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See detailIn silico simulations of bone remodeling with improved parameter estimation from local strains and dynamic morphometry in vivo
Levchuk, Alina; Sommer, Remo; Badilatti, Sandro D. et al

in JOURNAL OF BONE AND MINERAL RESEARCH (2013), 28(1),

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See detailIn silico study of antimicrobial cyclic peptides Sequence analysis, molecular modelling and multi-scale molecular dynamics
Crowet, Jean-Marc ULg; Soumillion, Patrice; Brasseur, Robert ULg et al

Poster (2013, February 26)

The selection and use of antimicrobial cyclic peptides is an active way of research. These peptides are naturally produced by several microorganisms et libraries of biosynthetic peptides are actually ... [more ▼]

The selection and use of antimicrobial cyclic peptides is an active way of research. These peptides are naturally produced by several microorganisms et libraries of biosynthetic peptides are actually build to find new antibiotics candidats. However, the mecanism of action of these peptides is not well known and it exists several hypothesis for their interactions with membrane. These peptides are causing broad perturbations to lipidic membranes and it has been shown that they can form disordered toroidal pores or self assemble as amphipathic nanotubes leading to lipid extrusion. Through the analysis of several peptides from the libraries of Pr Soumillion with increasing activity it will be possible to study the relation between the sequence/structure and the membrane activity of these peptides. This will help to decipher between preferential modes of action and the parameters important for the activity. [less ▲]

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See detailIn silico study of the interaction of the Myelin Basic Protein C-terminal a-helical peptide with DMPC and mixed DMPC/DMPE lipid bilayers
Bessonov, Kyrylo ULg

Conference (2010, May)

Biological membranes continue to be extensively investigated in different ways. This paper presents the benefits of Molecular Dynamics (MD) approaches to study the properties of biological membranes and ... [more ▼]

Biological membranes continue to be extensively investigated in different ways. This paper presents the benefits of Molecular Dynamics (MD) approaches to study the properties of biological membranes and proteins using the freely available GROMACS package, in the context of the Myelin Basic Protein (MBP) C-terminal a-helical peptide. A mixed membrane consisting of 2-Dimyristoyl-sn-Glycero-3-phosphocholine/1,2-Dimyristoyl-sn-Glycero-3- phosphoethanolamine (DMPC/DMPE), and pure DMPC membranes, composed of 188 and 248 lipids, respectively, were simulated for 200 ns at 309 K. The DMPC membrane was approximately three times more fluid compared to the DMPC/DMPE system, with the diffusion coefficients (D) being 0.0207x10-5 cm2/s and 0.0068x10-5 cm2/s, respectively. In addition, the 14-residue peptide representing the C-terminal a-helical region of murine Myelin Basic Protein (MBP), with amino acid sequence NH2-A141YDAQGTLSKIFKL154-COOH , was simulated in both membrane systems for 200 ns. The peptide penetrated further into the DMPC bilayer compared to the mixed DMPC/DMPE bilayer, potentially because of the reduced accessibility of the charged peptide amino acid side chains to the formal positive charge of the amine N atom surrounded by methyl and methylene groups in DMPC, that might have resulted in greater overall peptide mobility [3]. These findings are significant in their implication that membrane composition affects the behavior of MBP, providing further insights into myelin structure. Our preliminary results suggest that local changes in membrane composition (e.g. enrichment in DMPE molecules), as well as, electrostatic nature of primary amino acid sequence could cause localized denaturation / instability of external MBP a-helices possibly augmenting the degradation of myelin in multiple sclerosis (MS), resulting in a subsequent decrease of nerve impulse propagation efficiency. [less ▲]

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See detailIn Silico tilted properties of the 67-78 fragment of alpha-synuclein are responsible for membrane destabilization and neurotoxicity
Crowet, Jean-Marc ULg; Lins, Laurence ULg; Dupiereux-Fettweis, Ingrid ULg et al

in Proteins-Structure Function and Bioinformatics (2007), 68(4), 936-947

Alpha-synuclein is a 140 residue protein associated with Parkinson's disease. Intraneural inclusions called Lewy bodies and Lewy neurites are mainly composed of alpha-synuclein aggregated into amyloid ... [more ▼]

