References of "De Pauw, Edwin"
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See detailPutative DNA G-quadruplex formation within the promoters of Plasmodium falciparum var genes
Smargiasso, Nicolas ULiege; Gabelica, Valérie ULiege; Damblon, Christian ULiege et al

in BMC Genomics (2009), 10

Background. Guanine-rich nucleic acid sequences are capable of folding into an intramolecular four-stranded structure called a G-quadruplex. When found in gene promoter regions, G-quadruplexes can ... [more ▼]

Background. Guanine-rich nucleic acid sequences are capable of folding into an intramolecular four-stranded structure called a G-quadruplex. When found in gene promoter regions, G-quadruplexes can downregulate gene expression, possibly by blocking the transcriptional machinery. Here we have used a genome-wide bioinformatic approach to identify Putative G-Quadruplex Sequences (PQS) in the Plasmodium falciparum genome, along with biophysical techniques to examine the physiological stability of P. falciparum PQS in vitro. Results. We identified 63 PQS in the non-telomeric regions of the P. falciparum clone 3D7. Interestingly, 16 of these PQS occurred in the upstream region of a subset of the P. falciparum var genes (group B var genes). The var gene family encodes PfEMP1, the parasite’s major variant antigen and adhesin expressed at the surface of infected erythrocytes, that plays a key role in malaria pathogenesis and immune evasion. The ability of the PQS found in the upstream regions of group B var genes (UpsB-Q) to form stable Gquadruplex structures in vitro was confirmed using 1H NMR, circular dichroism, UV spectroscopy, and thermal denaturation experiments. Moreover, the synthetic compound BOQ1 that shows a higher affinity for DNA forming quadruplex rather than duplex structures was found to bind with high affinity to the UpsB-Q. Conclusions. This is the first demonstration of non-telomeric PQS in the genome of P. falciparum that form stable G-quadruplexes under physiological conditions in vitro. These results allow the generation of a novel hypothesis that the G-quadruplex sequences in the upstream regions of var genes have the potential to play a role in the transcriptional control of this major virulence-associated multi-gene family. [less ▲]

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See detailA Simple Method to Determine Electrospray Response Factors of Noncovalent Complexes
Gabelica, Valérie ULiege; Rosu, Frédéric ULiege; De Pauw, Edwin ULiege

in Analytical Chemistry (2009), 81(16), 6708-6715

The quantitative study of noncovalent complexes by electrospray mass spectrometry requires the determination of the relative response of each species. The method proposed here to determine the ... [more ▼]

The quantitative study of noncovalent complexes by electrospray mass spectrometry requires the determination of the relative response of each species. The method proposed here to determine the electrospray response factors is based on the use of (1) an internal standard and (2) the mass balance equation applied to one binding partner M, for which different complexes MxLy are detected in the electrospray mass spectra. A set of experiments providing various ratios between the complexes (e.g. different ligand concentrations in a titration experiment or different time points in a kinetics experiment) is used to generate a set of independent linear equations that can be solved using simple matrix algebra to find the response factors of each MxLy complex relative to that of the internal standard. The response factors can then be used to determine equilibrium dissociation constants or for the quantitative monitoring of reaction kinetics. The first is illustrated with a study of DNA-ligand complexes, where we show that neither minor groove binding nor intercalation dramatically affects the DNA response factor. The second is illustrated with a study of the association kinetics of the telomeric G-quadruplex dGGG(TTAGGG)3 with its complementary strand, where the response factors allow correcting for the relative response of the quadruplex and the long duplex and obtaining reproducible association rate constants independently of the source tuning potentials. [less ▲]

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See detailAdvances in quality control for dioxins monitoring and evaluation of measurement uncertainty from quality control data.
Eppe, Gauthier ULiege; De Pauw, Edwin ULiege

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2009), 877

This paper describes an application of multivariate and multilevel quality control charts with the aim of improving the internal quality control (IQC) procedures for the monitoring of dioxins and dioxin ... [more ▼]

