide obtained from frog skins plays a vital role in the innate immune defense mechanisms of these organisms. It also exhibits LPS binding activity that makes it an attractive target as an anti-endotoxic drug. Biochemical and biophysical characterization of these peptides reveal that they have the tendency to perturb both the inner and the outer membranes of E.coli. The peptides are amphiphilic and have helical structure in a membrane bound environment.
Three of the peptides tested have high affinities for lipid A that approach the values shown by PMB. The kinetic parameters obtained by stopped flow and SPR studies in conjunction with the therrnodynamic parameters obtained using ITC studies allow us to highlight the key structural features that need to be exhibited by peptides that are designed to be LPS recognizers. The studies also project the fact that ionic forces play an important role in the initial recognition of LPS by these peptides. Fortification of the might of these ionic charges increases affinity for LPS where as the hydrophobic residues that interact at the next phase of binding are more amenable to disruptions in contiguity. These factors are discussed using the helical wheel diagram that shows the clear amphiphilicity displayed by these peptides. (C.J Thomas et al Manuscript under preparation, 2000)
Chapter six discusses the mode of action of certain LPS binding proteins. Limulus anti endotoxic factor (LALF) plays a vital role in the innate immune based defense systems of the horseshoe crab. Galectin-3 is a metal ion independent, galactosc binding Icctin of human origin with unknown functions. Both these phylogcntically-unrclatcd proteins exhibit LPS/lipid A recognizing properties. ITC and SPR studies have been used to determine the binding constants displayed by these proteins for lipid A. LALF bind to lipid A with very high affinity than compared to Galectin-3 and is also able to take away selectively lipid A from both monolayers and tethered liposomes. Galectin-3 does not show this property of LALF, which might account for its lowered affinities. Also structurally LALF has amphiphilic nature that confers high lipid A binding activity, which is clearly lacking in Galectin-3. These studies in conjunction with the knowledge gained from the study of LPS-PMB interaction stress on the importance of amphiphilicity in LPS recognition. (C.J Thomas et al Manuscript under preparation, 2000).
The final chapter is a general discussion that attempts to collate all these kinetic and thermodynamic observations in the pursuit of designing small easily manipulatable peptides that exhibit high LPS binding activity. These studies are aimed to act as rough guidelines to the design of LPS sequestering peptides that might have better therapeutic and pharmacokinetic properties.
The appendix to the main body of work presented in thesis are two pieces of work pertaining to the elucidation the kinetics and mechanism of sugar lectin interactions, when sugars are presented as glycolipids in monolayers or bilaycrs liposomes. Mode of the presentation of sugars at cell-surfaces in the form of glycolipids as ligands influence their recognition by macromolecular receptors like lectins. Appendix 1 is a study of the mode of action of Ulex europeus I lectin binding to H-fucolipid containing tethered liposomes, by SPR. Fucosylated sugars are often used as key markers in histochemical analysis of malignant cancerous tissues. Ulex lectin plays a vital role as a marker for identification of these tissues. The kinetics and thermodynamic parameters that are obtained in this study throw some light on the mode of recognition of glycolipid receptor by Ulex europeus I lectin (C.J Thomas and A. Surolia 2000).
Appendix 2 is a study, that attempts to quantify the initial kinetic parameters that correlate the recognition of glycolipid receptors with their inclination at the membrane surface and the influence of charge on them by soyabean agglutinin (SBA), Abrus agglutinin I and II. Studies on the soyabean agglutinin-globoside interaction highlights the divalent cation mediated reorientation of these receptors on their accessibility and recognition to the agglutinin. The divalent cations are speculated to orient the oligosaccharide head groups in a spatial geometry that allows a heightened kinetics of their interaction by SBA. These studies reveal that the reorganization of the binding pocket of a lectin can also have a profound influence on ihc rates of recognition of a glycospingolipid ligand by a lectin as exemplified by Abrus agglutinin II- GM1 interactions (C.J Thomas ct al, Manuscript under preparation).
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Pavard-Ohanessian, Jacqueline. "Contribution à l'étude de la stéréochimie des chaines glycaniques de glycoprotéines et à l'étude de leurs interactions avec la lectine d'arachide spécifique des substrats d-galactosyles terminaux." Paris 13, 1986. http://www.theses.fr/1986PA132005.
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Sicard, Delphine. "Caractérisation par microscopie à force atomique des arrangements protéine/sucre impliquant la lectine PA-IL de la bactérie pseudomonas aeruginosa." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00904559.
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La bactérie Pseudomonas aeruginosa est un pathogène opportuniste responsable de graves infections chez les personnes affaiblies immunitairement. Présentant des souches résistantes aux antibiotiques, une nouvelle approche thérapeutique est en cours de développement avec pour objectif l'inhibition des facteurs de virulence de la bactérie. Lors de son processus d'infection, le pathogène utilise les lectines pour reconnaître et se lier de manière spécifique aux glycoconjugués des cellules-hôtes en formant une interaction lectine/glycoconjugué. Plus particulièrement, la lectine PA-IL, spécifique du galactose, a été étudiée. A l'aide de glycomimétique, il semble possible de bloquer l'action de la lectine en créant une interaction lectine/glycomimétique. Pour développer cette approche, de nombreux glycocluster sont donc été élaborés et leur affinité avec la lectine PA-IL a été évaluée par plusieurs méthodes de caractérisation (SPR, HIA, ELLA, puce à sucre,...).Dans ce projet de thèse, nous avons cherché à visualiser par microscopie à force atomique (AFM) l'arrangement des complexes lectine PA-IL/glycocluster formés pour trois glycoclusters différents. Nous avons ainsi pu montrer l'influence du cœur du glycocluster et des bras-espaceurs sur l'arrangement des complexes. Suivant le glycocluster, l'arrangement prend la forme de filaments 1D,de structures dentelées avec des bras sinueux ou encore de larges structures compactes. Dans le cas des filaments, la résolution de nos images AFM nous a permis d'identifier les lectines à l'intérieur même de la structure filaire. Nous avons aussi démontré, en observant les lectines seules, l'existence d'une interaction lectine/lectine. De plus, des expériences ont été menées pour déterminer les conditions expérimentales appropriées à leur observation à l'air et en milieu liquide.
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Monteiro, João Gonçalo Tereno Verfasser], Bernd [Akademischer Betreuer] [Lepenies, Ralph Akademischer Betreuer] Goethe, and Reinhard [Akademischer Betreuer] [Schwartz-Albiez. "A C-type lectin receptor (CLR)-Fc fusion protein library as a toolbox to detect novel CLR ligands and the interplay of CLR/virus interactions / João Gonçalo Tereno Monteiro ; Bernd Lepenies, Ralph Goethe, Reinhard Schwartz-Albiez." Hannover : Stiftung Tierärztliche Hochschule Hannover, 2019. http://d-nb.info/119175278X/34.
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Monteiro, João Gonçalo Tereno [Verfasser], Bernd [Akademischer Betreuer] Lepenies, Ralph [Akademischer Betreuer] Goethe, and Reinhard [Akademischer Betreuer] Schwartz-Albiez. "A C-type lectin receptor (CLR)-Fc fusion protein library as a toolbox to detect novel CLR ligands and the interplay of CLR/virus interactions / João Gonçalo Tereno Monteiro ; Bernd Lepenies, Ralph Goethe, Reinhard Schwartz-Albiez." Hannover : Stiftung Tierärztliche Hochschule Hannover, 2019. http://d-nb.info/119175278X/34.
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Wilkins, Simon. "Lectin-carbohydrate mediated interaction between Plasmodium ookinetes and the mosquito midgut." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367836.
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Dupin, Lucie. "Validation et criblage de nouvelles molécules anti-infectieuses sur microarray : applications à Pseudomonas aeruginosa." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC018/document.