Alpha-synuclein is a 140 residue protein associated with Parkinson's disease. Intraneural inclusions called Lewy bodies and Lewy neurites are mainly composed of alpha-synuclein aggregated into amyloid fibrils. Other amyloidogenic proteins, such as the beta amyloid peptide involved in Alzheimer's disease and the prion protein (PrP) associated with Creuztfeldt-Jakob's disease, are known to possess "tilted peptides". These peptides are short protein fragments that adopt an oblique orientation at a hydrophobic/hydrophilic interface, which enables destabilization of the membranes. In this paper, sequence analysis and molecular modelling predict that the 67-78 fragment of alpha-synuclein is a tilted peptide. Its destabilizing properties were tested experimentally. The alpha-synuclein 67-78 peptide is able to induce lipid mixing and leakage of unilamellar liposomes. The neuronal toxicity, studied using human neuroblastoma cells, demonstrated that the alpha-synuclein 67-78 peptide induces neurotoxicity. A mutant designed by molecular modelling to be amphipathic was shown to be significantly less fusogenic and toxic than the wild type. In conclusion, we have identified a tilted peptide in alpha-synuclein, which could be involved in the toxicity induced during amyloidogenesis of alpha-synuclein. [less ▲]

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See detailIn situ aortic allograft insertion to repair a primary aortoesophageal fistula due to thoracic aortic aneurysm
Pirard, Laurence ULg; Creemers, Etienne ULg; Van Damme, Hendrik ULg et al

in Vascular Surgery (2005), 42

Aortoesophageal fistula due to thoracic aortic aneurysm is an uncommon cause of gastrointestinal bleeding and has an extremely poor prognosis. In the English literature, we found only 27 successfully ... [more ▼]

Aortoesophageal fistula due to thoracic aortic aneurysm is an uncommon cause of gastrointestinal bleeding and has an extremely poor prognosis. In the English literature, we found only 27 successfully managed cases of primary aortoesophageal fistula due to thoracic aortic aneurysm. We present a case of 74-year-old man who experienced the erosion of a thoracoabdominal aortic aneurysm into the esophagus. We successfully performed resection and replacement of the thoracoabdominal aorta with a cryopreserved allograft and total thoracic esophagectomy. A few months later, the esophagus was reconstructed with orthotopic colonic interposition. The patient recovered well and resumed a normal life (12 months’ follow-up). [less ▲]

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See detailIn situ bidentate to tetradentate ligand exchange reaction in cobalt-mediated radical polymerization
Kermagoret, Anthony ULg; Jérôme, Christine ULg; Detrembleur, Christophe ULg et al

in European Polymer Journal (in press)

Organometallic-mediated radical polymerization (OMRP) has seen a significant growth in the last years notably due to the development of new metal complexes, especially cobalt derivatives. Despite of this ... [more ▼]

Organometallic-mediated radical polymerization (OMRP) has seen a significant growth in the last years notably due to the development of new metal complexes, especially cobalt derivatives. Despite of this, none of the reported complexes offers optimal control for monomers with very different reactivity, which somewhat limits the synthesis of copolymers. In order to expand the scope of cobalt-mediated radical polymerization (CMRP), we investigated an in situ ligand exchange reaction for modulating the properties of the cobalt complex at the polymer chain-end and adjusting the C-Co bond strength involved in the control process. With the aim of improving the synthesis of poly(vinyl acetate)-b-poly(n-butyl acrylate) copolymers, bidentate acetylacetonate ligands, which impart high level of control to the polymerization of vinyl acetate (VAc), were replaced in situ at the PVAc-cobalt chain-end by tetradentate Salen type ligands that are more suited to acrylates. [less ▲]

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See detailIn situ characterization in freeze-fractured mouse thymuses of lymphoepithelial complexes ultrastructurally similar to isolated thymic nurse cells.
Defresne, Marie-Paule ULg; Goffinet, Gerhard ULg; Boniver, Jacques ULg

in Tissue & Cell (1986), 18(3), 321-30

Scanning and transmission electron microscopy of the cracked surfaces of cryofractured pre-fixed C57BL/Ka mouse thymus reveals the existence of cell complexes, distinct from the surrounding cell ... [more ▼]

Scanning and transmission electron microscopy of the cracked surfaces of cryofractured pre-fixed C57BL/Ka mouse thymus reveals the existence of cell complexes, distinct from the surrounding cell organization, in which groups of lymphocytes are delimited by large cytoplasmic sheets or envelopes. These complexes, located in the subcapsular and cortical regions, display morphological features similar to that of the thymic nurse cells (TNCs), which can be isolated from the mouse or human thymus enzymatically dissociated. They can be considered as dynamic systems able to modify their three-dimensional organization, namely with regard to intrathymic cellular traffic involved in T-lymphocyte maturation. [less ▲]

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See detailIn situ conservation of wild populations of Phaseolus lunatus in the Central Valley of Costa Rica.
Maquet, A.; Baudoin, Jean-Pierre ULg

in Report of a Working Group on Grain Legumes. Third meeting, Krakow,Poland, 5-7 July 2001 (2002)

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See detailIn situ demonstration of germinal cell apoptosis during diethylstilbestrol-induced testis regression in adult male syrian hamsters
Nonclercq, D.; Reverse, D.; Toubeau, G. et al

in Biology of Reproduction (1996), 55(6), 1368-1376

Testis regression was induced in male Syrian hamsters by chronic exposure to diethylstilbestrol (DES), an estradiol-1713 agonist. Experimental groups (n = 4-5) were killed at increasing time intervals ... [more ▼]

