References of "De Pauw, Edwin"
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See detailFormation de radicaux anions d'ADN par irradiation laser UV et visible et nouveaux canaux de dissociation
Gabelica, Valérie ULg; Tabarin, Thibault; Kinet, Catherine ULg et al

Conference (2006, September 13)

Nous avons exploré récemment les effets de l'irradiation laser dans l'UV ou le visible de polyanions d'ADN dans un piège à ions quadripolaire. Lors de l'irradiation de simple brins ou de double hélices d ... [more ▼]

Nous avons exploré récemment les effets de l'irradiation laser dans l'UV ou le visible de polyanions d'ADN dans un piège à ions quadripolaire. Lors de l'irradiation de simple brins ou de double hélices d'ADN en UV autour de 260 nm, nous avons observé un détachement d'électrons, donnant lieu à des radicaux anions. L'étude de la dépendence de l'efficacité de ce photodétachement d'électrons en fonction de la séquence des brins a révélé que ce phénomène était corrélé au potentiel d'ionisation des bases nucléiques. La guanine est la base la plus facilement oxydée, suivie de l'adénine, de la cytosine et de la thymine. En pratique, plus un brin contient de guanines, plus la formation de radicaux par photodétachement d'électrons est efficace. L'efficacité du photodétachement montre également une dépendence envers l'état de charge du brin (les plus chargés ont une efficacité de détachement plus élevée) et en fonction de la longueur d'onde (avec un maximum d'efficacité autour de 265 nm), montrant que la transition vers un état électronique excité des bases facilite le détachement d'électrons. Plus surprenant encore, des complexes avec des chromophores (ligands du sillon de l'ADN et intercalants) montrent également un photodétachement d'électrons, et ce avec des énergies de photons encore plus basses, correspondant à une absorption dans le visible (i.e. 550 nm pour l'éthidium). Ceci montre que les énergies de liaisons des électrons sont relativement faibles, puisqu'ils peuvent être détachés par des photons de 2.25 eV. Nous avons également étudié la fragmentation des radiaux ainsi produits, par CID dans le piège. Dans le cas des complexes avec les chromophores, les canaux de fragmentation principaux sont des pertes de neutres, y compris des morceaux de ligands. Il est intéressant de constater que les radicaux se fragmentent de la même manière, quel que soit le chromophore irradié qui a donné lieu à sa formation. Cecis suggère que les radicaux se réorganisent rapidement par rapport au temps de l'expérience. Dans le cas de simples brins (12-mères à 20-mères), nous avons constaté une fragmentation plus efficace des radicaux comparés aux ions à couches complètes de même charge. Plus intéressant, les canaux de dissociation sont très particuliers : alors que la CID sur ions à couches complètes donne majoritairement des ions 'w' et 'a-Base', la CID sur les radicaux donne des ions 'w', 'd', 'a radicalaires', et 'z radicalaires'. Il est aisé d'obtenir une bonne couverture de séquence à des énergies de collision faibles. A nouveau, bien que le détachement d'électrons soit initié par les bases guanines, la couverture de séquence est indépendante de la composition, suggérant une redistribution dans les radicaux. L'avantage principal de la fragmentation des radicaux est l'absence de fragments internes (ou 'double fragments'), ce qui facilite le séquencage de novo. De plus, selon notre expérience, la formation des radicaux est plus aisée par irradiation laser que par EDD. [less ▲]

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See detailSuitability of tandem-in-time mass spectrometry for polybrominated diphenylether measurement in fish and shellfish samples: Comparison with high resolution mass spectrometry
PIRARD, Catherine ULg; De Pauw, Edwin ULg; Focant, Jean-François ULg

in Journal of Chromatography. A (2006), 1115(1-2), 125-132

The first part of the present study focused on the development of an alternative automated sample preparation method for the measurement of selected polybrominated diphenyl ethers (PBDEs) in fish and ... [more ▼]