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Pseudomonas aeruginosa (PA) est la troisième bactérie impliquée dans les maladies nosocomiales et est la principale cause de mortalité des patients atteints de la mucoviscidose. PA est résistante à la plupart des traitements antibiotiques. Trouver de nouvelles stratégies thérapeutiques est devenu un enjeu majeur de santé publique, l’une d’entre elles est l’inhibition de facteurs de virulence. Parmi ceux-ci, les lectines sont des protéines impliquées dans l’adhésion et la formation de biofilm via des interactions avec des sucres (PA-IL, PA- IIL, FliC, FliD, PilA, PilY1 et CupB6).Le but de ce travail est donc de trouver des leurres moléculaires ayant une forte affinité pour ces lectines. Ceux-ci sont des motifs saccharidiques présentés de façon multivalente : glycoclusters. De part leur grande diversité structurale et leur faible quantité, un outil de criblage innovant a été développé qui consiste en une lame de verre microstructurée : le glycocluster-microarray. Les glycoclusters sont immobilisés de manière ordonnée par DNA Directed Immobilization (DDI). Deux méthodes de criblage ont été développées grâce à cet outils : 1) le criblage en solution et par compétition d’une bibliothèque de motifs saccharidiques et 2) le criblage d’une bibliothèque de glycoclusters immobilisés sur le microarray. Avec cet outil, des protocoles de mesures d’IC50 et de Kd ont aussi été fiabilisés pour caractériser les meilleurs candidats inhibiteurs des lectines. Le glycocluster- microarray présente l’avantage de n’utiliser qu’une très faible quantité de matériel (quelques picomoles) et permet de réaliser diverses analyses en parallèle.Afin de valider cet outil, une étude sur l’impact de la densité de surface en glycocluster a été menée. Le criblage de plus de 150 motifs saccharidiques a permis de sélectionner ceux ayant une forte affinité pour les lectines. L’analyse sur microarray complétée par de la modélisation moléculaire d’une bibliothèque de glycoclusters, possédant ces motifs et différentes topologies, valences et propriétés (aromaticité, charge,…), a permis d’identifier les paramètres clés dirigeant les relations structure-affinité. Une activité anti-biofilm chez PA a été démontrée avec les meilleurs glycoclusters ciblant PA-IL.Tester l’activité in vivo, chez l’animal, des meilleurs candidats est une voie à explorer. Cibler d’autres lectines comme celles présentes sur le flagelle et les pili de PA et notamment impliquées dans son adhésion précoce est aussi une voie à développer. Pour cela, des tests préliminaires ont été présentés et d’autres sont en cours faisant appel à l’utilisation de bactéries entières ainsi qu’à une détection sans marquage des lectinesSummary: Pseudomonas aeruginosa (PA) is the third pathogen involved in nosocomial diseases and the major cause of mortality of cystic fibrosis patients. PA develops resistance to antibiotics treatments. And so, developing new therapeutic strategies is a public health issue. One of the promising strategies is to inhibit virulence factors involved in the adhesion and the biofilm formation of PA. Some of these virulence factors are lectins which interact with sugars (PA-IL, PA-IIL, FliC, FliD, PilA, PilY1 and CupB6).The goal of this work is to find molecular decoys which have a strong affinity for these lectins. These are saccharidic units with a multivalent display: glycoclusters. An innovative screening tool has been developed: the glycocluster-microarray, to study lectin/glycocluster interactions. It is a microstructured glass slide where glycoclusters are immobilized by DNA Directed Immobilization (DDI). Two screening methods have been developed with this microarray: 1) the screening in solution and by competition of a saccharidic units library and2) the screening of a glycoclusters library immobilized on the microarray. Protocols of IC50 and Kd measurements have also been developed with this tool to characterize the best lectins inhibitors. This tool allows to use few amount of material (few picomoles) and to do parallel analysis.To validate the microarray, a study of the impact of glycoclusters surface density has been done. The screening of more than 150 saccharidic units allowed the selection of the ones that display the best affinity forlectins. The analysis, on microarray and molecular simulations, of the glycoclusters library displaying thesesaccharidic units and several topologies, valences and properties (aromaticity, charge,…) enable to identify key parameters of structure-affinity relationships. An anti-biofilm activity has been observed for the best glycoclusters targeting PA-IL.Testing in vivo activity of these best candidates will be explored. Targeting others lectins such as the ones on the flagella and pili of PA and involved in the early adhesion needs also to be developed. To this end, preliminary tests have been showed and some are in progress
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Neto, Antonio EufrÃsio Vieira. "CaracterizaÃÃo estrutural da frutalina, uma lectina α-D-Galactose ligante de sementes de Artocarpus incisa e anÃlise das suas bases moleculares de ligaÃÃo a D-galactose." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15539.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorAs lectinas sÃo proteÃnas que contÃm pelo menos um domÃnio nÃo catalÃtico que lhes permite reconhecer seletivamente e se ligar de uma forma reversÃvel a glicanos especÃficos. A Frutalina à uma lectina obtida a partir das sementes de Artocarpus incisa, conhecida popularmente como fruta-pÃo. O isolamento foi realizado por cromatografia de afinidade em coluna de Agarose-D-Galactose e sua caracterizaÃÃo demonstrou que a Frutalina à uma glicoproteÃna, principalmente α-D-galactose ligante, mas que tambÃm reconhece α-D-Manose. Possui 2,1% de carboidratos e apresenta, em seu perfil de SDS-PAGE, duas bandas protÃicas com massas moleculares aparentes de 12 e 15 kDa, sendo uma proteÃna oligomÃrica, encontrando-se como tetrÃmero apenas em pH alcalino, com massa molecular aparente de 60 kDa. Massas diversas em torno de 16 kDa foram observadas nos espectros deconvoluÃdos em espectrometria de massas, o que corrobora a presenÃa de isoformas. Este trabalho mostra a cristalizaÃÃo e anÃlises dos dados obtidos por difraÃÃo de raios-x para determinaÃÃo da estrutura tridimensional desta lectina, e para isso foram realizados ensaios de cristalizaÃÃo da Frutalina isolada a partir das sementes maduras, na presenÃa do ligante (α-D-galactose) e na sua forma apo (sem ligantes). Os cristais de Frutalina cresceram principalmente em poÃos de pH 8,5 contendo PEG como precipitante e etileno-glicol e os melhores cristais apareceram apÃs uma semana de maturaÃÃo, sendo difratados a uma resoluÃÃo mÃxima de 1,81 Ã. A melhor soluÃÃo para o grupo espacial, considerando eixos e planos de simetria, foi obtida para o grupo espacial I2 com a obtenÃÃo de um Rfactor de 38,6% e LLG de 19,9. A estrutura da Frutalina apresenta, em cada unidade monomÃrica, um β prisma simÃtrico, com trÃs grupos de 4 folhas beta, cada. O sÃtio de reconhecimento a carboidratos, à semelhante ao da Jacalina, e envolve o N-terminal da cadeia α, demonstrando, na regiÃo, um enovelamento caracterÃstico de lectinas da famÃlia Moraceae. O sÃtio de ligaÃÃo da Frutalina consiste numa cavidade prÃxima ao N-terminal da cadeia α, formada por quatro resÃduos-chave: Gly25, Tyr146, Trp147 e Asp149. As bases de interaÃÃo com o ligante sÃo relacionadas ao nÃmero de interaÃÃes, que ocorrem entre a hidroxila do C1 e o resÃduo Tyr146, a hidroxila do C3 e o resÃduo Gly25, a hidroxila do C4 e os resÃduos de Gly25 e Asp149 e a hidroxila do carbono 6 aos resÃduos Tyr146, Trp147 e Asp149. Algumas hidroxilas da α-D-Galactose tambÃm utilizam de interaÃÃes com molÃculas de Ãgua estruturais, para buscar estabilidade no sÃtio de reconhecimento a carboidratos. O grande nÃmero de interaÃÃes corrobora com a grande afinidade que a Frutalina tÃm a galactose e à sua grande capacidade de aglutinaÃÃo, alÃm de proporcionar uma anÃlise das dimensÃes da lectina em relaÃÃo ao ligante, onde se visualiza que o sitio de ligaÃÃo à muito maior que o aÃÃcar, o que pode justificar a preferÃncia que a Frutalina costuma apresentar por glicoconjugados de maior massa molecular, proporcionando maior encaixe, e maior nÃmero de interaÃÃes quÃmicas entre um glicoconjugado maior.