This paper describes an application of multivariate and multilevel quality control charts with the aim of improving the internal quality control (IQC) procedures for the monitoring of dioxins and dioxin-like PCBs analysis in food. Dioxin analysts have to use the toxic equivalent concept (TEQ) to assess the toxicity potential of a mixture of dioxin-like compounds. The TEQ approach requires quantifying individually 29 dioxin-like compounds. Monitoring the congeners separately on univariate QC charts is misleading owing to the increase of false alarm rate. We propose to subdivide the TEQ value into 3 sub-groups and to control simultaneously the 3 variables in a T(2) chart. When a T(2) exceeds the upper control limit, it acts as a warning to trigger additional investigations on individual congeners. We discuss the minimum number of runs required to reliably estimate the QC chart parameters and we suggest using data from multilevel QC charts to properly characterize the standard deviations and the correlation coefficients. Moreover, the univariate QC chart can be sensitised to detect systematic errors by using exponentially weighted moving average (EWMA) technique. The EWMA chart provides an additional guidance on setting appropriate criteria to control the method bias and to support trend analysis. Finally, we present an estimate of measurement uncertainty by computing the accuracy profile in a retrospective way with the QC data generated and we discuss assessment of compliance with regulatory maximum levels. [less ▲]

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See detailTranscriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid
LE TRIONNAIRE, G.; Francis, Frédéric ULiege; JAUBERT-POSSAMAI, S. et al

in BMC Genomics (2009), 29

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See detailMCF-7/BOS cells membrane proteome: comparison of two isolation methods using mass spectrometry
Bertrand, Virginie ULiege; Massart, Anne-Cécile ULiege; De Pauw-Gillet, Marie-Claire ULiege et al

Poster (2009)

Membrane proteins play an important role in biological processes but their isolation and quantification using classical techniques is often limited due to their poor solubility and relatively low ... [more ▼]

Membrane proteins play an important role in biological processes but their isolation and quantification using classical techniques is often limited due to their poor solubility and relatively low abundance. These membrane markers have to be accessible to antibodies and should be potential therapeutic targets. The tests were conducted on MCF-7 / BOS cell line, immortal and easier to cultivate. The goal of this work is to obtain a pure membrane fraction to facilitate the analysis of the sample. To isolate transmembrane proteins, we compared two methods. The first one used different extraction cycles characterized by different buffers to isolate membrane proteins. The second method labelled accessible extracellular domains at the surface of MCF-7 cells with biotin prior to differential centrifugation. [less ▲]

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See detailMCF-7/BOS cells membrane proteome: comparison of two isolation methods using mass spectrometry
Bertrand, Virginie ULiege; Massart, Anne-Cécile ULiege; De Pauw-Gillet, Marie-Claire ULiege et al

Poster (2009)

Membrane proteins (MP) play an important role in biological processes. Isolation and quantification of these MP using classical techniques is often limited due to their poor solubility and relatively low ... [more ▼]

Membrane proteins (MP) play an important role in biological processes. Isolation and quantification of these MP using classical techniques is often limited due to their poor solubility and relatively low abundance. These membrane proteins enclosed markers which could be potential therapeutic targets. These potential therapeutic targets have to be accessible to antibodies and need to be presented in the plasmic membrane. Assays were conducted on MCF-7 / BOS cell line, immortal and easier to cultivate. The goal of this work is to obtain an enriched membrane fraction to facilitate the analysis of the sample and to simplify the complex proteins mixture. To isolate transmembrane proteins, we compared two methods. The first one used different extraction cycles characterized by different buffers to isolate membrane proteins. The second method labelled accessible extracellular domains at the surface of MCF-7 cells with biotin prior to differential centrifugation. The obtained enriched membrane proteome was digested with trypsin and/or Lysyl Endopeptidase. Obtained peptides were separated by 2D-HPLC chromatography and on-line analysed ion trap mass spectrometer, the Esquire HCT. [less ▲]