The first part of the present study focused on the development of an alternative automated sample preparation method for the measurement of selected polybrominated diphenyl ethers (PBDEs) in fish and shellfish. A previously developed automated method has been further optimized and simplified to decrease blank levels and cost. Sorbent and solvent quantities have been significantly reduced without altering extract quality. The second part of the study consisted of comparing tandem-in-time quadrupole ion storage mass spectrometry (QISTMS/MS) to high resolution mass spectrometry (HRMS) for the isotope dilution (ID) measurement step after gas chromatography (GC) separation. Both mass spectrometric methods performed similarly in terms of accuracy but better precision was observed for HRMS. Although better sensitivity can be attained with the high resolution sector instrument, method limits of quantification (mLOQs) were very similar for both approaches as they were dependent on the procedural blanks levels. The mLOQ values ranged between 0.04 and 3.56 ng/g fat, depending on the congener. They allowed the unambiguous identification and quantification of all target analytes, except for BDE-183, in most considered fish extracts. An analytical procedure based on rapid automated sample preparation and QISTMS/MS appeared to be suitable for the measurement of PBDEs in fish and shellfish speciment under quality assurance/quality control (QA/QC) criteria. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailSaccharomyces cerevisiae mitoproteome plasticity in response to recombinant alternative ubiquinol oxidase
Mathy, Grégory ULg; Navet, Rachel ULg; Gerkens, Pascal et al

in Journal of Proteome Research (2006), 5(2), 339-348

The energy-dissipating alternative oxidase (AOX) from Hansenula anomala, was expressed in Saccharomyces cerevisiae. The recombinant AOX was functional. A comparative analysis by two-dimensional ... [more ▼]

The energy-dissipating alternative oxidase (AOX) from Hansenula anomala, was expressed in Saccharomyces cerevisiae. The recombinant AOX was functional. A comparative analysis by two-dimensional differential in-gel electrophoresis (2D-DIGE) of mitochondrial protein patterns found in wild-type and recombinant AOX strains was performed. 60 proteins exhibiting a significant difference in their abundance were identified. Interestingly, proteins implicated in major metabolic pathways such as Krebs cycle and amino acid biosynthesis were up-regulated. Surprisingly, an up-regulation of the respiratory-chain complex III was associated with a down-regulation of the ATP synthase complex. [less ▲]

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See detailUncoupling protein 1 affects the yeast mitoproteome and oxygen free radical production
Douette, Pierre ULg; Gerkens, Pascal; Navet, Rachel ULg et al

in Free Radical Biology & Medicine (2006), 40(2), 303-315

Uncoupling protein I (UCP1) is a mitochondrial inner membrane protein that dissipates the proton electrochemical gradient built up by the respiratory chain. its activity is stimulated by free fatty acids ... [more ▼]

Uncoupling protein I (UCP1) is a mitochondrial inner membrane protein that dissipates the proton electrochemical gradient built up by the respiratory chain. its activity is stimulated by free fatty acids and inhibited by purine nucleotides. Here we investigated how active and regulated recombinant UCP1 expressed in yeast at similar to 1 and similar to 10 mu g/mg of total mitochondrial proteins induced changes in the mitochondrial proteome and in oxygen free radical production. Using two-dimensional differential in-gel electrophoresis (2D-DIGE), we found that most of the proteins involved in the response to ectopically expressed UCP1 are related to energy metabolism. We also quantified the cellular H2O2 release in the absence or in the presence of UCP1. Our results suggest that UCP1 has a dual influence on free radical generation. On one side, FFA-activated UCP1 was able to decrease the superoxide anion production, demonstrating that a decrease in the generation of reactive oxygen species is an obligatory outcome of UCP1 activity even in a heterologous context. On the other side, an increase in UCP1 content was concomitant with an increase in the basal release of superoxide anion by mitochondria as a side consequence of the overall increase in oxidative metabolism. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailStrategy for DR-CALUX dioxin screening in feed under EC regulation
Scippo, Marie-Louise ULg; Rybertt, M. S.; Focant, Jean-François ULg et al

in Organohalogen Compounds (2006), 68

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See detailProteome variations of the Myzus persicae aphid according to host plant change.
Francis, Frédéric ULg; GERKENS, P.; Harmel, Nicolas ULg et al

in Insect Biochemistry and Molecular Biology (2006), 36(3), 219-227

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See detailProteomics in Myzus persicae: effect of aphid host plant switch.
Francis, Frédéric ULg; Gerkens, Pascal; Harmel, Nicolas ULg et al

in Insect Biochemistry and Molecular Biology (2006), 36(3), 219-27

Chemical ecology is the study of how particular chemicals are involved in interactions of organisms with each other and with their surroundings. In order to reduce insect attack, plants have evolved a ... [more ▼]