Lectins are proteins containing at least one non-catalytic domain that allows them to recognize and selectively bind a reversible specific glycans. Frutalin is a lectin obtained from Artocarpus incisa seeds, popularly known as breadfruit. The isolation was performed by affinity chromatography on column of Agarose-D-Galactose and their characterization shows that frutalin is a glycoprotein mainly α-D-galactose ligand, because it also recognizes epimers of α-D-mannose. It has 2.1% of carbohydrates and presents, in its SDS-PAGE profile, two protein bands with apparent molecular masses of 12 and 15 kDa, with an oligomeric protein, lying as tetramer only in alkaline pH, with apparent molecular mass of 60 kDa. Several masses around 16 kDa was observed in deconvoluted spectra in Mass Spectrometry, which confirms the presence of isoforms. This work shows the crystallization and analysis of data obtained by x-ray diffraction to determine the three-dimensional structure of this lectin, and that were performed crystallization trials of frutalin isolated from the mature seeds in the presence of ligand (D-galactose) and the way apo (no binders). The frutalin crystals have grown primarily in wells of pH 8.5 containing PEG as precipitant and ethylene glycol and the best crystals appeared after one week of maturation being diffracted to a maximum resolution of 1.81 Ã. The best solution, for the space group, considering axes and planes of symmetry, has been obtained for the I2 space group, with the construction of an Rfactor of 38.6% and LLG = 19.9. The structure of frutalin presents in each monomeric unit, a symmetrical β-prism with three groups of four beta strands each. The carbohydrate recognition site is similar to the jacalin, and involves the N-terminus of the α chain, showing, in the region, a characteristic folding of the Moraceae family. The frutalin binding site cavity is near the N-terminus of the α chain formed by four key residues Gly25, Tyr146, Asp149, and Trp147. The bases of interaction with the binder are related to the number of interactions occurring between the C1 hydroxyl and Tyr146 residue, C3 hydroxyl and Gly25 residue, C4 hydroxyl and Asp149/Gly25 residues, and C6 hydroxyl and Tyr146/Trp147/Asp149 residues. Some hydroxyls of α-D-galactose also utilize interactions called structural waters, to seek stability in the carbohydrate recognition site. The large number of interactions agrees with the high affinity that frutalin has with galactose and its great capacity for agglutination, in addition to providing an analysis of the dimensions of the lectin in relation to the binder, which may justify the preference that frutalin tends to present by higher molecular weight glycoconjugates, and that happens due to the most fitting, and the greatest number of chemical interactions among a larger glycoconjugate.
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Arnold, James Noble. "Mannan binding lectin and its interaction with immunoglobulins and other serum glycoproteins." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427902.
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Gemma, Emiliano. "Synthesis of Oligosaccharides for Interaction Studies with Various Lectins." Doctoral thesis, Stockholm : Department of Organic Chemistry, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-459.
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Hakkarainen, Birgit. "¹H NMR studies of molecular interactions of carbohydrates in aqueous solutions /." Uppsala : Dept. of Chemistry, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200705.pdf.
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Goudot, Alice. "Développement d'une plateforme de criblage pour la recherche de nouvelles molécules anti-infectieuses : applications à Pseudomonas aeruginosa." Thesis, Ecully, Ecole centrale de Lyon, 2013. http://www.theses.fr/2013ECDL0023/document.
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Pseudomonas aeruginosa (PA) est l’un des principaux germes impliqués dans les maladies nosocomiales et est aussi la principale cause de mortalité et morbidité des patients atteints de la mucoviscidose malgré l’utilisation massive d’antibiotiques. Dans la lutte contre PA, une alternative aux antibiotiques est l’inhibition de ses facteurs de virulence notamment ceux impliqués dans l’adhésion et la formation du biofilm via des interactions de type sucres/protéines. Ces protéines sont appelées lectines (PA-IL, PA-IIL, FliD). L’objectif de ce travail est la recherche de molécules inhibitrices (glycoclusters) de ces lectines impliquées dans la virulence de PA. Compte tenu du grand nombre de glycoclusters à tester et des faibles quantités de matériels biologiques disponibles, un outil de criblage innovant a été développé (glycoarray) à partir d’une lame de verre microstructurée et fonctionnalisée chimiquement afin d’immobiliser de manière organisée et ordonnée les glycoclusters. La méthode d’immobilisation choisie est la méthode d’immobilisation spécifique par hybridation de l’ADN appelée DDI : DNA Directed Immobilization. Sur ces glycoarrays, 3 méthodes indépendantes (lecture de fluorescence directe, IC50 et Kd) de mesure des interactions glycoclusters/lectines ont été mises au point et validées par une étude comparative donnant un classement similaire des glycoclusters pour leur affinité vis-à-vis des lectines Il faut noter que ces mesures faites sur glycoarrays ne consomment que quelques picomoles de glycoclusters comparées aux méthodes classiques (ITC, ELLA, RMN, …) qui nécessitent des micromoles de produits. A l’aide de ces glycoarrays, un criblage d’une bibliothèque d’une centaine de glycoclusters multivalents, de différentes topologies, charges et linkers a permis d’identifier deux structures montrant une très forte affinité vis-à-vis des lectines de PA. Ces glycoclusters sont actuellement en test in vitro et in vivo. Ces études d’interactions sur DDI-glycoarray ont été étendues à d’autres agents pathogènes tels que les bactéries Burkholderia ambifaria, Viscum album ou contre le virus de la grippe. Dans le futur, pour mieux appréhender les mécanismes d’interactions sucres/protéines, il serait intéressant de pouvoir suivre en temps réel ces interactions en utilisant des systèmes de détection sans marquage tel que, par exemple, la résonance plasmonique de surface. Aussi, le dernier chapitre donne les prémices d’une adaptation de la méthode DDI sur glycoarray sur surface d’orPseudomonas aeruginosa (PA) is one of the predominant bacterium encountered in nosocomial infections. PA infections often lead to chronic inflammation and eventually to death despite aggressive antibiotic therapy. A promising approach is to inhibit the virulence factors of PA such as PA-IL, PA-IIL, FliD (lectins). Therefore, there is a great interest for studying carbohydrate/lectin interactions in order to design new treatments. The goal of this work is the research for inhibitory molecules (glycoclusters ) of these lectins involved in the virulence of PA. An innovative screening tool for studying carbohydrate/lectin interactions has been developed (glycoarray). Glycoarray are microstructured glass-slides, chemically functionalized in order to immobilize, organized and orderly, glycoclusters at the surface. The immobilization method is the specific immobilization method based on DNA hybridization called DDI (DNA Directed Immobilization). This miniaturized analytical biosystem allows multiplex test performed in one single microwell. Moreover, three independent methods of affinity measurement (direct fluorescence read-out, IC50 and Kd) have been developed and validated by a comparative study giving a similar ranking of glycoclusters for their affinity towards PA-IL. These measurements on glycoarrays consume only a few picomoles glycoclusters compared to conventional methods (ITC, ELLA...) that require micromoles of products. Using these glycoarrays, the screening of a library of hundreds of glycoclusters presenting different topologies, multivalencies, charges and linkers led to the identification of two structures showing a very strong affinity for PA lectins. These glycoclusters are currently in vitro assay and in vivo. These interaction studies on DDI-glycoarray were extended to other pathogens such as Burkholderia ambifaria bacteria, Viscum album or against the influenza virus. In the future, to better understand the mechanisms of sugar / protein interactions, it would be interesting to monitor in real time the interactions using label-free detection systems such as, for example, the surface plasmon resonance (SPR). Also, the last chapter gives the beginnings of an adaptation of the method of DDI glycoarray on gold surface
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Nurisso, Alessandra. "Études in silico des interactions proteines-glucides." Grenoble, 2010. http://www.theses.fr/2010GRENV015.