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See detailMembrane and cytoplasmic proteome biology of anterior mice hippocampus
Jackers, Pascale ULiege; Massart, Anne-Cécile; Depaulis, Antoine et al

Poster (2008, October 10)

The prevalence of neurodegenerative diseases increases steadily and proteomics on disease-related brain areas become more and more complex, whereas suitable samples are scarce. Due to this difficulty ... [more ▼]

The prevalence of neurodegenerative diseases increases steadily and proteomics on disease-related brain areas become more and more complex, whereas suitable samples are scarce. Due to this difficulty, animal models are indispensable in understanding human biology and disease, and the most commonly used model is the mouse (Mus musculus). Mice share many genetic and physiological characteristics with humans, breed rapidly, and can be genetically modified leading to the functional characterisation of many proteins. As for human, the mouse hippocampus is one of the most important areas of the brain and has therefore been an object of intensive investigation for many years. Mouse hippocampus has served as models for degenerating brain diseases associated with Alzheimer's disease, Parkinson's disease, ischemia, epilepsy, synaptic plasticity and underlying mechanisms of learning and memory. Using 2 anterior parts of normal mouse hippocampi, we intend to characterize membrane and cytoplasmic proteome using a modified procedure previously established (WISNIEWSKI et al., 2008). This method permit the preparation and analysis of 2 individual fractions enriched in membrane and cytoplasmic proteins. The method for separation of membrane and cytoplasm fractions comprises a stepwise depletion of non-integral membrane proteins from entire tissue homogenate by high-salt, carbonate, and urea washes. The cytoplasmic proteins obtained from high-salt depletion are considered as the soluble fraction. The membrane proteins obtained from the stepwise depletion are considered as the insoluble fraction. Enzymatic digestion of both membrane and cytoplasmic fractions are carried out without use of detergents by double digestion with endoproteinase Lys-C and trypsin. Digested peptide fractions are loaded on StageTips for rapid desalting and are separated by online reversed-phase (RP) nanoscale capillary liquid chromatography (nanoLC). Separated peptides are analyzed by electrospray tandem mass spectrometry (HPLC-ESI-MS/MS). The entire procedure allows rapid processing and preparation of samples from minute amounts as 30-40 mg frozen tissue leading to about 70 g of membrane proteins and 500 g of cytoplasmic proteins. This can be extremely helpful for proteomic profiling of small pieces of tissue and clinical material. Analyses of membrane fraction identified about 45% total membrane proteins. This fraction includes glutamate receptor 1 and 2, proteins involved into the trafficking of synaptic vesicles, lipid-anchor proteins, G proteins involved in various transmembrane signalling systems, NMDAR signalling complex proteins, voltage channel proteins… Analyses of the cytoplasmic fraction identify various proteins belonging to different compartments and/or pathways. A large amount of these proteins are specifically expressed into the hippocampus and/or into the nervous system. [less ▲]

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See detailFunctionalized plasmonic gold nanoparticles for optoacoustic cancer detection
Schol, Daureen ULiege; Fleron, Maximilien ULiege; Greisch, Jean-François et al

Poster (2008, September 12)

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See detailStudies of sequence specific recognition and interaction of bis-hairpin polyamide minor groove binders with target DNA duplexes
Boutorine, A. S.; Buchmann, W.; Halby, L. et al

in Nucleic Acids Symposium Series (2008), 52

Study of the binding of bis-MGB using DNA footprinting, native gel shift, thermal denaturation, mass spectrometry and circular dichroism. Elaboration of a method to determin

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See detailVALAPODYN: A new systems biology approach to develop predictive dynamic models of complex intracellular networks for neurological disease
Sanoudou, Despina; Depaulis, Antoine; Vafiadaki, Elizabeth et al

Poster (2008, August 22)

Objective: VALAPODYN, a European Commission funded research network, is using an original systems biology approach for the development of an innovative dynamic model of molecular interaction networks (MIN ... [more ▼]

