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See detailProbing liquid-mirror surface quality using the CCD triangulation technique
Finet, François; Surdej, Jean ULg

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2013)

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See detailProbing of Actinobacillus pleuropneumoniae ApxIIIA toxin-dependent cytotoxicity towards mammalian peripheral blood mononucleated cells
Vanden Bergh, Philippe ULg; Zecchinon, Laurent ULg; Fett, Thomas ULg et al

in BMC Research Notes (2008)

BACKGROUND: Actinobacillus pleuropneumoniae, the causative bacterial agent of porcine pleuropneumonia, produces Apx toxins which belong to RTX toxin family and are recognized as the major virulence ... [more ▼]

BACKGROUND: Actinobacillus pleuropneumoniae, the causative bacterial agent of porcine pleuropneumonia, produces Apx toxins which belong to RTX toxin family and are recognized as the major virulence factors. So far, their target receptor(s) has not been identified and the disease cytopathogenesis remains poorly understood. Production of an active Apx toxin and characterization of its toxic activity constitute the premises necessary to the description of its interaction with a potential receptor. From this point of view, we produced an active recombinant ApxIIIA toxin in order to characterize its toxicity on peripheral blood mononucleated cells (PBMCs) isolated from several species. FINDINGS: Toxin preparation exercises a strong cytotoxic action on porcine PBMCs which is directly related to recombinant ApxIIIA since preincubation with polymyxin B does not modify the cytotoxicity rate while preincubation with a monospecific polyclonal antiserum directed against ApxIIIA does. The cell death process triggered by ApxIIIA is extremely fast, the maximum rate of toxicity being already reached after 20 minutes of incubation. Moreover, ApxIIIA cytotoxicity is species-specific because llama, human, dog, rat and mouse PBMCs are resistant. Interestingly, bovine and caprine PBMCs are slightly sensitive to ApxIIIA toxin too. Finally, ApxIIIA cytotoxicity is cell type-specific as porcine epithelial cells are resistant. CONCLUSION: We have produced an active recombinant ApxIIIA toxin and characterized its specific cytotoxicity on porcine PBMCs which will allow us to get new insights on porcine pleuropneumonia pathogenesis in the future. [less ▲]

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See detailProbing of the reaction progress at a PMMA/PS interface by using anthracene-labeled reactive PS chains
Yin, Zhihui; Koulic, Christian; Pagnoulle, Christophe et al

in Langmuir (2003), 19(2), 453-457

The progress of the interfacial reaction of polystyrene chains end-capped by a primary amine (PS-NH2) and PMMA chains end-capped by an anhydride (PMMA-anh) has been monitored by SEC-UV, by using ... [more ▼]

The progress of the interfacial reaction of polystyrene chains end-capped by a primary amine (PS-NH2) and PMMA chains end-capped by an anhydride (PMMA-anh) has been monitored by SEC-UV, by using anthracene-labeled polystyrene chains (anth-PS-NH2) as a probe. Assemblies of an anth-PS-NH2 layer and a PMMA-anh layer were annealed at 200 degreesC for various periods of time. The interfacial reaction rate depends on the molecular weight (MW) of the reactive precursors in relation to the gammaN value of the chains. For chains of low gammaN (chiN = 6), the reaction is faster because the interface becomes more diffuse with time, as observed by TEM and AFM, consistent with compatibilization of the weakly immiscible polymers by the copolymer formed in-situ. For chains of higher molecular weight and chiN (10, instead of 6), the interface is much sharper and the residence time at the interface of the symmetric diblock copolymer of higher molecular weight is also increased, which dramatically restricts the progress of the interfacial reaction under the annealing conditions used in this work. [less ▲]

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See detailProbing Organization and Structural Characteristics of Alkanethiols Adsorbed on Gold and of Model Alkane Compounds through their Valence Electronic Structure: an Ultraviolet Photoelectron Spectroscopy Study
Duwez, Anne-Sophie ULg; Pfister-Guillouzo, G.; Delhalle, Joseph et al

in Journal of Physical Chemistry B (2000), 104

In this paper we report an ultraviolet photoelectron spectroscopy (UPS) study of saturated alkane chains in various configurations and conformations. The dependence of the valence spectra on molecular ... [more ▼]