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Différentes approches d'amarrage moléculaire sur des systèmes lectines calcium dépendantes - glucides ont été comparées, afin de reproduire les données expérimentales. En utilisant la méthode d'amarrage la plus appropriée, le site de liaison de la lectine humaine Langerine a été étudié, en rationalisant le mécanisme de reconnaissance de l'épitope du virus VIH. Les caractéristiques de la lectine Pseudomonas aeruginosa l'ont été également étudiées par des calculs d'amarrage moléculaire, de dynamique moléculaire et d'énergie libre. Une analyse conformationnelle es facteurs Nod, signaux bactériens nécessaires à l'induction de la symbiose, a révélé des états conformationnels spécifiques en accord avec les résultats obtenus par RMN. Les modèles par homologie du domaine LysM2 et du domaine catalytique de la kinase LYK3, récepteurs hypothétiques des facteurs Nod exprimés sur les cellules racinaires de Medicago truncatula, ont été construits et utilisés comme support des données biologiquesDifferent molecular docking approaches have been compared on calcium-dependentlectin - carbohydrate systems in order to reproduce the experimental data. Using the most appropriate docking method, the binding site of human lectin Langerin has been studied, unraveling the mechanism of recognition of the epitopeof the HIV virus. The characteristics of Pseudomonas aeruginosa lectin 1 have a/so been studied by mo/eculardocking, molecu/ardynamics simulations and free energy calculations. A conformational analysis of Nod factors, bacterial signais required for the symbiosis induction, revealed specific conformationa/states in agreement with the results obtained by NMR. The homology models of the LysM2 domain and the cata/ytic do main of the kinase LYK3, Hypothetica/ Nod factorreceptors expressed on the root cells of Medicago truncatula, have been built and used as support for biological data
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Smadhi, Meriem. "Nouveaux glycoclusters polysulfurés à coeur triazine : synthèse et interaction envers PA-IL." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10123.
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Les interactions protéines-carbohydrates sont à la base de nombreux processus biologiques physiologiques aussi bien que pathologiques. Ces interactions incluent la synthèse et la dégradation enzymatique des oligosaccharides, la cohésion des tissus, l'immunité, le cancer ou encore l'infection bactérienne et virale. L'inhibition de ce type d'interaction par des molécules multivalentes synthétiques telles les glycopolymères, glycodendrimères, glycoclusters, etc. fait l'objet d'études importantes depuis plusieurs décennies. L'obtention de telles molécules pourrait permettre de développer de nouvelles thérapies qui pourraient palier notamment la multi-résistance aux antibiotiques. De plus, la détection de telles interactions par des méthodes simples et faciles à mettre en oeuvre permettrait une amélioration de la compréhension de ces phénomènes, ainsi que le diagnostic rapide de la présence de microorganismes. C'est dans ce contexte, que nous avons développé une nouvelle classe de composés glycosylés multivalents à coeur triazine. Ces glycoclusters de basse valence, ont la particularité de présenter une double fonctionnalité : l'inhibition d'interactions lectine-sucre par des effets de multivalence ainsi que la détection de ces interactions. Nous présentons dans ce manuscrit, la synthèse d'une nouvelle famille de glycoclusters polysulfurés à coeur triazine portant des épitopes saccharidiques tels que D-glucose, D-galactose, D-mannose, L-fucose, ainsi que leurs évaluations biologiques réalisées sur des lectines de Pseudomonas aeuriginosa. Nous avons ainsi mis en évidence la possibilité de reconnaître et de détecter les interactions lectine-sucre dans un premier temps par association d'un cluster mixte portant un fluorophore, et de façon plus sophistiquée, grâce à un système à géométrie variable incorporant dans le scaffold même un switch photochimique variant l'arrangement des sucres dans l'espaceProtein-carbohydrate interactions mediate a wide range of biochemical processes. Amongst these is the process of bacterial infection, which often proceeds through carbohydrate-binding lectins involved in biofilm formation. Even if the individual associations result from weak interactions, the assembly of multiple carbohydrate-protein interactions, typically more than additive, confers to the system the required specificity and avidity for their biological functions. In order to study this « glycocluster effects », a number of scaffold systems presenting multivalent carbohydrate ligands have been prepared in the literature. Dendrimers, polymers, peptides, calixarenes, to name a few, have been used as core molecules for the synthesis of multivalent glycoconjugates. The purpose of this work is to design new glycoclusters which exhibit dual functionality: the inhibition of carbohydrate-protein interactions via a multivalency effect; and detection of the interactions via fluorescence spectroscopy. A first generation of polysulfurated glycoclusters, organized around a heteroaromatic core, was synthesized using click chemistry reactions, which provided a family of highly soluble and readily accessible clusters. The glycoclusters were evaluated for their ligand-lectin interactions, multivalency effects, thermodynamic parameters, and abilty to modulate biofilm formation by Pseudomonas aeruginosa, a major causative agent of lung infections in cystic fibrosis patients. We describe a new family of ‘switchable glycoclusters’ based on photochromic behavior. They are designed to generate a modulated fluorescence signal as well as a defined change in the three-dimensional arrangement of the sugar epitopes, and may eventually provide significantly improved probes for studying the distribution, dynamics, interactions, and activities of specific lectins
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Pickford, Wendy Jane. "Novel Moraceae lectins and their interactions with intestinal and lymphoid cell surfaces." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364689.
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The aims of this study were to screen an array of plant families for novel lectins, to isolate candidate lectins whose reactivity suggested may be functionally useful and to assess the reactivity and modulatory effects of the novel lectins on the cells of the gastrointestinal tract (including the immune regions) and lymphocytes. Few of the seed and bulb samples screened had significant levels of lectin. However, the seeds, roots, stem and bark of Morus nigra, the black mulberry tree from the Moraceae plant family, were found to contain particularly high lectin activity. Two new lectins Morus nigra agglutinin-I (MNAI) and Morus nigra agglutinin-II (MNAII) were isolated. They were found to differ significantly from each other in their sugar specificity, subunit structure, amino acid sequence identity, glycosylation and haemagglutinating activity. MNAI has similarities in sugar inhibition characteristics (GalNAc) and amino acid identity to both MPA and jacalin, which also belong to the Moraceae family. MNAI recognises the similar intestinal glycan structures as jacalin and recognises T/Tn blood group antigen, both with and without sialylation. However, it differs significantly from MPA and jacalin in its lymphocyte stimulatory properties. MNAII appears to be novel and did not show amino acid sequence identity with any known proteins contained in the deltamass database. It is inhibitable by α-D-methyl mannoside. It may have an affinity for structures such as some form of N-linked glycans and appears to have low affinity for α2,6 sialylated structures. It labelled glycan structures present on the villus brush border, dome FAE and most M cells of many of the species tested in vitro.
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Dubois, Marie Pierre. "Conception d'un biocapteur électrochimique pour la détection des interactions oligosaccharides/protéines." Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10243.
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Les oligosaccharides situés à la surface des cellules, en interagissant de manière spécifique avec certaines protéines (lectines), jouent un rôle majeur dans la vie sociale de ces cellules et sont directement impliqués dans différents processus biologique. Dans ce contexte, la mise en place d'outils de diagnostique et de détection d'agents pathogènes, tel qu'un biocapteur a été envisagée. Les oligosaccharides (lactose et sialyllactose) ont été immobilisés à la surface d'une électrode via un film polypyrrole, afin de pouvoir par la suite détecter directement la reconnaissance oligosaccharides/lectines par électrochimie. Les lectines étudiées sont la lectine PNA pour le lactose et la lectine de Maackia Amurensis pour le sialyllactose. Les interactions oligosaccharides/lectines ont pu être mises en évidence par voltampérométrie cyclique, perméabilité et spectroscopie d'impédance. Deux études quantitatives ont été menées, l'une en résonance plasmonique de surface permettant l'obtention d'un seuil de détection des deux couples étudiés, ainsi que l'estimation des constantes de dissociation, et l'autre en spectroscopie d'impédance permettant l'obtention d'un biocapteur, avec une limite de détection de 1,5 nmo1. L-1Molecular recognition between carbohydrates and proteins (lectins) displayed on the cell surface of living organisms plays key roles in many biological processes. Ln this perspective, the development of diagnostic tools like carbohydrate sensor, has gained much attention over the last five years. We tumed our attention to carbohydrate (lactose and sialyllactose) immobilization via electropolymerized polypyrrole films that may allow direct detection of carbohydrate-protein interactions by electrochemical methods. PNA lectin for the latose and lectin of Maackia amurensis for the sialyllactose have been used like models for our study. The oligosaccharides/proteins interactions have been given prominence to voltamperommetry cyclic, permeation, and impedance spectroscopy. Two quantitative studies have been performed. The first with the surface plasmon resonance, limit of detection and dissociation coefficient have been specified. The second permit the obtention of a biosensor, with 1,5 nmo1. L-1 for the limit of detetion
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Mastouri, Amira. "Etude des phénomènes de reconnaissance moléculaire spécifique aux interfaces biologiques par AFM : investigation de l'influence de la multivalence sur les interactions sucre-lectine." Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-01067126.
