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See detailEtude des propriétés biomécaniques du tissu cutané dans l'acromégalie
Betea, Daniela ULg; Braham, C.; Pierard-Franchimont, Claudine ULg et al

in Annales d'Endocrinologie : XIXe Congrès de la Société Française d'Endocrinologie - Abstract book (2001)

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See detailEtude des propriétés de repliement d’une protéine hélice bêta parallèle droite la pectine méthylesterase d’Erwinia chrysanthemi 3937
Guillerm, Jessica ULg

Doctoral thesis (2013)

The aim of protein folding studies is to elucidate the process by which a polypeptide chain spontaneously adopts its functional three-dimensional structure in vivo. This issue, known as the « protein ... [more ▼]

The aim of protein folding studies is to elucidate the process by which a polypeptide chain spontaneously adopts its functional three-dimensional structure in vivo. This issue, known as the « protein folding problem », is one of the major challenges in modern structural biology. Indeed, a better understanding of the fundamental principles underlying protein folding could have many applications, either in the understanding of various diseases related to protein misfolding, in the exploitation of advances in genomics, or in the design of proteins with new functions. Pectin methylesterase of Erwinia chrysanthemi 3937 (PemA) was chosen as a model protein for folding studies. It is a 37 kDa protein that is involved in the degradation of pectin, a major component of the plant cell wall. This enzyme has a right-handed parallel beta-helix structure, which has been proposed as a plausible model to describe the structure of amyloid fibrils. Characterization of PemA thermodynamic properties led to the determination of its conformationnal stability, whereas kinetic studies highlighted occurence of at least two obligatory intermediates on the folding patway of the the protein when it acquires its native structure. We first developed an effective procedure to obtain the protein of interest in sufficient quantities to perform various biophysical studies. PemA gene was cloned into an expression vector allowing improved production yields of the recombinant protein. The purification protocol was also improved and we developed an efficient activity test in order to probe the functionality of the enzyme.The conformational stability of PemA was assessed by destabilizing the native protein using different denaturing agents (guanidinium chloride, urea, temperature, pH, pressure) and probing the structural integrity of the protein with the help of one or more spectroscopic technique(s) (fluorescence, circular dichroism and FTIR spectroscopy). Data showed that PemA is particularly resistant to high pressure, while its chemical and thermal stability are in the range of what is commonly observed for mesophilic proteins. On the other hand, characterization of PemA folding kinetics highlighted that it folds along a sequential pathway, characterized by the formation of at least two obligatory kinetic intermediates. Simulation of the kinetics on the basis of the experimental data reinforced the view that PemA folding is adequatly described by a four states model. [less ▲]

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See detailEtude des propriétés de surface d'émulsifiants destinés à la panification
Delacharlerie, Sophie ULg

Master's dissertation (2003)

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See detailEtude des propriétés de surface et techno-fonctionnelles des fractions protéose-peptones
Karamoko, Gaoussou ULg

Doctoral thesis (2014)

The total proteose-peptone fractions are complex heterogeneous mixture of thermoresistant proteins of whey. The general objective of this work was to contribute to a better knowledge and understanding of ... [more ▼]

The total proteose-peptone fractions are complex heterogeneous mixture of thermoresistant proteins of whey. The general objective of this work was to contribute to a better knowledge and understanding of surface properties and techno-functional properties (foaming and emulsifying properties) and well as setting a relationship between the different properties. In this work, PPT fractions were extracted according to a classical approach and other industrially transposable by considering respectively the skimmed UHT milk and whey protein concentrate (WPC) as raw materials. The using of such both sources allowed to highlight the fundamental differences in the composition of the extracts of PPT. This has begotten a direct impact on the surfactant properties of the PPT. It has been therefore established that these differences at interfaces can have major consequences on their techno-functional behavior. This study also made it possible to determine the contribution of components especially non-hydrophobic and hydrophobic fractions in the interfacial behavior of PPT and the influence of pH, protein concentration, source and method of extraction. The setting in relationship of properties showed the existence of some statistically significant correlations between the interfacial parameters and, foaming and emulsifying properties. It will be therefore possible to predict the behavior of techno-functional PPT from some physico-chemical parameters. Finally, this study also showed that PPT fractions can be used as techno-functional agents in various food formulations based foams or emulsions. [less ▲]