Chemical ecology is the study of how particular chemicals are involved in interactions of organisms with each other and with their surroundings. In order to reduce insect attack, plants have evolved a variety of defence mechanisms, both constitutive and inducible, while insects have evolved strategies to overcome these plant defences (such as detoxification enzymes). A major determinant of the influence of evolutionary arms races is the strategy of the insect: generalist insect herbivores, such as Myzus persicae aphid, need more complex adaptive mechanisms since they need to respond to a large array of different plant defensive chemicals. Here we studied the chemical ecology of M. persicae associated with different plant species, from Brassicaceae and Solanaceae families. To identify the involved adaptation systems to cope with the plant secondary substances and to assess the differential expression of these systems, a proteomic approach was developed. A non-restrictive approach was developed to identify all the potential adaptation systems toward the secondary metabolites from host plants. The complex protein mixtures were separated by two-dimensional electrophoresis methods and the related spots of proteins significantly varying were selected and identified by mass spectrometry (ESI MS/MS) coupled with data bank investigations. Fourteen aphid proteins were found to vary according to host plant switch; ten of them were down regulated (proteins involved in glycolysis, TCA cycle, protein and lipid synthesis) while four others were overexpressed (mainly related to the cytoskeleton). These techniques are very reliable to describe the proteome from organisms such as insects in response to particular environmental change such as host plant species of herbivores. [less ▲]

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See detailElectron photodetachment dissociation of DNA polyanions in a quadrupole ion trap mass spectrometer
Gabelica, Valérie ULg; Tabarin, Thibault; Antoine, Rodolphe et al

in Analytical Chemistry (2006), 78(18), 6564-6572

We hereby explore the effects of irradiating DNA polyanions stored in a quadrupole ion trap mass spectrometer with an optical parametric oscillator laser between 250 and 285 nm. We studied DNA 6-20-mer ... [more ▼]

We hereby explore the effects of irradiating DNA polyanions stored in a quadrupole ion trap mass spectrometer with an optical parametric oscillator laser between 250 and 285 nm. We studied DNA 6-20-mer single strands and 12-base pair double strands. In all cases, laser irradiation causes electron detachment from the multiply charged DNA anions. Electron photodetachment efficiency directly depends on the number of guanines in the strand, and maximum efficiency is observed between 260 and 275 nm. Subsequent collision-induced dissociation (CID) of the radical anions produced by electron photodetachment results in extensive fragmentation. In addition to neutral losses, a large number of fragments from the w, d, a*, and z* ion series are obtained, contrasting with the w and (a-base) ion series observed in regular CID. The major advantage of this technique, coined electron photodetachment dissociation (EPD) is the absence of internal fragments, combined with good sequence coverage. EPD is therefore a highly promising approach for de novo sequencing of oligonucleotides. EPD of nucleic acids is also expected to give specific radical-induced strand cleavages, with conservation of other fragile bonds, including noncovalent bonds. In effect, preliminary results on a DNA hairpin and on double strands suggest that EPD could also be used to probe intra- and intermolecular interactions in nucleic acids. [less ▲]

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See detailPositive and negative ion mode ESI-MS and MS/MS for studying drug-DNA complexes
Rosu, Frédéric ULg; Pirotte, Sophie ULg; De Pauw, Edwin ULg et al

in International Journal of Mass Spectrometry (2006), 253(3), 156-171

We report systematic investigation of duplex DNA complexes with minor groove binders (Hoechsts 33258 and 33342, netropsin and DAPI) and intercalators (daunomycin, doxorubicin, actinomycin D, ethidium ... [more ▼]