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Le présent projet vise à analyser l'influence de la multivalence dans les interactions sucres-lectines. En collaboration avec des équipes externes, une étude par microscopie à force atomique (AFM) de l'interaction entre des ligands synthétiques de différentes valences et leurs lectines spécifiques a été entreprise. Dans le cadre de cette étude, une première caractérisation fondamentale de l'interaction sucre-lectine a été menée. Cette caractérisation concerne plus particulièrement l'influence de la multivalence sur les forces d'adhésion et la dynamique de l'interaction entre les ligands synthétiques multivalents et une lectine modèle, la lectine d'arachide PNA. Une seconde caractérisation, d'aspect plus appliqué, concerne l'utilisation des ligands synthétiques multivalents dans une approche thérapeutique antiadhésive pour le traitement des infections urinaires chroniques dues à Escherichia coli uropathogène (UPEC). Le caractère innovant des ligands (obtenus par une synthèse chimique rationnelle) ainsi que l'approche utilisée pour caractériser leurs interactions avec les lectines à l'échelle moléculaire par AFM témoigne de l'originalité du projet.
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Naisbett, B. "The interaction of tomato lectin with adult rat small intestine : potential for oral drug delivery." Thesis, Keele University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293534.
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Jiménez-Castells, Carmen 1982. "Capture and identification of carbohydrate-binding proteins by SPR and CREDEX-MS." Doctoral thesis, Universitat Pompeu Fabra, 2010. http://hdl.handle.net/10803/7237.
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Carbohydrate-binding proteins of non-immunological origin -lectins- have been recognized over the last decades as decisive players in numerous biological processes, ranging from cellcell communication, fertilization, pathogen-cell adhesion to metastasis. Consequently, there is an increasing interest in finding powerful and nanosized tools to screen for these molecules and to study their carbohydrate interactions in detail. Here, two complementary approaches are described to characterize lectin-carbohydrate interactions with high sensitivity, low sample consumption, and without the need for sample labelling: SPR and CREDEX-MS. In SPR, we have developed an approach where the sugar is immobilized onto a sensor surface through a tailor-made peptide module that allows (1) to capture the lectin, (2) to characterize the interaction through kinetic and thermodynamic parameters, and (3) to identify the interacted protein by mass spectrometry. In CREDEX-MS, based on proteolytic excision of proteincarbohydrate complexes and mass spectrometric analysis, the peptides comforming the carbohydrate binding domain are identified.Las lectinas (proteínas de origen no inmune capaces de reconocer azúcares) se han revelado en las últimas décadas como participantes cruciales en multitud de procesos biológicos, tales como la comunicación célula-célula, la fertilización, la adhesión del patógeno a la célula y la metástasis, entre muchos otros. Por lo tanto, existe un gran interés en el desarrollo de técnicas analíticas potentes para el estudio de las interacciones lectina-carbohidrato. En este trabajo, se describen dos aproximaciones complementarias mediante las cuales se pueden caracterizar las interacciones lectinas-azúcar con gran sensibilidad, poca utilización de muestra y sin la necesitad de ningún marcaje. En la técnica basada en resonancia de plasmón superficial (SPR), el azúcar es inmovilizado sobre una superficie a través de un módulo peptídico, lo cual permite (1) capturar la lectina, (2) caracterizar su interacción mediante parámetros cinéticos y termodinámicos y (3) identificar posteriormente la proteína mediante espectrometría de masas. Complementariamente, la técnica CREDEX-MS, basada en la excisión proteolítica del complejo proteína-azúcar y posterior análisis por espectrometría de masas, nos permite identificar los péptidos que forman parte del dominio de unión al azúcar.
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Gouget, Anne. "Etude fonctionnelle d'un récepteur lectine kinase (LecRK79) potentiel partenaire dans les contacts paroi-plasmalemme chez Arabidopsis thaliana." Toulouse 3, 2006. http://www.theses.fr/2006TOU30285.
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Les contacts paroi-plasmalemme d'A. Thaliana, sont rompus à l'aide de peptides contenant le motif RGD (Arg-Gly-Asp). Il est montré que le domaine extracellulaire de type lectine de LecRK79, un récepteur kinase, interagit avec les motifs RGD et RGE de peptides synthétiques et de la protéine IPI-O de Phytophthora infestans. Une forte expression de LecRK79 est observée dans les racines: apex et stèle des racines primaires et latérales, primordia, racines adventives. Un mutant insertionnel n'exprimant plus le gène possède un phénotype racinaire, caractérisé par un dédoublement de l'endoderme. Une induction rapide et transitoire de LecRK79 est observée après inoculation de souches avirulentes de la bactérie pathogène P. Syringae pv. Tomato. L'ensemble des résultats indique que LecRK79 est capable de participer à des interactions protéine-protéine afin d'établir des contacts paroi-plasmalemme. LecRK79 peut être impliquée dans le développement racinaire et les interactions plantes-pathogènes. Les contacts paroi-plasmalemme d'A. Thaliana, sont rompus à l'aide de peptides contenant le motif RGD (Arg-Gly-Asp). Il est montré que le domaine extracellulaire de type lectine de LecRK79, un récepteur kinase, interagit avec les motifs RGD et RGE de peptides synthétiques et de la protéine IPI-O de Phytophthora infestans. Une forte expression de LecRK79 est observée dans les racines: apex et stèle des racines primaires et latérales, primordia, racines adventives. Un mutant insertionnel n'exprimant plus le gène possède un phénotype racinaire, caractérisé par un dédoublement de l'endoderme. .Plasma membrane – cell wall contacts in A. Thaliana are disrupted by addition of RGD (Arg-Gly-Asp) containing peptides or proteins. Here we show that the extracellular legume-lectin domain of LecRK79, a receptor kinase, is able to interact with RGD- or RGE-containing peptides or proteins: the RGD motif of IPI-O, a protein from Phytophthora infestans, is also recognized. A strong expression of LecRK79 was observed in roots: apex and stele of apical and lateral roots, primordia, adventive roots. LecRK79 knock-out plants revealed that the endodermis layer splits into two rows of cells starting at the apex of apical and lateral roots. The induction of LecRK79 expression was detected in response to avirulent strains of Pseudomonas syringae pv. Tomato. Altogether, our results indicate that LecRK79 is able to mediate protein-protein interactions to possibly establish plasma membrane – cell wall contacts. They suggest LecRK79 is involved in root development and in plant-pathogen interactions. .
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Zhang, Jing. "Design and implementation of DNA-Directed Immobilisation (DDI) glycoarrays for probing carbohydrate-protein interactions." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00605541.
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Carlsson, Jenny. "Interaction Studies in Complex Fluids with Optical Biosensors." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-14694.
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In this thesis interactions in complex fluids, such as serum and meat juice, were analysed with optical biosensor techniques. Panels of lectins immobilised on gold surfaces were used for investigation of differences in protein glycosylation pattern in sera and meat juices between various species. The present panel was also used for investigation of global glycosylation changes of serum proteins in type 1 diabetes patients. Biorecognition was evaluated with null ellipsometry and scanning ellipsometry combined with multivariate data analysis techniques (MVDA). Principal component analysis (PCA) showed that the lectin panel enabled discrimination between sera from the different species as well as for the different meat juices. The results also indicate that there is a measurable global alteration in glycosylation pattern of serum proteins in type 1 diabetic patients compared to healthy subjects. Using an artificial neuronal net (ANN), it was also possible to correctly categorise unknown serum samples into their respective class or group. The analytical potential of combining information from lectin panels with multivariate data analysis was thereby demonstrated. Also, a sensitive and specific method based on surface plasmon resonance (SPR) for detection of insulin autoantibodies (IAA) in serum samples from individuals at high risk of developing type 1 diabetes (T1D) has been developed. When measuring trace molecules, such as autoantibodies, in undiluted sera with label-free techniques like SPR, non-specific adsorption of matrix proteins to the sensor surface is often a problem, since it causes a signal that masks the analyte response. The developed method is an indirect competitive immunoassay designed to overcome these problems. Today, IAA is mainly measured in radio immunoassays (RIAs), which are time consuming and require radioactively labelled antigen. With our SPR-based immunoassay the overall assay time is reduced by a factor of >100 (from 4 days to 50 min), while sensitivity is maintained at a level comparable to that offered by RIA. Finally, the assay was used in a screening study of newly diagnosed type 1 diabetes patients and non-diabetic subjects.