In this paper we report an ultraviolet photoelectron spectroscopy (UPS) study of saturated alkane chains in various configurations and conformations. The dependence of the valence spectra on molecular structure characteristics has been assessed by comparing the results obtained from n-alkanethiol, R,ö-alkanedithiol, and R-cycloalkyl-ö-alkanethiol monolayers adsorbed on gold, and from gas-phase model alkane compounds. The differences between the spectra reflect directly the structural changes induced in the electronic structure of the alkane chains. We have determined the type of folding sequences adopted in a 1,12-dodecanedithiol monolayer. Angular dependent measurements and investigations on the photoelectron attenuation length have evidenced very fine structural differences between films obtained on deposited gold films, annealed gold films, and gold single crystals [less ▲]

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See detailProbing Peptide-Membrane Interactions Using Afm
Brasseur, Robert ULg; Deleu, Magali ULg; Mingeot-Leclercq, Mp. et al

in Surface and Interface Analysis [=SIA] (2008), 40(3-4), 151-156

Atomic force microscopy (AFM) has become a powerful addition to the range of instruments available to probe the organization of lipid monolayers and bilayers. Currently, AFM is the only tool that can ... [more ▼]

Atomic force microscopy (AFM) has become a powerful addition to the range of instruments available to probe the organization of lipid monolayers and bilayers. Currently, AFM is the only tool that can provide nanoscale topographic images of supported lipid membranes under physiological conditions, enabling researchers to resolve their detailed structure and to monitor their interaction with drugs, peptides and proteins. Here, we survey recent data obtained by our research groups that demonstrate the power of the technique for exploring peptide–membrane interactions, with an emphasis on microbial lipopeptides and on tilted peptides. [less ▲]

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See detailProbing populations of red giants in the galactic disk with CoRoT
Miglio, Andrea ULg; Montalban Iglesias, Josefa ULg; Baudin, F. et al

in Astronomy and Astrophysics (2009), 503

Context: The detection with CoRoT of solar-like oscillations in nearly 800 red giants in the first 150-days long observational run paves the way for detailed studies of populations of galactic-disk red ... [more ▼]

Context: The detection with CoRoT of solar-like oscillations in nearly 800 red giants in the first 150-days long observational run paves the way for detailed studies of populations of galactic-disk red giants. <BR />Aims: We investigate which information on the observed population can be recovered by the distribution of the observed seismic constraints: the frequency of maximum oscillation power (ν_max) and the large frequency separation (Δν). <BR />Methods: We propose to use the observed distribution of ν_max and of Δν as a tool for investigating the properties of galactic red-giant stars through comparison with simulated distributions based on synthetic stellar populations. <BR />Results: We can clearly identify the bulk of the red giants observed by CoRoT as red-clump stars, i.e. post-flash core-He-burning stars. The distribution of ν_max and of Δν gives us access to the distribution of the stellar radius and mass, and thus represent a most promising probe of the age and star formation rate of the disk, and of the mass-loss rate during the red-giant branch. <BR />Conclusions: CoRoT observations are supplying seismic constraints for the most populated class of He-burning stars in the galactic disk. This opens a new access gate to probing the properties of red-giant stars that, coupled with classical observations, promises to extend our knowledge of these advanced phases of stellar evolution and to add relevant constraints to models of composite stellar populations in the Galaxy. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. [less ▲]

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See detailProbing rapidly ionzing super-atom molecular orbitals (SAMO) in fullerenes
Mignolet, Benoît ULg

Scientific conference (2013, May 29)

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See detailProbing Rapidly-Ionizing Super-Atom Molecular Orbitals in C60: A Computational and Femtosecond Photoelectron Spectroscopy Study
Mignolet, Benoît ULg; Johansson, Olof; Campbell, Eleanor E. B. et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2013)

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See detailProbing recognition processes, forces and motions within single molecules
Willet, Nicolas ULg

Scientific conference (2011, June)

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See detailProbing recognition processes, forces and motions within single molecules
Willet, Nicolas ULg; Duwez, Anne-Sophie ULg

Scientific conference (2012, May 09)

