References of "Crommen, Jacques"
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See detailDéveloppement de méthodes de quantification en milieu complexe par chromatographie liquide microfluidique couplée à la spectrometrie de masse
Houbart, Virginie ULg; Rozet, Eric ULg; Crommen, Jacques ULg et al

Conference (2013, June)

L’hepcidine est un biomarqueur peptidique dont l’intérêt tant comme outil de diagnostic que de suivi de pathologies est de plus en plus solidement établi. Il existe donc une demande forte d’outils ... [more ▼]

L’hepcidine est un biomarqueur peptidique dont l’intérêt tant comme outil de diagnostic que de suivi de pathologies est de plus en plus solidement établi. Il existe donc une demande forte d’outils sensibles et robustes afin de la doser au sein de milieux biologiques tels que le plasma ou le sérum. Une méthode analytique a été développée à l’aide d’un système chromatographique miniaturisé (nanoLC-chip) couplé à un spectromètre de masse permettant d’assurer un dosage de l’hepcidine à la fois sensible et fiable. Lors du développement de cette méthode, il a été constaté que la composition de l’échantillon avait une influence majeure sur la réponse analytique. Or, l’utilisation de systèmes chromatographiques miniaturisés implique souvent l’injection de volumes proportionnellement très importants par rapport aux dimensions du système, ce qui amplifie encore l’impact de sa composition. C’est pourquoi il est capital d’avoir une bonne compréhension des phénomènes qui ont lieu entre l’injection de l’échantillon dans le système chromatographique et la détection par spectrométrie de masse, et particulièrement lors du développement de méthodes analytiques quantitatives. Dans cette étude, nous avons utilisé la planification expérimentale afin de mieux comprendre le comportement chromatographique des peptides, ainsi que les facteurs qui influencent la sensibilité de la méthode développée. Un mélange de peptides a été sélectionné, varié tant du point de vue du poids moléculaire que du point isoélectrique et de l’hydropathie. Un plan de criblage a permis de délimiter le domaine expérimental ainsi que les facteurs significatifs parmi la composition de la phase mobile (proportion et nature de l’agent de paire d’ions) et de l’échantillon en lui-même (nature de l’agent de paire d’ions et proportion de solvant organique). Ensuite, un plan d’expériences factoriel complet a été mis en œuvre afin d’observer plus finement le rôle de chaque facteur ainsi que les interactions éventuelles qui les lient. Certains facteurs ont montré un effet très marqué tant sur l’intensité de la réponse que sur la rétention. Entre autres, la composition de l’échantillon, facteur parfois négligé lors du développement de méthodes, a démontré son importance capitale, en particulier sur les phénomènes de rétention des peptides. Les données obtenues ont également permis de dégager des conditions optimales d’analyse en termes de rétention et de sensibilité. Enfin, une analyse en composantes principales a également été réalisée sur le grand nombre de données récoltées dans le but de mettre en évidence d’éventuels propriétés physicochimiques des peptides qui pourraient avoir un impact significatif sur les réponses étudiées. [less ▲]

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See detailFalsification des médicaments: mythe ou réalité ?
Marini Djang'Eing'A, Roland ULg; Fillet, Marianne ULg; Vancauwenberghe, Roy et al

Conference (2013, April 24)

La santé publique est de nos jours minée par la problématique des médicaments falsifiés ou de qualité inférieure, avec plusieurs conséquences sanitaires, économiques voire professionnelles. On estime à 7 ... [more ▼]