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Cecioni, Samy. "Approche multivalente des interactions saccharides - lectines : synthèse de glycoclusters et analyse de la reconnaissance biomoléculaire." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00732336.
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L'interaction non-covalente entre un ligand et un récepteur selon un modèle clé-serrure constitue une des bases essentielles de tout système biologique. La présence de multiples clés et serrures sur les biomolécules conduit à des interactions multivalentes. Les lectines sont très fréquemment structurées en homo-multimères et sont donc des cibles de choix pour l'étude des interactions avec des structures multivalentes glycosylées. Ligands et récepteurs multivalents peuvent obéir à plusieurs mécanismes d'association conduisant à des profils thermodynamiques et cinétiques permettant de rationnaliser les améliorations spectaculaires d'affinité souvent observées. L'utilisation de ligands de faible valence et de petite taille permet une présentation contrôlée des sucres au travers d'une structure unique bien définie. Ces glycoclusters sont des plateformes adaptées à l'étude de l'influence de la topologie de la présentation des sucres sur l'interaction. La synthèse de glycoclusters a été optimisée selon une voie convergente de glycosylation puis de couplage par CuAAC permettant la synthèse de structures multi-glycosylées telles que des calix[4]arènes de différentes conformations, des peptoïdes linéaires et cycliques ou encore des porphyrines. Ces ligands ont été évalués par quatre techniques d'analyse des interactions (HIA, ELLA, SPR, ITC) principalement en présence de la lectine PA-IL de Pseudomonas aeruginosa mais également avec la Galectine-1 humaine et la lectine d'Erythrina cristagalli (légumineuse). Des glycoclusters de seconde génération ont été ensuite été préparés avec l'objectif d'optimiser les composantes enthalpiques et entropiques de l'interaction. Les résultats indiquent que de légères modifications de la présentation des sucres peuvent induire des mécanismes d'association différents. La conception de structures rigidifiées a révélé des profils thermodynamiques contre-intuitifs qui ont pu être modélisés. Par cette étude, plusieurs ligands ont montré des affinités sans précédent pour la lectine PA-IL. Le meilleur ligand multivalent de première génération a confirmé un potentiel thérapeutique prometteur in vivo.
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Beatson, Richard. "Defining the interaction of specific glycoforms of MUC1 with lectin-like receptors of the innate immune system." Thesis, King's College London (University of London), 2010. https://kclpure.kcl.ac.uk/portal/en/theses/defining-the-interaction-of-specific-glycoforms-of-muc1-with-lectinlike-receptors-of-the-innate-immune-system(e406c1e6-1c3e-4206-883b-35131efb7784).html.
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Faivre, Vincent. "Interactions specifiques a l'interface air/eau, entre des proteines et leurs ligands (doctorat : pharmacotechnie et biopharmacie)." Paris 11, 2000. http://www.theses.fr/2000PA114819.
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Vinson, Mary. "Structural and functional studies on sialoadhesin." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362115.
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Félin, Murielle. "Interactions glycoproteine-lectine dans le noyau des cellules de la lignee myeloblastique leucemique humaine hl60." Paris 5, 1996. http://www.theses.fr/1996PA05S012.
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La regulation de certaines activites nucleaires par des interactions glycoproteine-lectine est supposee depuis la decouverte de ces proteines dans le noyau cellulaire. Toutefois, l'existence de telles interactions restait hypothetique. En effet, les lectines nucleaires isolees jusqu'alors se fixaient, soit au glucose, soit aux galactosides, tandis que les glycoproteines nucleaires les mieux caracterisees comportaient des residus n-acetylglucosamine. Notre travail, realise sur la lignee myeloblastique leucemique humaine hl60, a donc consiste a rechercher des lectines nucleaires et leurs ligands glycosyles, afin d'etudier le role de ces complexes. Les resultats essentiels obtenus sont : i) la description de la lectines nucleaires potentiellement capables de reconnaitre des glycoproteines contenant des residus n-acetylglucosamine : la cbp70 (cbp carbohydrate-binding protein), qui reconnait le glucose mais avec une meilleure affinite la n-acetylglucosamine et la cbp22, qui est specifique de la n-acetylglucosamine, ii) la mise en evidence d'une interaction proteine-proteine entre la cbp35 (specifique des galactosides) et la cbp70, rompue par la fixation soit de lactose sur la cbp35, soit de n-acetylglucosamine sur la cbp70. Ainsi, des interactions glycoproteine-lectine pourraient moduler des interactions proteine-proteine au sein du noyau. Un tel systeme pourrait etre implique dans la regulation de l'epissage des pre-arnm, iii) l'isolement d'un ligand glycosyle de la cbp70 et la demonstration que l'interaction des deux partenaires est de type glycoproteine-lectine. Ce ligand est uniquement nucleaire mais d'autres ligands potentiels de la cbp70 existent dans le cytoplasme, ou cette derniere a egalement ete detectee. En conclusion, l'isolement, pour la premiere fois, d'une lectine nucleaire et de son ligand glycosyle, ouvre des perspectives nouvelles dans la comprehension des mecanismes de regulation de l'expression genetique.
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Ayouba, Ahidjo. "Interaction des lectines végétales avec les constituants du peptidoglycane bactérien." Toulouse 3, 1992. http://www.theses.fr/1992TOU30211.
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L'interaction des constituants du peptidoglycane bacterien (acide muramique, n-acetylmuramique et muramyl dipeptides) avec quarante-cinq lectines/isolectines extraites de plantes appartenant a diverses familles botaniques a ete etudiee. Cette etude a ete realisee par les techniques d'inhibition d'hemagglutination et d'hemadsorption et par modelisation moleculaire a partir de modeles tri-dimensionnels obtenus par cocristallisation de la lectine de lathyrus ochrus avec l'acide muramique et le muramyl-dipeptide d-d (n-acetylmuraminyl-d ala d isogln). L'interaction observee varie de tres forte a forte avec les lectines de legumineuses et de faible a tres faible avec les lectines d'autres familles. Elle semble, en outre, independante de la specificite glucidique des lectines. Les resultats obtenus par inhibition de l'hemagglutination ou de l'hemadsorption indiquent que l'affinite des acides muramique et n-acetylmuramique et des muramyl-dipeptides (mdp d-d essentiellement) pour les lectines de vicieae est aussi forte qu'avec les oses(mannose) et derives d'oses(methyl alpha-d-mannopyrannoside) consideres comme leurs meilleurs inhibiteurs. L'etude des modeles tri-dimensionnels obtenus par co-cristallographie et la modelisation moleculaire, montrent que ce sont les memes residus d'acides amines du site actif des lectines de victime qui sont impliques dans l'interaction. L'absence de modeles tri-dimensionnels pour les lectines appartenant a d'autres familles ne permet pas d'expliquer la faible reactivite de ces lectines vis-a-vis des constituants du peptidoglycane. Des phenomenes d'empechement sterique permettent d'expliquer la reactivite plus reduite de lectines issues de la tribu des diocleae. Les lectines des vicieae reagissent egalement avec le peptidoglycane entier. Les resultats obtenus posent le probleme de la reconnaissance du peptidoglycane bacterien par les lectines de legumineuses et de son implication dans les relations plantes-bacteries
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Mantovani, Raphaela de Araujo 1986. "Estabilidade e digestibilidade de emulsões contendo lecitina e proteínas do soro." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255576.