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See detailEtude des propriétés des variants amyloïdogéniques du lysozyme humain à l’aide de fragments d’anticorps à chaînes lourdes comme sondes structurales
Dumont, Janice ULg

Doctoral thesis (2014)

Les fibres amyloïdes sont des agrégats de protéines hautement organisés qui sont associés à une trentaine de maladies appelées amyloses, dont les maladies d'Alzheimer et de Parkinson et la maladie de la ... [more ▼]

Les fibres amyloïdes sont des agrégats de protéines hautement organisés qui sont associés à une trentaine de maladies appelées amyloses, dont les maladies d'Alzheimer et de Parkinson et la maladie de la vache folle. L'amylose systémique à lysozyme est une amylose non-neuropathique héréditaire associée à sept variants de la protéine (Y54N, I56T, F57I, W64R, D67H, F57I/T70N et W112R/T70N). Ces protéines forment des fibres amyloïdes extracellulaires qui se déposent dans de nombreux tissus et organes tels que le foie, la rate et les reins. Il a été montré que les mutations I56T et D67H diminuent la stabilité et la coopérativité globale de la protéine. Ainsi, dans des conditions proches des conditions physiologiques, ces variants forment, in vitro, transitoirement un état intermédiaire dans lequel le domaine β et l'hélice C se déplient de manière coopérative, alors que le reste du domaine α conserve sa structure native. La formation d'interactions intermoléculaires entre les régions dépliées serait à l'origine du processus d'agrégation qui conduit à la formation et au dépôt de fibres amyloïdes dans les tissus des patients porteurs de ces mutations. Il a également été montré que la liaison de trois fragments d'anticorps à chaînes lourdes de camélidés (VHH), dirigés contre le lysozyme humain de sauvage, inhibe in vitro la formation de fibres amyloïdes par les variants D67H et I56T. Ces trois VHH se lient à des régions différentes du lysozyme et inhibent la formation de fibres amyloïdes selon différents mécanismes. Au cours de ce doctorat, seize nouveaux VHH spécifiques du lysozyme humain ont été générés. Des expériences de liaisons compétitives suivies par résonnance plasmonique de surface ont montré que les 16 VHH se lient à cinq épitopes distincts à la surface du lysozyme. Quatre d’entre eux sont capables de se lier au lysozyme dans les conditions utilisées in vitro pour induire la formation de fibres amyloïdes par les variants du lysozyme. Leur site de liaison a été déterminé par RMN. Deux d'entre eux reconnaissent des épitopes différents de ceux des trois VHH caractérisés précédemment. Des expériences d’échange H/D analysés par spectrométrie de masse ont montré que les 4 VHH ont des capacités différentes à restaurer la coopérativité globale du variant D67H du lysozyme. L’analyse de l’ensemble des résultats nous a permis d’identifier qu'elles sont les régions du lysozyme qui doivent être affectées par la liaison d'un VHH afin de restaurer la coopérativité globale de la protéine. La liaison simultanée aux deux domaines (i.e. α et β) semble être le dénominateur commun de tous les VHH restaurant la coopérativité globale du variant D67H. La liaison aux hélices B et C, ainsi que de l'interface des deux domaines semble aussi contribuer à la restauration de la coopérativité globale. A l'inverse, une liaison qui perturbe la partie N-terminale ne permet pas de restaurer la coopérativité globale de la protéine. La liaison d’un VHH, cAb-HuL9a, au variant D67H du lysozyme inhibe de manière similaire la formation de l’intermédiaire partiellement déplié, l'élongation de fibres amyloïdes préformées et la formation de fibres amyloïdes in vitro. Cette observation est en accord avec l’hypothèse selon laquelle, la formation de cet intermédiaire est à l’origine de l’amyloïdogénicité des variants du lysozyme. Afin d'étudier les effets des mutations amyloïdogéniques récemment identifiées sur les propriétés du lysozyme et ainsi obtenir une meilleure connaissance du mécanisme de formation des fibres amyloïdes, il est nécessaire de produire ces variants en grande quantité. Les variants D67H, I56T et F57I sont produits dans Aspergillus niger. L'expression des variants dans ce micro-organisme est toutefois particulièrement chronophage alors que les rendements de production sont relativement faibles. Les tentatives d'utiliser d'autres systèmes de production tels que Pichia pastoris ou le système bacculovirus n'ont pas été concluantes. Aussi, dans le cadre de mon doctorat, j’ai étudié la possibilité de produire le variant D67H sous forme de corps d'inclusion dans Escherichia. coli. Un protocole permettant de produire 20 mg de protéine sous forme de corps d’inclusion par litre de culture a été développé. Différents stratégies ont été testées pour replier la protéine à partir des corps d’inclusion. Cette approche a permis d’obtenir une protéine ayant 90% d’activité spécifique du lysozyme. Le rendement massique obtenu après repliement est néanmoins très faible. [less ▲]