La santé publique est de nos jours minée par la problématique des médicaments falsifiés ou de qualité inférieure, avec plusieurs conséquences sanitaires, économiques voire professionnelles. On estime à 7% la part du marché pharmaceutique mondial que représenterait ce fléau; l’Afrique, l’Asie et de nombreux pays d'Amérique latine étant les régions les plus touchées avec plus de 30% de médicaments falsifiés. D’après l'OMS, plus de 50% des médicaments achetés à partir des sites internet illégaux sont contrefaits, annihilant très fortement les chances de succès thérapeutique. Ces médicaments viennent dans la plupart des cas des pays asiatiques et de l’Eurasie. Le trafic de faux médicaments est un crime contre l'humanité qui représente environ 50 milliards de dollars par an (10-15 % de plus que le marché de la drogue). Au travers de deux leçons, la situation de la falsification des médicaments sera présentée au grand public dans le but de le sensibiliser à ce fléau. La première leçon présentera la situation en Europe avec un accent sur la Belgique. La problématique du droit à la propriété intellectuelle et de l’encadrement législatif sera abordée, ainsi que la falsification des médicaments modernes et des phytomédicaments, ces derniers étant utilisés par plus de 40% de la population en Europe et aux Etats-Unis. Dans la seconde leçon sera abordée la situation vécue en Afrique. L’approvisionnement en médicaments de qualité par le partage de l’information sera présenté ainsi que les moyens analytiques à la disposition de ce continent pour combattre ce fléau. Des membres du Département de Pharmacie de l’Université de Liège, de l’Agence Fédérale des Médicaments et des Produits de Santé ainsi que du programme QUAMED (Quality Medicines for All) feront partager leur expérience sur cette question d’une brûlante actualité.  [less ▲]

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See detailUnusual Amino Acids and Monofluoroacetate from Dichapetalum michelsonii (Umutambasha), a Toxic Plant from Rwanda
Esters, Virginie ULg; Karangwa, Charles; Tits, Monique ULg et al

in Planta Medica (2013), 79

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly ... [more ▼]

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly identified as Dichapetalum michelsonii Hauman. Conclusive evidence for a monofluoroacetate presence came from its isolation from the freeze-dried extract of stem bark. Three free unusual amino acids, named N-methyl-α-alanine, N-methyl-β-alanine, and 2,7-diaminooctan-1,8-dioic acid, described for the first time in a plant, and known trigonelline were also isolated from the stem bark of D. michelsonii. Structure elucidations were mainly achieved by spectroscopic methods (1H-NMR, 2D-NMR, MS) and by comparison with authentic references. These unusual amino acids were detected by a fast, reliable TLC analysis in all our batches of Umutambasha, suggesting that they could be used for identification purposes in case of human or livestock intoxications. Finally, EEG recordings and behavioural observations performed in mice suggested that the convulsive patterns produced by Umutambasha are the consequence of monofluoroacetate presence in D. michelsonii. [less ▲]

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See detailHigh inorganic triphosphatase activities in bacteria and mammalian cells: Identification of the enzymes involved.
Kohn, Grégory ULg; Delvaux, David ULg; Lakaye, Bernard ULg et al

in PLoS ONE (2012), 7(9), 43879

Background: We recently characterized a specific inorganic triphosphatase (PPPase) from Nitrosomonas europaea. This enzyme belongs to the CYTH superfamily of proteins. Many bacterial members of this ... [more ▼]

Background: We recently characterized a specific inorganic triphosphatase (PPPase) from Nitrosomonas europaea. This enzyme belongs to the CYTH superfamily of proteins. Many bacterial members of this family are annotated as predicted adenylate cyclases, because one of the founding members is CyaB adenylate cyclase from A. hydrophila. The aim of the present study is to determine whether other members of the CYTH protein family also have a PPPase activity, if there are PPPase activities in animal tissues and what enzymes are responsible for these activities. Methodology/Principal Findings: Recombinant enzymes were expressed and purified as GST- or His-tagged fusion proteins and the enzyme activities were determined by measuring the release of inorganic phosphate. We show that the hitherto uncharacterized E. coli CYTH protein ygiF is a specific PPPase, but it contributes only marginally to the total PPPase activity in this organism, where the main enzyme responsible for hydrolysis of inorganic triphosphate (PPPi) is inorganic pyrophosphatase. We further show that CyaB hydrolyzes PPPi but this activity is low compared to its adenylate cyclase activity. Finally we demonstrate a high PPPase activity in mammalian and quail tissue, particularly in the brain. We show that this activity is mainly due to Prune, an exopolyphosphatase overexpressed in metastatic tumors where it promotes cell motility. Conclusions and General Significance: We show for the first time that PPPase activities are widespread in bacteria and animals. We identified the enzymes responsible for these activities but we were unable to detect significant amounts of PPPi in E. coli or brain extracts using ion chromatography and capillary electrophoresis. The role of these enzymes may be to hydrolyze PPPi, which could be cytotoxic because of its high affinity for Ca2+, thereby interfering with Ca2+ signaling. [less ▲]