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See detailProbing the conformational changes during desolvation of ions using orthogonal mobility methods (CE-IM MS)
Far, Johann ULg; Kune, Christopher ULg; Delvaux, Cédric ULg et al

Poster (2014, June 24)

Routine analyses using Mass Spectrometry (MS) detection became a very popular due to the low limit of detection, great sensitivity, selectivity and specificity. Moreover MS enables structural elucidation ... [more ▼]

Routine analyses using Mass Spectrometry (MS) detection became a very popular due to the low limit of detection, great sensitivity, selectivity and specificity. Moreover MS enables structural elucidation and physical (or physicochemical) properties determination using low amount of not especially pure samples. One of these properties is substantially the stoichiometry determination of non-covalent complexes such as Ligand receptor systems (e.g. DNA-drugs, Hormones/drugs-receptor, quaternary structure arrangement of polypeptides, …). MS determination in native condition (Native MS) of this stoichiometry allows large scale screening of potential drugs candidates in pharmaceutical context. The addition of Ion-Mobility (IM) to mass spectrometry (IM-MS) with computational chemistry support allows the structural conformation monitoring (as Collisional Cross Section or CCS) and the elucidation of interactions of the non-covalent complexes. Nonetheless such determinations suppose/assume that desolvation steps and gas phase transfer during MS detection do not modify the tridimensional structure of these systems or the magnitude order of the involved interactions (dipole-dipole, dipole-ion, ion-ion, hydrophobic interactions). Further studies (Circular Dichroism, Nuclear Magnetic resonance, UV-Visible spectra …) are generally required to confirm the MS data but there are unfortunately time consuming. This project proposes the coupling of Capillary Electrophoresis (CE) to IM-MS in order to obtain in one injection the quantitative and qualitative data of non-covalent complexes and the monitoring of tridimensional conformation modification between the liquid and gas phase. Indeed CE allows the determination of numerous physicochemical properties (dissociation constant, pK values, hydrodynamic radius determination …). The structural data (i.e. hydrodynamic radius and CCS) are compared to the data obtained by IM-MS as a proof of concept using tryptic digest of Bovine Serum Albumine (BSA). [less ▲]

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See detailProbing the conformational changes during desolvation of ions using orthogonal mobility methods (CE-IMS)
Far, Johann ULg; Kune, Christopher ULg; Delvaux, Cédric ULg et al

Poster (2014, April 08)

The transfer of ions from the solution to the gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find a new equilibrium ... [more ▼]

The transfer of ions from the solution to the gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find a new equilibrium conformation in the gas phase. The pathway to reach the thermodynamically stable conformation involves crossing potential barriers of different heights. When these barriers are too high compared to the internal energy of the ions, it will result in “partial memories” (as structural preservation) of the conformation in solution. In order to evaluate the effect of the solvent evaporation and of the various collision processes encountered by the ions in the mass spectrometer. The strategy consists in comparing in a single experiment the shape of the ions in solution and in the gas phase. Data are obtained by coupling capillary electrophoresis with Ion Mobility Mass Spectrometry. Drift times in solution and in the gas phase are directly compared. Deviations from their correlation points out changes in folding upon desolvatation. Preliminary results show that among peptides issued from tryptic digest of BSA some of them clearly change their conformation during desolvatation. This work intends to evaluate the extent of conformational “memory” of the ions of different nature for best experimental condition allowing “native mass spectrometry”. [less ▲]

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See detailProbing the cores of Extreme Horizontal Branch stars by gravity-mode seismology
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

Conference (2011, June)

We present a seismic analysis of the pulsating subdwarf B star KPD 0629-0016 on the basis of the long-period, gravity-mode pulsations uncovered by CoRoT. Thanks to space- based facilities, g-mode ... [more ▼]

We present a seismic analysis of the pulsating subdwarf B star KPD 0629-0016 on the basis of the long-period, gravity-mode pulsations uncovered by CoRoT. Thanks to space- based facilities, g-mode seismology can now be exploited quantitatively for stars on the ex- treme horizontal branch, an objective undermined so far by the limitations of ground-based observations. The optimal seismic model offers an excellent fit, with a relative dispersion of 0.23%, to the 18 observed periods identified with theoretical modes of degrees l =1 and 2. The inferred structural parameters for KPD 0629–0016 include the total stellar mass, the thickness of the H-rich envelope, and, thanks to the sensitivity of g-modes, the size and the composition of the convective core. Our results suggest that extra mixing processes shape the helium-burning cores, that are representative of all horizontal branch stars in general, an intermediate and underrated stage of stellar evolution. [less ▲]