Objective: VALAPODYN, a European Commission funded research network, is using an original systems biology approach for the development of an innovative dynamic model of molecular interaction networks (MIN) in relation to cell death and survival for the detection of new therapeutic targets for human neurological diseases. To this end, a comprehensive multidisciplinary strategy has been established combining functional genomics, proteomics and bioinformatics. Results: Using a mouse model of induced hippocampal sclerosis associated with focal epilepsy, dynamic expression analyses are conducted at different time points. Proteomic databases are being used along with advanced microarray and proteomics platform systems to investigate protein-protein interactions and regulation networks, identify and validate biological targets in complex intracellular pathways. The first phase involves whole genome and proteome analysis, integrating biological and statistical data in order to functionally annotate genes and proteins. Using Affymetrix microarrays, 2D-DIGE and MALDI/TOF-TOF, we are evaluating whole genome and proteome expression profiles bringing to light critical new pathways and molecular targets implicated in neurodegeneration. Conclusion: VALAPODYN develops a dynamic and quantitative analysis method for new therapeutic targets through MIN dynamic models and specifically addresses the systems biology of complex cellular pathways and transcriptional networks. Novel predictive dynamic models will be validated by testing the selected drug targets on innovative in vivo and in vitro models of CNS pathologies. VALAPODYN will provide a cutting-edge highly accurate in silico tool for identifying novel and effective therapeutic targets in a faster, more efficient and more economical way than it is possible today. [less ▲]

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See detailDeveloping predictive dynamic models of complex intracellular networks for neurological disease
Vafiadaki, Elizabeth; Depaulis, Antoine; Jackers, Pascale ULiege et al

in FEBS Journal (2008, June 28), 275(Issue s1), 206

Introduction: VALAPODYN, a European Commission funded research network, is an original systems biology approach for the development of an innovative model on the dynamics of molecular interaction networks ... [more ▼]

Introduction: VALAPODYN, a European Commission funded research network, is an original systems biology approach for the development of an innovative model on the dynamics of molecular interaction networks (MIN) in relation to cell death and survival for the detection of new therapeutic targets for human neurological diseases. To this end, a comprehensive multidisciplinary strategy has been established combining functional genomics, proteomics and bioinformatics. Methods and Results: Using a mouse model of induced hippocampal sclerosis associated with focal epilepsy, dynamic expression analyses are conducted at different time points. Proteomic databases are being used along with advanced microarray and proteomics platform systems to investigate protein-protein interactions and regulation networks, identify and validate biological targets in complex intracellular pathways. The first phase involves whole genome and proteome analysis, integrating biological and statistical data in order to functionally annotate genes and proteins. Using Affymetrix microarrays, 2D-DIGE and MALDI/TOF-TOF, we are evaluating whole genome and proteome expression profiles bringing to light critical new pathways and molecular targets implicated in neurodegeneration. Discussion: VALAPODYN develops a dynamic and quantitative analysis method for new therapeutic targets through MIN dynamic models and specifically addresses the systems biology of complex cellular pathways and transcriptional networks. Novel predictive dynamic models will be validated by testing the selected drug targets on innovative in vivo and in vitro models of CNS pathologies. VALAPODYN will provide a cutting-edge highly accurate in silico tool for identifying novel and effective therapeutic targets in a faster, more efficient and more economical way than it is possible today. [less ▲]

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See detailIR and UV spectroscopic signatures of DNA higher-order structures in the gas phase
Gabelica, Valérie ULiege; Rosu, Frédéric ULiege; Gregoire, Gilles et al

Conference (2008, June 03)

Introduction Electrospray mass spectrometry (ESI-MS) can be used to transfer large biomolecular complexes from the solution to the gas phase. However, a longstanding question is whether the gas-phase ... [more ▼]