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See detailDevelopment of a generic micellar electrokinetic chromatography method for the separation of 15 antimalarial drugs as a tool to detect medicine counterfeiting
Lamalle, Caroline ULg; Marini Djang'Eing'A, Roland ULg; Debrus, Benjamin ULg et al

in Electrophoresis (2012), 33

Since antimalarial drugs counterfeiting is dramatically present on the African market, the development of simple analytical methods for their quality control is of great importance. This work consists in ... [more ▼]

Since antimalarial drugs counterfeiting is dramatically present on the African market, the development of simple analytical methods for their quality control is of great importance. This work consists in the CE analysis of 15 antimalarials (artesunate, artemether, amodiaquine, chloroquine, piperaquine, primaquine, quinine, cinchonine, mefloquine, halofantrine, sulfadoxine, sulfalen, atovaquone, proguanil, and pyrimethamine). Since all these molecules cannot be ionized at the same pH, MEKC was preferred because it also allows separation of neutral compounds. Preliminary experiments were first carried out to select the most crucial factors affecting the antimalarials separation. Several conditions were tested and four parameters as well as their investigation domain were chosen: pH (5–10), SDS concentration (20–90 mM), ACN proportion (10–40%), and temperature (20–35°C). Then, the experimental design methodology was used and a central composite design was selected. Mathematical modeling of the migration times allowed the prediction of optimal conditions (29°C, pH 6.6, 29 mM SDS, 36% ACN) regarding analyte separation. The prediction at this optimum was verified experimentally and led to the separation of 13 compounds within 8 min. Finally, the method was successfully applied to the quality control of African antimalarial medicines for their qualitative and quantitative content. [less ▲]

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See detailOptimization of the liquid chromatography enantioseparation of chiral acidic compounds using cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector and polar organic mobile phases.
Dossou, K. S. S.; Farcas, Elena ULg; Servais, Anne-Catherine ULg et al

in Journal of Chromatography. A (2012), 1234

The LC enantioseparation of chiral acidic and zwitterionic drugs selected as model compounds was optimized using chlorine containing cellulose based chiral stationary phases and polar organic mobile ... [more ▼]

The LC enantioseparation of chiral acidic and zwitterionic drugs selected as model compounds was optimized using chlorine containing cellulose based chiral stationary phases and polar organic mobile phases. The main solvent of the mobile phase was acetonitrile, the temperature was settled at 25 degrees C and a stationary phase with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector (3-Cl-4-Me-PC) was selected. In the screening step, the nature and concentration of both acidic and basic additives were found to have a significant effect on retention, selectivity and resolution. Acetic acid (AcA) was selected as acidic additive for the optimization step since it could lead to the enantioseparation of more acidic compounds than trifluoroacetic acid (TFA) and formic acid (FA), while among the three basic additives tested, diethylamine (DEA) most often gave better results with respect to enantioresolution and selectivity than butylamine (BuA) and triethylamine (TEA). The optimization was performed using a central composite face-centered design with two factors, namely the concentration of acetic acid (0.1-0.3%) and the concentration of DEA (0.01-0.1%) in the mobile phase. On the basis of the results obtained in the screening and optimization steps, a strategy for the rapid development of methods for the enantioseparation of acidic or neutral compounds was proposed. [less ▲]

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See detailCombination of capillary electrophoresis, molecular modelling and nuclear magnetic resonance to study the interaction mechanisms between single-isomer anionic cyclodextrin derivatives and basic drug enantiomers in a methanolic background electrolyte.
Servais, Anne-Catherine ULg; Rousseau, Anne; Dive, Georges ULg et al

in Journal of Chromatography. A (2012), 1232

In order to improve our knowledge of the mechanisms of enantiomer recognition pattern in nonaqueous systems, an approach combining nonaqueous CE (NACE), molecular modelling and NMR was undertaken ... [more ▼]