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See detailEtude des propriétés électriques des hétérojonctions de semi-conducteurs II-VI
Dreesen, Laurent ULg

Master's dissertation (1990)

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See detailEtude des propriétés hémato-supportives in vitro des cellules souches mésenchymateuses
Briquet, Alexandra ULg

Doctoral thesis (2009)

Bone marrow (BM) mesenchymal stem cells (MSC) support proliferation and differentiation of hematopoietic progenitor cells (HPC) in vitro. Since they represent a rare subset of BM cells, MSC preparations ... [more ▼]

Bone marrow (BM) mesenchymal stem cells (MSC) support proliferation and differentiation of hematopoietic progenitor cells (HPC) in vitro. Since they represent a rare subset of BM cells, MSC preparations for clinical purposes involves a preparative step of ex vivo multiplication. The aim of our study was to analyze the influence of culture duration on MSC supportive activity. MSC were expanded for up to 10 passages. MSC and CD34+ cells were seeded in cytokinefree co-cultures after which the phenotype, clonogenic capacity and in vivo repopulating activity of harvested hematopoietic cells were assessed. Early passage MSC supported HPC expansion and differentiation toward both B lymphoid and myeloid lineages. Late passage MSC did not support HPC and myeloid cell outgrowth but maintained B cell supportive ability. In vitro maintenance of NOD/SCID mouse repopulating cells cultured for one week in contact with MSC was effective until the fourth MSC passage and declined afterwards. CD34+ cells achieved higher levels of engraftment in NOD/SCID mice when co-injected with early passage MSC; however MSC expanded beyond 9 passages were ineffective in promoting CD34+ cell engraftment. Non-contact cultures indicated that MSC supportive activity involved diffusible factors. Among these, interleukin (IL)-6 and IL-8 contributed to the supportive activity of early passage MSC but not of late passage MSC. MSC phenotype as well as fat, bone and cartilage differentiation capacity did not change during MSC culture. Extended MSC culture alters their supportive ability toward HPC without concomitant changes in phenotype and differentiation capacity. [less ▲]

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See detailEtude des propriétés moussantes de la sève du palmier dattiers (Phoenix Dactylifera L.)
Makhlouf, Ines; Razafindralambo, Hary; Attia, Hamadi et al

Conference (2015, March 17)

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See detailEtude des propriétés physico-chimiques et technofonctionnelles des crèmes végétales en relation avec les conditions de reconstitution
Anihouvi, Prudent Placide ULg