Introduction Electrospray mass spectrometry (ESI-MS) can be used to transfer large biomolecular complexes from the solution to the gas phase. However, a longstanding question is whether the gas-phase multiply-charged ions produced by ESI-MS keep a folded conformation in the absence of solvent. Nucleic acid secondary structures are determined by hydrogen bonding interactions between nucleic bases and by stacking interactions between neighboring base pairs. Here we will show that infrared (IR) and ultraviolet (UV) action spectroscopies provide useful and complementary information on the structure of nucleic acid ions in the gas phase. Methods IR spectroscopy experiments on DNA negative ions were carried out at the CLIO free electron laser (FEL) center (Orsay, France) using an Esquire 3000 (Bruker) mass spectrometer modified to inject the IR beam through the ring electrode. IRMPD spectra are recorded by monitoring the fragmentation of mass-selected parent ions as a function of the excitation wavenumber, in the range 1000-2000 cm-1. UV spectroscopy experiments were carried out using a tunable OPO laser (Continuum Lasers) with frequency doubling. The laser is interfaced with either a Finnigan LCQ ESI-QIT mass spectrometer or a Bruker Apex-Qe 9.4 T ESI-FTICR mass spectrometer. The UV action spectra were recorded by monitoring electron detachment as a function of the wavelength between 220 and 300 nm. Preliminary results First, DNA oligonucleotide ions forming G-quadruplex structures were studied in the gas phase using IR multiple-photon dissociation spectroscopy. Data interpretation on these large biomolecule ions is made using carefully chosen control experiments. The IR spectrum of the (dTG4T)4 quadruplex has been recorded, and compared to that of the single strand. Given the strand stoichiometry and the selective incorporation of three ammonium cations, there is little doubt about the quadruplex structure of [(dTG4T)4•(NH4+)3]5-. The major finding is a fingerprint of hydrogen bonding in the gas phase in the guanine C6=O6 stretching mode, that allows probing the conservation of G-quartets in the gas phase. Further experiments also demonstrate the conservation of G-quadruplex hydrogen bonds in the human telomeric sequence d(TTAGGG)4 [Gabelica et al., JACS, accepted]. Second, we also studied DNA duplexes and G-quadruplex ions in the gas phase by UV spectroscopy. We recorded the UV spectra of the (dTG4T)4 quadruplex, with and without ammonium ions. Molecular modeling [Rueda et al., JACS, 2006, p3608] and ion mobility spectrometry data [Gabelica et al., JACS, 2007, 895] showed that G-quadruplexes keep their hydrogen-bonded structure but become more floppy if inner cations are removed. We found that the UV spectra differ dramatically with and without inner cations, suggesting that UV spectroscopy is very sensitive to stacking interactions between neighboring G-quartets. We also used UV spectroscopy to probe the structure of 12-mer DNA duplexes, by comparing the duplex spectra to those obtained on single strands. Preliminary results show that stacking interactions may be preserved in duplexes containing GC base pairs, but not in duplexes containing AT base pairs. Altogether, these results show the complementarities between IR and UV spectroscopy to characterize DNA structures in the gas phase: IR data mainly give access to information on hydrogen bonding of bases, and UV spectroscopy provides information on stacking interactions. [less ▲]

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See detailDynamic proteomics of mice hippocampus to study apoptosis
Jackers, Pascale ULiege; Bertrand, Virginie ULiege; Vafiadaki, Elizabeth et al

Poster (2008, May 30)

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See detailElectron Photodetachment of DNA Polyanions: Photoelectron Spectroscopy and UV Action Spectroscopy
Gabelica, Valérie ULiege; Rosu, Frédéric ULiege; De Pauw, Edwin ULiege et al

Conference (2008, April 15)

DNA polyanions trapped in a mass spectrometer undergo electron detachment following irradiation with UV light [1-3]. Electron photodetachment is a 1-photon process, and its efficiency depends on: - The ... [more ▼]