Testis regression was induced in male Syrian hamsters by chronic exposure to diethylstilbestrol (DES), an estradiol-1713 agonist. Experimental groups (n = 4-5) were killed at increasing time intervals over a period of 6 mo after initiation of treatment. Apoptosis in testes was demonstrated by in situ analysis of DNA fragmentation. Cell proliferation was monitored by immunostaining nuclei of S-phase cells after pulse labeling with 5-bromo-2'-deoxyuridine. Levels of FSH and testosterone, measured by RIA, fell rapidly in DES-treated hamsters. In parallel, testis weight and seminiferous tubule area underwent an 80% decrease during the first 2 wk of DES administration. The composition of seminiferous epithelium was also drastically affected by DES, since it became progressively confined to Sertoli cells, spermatogonia, and spermatocytes. Testis regression was associated with an important increase of apoptosis, which started 3 days after the beginning of DES administration. Apoptosis was still 10- to 50-fold higher than in control testes by the end of treatment; it affected primarily spermatocytes and, to a much lesser extent, spermatogonia. Cell proliferation was not inhibited by chronic DES administration. In conclusion, these data indicate that apoptosis can by itself account for estrogen-induced testis regression. [less ▲]

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See detailIn situ development and application of cDNA-AFLP to isolate genes of Candida oleophila (strain O) potentially involved in antagonistic properties against Botrytis cinerea.
Massart, Sébastien ULg; Luna-Guarda, M.; Jijakli, Haissam ULg

in Communications in agricultural and applied biological sciences (2004), 69(4), 595-599

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See detailIn situ dynamic analysis of solid or aqueous solutions undergoing chemical reactions by RBS or PIXE with external beam
Bouquillon, A.; Dran, J*-C; Lagarde, G. et al

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2002), 188

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See detailIn situ filtration responses of Daphnia galeata to changes in food quality
Darchambeau, François ULg; Thys, I.

in Journal of Plankton Research (2005), 27(3), 227-236

In the stoichiometric study of phyto-zooplankton interactions, a controversy exists about how Daphnia species regulate their feeding rate when submitted to low-quality food (i.e. high dietary carbon ... [more ▼]

In the stoichiometric study of phyto-zooplankton interactions, a controversy exists about how Daphnia species regulate their feeding rate when submitted to low-quality food (i.e. high dietary carbon:phosphorus [C:P] ratio). In this study, we gathered data over 3 years on in situ clearance rates of a Daphnia galeata population, by conducting grazing experiments from April 1998 to October 2000 in the Esch-sur-Sure reservoir (Grand-Duchy of Luxembourg). Observed clearance rates (2.5-13.5 mL individual(-1) day(-1), mean 7.0 mL individual(-1) day(-1)) were correlated with population and environmental variables. Mean body size of Daphnia individuals was the best predictor of clearance rate (r(2) = 0.639), followed by water temperature (r(2) = 0.262) and P concentration in the seston (r(2) <= 0.241). When combined with body size, seston C:P or nitrogen:P ratios provided the best predictive regression model of clearance rate (r(2) = 0.852-0.897). The clearance rate was always correlated negatively with P concentration in the food. Thus, Daphnia reacts to a decrease of food quality (i.e. higher C:P ratio) by an increase of its feeding rate. However, the filtration response to food quality was inhibited by high population density. We suggest that, when food quality is low and population density high, this inhibition may favour fitness of future conspecific generations. In conclusion, our results emphasize the effect of P availability on transfer rate of organic matter between lacustrian autotrophs and herbivores and pose questions about consequent effects on nutrient biogeochemical cycles. [less ▲]

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See detailIn situ follow-up of adsorption in activated carbon beds using X-ray microtomography
Almazan, Maria del Carmen; Léonard, Angélique ULg; Toye, Dominique ULg et al

in Kaskel, S.; Llewellyn, P.; Rodriguez-Reinoso, F. (Eds.) et al Characterisation of Porous Solids VII - Proceedings of the 8th International Symposium on the Characterisation of Porous Solids (2009)

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See detailThe in situ formation of a new initiator system for the syndiotactic anionic polymerization of methyl methacrylate in toluene at 0°C
Zundel, Thomas; Teyssié, Philippe; Jérôme, Robert ULg

in Polymer (2002), 43(25), 7191-7193

This paper reports on an efficient 'in-situ' one pot synthesis of an initiatior/ligand adduct, which can be used to initiate the anionic polymerization of methyl methacrylate in toluene at 0 °C ... [more ▼]