Doctoral thesis (2011)

In this work, an integrated approach was adopted to study vegetal creams in order to have a global understanding of their properties. This approach included: (i) the influence of fat and other ingredients ... [more ▼]

In this work, an integrated approach was adopted to study vegetal creams in order to have a global understanding of their properties. This approach included: (i) the influence of fat and other ingredients of the formulation, particularly a low molecular weight surfactant, Tween 60 (ii) and the manufacturing process implemented for their preparation. The effect of fat was investigated by adopting an original approach that consisted in studying both the thermal and structural behavior of the non-emulsified fat (NEF) and the emulsified fat (EF). This clearly demonstrated the impact of the physicochemical characteristics of fat on the physicochemical and technofunctional properties of creams. It well established that small differences in the composition of fats may have great effects on the technofunctional behavior of creams. The influence of fat on the final properties of creams was mainly marked through the crystallization and melting behaviors of fat, and through the crystalline varieties formed during maturation. The effect of temperature on the stability of creams based on the physical evolution of the fat was also highlighted. The addition of tween 60 to the formulation significantly improved the properties of particle size, rheology, stability and whipping of creams. This improvement was the result of not only synergistic effect of surfactant molecules of buttermilk and tween 60 during emulsification but also desorption of proteins from the drop surfaces and modification of crystallization of the EF. The study of the influence of the process showed that the choice of the emulsification method and operating parameters are important considerations in the reconstitution of creams. It was shown that it was possible to modulate the properties of creams by only modifying the process. [less ▲]

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See detailÉTUDE DES PROPRIETES RHEOLOGIQUES DES PATES A PAIN SANS GLUTEN
DOUIRI, Sabrine; Blecker, Christophe ULg; ATTIA, Hamadi et al

Conference (2016, March 22)

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See detailEtude des protéines totales et de l’ADN issus des feuilles de Moricandia arvensis collectées de quatre régions du sud tunisien
Hasnaoui, Nejib ULg; Daly, Dalia; Haj Khelil, Amel et al

in Revue des Régions Arides (2006)

A partir des protéines et de l'ADN extraits des feuilles de Moricandia arvensis, collectées de quatre régions du sud tunisien, nous avons étudié la variabilité de cette plante reconnue pour ses vertus ... [more ▼]

A partir des protéines et de l'ADN extraits des feuilles de Moricandia arvensis, collectées de quatre régions du sud tunisien, nous avons étudié la variabilité de cette plante reconnue pour ses vertus médicinales. Nous avons analysé d’une part les protéines totales extraites puis séparées par la technique SDS-PAGE. Cette méthode a révélé un degré de similitude très remarquable entre les plantes issues des quatre régions et qui varie entre 0.77 et 0.91. Nous avons effectué d’autre part, une analyse de la variabilité génétique par l’amplification aléatoire de l'ADN polymorphe par la technique PCR-RAPD en utilisant trois amorces différentes. Nous avons remarqué que la similitude est plus accentuée entre les plantes collectées des régions du Sud Ouest, avec un degré de similitude pouvant atteindre 100%. Celles issues du Sud Est présentent un degré de similitude de 66%. [less ▲]

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See detailEtude des racémases RacX et YlmE et de la protéine PBP4* de Bacillus subtilis en relation avec la désintégration de biofilms
Vanden Broeck, Arnaud ULg

Master's dissertation (2014)

Bacillus subtilis is a PGPR (Plant Growth Promoting Rhizobacterium) Gram positive bacterium and a model for studying the in vitro formation, maturation or disruption of biofilms. Biofilms have been ... [more ▼]