DNA polyanions trapped in a mass spectrometer undergo electron detachment following irradiation with UV light [1-3]. Electron photodetachment is a 1-photon process, and its efficiency depends on: - The nature of the DNA bases: guanine-containing strands are the most prone to electron photodetachment, followed by adenine, cytosine, and finally thymine. - The excitation wavelength: electron detachment is maximum around 260 nm, corresponding to base excitation. - The charge of the polyanion: higher charge state ions undergo more efficient electron detachment because of the Coulombic repulsion. Here we will discuss the electron photodetachment mechanism in the light of the most recent experimental results. Because the base-dependence of electron photodetachment efficiency is correlated with the base ionization potential and is maximum at wavelengths corresponding to the base absorption, we initially proposed that electron photodetachment might occur directly from the base, and that the photodetachment yield was correlated with the electron binding energy to the base [2]. Photoelectron spectroscopy experiments were performed on DNA multiply charged anions with varying base composition to probe how the electron binding energies changes with the base composition. Finally, the electron detachment channel was used to perform UV spectroscopy experiments on large DNA polyanions trapped in the gas phase. Gas-phase UV spectra of DNA duplexes and G-quadruplexes containing up to 24 bases (> 7000 Da) will be presented. [1] V. Gabelica, T. Tabarin, R. Antoine, F. Rosu, I. Compagnon, M. Broyer, E. De Pauw, and P. Dugourd, Anal. Chem. 78, 6564 (2006). [2] V. Gabelica, F. Rosu, T. Tabarin, C. Kinet, R. Antoine, M. Broyer, E. De Pauw, and P. Dugourd, J. Am. Chem. Soc. 129, 4706 (2007). [3] V. Gabelica, F. Rosu, E. De Pauw, R. Antoine, T. Tabarin, M. Broyer, and P. Dugourd, J. Am. Soc. Mass Spectrom. 18, 1990 (2007). [less ▲]

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See detailDetection of Oligonucleotide Gas-Phase Conformers: H/D Exchange and Ion Mobility as Complementary Techniques
Balbeur, Dorothée ULiege; Widart, Joëlle ULiege; Leyh, Bernard ULiege et al

in Journal of the American Society for Mass Spectrometry (2008), 19(7), 938-946

Gas-phase hydrogen/deuterium exchange of small oligonucleotides (dTG, dC6 and C6) with CD3OD was performed in the second hexapole of a Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer ... [more ▼]

Gas-phase hydrogen/deuterium exchange of small oligonucleotides (dTG, dC6 and C6) with CD3OD was performed in the second hexapole of a Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer. Ion activation experiments were conducted by accelerating the ions at the entrance of the H/D exchange cell under conditions promoting exclusively collisional isomerization. These experiments allowed us to assess the presence of several conformers, and to probe the height of the isomerization barrier separating these conformers. Ion mobility experiments were also performed. Their results were consistent with the H/D exchange data. A model accounting for the competing isomerization and H/D exchange reactions is proposed. Comparing the ion acceleration experiments for H/D exchange and for ion mobility reveals that the most compact conformer displays the fastest H/D exchange. This observation shows that H/D exchange and ion mobility provide us with complementary information because hydrogen accessibility and macromolecule compactness are not univocally associated. [less ▲]

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See detailOptoacoustic specific detection of prostate cancer using functionalized gold nanorods
Schol, Daureen ULiege; Fleron, Maximilien ULiege; Greisch, Jean-François et al

Poster (2008, March 12)

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See detailCoating of gold nanoparticles by thermosensitive poly(N-isopropylacrylamide) end-capped by biotin
Aqil, Abdelhafid ULiege; Qiu, Hongjin; Greisch, Jean-François ULiege et al

in Polymer (2008), 49(5), 1145-1153

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free ... [more ▼]