This paper reports on an efficient 'in-situ' one pot synthesis of an initiatior/ligand adduct, which can be used to initiate the anionic polymerization of methyl methacrylate in toluene at 0 °C. Predominantly syndiotactic PMMA is formed. [less ▲]

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See detailIn situ formation of stabilizers for the implementation of dispersion nitroxide mediated polymerization of MMA in supercritical carbon dioxide
Grignard, Bruno ULg; Gigmes, Didier; Jérôme, Christine ULg et al

Poster (2009, September 17)

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2 ... [more ▼]

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2-philic perfluorinated surfactant that was generated “in situ”. The control of the MMA polymerization relies on the strategy developed by Charleux et al. that consists of using a SG1-based alkoxyamine, i.e. the block-builder, in the presence of small amount of styrene. In a first step, CO2 soluble polyheptadecafluorodecylacrylate was prepared in scCO2 using block-builder as an alkoxyamine. In a second step, nitroxide SG1 mediated dispersion polymerization of MMA was conducted at 70°C and 300 bar in the presence of 5 w% of SG1 terminated surfactant compared to the monomer. Different monomer to alkoxyamine molar ratios were investigated in order to target different molecular weights. In each case, the monomer conversion was high (>90 %), the experimental molecular weight was in good agreement with the theoretical value and the polydispersity was narrow (Mw/Mn ~1.2). Moreover, after depressurisation of the cell, PMMA was collected as a free flowing powder consisting of small sized microspheres. [less ▲]

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See detailIn situ formation of yttrium alkoxides: A versatile and efficient catalyst for the ROP of epsilon-caprolactone
Martin, Eric; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (2003), 38(16), 5934-5941

[Tris(hexamethyldisilyl)amide] yttrium is a catalyst for the controlled ring-opening polymerization of epsilon-caprolactone when reacted with an excess of alcohol. Up to an alcohol-to-yttrium molar ratio ... [more ▼]

[Tris(hexamethyldisilyl)amide] yttrium is a catalyst for the controlled ring-opening polymerization of epsilon-caprolactone when reacted with an excess of alcohol. Up to an alcohol-to-yttrium molar ratio of 50, the chain transfer to the alcohol is quantitative, and the molecular weight of the chains can be predicted from the monomer-to-alcohol molar ratio. At alcohol-to-yttrium ratios higher than 100, the alcohol is quantitatively consumed provided that 1,1,1,3,3,3-hexamethyldisilazane, which is formed as a byproduct, is removed from the reation medium. Depending on the structure of the alcohol, end-functional polyesters can be prepared (e.g., with N-pyrrolyl and 3-thienyl end groups). Well-defined block and random copolymers of epsilon-CL with lactides and gamma-bromo-epsilon-caprolactone, respectively, have also been synthesized. Compared to aluminum alkoxides, the in situ formed yttrium alkoxides have the advantage of a much faster polymerization kinetics while preserving control. [less ▲]

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See detailIn situ FTIR micro-spectroscopy to investigate polymeric fibers under supercritical carbon dioxide: CO2 sorption and swelling measurements
Champeau, Mathilde; Thomassin, Jean-Michel ULg; Jérôme, Christine ULg et al

in Journal of Supercritical Fluids (2014), 90

An original experimental set-up combining a FTIR (Fourier Transformed InfraRed) microscope with a high pressure cell has been built in order to analyze in situ and simultaneously the CO2 sorption and the ... [more ▼]

An original experimental set-up combining a FTIR (Fourier Transformed InfraRed) microscope with a high pressure cell has been built in order to analyze in situ and simultaneously the CO2 sorption and the polymer swelling of microscopic polymer samples, such as fibers, subjected to supercritical carbon dioxide. Thanks to this experimental set-up, we have determined as a function of the CO2 pressure (from 2 to 15 MPa) the CO2 sorption and the polymer swelling at T = 40 °C of four polymer samples, namely PEO (polyethylene oxide), PLLA (poly-l-lactide acid), PET (polyethylene terephtalate) and PP (polypropylene). The quantity of CO2 sorbed in all the studied polymers increases with pressure. PEO and PLLA display a significant level of CO2 sorption (20 and 25% respectively, at P = 15 MPa). However, we observe that a lower quantity of CO2 can be sorbed into PP and PET (7 and 8% respectively, at P = 15 MPa). Comparing their thermodynamic behaviors and their intrinsic properties, we emphasize that a high CO2 sorption can be reach if on one hand, the polymer is able to form specific interaction with CO2 in order to thermodynamically favor the presence of CO2 molecules inside the polymer and on the other, displays high chains mobility in the amorphous region. PLLA and PEO fulfilled these two requirements whereas only one property is fulfilled by PET (specific interaction with CO2) and PP (high chains mobility). Finally, we have found that for a given CO2 sorption, the resulting swelling of the polymer depends mainly on its crystallinity. [less ▲]

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