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Orientadores: Rosiane Lopes da Cunha, Ângelo Luiz Fazani CavallieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: As proteínas do soro do leite (WPI) e lecitina de soja são amplamente utilizadas em alimentos devido às suas excelentes propriedades emulsificantes. Este trabalho visou avaliar as propriedades emulsificantes da mistura de WPI e lecitina em diferentes condições de pH e concentração dos ingredientes. A primeira etapa consistiu no estudo das interações entre os emulsificantes em meio aquoso em diferentes razões WPI:lecitina e condições de pH. Os resultados mostraram que na razão 1:1 e em pH abaixo do pI da proteína, no qual os emulsificantes encontravam-se opostamente carregados, foi favorecida a formação de complexos eletrostáticos. Na segunda etapa, emulsões O/A contendo proteínas do soro e/ou lecitina foram avaliadas através da estabilidade à cremeação, microestrutura, distribuição do tamanho de gota, densidade de carga superficial, reologia, eletroforese em gel de poliacrilamida e digestão in vitro, verificando-se a influência do pH e da pressão de homogeneização. As emulsões estabilizadas somente por proteínas apresentaram separação de fases e comportamento não-Newtoniano somente em pH próximo ao pI. As emulsões contendo somente lecitina não separaram de fases e apresentaram comportamento Newtoniano. Os sistemas em pH abaixo do pI, contendo a mistura de emulsificantes apresentaram elevada instabilidade cinética devido à forte interação eletrostática entre os componentes. No entanto, em pH próximo ao pI da prote, a interação foi favorável e levou ao aumento da estabilidade das emulsões e a menores tamanhos de gota, resultando em fluidos pouco viscosos. O aumento da pressão de homogeneização, em emulsões com pH próximo e acima do pI favoreceu a formação de agregados de alta massa molecular, o que não foi observado em pH mais ácido. Também não foi notada a formação de agregados na presença de lecitina em nenhuma das condições de pH. Os ensaios de eletroforese deram indícios de que a interação entre os emulsificantes levou a modificações na estrutura das proteínas e revelaram maior afinidade da lecitina com a ?-lactoalbumina (?-la). Finalmente, na etapa de simulação do processo de digestão as proteínas mostraram-se mais resistentes, uma vez que a presença de lecitina promoveu a liberação do óleo da emulsão logo no início da etapa gástrica. De maneira geral, a utilização das proteínas do soro juntamente com a lecitina como emulsificante levou a resultados satisfatórios pois permitiu o desenvolvimento de sistemas estáveis à cremeação em diferentes valores de pH, inclusive em pH próximo ao pI, e consideravelmente resistentes às condições adversas do trato gastrointestinal
Abstract: Whey proteins (WPI) and soybean lecithin are widely used in food due to its excellent emulsifying properties. This study aimed to evaluate the emulsifying properties of the mixture of whey protein and lecithin at different conditions of pH and concentration of ingredients. Firstly, the interactions between emulsifiers in an aqueous medium at different ratios (WPI:lecithin) and pH conditions were studied. The results showed that at mixing ratio of 1:1 and at pH below the isoelectric point of the protein (pI) in which the emulsifiers were oppositely charged, was favored the formation of electrostatic complexes. Afterwards, O/W emulsions containing WPI and/or lecithin were prepared and the influence of pH and pressure homogenization were studied. Stability, microstructure, droplet size distribution, surface charge density, rheology, electrophoresis in polyacrylamide gel (SDS-PAGE) and digestion in vitro were evaluated. The emulsions stabilized by proteins showed phase separation and non-Newtonian behavior only in pH close to the pI. The emulsions containing only lecithin were stable and showed Newtonian behavior. Systems containing the mixture of emulsifiers at pH below the pI showed high kinetic instability due to the strong electrostatic interactions between the components. However, at pH close to the pI the interaction was favorable and led to an increase of the emulsion stability and to smaller droplet sizes, resulting in lower viscosities. When the pressure homogenization was increased, emulsions at a pH close to and above the pI favored the formation of high molecular weight protein aggregates which was not observed in emulsions at lower pH. In the presence of lecithin, protein aggregates were not formed in any of the pH conditions. The SDS-PAGE analysis showed that the interaction between emulsifiers led to modifications in the structure of proteins and indicated a higher affinity of lecithin to ?-lactalbumin (?-la). Finally, proteins were more resistant to digestion, since the presence of lecithin promoted release of oil emulsion at the beginning of gastric step. In general, the use of whey protein with lecithin as emulsifier led to satisfactory results because it allowed the development of stable emulsions to creaming at different pH values, even at pH close to the pI, and substantially resistant to the adverse conditions of the gastrointestinal tract
Mestrado
Engenharia de Alimentos
Mestre em Engenharia de Alimentos
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Wilczewski, Marie. "Les interactions multivalentes : leurs rôles dans les processus de reconnaissance biomoléculaire et leur application dans la construction d'assemblage supramoléculaire." Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00196867.
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Ce travail décrit une étude quantitative de plusieurs systèmes de reconnaissance biomoléculaire impliquant des interactions multivalentes.Deux chapitres sont axés sur l'utilisation de plateformes supramoléculaires cyclodécapeptidiques appelées RAFT (Regioselectively Adressable Functionnalized Template) permettant la présentation multiple de ligand saccharidique ou cyclopeptidique. Une étude cinétique et thermodynamique des interactions entre les ligands RAFT-saccharide et une lectine modèle, la concanavaline A, a permis de démontrer que deux mécanismes moléculaires sont à l'origine de la meilleure affinité des RAFT multivalents par rapport à leurs homologues monovalents : d'une part un effet de « proximité-statistique » dû à la concentration locale élevée en motif sucre et d'autre part la capacité des RAFT multivalents à se lier à plusieurs lectines selon un effet « cluster ». Des études préliminaires ont également concerné l'analyse de l'interaction entre RAFT-RGD et des récepteurs cellulaires.
Dans un dernier chapitre, nous avons démontré, pour la première fois, la formation de films multicouches grâce à des interactions de type hôte-invité entre deux biopolymères de chitosane, l'un fonctionnalisés par des cavités Β-cyclodextrine et l'autre par des entités adamantane. Bien que la stabilité de l'assemblage soit assurée par des interactions de complexation multivalentes, la croissance de l'assemblage, quant à elle, dépend de la disponibilité des sites de complexation offerts par chacune des couches. De plus, les deux polymères chargés positivement confèrent à l'assemblage des propriétés de gonflement-dégonflement en réponse à des variations de force ionique et pH.
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Cendret, Virginie. "Mimes de haut-mannose et glycoclusters pour l’étude des interactions sucres-lectines." Amiens, 2010. http://www.theses.fr/2010AMIE0116.