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free-radical polymerization leading to polymer without any reactive end-group, and (ii) Reversible Addition–Fragmentation chain Transfer (RAFT) polymerization with 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP) as a RAFT agent. PNIPAM with low polydispersity was then end-capped by an α-carboxylic acid and an ω-trithiocarbonate that was converted into an ω-thiol upon hydrolysis. This hetero-telechelic polymer was analyzed by mass spectroscopy, size exclusion chromatography (SEC) and 1H NMR. Even without thiol end-group, known for chemisorption onto gold, PNIPAM was effective in stabilizing gold NPs (1–5 nm). The thermosensitivity of PNIPAM at the surface of gold NPs was, however, dependent on the molecular weight of the chains. Finally, the α-carboxyl end-group of PNIPAM was used to anchor biotin, which is indeed known for complexation with avidin, which is a possible strategy for the coated gold NPs to be involved as building blocks in supramolecular assemblies. TEM and UV–vis spectroscopy were used to characterize the gold nanoparticles. [less ▲]

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See detailEmpirical Relationship between Precision and Ultra-Trace Concentrations of Pcdd/Fs and Dioxin-Like Pcbs in Biological Matrices
Eppe, Gauthier ULiege; Van Cleuvenbergen, Rudy; Smastuen Haug, Line et al

in Chemosphere (2008), 71(2), 379-87

Dioxin analysis in food and feed can be characterized as an analytical application where very high accuracy is required at very low levels of contamination. Gas chromatography (GC) in combination with (13 ... [more ▼]

Dioxin analysis in food and feed can be characterized as an analytical application where very high accuracy is required at very low levels of contamination. Gas chromatography (GC) in combination with (13)C-label isotope dilution (ID) high resolution mass spectrometry (HRMS) is the reference congener-specific technique characterized by pronounced selectivity, precision and trueness at parts-per-trillion (ppt) and sub-parts-per-trillion (sub-ppt) levels. The quality of the analytical data produced routinely by a laboratory should be adequate for its intended purpose, i.e., one will seek a compromise between the cost and time needed and the consequences of incorrect decisions due to erroneous results. The requirements for reproducibility are usually dependent on the analyte concentrations and have been expressed in various empirical functions. While Horwitz or modified functions are widely useful for many purposes, it would be difficult to expect these functions to cover every analytical problem. This study reports on precision characteristics achieved by the GC-ID-HRMS reference method for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in food and feed in two interlaboratory method-performance studies among expert laboratories with long-standing experience in this field. Striking linear functions in log scale between reproducibility standard deviation and congener's level over a concentration range of 10(-8)-10(-14)g per g fresh weight are observed. The data fit very well to a Horwitz-type function of the form s(R)=0.153c(0.904), where s(R) and c are dimensionless mass ratios expressed in pgg(-1) on fresh weight, regardless of the nature of the toxic congeners, food and feed matrices, or sample preparation methods. We demonstrate that the proposed function is suitable for use as a fitness-for-purpose criterion for proficiency assessment in interlaboratory comparisons on dioxins and related compounds in food. [less ▲]

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See detailMCF-7/BOS cells membrane proteome profiling for the analysis of plasmic proteins in pancreatic beta cells
Bertrand, Virginie ULiege; Massart, Anne-Cécile; Flamez, Daisy et al

Poster (2008, February 15)

Type I and type II diabetes are diseases characterized by the activation of the apoptotic processes in pancreatic islet of beta-cells. To highlight specific proteins of beta cells in medical imaging ... [more ▼]

Type I and type II diabetes are diseases characterized by the activation of the apoptotic processes in pancreatic islet of beta-cells. To highlight specific proteins of beta cells in medical imaging (positron emission tomography or PET), the development of antibodies directed against membrane markers of the beta cells is undertaken. These membrane markers have to be accessible to antibodies and should be potential therapeutic targets. In order to isolate membrane proteins of beta cells, preliminary tests were conducted on MCF-7 / BOS cell line, immortal and easier to cultivate. The goal of this work is to obtain a pure membrane fraction to facilitate the analysis of the sample. To isolate transmembrane proteins, we compared two methods. The first one used a differential centrifugation to isolate membrane proteins. The second method labelled accessible extracellular domains at the surface of MCF-7 cells with biotin prior to differential centrifugation. The labelling technique used can provide 50% of membrane proteins. This second method will be used to isolate membrane proteins of pancreatic beta cells. [less ▲]

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