We report systematic investigation of duplex DNA complexes with minor groove binders (Hoechsts 33258 and 33342, netropsin and DAPI) and intercalators (daunomycin, doxorubicin, actinomycin D, ethidium, cryptolepine, neocryptolepine, m-Amsacrine, proflavine, ellipticine and mitoxantrone) by ESI-MS and ESI-MS/MS in the negative ion mode and in the positive ion mode. The apparent solution phase equilibrium binding constants can be determined by measuring relative intensities in the ESI-MS spectrum. While negative ion mode gives reliable results, positive ion mode gives a systematic underestimation of the binding constants and even a complete suppression of the complexes for intercalators lacking functional groups capable of interacting in the grooves. In the second part of the paper we systematically compare MS/MS fragmentation channels and breakdown curves in the positive and the negative modes, and discuss the possible uses and caveats of MS/MS in drug-DNA complexes. In the negative mode, the drugs can be separated in three groups: (1) those that leave the complex with no net charge; (2) those that leave the complex with a negative charge; and (3) those that remain attached on the strands upon dissociation of the duplex due to their positive charge. In the positive ion mode, all complexes fragment via the loss of protonated drug. Information on the stabilization of the complex by drug-DNA noncovalent interactions can be obtained straightforwardly only in the case of neutral drug loss. In all other cases, proton affinity (in the positive ion mode), gas-phase basicity (in the negative ion mode) and coulombic repulsion are the major factors influencing the fragmentation channel and the dissociation kinetics. [less ▲]

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See detailG-quadruplexes in telomeric repeats are conserved in a solvent-free environment
Baker, Erin Shammel; Bernstein, Summer L; Gabelica, Valérie ULg et al

in International Journal of Mass Spectrometry (2006), 253(3), 225-237

The structural properties of G-quadruplex forming sequences. such as the human telomeric repeat d(T(2)AG(3))(n), are of great interest due to their role in cancer and cellular aging. To determine if G ... [more ▼]

The structural properties of G-quadruplex forming sequences. such as the human telomeric repeat d(T(2)AG(3))(n), are of great interest due to their role in cancer and cellular aging. To determine if G-quadruplexes are present in a solvent-free environment. different lengths of the telomeric repeat d(T(2)AG(3))(n) (where n = 1, 2, 4 and 6) and dTG(4)T were investigated with mass specteometry, ion mobility and molecular dynamics calculations. Nano-ESI-MS illustrated quadruples stoichiometries compatible with G-quadruplex Structure.; for each sequence, with dT(2)AG(3) and dTG(4)T forming 4-strand complexes with two and three NH4+ adducts. d(T(2)AG(3))(2) a 2-strand complex. and d(T(2)AG(3))(4) and d(T(2)AG(3))(6) remaining single-stranded. Experimental cross sections were obtained for all species using ion mobility method.,. In all case.,. these could be quantitatively matched to model cross sections with specific strand orientations (parallel/antiparallel) and structures. For each species, the solvent-free structures agreed with the solution CD measurements, but the ion mobility/modeling procedure often gave Much more detailed structural information. (C) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailDioxin analysis in feed: cell-based assay versus mass spectrometry method
Scippo, Marie-Louise ULg; Rybertt, Soledad; Eppe, Gauthier ULg et al

in Accreditation and Quality Assurance (2006), 11(1-2), 38-43

In the determination of contaminants (dioxins, polychlorinated biphenyls, polyaromatic hydrocarbons), cell-based assays are useful methods for screening purposes: they are mainly characterized by high ... [more ▼]

In the determination of contaminants (dioxins, polychlorinated biphenyls, polyaromatic hydrocarbons), cell-based assays are useful methods for screening purposes: they are mainly characterized by high sample throughput and lower costs than the Mass Spectrometry (MS)-based methods. Although cell-based assays can be sensitive enough for the determination of dioxins and related substances in agreement with the presently tolerable limits in food and feed (Regulation No. 2375/2001/EC and Directive 2003/57/EC respectively), their lack of specificity make their use rather questionable in control laboratories. In this paper, we present and compare results obtained from the analysis of a limited number of feed samples by both gas chromatography-high resolution mass spectrometry (GC-HRMS) and cell-based assay (DR-CALUX: dioxin responsive-chemically activated luciferase gene expression) methods. The DR-CALUX screening led to less than 10% false non-compliant and no false compliant results. In addition, there is a good correlation between GC-HRMS and DR-CALUX data. However, these preliminary results have to be confirmed on a larger number of samples to demonstrate that total toxic equivalent (TEQ), including dioxins, furans and dioxin-like polychlorobiphenyls (PCBs) can be monitored in feed and food with a cell-based assay. [less ▲]

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