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Les oligosaccharides présents à la surface des cellules sont à l’origine de nombreux processus de reconnaissance. Ils sont en effet des points d’ancrages sur lesquels peuvent se fixer de manière spécifique d’autres cellules ou des agents pathogènes. Dans la famille des N-glycanes, lesoligosaccharides de type haut-mannose sont par exemple les premières espèces impliquées lors del’infection d’une cellule hôte par un virus ou un parasite. Pour la recherche, les hauts-mannoses constituent donc des cibles intéressantes. Toutefois, la synthèse de ces oligosaccharides reste difficile et fastidieuse. Dans ce contexte, nous avons entrepris deux projets en parallèle. L’objectif du premier projet était dans un premier temps de développer une méthodologie donnant accès plus rapidement à des structures similaires à celles des hauts-mannoses. Pour simplifier les synthèses, nous avons donc choisi de remplacer des unités mannoses par des groupements triazoles. Nous avons pour cela associé la réaction de glycosylation classique à une réaction de click chemistry et après avoir exploré plusieurs voies, nous sommes parvenus à synthétiser un pseudo-octamannoside. La seconde phase de ce projet, à savoir l’évaluation de ce composé en tant que mime de N-glycanes est sur le point de débuter. Le second projet qui a été mis en oeuvre est issu d’une collaboration entre le Laboratoire des Glucides et l’équipe du Dr. Sébastien Vidal et fut dédié à la synthèse de glycoclusters multivalents. Au cours de ce projet, un trimannoside a été couplé par réaction de click chemistry à des plateformes multivalentes de type porphyrine et calixarène. Quatre nouveaux glycoclusters protégés ont été obtenus. Toutefois, l’étape de déprotection de ces derniers pose quelques difficultés. Pour résoudre ce problème, le couplage sur la porphyrine de l’oligosaccharide libre a été réalisé. Les premiers résultats sont encourageants et suggèrent que cette approche est la plus appropriée pour l’obtention des glycoclusters souhaités. A l’issue des évaluations biologiques de ces composés, nous pourrons conclure quant à l’importance de la densité de ligand dans le processus de reconnaissance sucres-lectinesCells surface oligosaccharides are at the heart of many recognition processes: they are anchors to which other cells or pathogenic agents can specifically bind. In the N-glycan family, high-mannose type oligosaccharides are for instance the first species involved whenever a virus or a parasite infects a host cell. For research studies, high-mannoses therefore constitute interesting targets. However, the synthesis of these oligosaccharides remains difficult and tedious. In this context, we undertook two projects in parallel. The first one was firstly aimed at the development of a methodology providing faster access to high-mannose analogues. In order to simplify the synthesis, we chose to replace mannosidic units by triazole groups. Thus, we combined the classical glycosylation with a click chemistry reaction and after exploring several routes, we achieved the synthesis of a pseudo-octamannoside. The second stage of this project, that is to say the evaluation of this compound as N-glycans mime, is about to start. The second project stemmed from collaboration between the Laboratoire des Glucides and Dr. Sébastien Vidal team and was devoted to the synthesis of multivalent glycoclusters. In this work, a trimannoside was coupled to multivalent scaffolds such as porphyrins and calixarenes by a click chemistry reaction. Four new glycoclusters were obtained. However, their final deprotection at the end proved non trivial. To solve this problem, the coupling was realized with the free oligosaccharide. The first results are encouraging and suggest that this approach is the most appropriate for the synthesis of the desired glycoclusters. At the end of the biological assays of these compounds, we will be able to conclude about the importance of the ligand density in the carbohydrates-lectins recognition process
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Yu, Lu-Gang. "Interactions between intestinal epithelial cells and dietary lectins and monoclonal antibodies which bind the Thomsen-Friedenreich antigen." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321156.
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Tantipolphan, Ruedeeporn, and n/a. "Characterisation of protein-phospholipid interactions in implantable delivery systems." University of Otago. School of Pharmacy, 2007. http://adt.otago.ac.nz./public/adt-NZDU20071218.162425.
Full textAbstract:
Purpose: This thesis aimed to gain a better understanding of the effects of salts in modifying in vitro phase behaviour of lecithin and cholesterol solid implants and to obtain further information on in vitro protein release and stability.
Methods: Raman spectroscopy and partial least squares regression (PLSR) were used to investigate lecithin-cholesterol molecular interactions as a function of method of preparation. Lipid-salt interactions were studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopy using principal component analysis (PCA). In vitro release of bovine serum albumin (BSA), a model protein, from lecithin and lecithin:cholesterol implants comprising 10 and 30% NaCl and CaCl₂ were performed. Size exclusion (SE) HPLC was used for quantitative and qualitative analysis of the released BSA. On hydration, changes in phase behaviour and implant morphology were studied by ATR spectroscopy and light microscopy. SE-HPLC, ATR and fluorescence spectroscopy were used to evaluate the structure of unreleased BSA. Protein adsorption on lipid films was studied by flow through ATR spectroscopy. Increased amide II peak area upon recirculation of BSA in salt solutions over hydrated lecithin and lecithin:cholesterol films cast on ZnSe prisms was used to quantify the deposition of BSA onto the lipid surfaces.
Results: Shifts in the Raman spectra suggested the lecithin headgroup may be involved in lecithin-cholesterol interactions. Greater R� and root mean square error of cross validation in the calibration curves of physical mixing and heating (120�C) methods reflected poor mixing in these preparations. The mean absolute residue and mean Mahalanobis distance values from the physical mixing and granulation methods indicated their spectral similarity and comparable level of lecithin-cholesterol interactions. Calcium exhibited stronger affinity for phospholipids than sodium and it induced headgroup hydration and reorganisation upon binding. PCA of ATR spectra was sensitive to cholesterol addition, calcium binding and method of preparation whilst PCA of Raman spectra only differentiated the presence of cholesterol. In vitro release of BSA from implants produced from wet granulation mixtures of lecithin and lecithin:cholesterol in the absence of salt showed retention of a high monomer content and the release profiles were similar to the literature. Cholesterol increased the swelling, induced phase transformation of lecithin and, subsequently, reduced the BSA release. Salts only slightly modified the BSA release from the lecithin implants. In contrast, for lecithin:cholesterol matrices salts greatly enhanced implant swelling, induced the formation of hydrated lecithin of heterogeneous size and inhibited the in vitro BSA release. Analyses of the protein showed increased aggregation of BSA with a high retention of native structure while retained within the swollen matrices. ATR spectra suggested that salts promoted protein adsorption onto hydrated lecithin surfaces and the effects depend on salt types (NaCl > CaCl₂) and concentration (0.1 M > 1.0 M) but not on lecithin:cholesterol surfaces.
Conclusion: PLSR and PCA can be used to investigate molecular interactions in the solid lipid matrices. In lecithin:cholesterol implants, salts modified the phase behaviour of lecithin which resulted in enhanced swelling, formation of hydrated lecithin of altered morphology and inhibition of in vitro BSA release.
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Flood, Warren. "The interaction of Helicobacter pylori O-antigen with the immunomodulatory lectins DC-SIGN and galectin-3." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/the-interaction-of-helicobacter-pylori-oantigen-with-the-immunomodulatory-lectins-dcsign-and-galectin3(f1901b50-7370-4178-a392-f0a6445a1e29).html.
Full textAbstract:
Helicobacter pylori are unique in their ability to colonise the human gastric mucosa. They persist lifelong in untreated individuals despite the presence of a continuous and specific immune response being mounted against it. H. pylori O-antigen is thought to be involved in immune-evasion and subversion by the bacteria and expression has been shown to facilitate colonisation and exacerbate pathology in murine models. This study investigates immuno-relevant roles of H. pylori O-antigen as a pathogen-associated molecular pattern (PAMP) and its interaction with two pattern recognition receptors (PRRs); galectin-3 and DC-SIGN. These PRRs possess distinct carbohydrate recognition domain (CRD) structures and binding affinities. Despite this, we have demonstrated that they compete for adhesion to both Lewis antigen glycoconjugates and whole cell H. pylori 26695 in solid phase binding assays. Galectin-3 significantly reduces DC-SIGN adhesion at a 2:1 stoichiometric ratio in both Lex glycoconjugate and whole cell H. pylori 26695 assays, and abrogates carbohydrate-specific binding in Lex glycoconjugate assays at a 22:1 ratio. These results suggest that galectin-3 may play a role in inhibiting or modulating the interaction between H. pylori O-antigen and DC-SIGN in vivo. Supporting this, we have shown that galectin-3 secreted by AGS cells during competitive infection with H. pylori 26695 is sequestered by H. pylori O-antigen. We have demonstrated that competitive infection of the O-antigen deficient mutant H. pylori 26695 galE in DC-SIGN expressing THP-1 cells reveals a significant reduction in intracellular survival at 8 hours compared to H. pylori 26695 Wt. Co-incubation of H. pylori 26695 Wt with 10 µg ml-1 galectin-3 reduced intracellular survival to the levels of H. pylori 26695 galE at 8 hours. Furthermore, H. pylori 26695 galE displayed rapid association of the endocytic markers Rab5 and Rab7 at 15 minutes compared to H. pylori 26695 Wt. Monoclonal antibody-mediated blocking of DC-SIGN in H. pylori 26695 Wt-THP-1 infections resulted in rapid association of the endocytic markers Rab5 and Rab7, corresponding to that of H. pylori 26695 galE, indicating that DC-SIGN-O-antigen interactions alters intracellular processing of the bacteria and reduces the rate at which these markers are recruited. Together these results elucidate novel mechanisms of H. pylori O-antigen and its interaction with galectin-3 and DC-SIGN that warrant further investigation in vivo. The identification of two PRRs competing for the same PAMP is unconventional and inspires a re-evaluation of PRRs in innate immune recognition.