Bacillus subtilis is a PGPR (Plant Growth Promoting Rhizobacterium) Gram positive bacterium and a model for studying the in vitro formation, maturation or disruption of biofilms. Biofilms have been studied for many years because of their adverse effects in the medical sphere. Some D-amino acids have been reported among the factors playing a role in the disassembly of B. subtilis biofilms and a double ylmE and racX mutant (in which both YlmE and RacX racemases are absent) shows a delay in pellicle disruption [I. Kolodkin et al. Science (2010) 328:627-629]. The racX encoding gene is part of a bicistronic operon in which the first gene (pbpE) codes for a putative Penicillin-Binding Protein, the PBP4* whose function is not characterized. Results from DNA microarrays and Proteomics [D. Ren et al. Biotechnology and Bioengineering (2004) 86:344-364] have shown that in B. subtilis biofilms, the expression of the gene coding for PBP4* is increased. Our study in this master thesis aimed to investigate the functions and the structures of the RacX, YlmE and PBP4* proteins. A wide range of techniques such as cloning, into expression vectors, purification, treatment of the recombinant proteins by specific proteases to eliminate the chromatography affinity tags, structural and biochemical characterizations of the proteins have been used. According to sequence analyses, RacX belongs to the Asp/Glu racemase family. We succeeded to produce and purify 34 mg of RacX whose His-tag has been completely eliminated. The protein appeared active on D-Glutamate as substrate but inactive on D-Aspartate. A physiological role is proposed for RacX in the recovery of D-Glu from the peptidoglycan peptides. However, its implication in the biofilm disassembly process is still elusive. The YlmE racemase was also produced and purified (46 mg). Although a role in the in vivo production of D-Tyrosine in B. subtilis ageing biofilms has been proposed for this protein, our attempts to detect an activity on L-Tyr or any other amino acid remained unsuccessful. Bioinformatic studies relate YlmE to type III PLP dependent enzymes close to Alanine racemases. Alignments of YlmE with Alanine racemases pointed out that a C-terminal domain was missing in YlmE. A model has been proposed to explain the absence of YlmE activity. Several constructs were performed to restore a racemase activity: e.g. a fusion of YlmE to the C-terminal domain of the AlaR2 racemase from B. subtilis, but the chimeric protein was insoluble, or the fusion of the AlaR2 C-terminal domain to TrxA in view to obtain in trans complementation with purified YlmE. PBP4* (encoded by pbpE) has been purified (63 mg) and two activities were detected: L-aminopeptidase and DD-carboxypeptidase activities. This PBP is composed of two distinct domains : a N-Terminal catalytic domain related to the D-aminopeptidase from Ochrobactrum anthropic and a C-terminal one that has a lipocalin-like fold. This domain seems involved in the oligomerization of the protein. First attempts of X-Ray diffraction of the entire protein crystals did not give data with sufficient resolution. Therefore, each domain has been separately produced to determine the 3D structure of this unusual PBP. [less ▲]

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See detailEtude des relations entre les microstructures obtenues par vieillissement isotherme et le comportement mécanique (fatigue, résilience) dans des alliages Zn-Al et Zn-Al-Cu
Lecomte-Beckers, Jacqueline ULg; Terziev, L.; Wegria, J.

in Revue de Métallurgie [=Revue de Métallurgie. Cahiers d'Informations Techniques] (1994), 91[5]

L’article présenté établit une corrélation entre le comportement mécanique (fluage, résilience) et les microstructures qui apparaissent au cours d’un traitement thermique isotherme (100 ou 250 °C) dans ... [more ▼]

L’article présenté établit une corrélation entre le comportement mécanique (fluage, résilience) et les microstructures qui apparaissent au cours d’un traitement thermique isotherme (100 ou 250 °C) dans des alliages Zn-Al et Zn-Al-Cu1. Le but est de mettre en évidence l’intérêt pratique des modifications structurales obtenues. On observe un meilleur résultat pour des échantillons vieillis pendant une semaine environ. La température de traitement la plus favorable est 250 °C. De plus, les alliages contenant du cuivre possèdent un meilleur comportement que les alliages binaires Zn-Al. [less ▲]

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