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See detailProbing the discrete motion of vortices with rf excitations
Van de Vondel, J.; Silhanek, Alejandro ULg; Moshchalkov, V. V. et al

in Physica C: Superconductivity (2010), 470(19), 857-859

In this work we present experimental results on the rectification of vortices in a superconductor/ferromagnet system under a high frequency drive. The two-dimensional pinning landscape, induced by the ... [more ▼]

In this work we present experimental results on the rectification of vortices in a superconductor/ferromagnet system under a high frequency drive. The two-dimensional pinning landscape, induced by the stray fields of the ferromagnetic template, has no intrinsic asymmetry. Nevertheless, an asymmetric potential is artificially induced by an applied dc bias. The experimental results unambiguously show a biased, discrete motion of the vortices in the periodic potential at frequencies above 10 MHz. This synchronized motion is very sensitive to the external applied field. Increasing temperature leads to a reduction of the pinning potential, which in turn results in a lower ac power needed to drive the vortex lattice. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailProbing the existence of axions with the polarization of objects at cosmological distances
Hutsemekers, Damien ULg

Conference (2006)

Photon - axion conversion within a magnetic field over cosmological distances can affect the polarization of distant objects like quasars. We report the observation of large-scale alignments of quasar ... [more ▼]

Photon - axion conversion within a magnetic field over cosmological distances can affect the polarization of distant objects like quasars. We report the observation of large-scale alignments of quasar polarization vectors as well as a rotation of their polarization angles with distance. This effect might be due to the presence of axions along the line of sight. [less ▲]

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See detailProbing the inner structure of distant AGNs with gravitational lensing
Sluse, D.; Hutsemekers, Damien ULg; Courbin, F. et al

in Proceedings of Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation. Proceedings of Science, PoS (Seyfert 2012) 057 (2012)

Microlensing is a powerful technique which can be used to study the continuum and the broad line emitting regions in distant AGNs. After a brief description of the methods and required data, we present ... [more ▼]

Microlensing is a powerful technique which can be used to study the continuum and the broad line emitting regions in distant AGNs. After a brief description of the methods and required data, we present recent applications of this technique. We show that microlensing allows one to measure the temperature profile of the accretion disc, estimate the size and study the geometry of the region emitting the broad emission lines. [less ▲]

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See detailProbing The Interaction Forces Between Hydrophobic Peptides And Supported Lipid Bilayers Using Afm
Andre, G.; Brasseur, Robert ULg; Dufrene, Yf.

in Journal of Molecular Recognition (2007), 20(6), 538-45

Despite the vast body of literature that has accumulated on tilted peptides in the past decade, direct information on the forces that drive their interaction with lipid membranes is lacking. Here, we ... [more ▼]

Despite the vast body of literature that has accumulated on tilted peptides in the past decade, direct information on the forces that drive their interaction with lipid membranes is lacking. Here, we attempted to use atomic force microscopy (AFM) to explore the interaction forces between the Simian immunodeficiency virus peptide and phase-separated supported bilayers composed of various lipids, i.e. dipalmitoylphosphatidylcholine, dioleoylphosphatidylcholine, dioleoylphosphatidic acid and dipalmitoylphosphatidylethanolamine. Histidine-tagged peptides were attached onto AFM tips terminated with nitrilotriacetate and tri(ethylene glycol) groups, an approach expected to ensure optimal exposure of the C-terminal hydrophobic domain. Force-distance curves recorded between peptide-tips and the different bilayer domains always showed a long-range repulsion upon approach and a lack of adhesion upon retraction, in marked contrast with the hydrophobic nature of the peptide. To explain this unexpected behaviour, we suggest a mechanism in which lipids are pulled out from the bilayer due to strong interactions with the peptide-tip, in agreement with the very low force needed to extract lipids from supported bilayers. [less ▲]

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