In order to improve our knowledge of the mechanisms of enantiomer recognition pattern in nonaqueous systems, an approach combining nonaqueous CE (NACE), molecular modelling and NMR was undertaken. Bupivacaine and propranolol were selected as model compounds and their interactions with two single-isomer highly charged beta-CD derivatives, namely heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD (HDAS-beta-CD), were studied. The CD-bupivacaine complexes were evaluated by 2-D Rotating-frame Overhauser Effect SpectroscopY (ROESY) experiments. From these experiments, it can be assumed that inclusion complexes are not formed, whatever the CD derivative used. Molecular modelling was performed at the RHF/MINI-1 or B3LYP/6-31G(d) level. External as well as inclusion type complexes with the alkyl chain of propranolol into both CD cavities were located. Interaction energies calculated for bupivacaine and propranolol correlated with the enantiomer migration order observed in the NACE experiments using both anionic CD derivatives. The interaction of propranolol with HDMS-beta-CD or HDAS-beta-CD gives rise to a family of external and inclusion complexes in which some are more probably obtained. [less ▲]

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See detailComparative enantioseparation of talinolol in aqueous and non-aqueous capillary electrophoresis and study of related selector-selectand interactions by nuclear magnetic resonance spectroscopy.
Chankvetadze, Lali; Servais, Anne-Catherine ULg; Fillet, Marianne ULg et al

in Journal of Chromatography. A (2012)

The enantiomers of the chiral beta-blocker drug talinolol were separated with two single component sulfated beta-cyclodextrin (CD) derivatives, namely heptakis (2,3-di-O-methyl-6-sulfo)-beta-CD) (HDMS ... [more ▼]

The enantiomers of the chiral beta-blocker drug talinolol were separated with two single component sulfated beta-cyclodextrin (CD) derivatives, namely heptakis (2,3-di-O-methyl-6-sulfo)-beta-CD) (HDMS-beta-CD) and heptakis (2,3-di-O-acetyl-6-sulfo)-beta-CD) (HDAS-beta-CD), in aqueous and non-aqueous capillary electrophoresis (CE). The enantiomer affinity pattern of talinolol toward these two CDs was opposite in both aqueous and non-aqueous CE. However, the enantiomer affinity pattern for a given CD derivative did not change when aqueous buffer was replaced with non-aqueous background electrolyte. The structures of the analyte-selector complexes in both, aqueous and non-aqueous electrolytes were studied using rotating frame nuclear Overhauser effect (ROESY) NMR spectroscopy. Inclusion complex formation between the enantiomers of talinolol and HDAS-beta-CD was confirmed in aqueous buffer, while the complex between the enantiomers of talinolol and HDMS-beta-CD was of the external type. The complex of the talinolol enantiomers with HDAS-beta-CD in non-aqueous electrolyte was also of the external type. In spite of external complex formation excellent separation of the enantiomers was observed in non-aqueous CE. [less ▲]

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See detailChemo- and enantio-selective method for the analysis of amino acids by capillary electrophoresis with in-capillary derivatization.
Fradi, Ines ULg; Servais, Anne-Catherine ULg; Lamalle, Caroline ULg et al

in Journal of Chromatography. A (2012)

A novel dual chiral CE method was developed for the separation of l- and d-amino acids (AAs), using in-capillary derivatization with 9-fluoroenylmethyl chloroformate (FMOC). Firstly, using pre-column ... [more ▼]

A novel dual chiral CE method was developed for the separation of l- and d-amino acids (AAs), using in-capillary derivatization with 9-fluoroenylmethyl chloroformate (FMOC). Firstly, using pre-column derivatization, the enantioseparation of FMOC-AAs was optimized according to the nature of cyclodextrins (CD). A background electrolyte (BGE) composed of 30mM beta-CD, 30mM octakis(2,3-dihydroxy-6-O-sulfo)-gamma-CD (OS-gamma-CD), 40mM tetraborate and 15% isopropanol (IPA) was selected and led to 17 baseline resolved pairs (R(s)=1.7-5.8) and two partially resolved pairs (Lys, R(s)=0.5 and Arg, R(s)=1.2). Experimental conditions for in-capillary derivatization were then optimized. Several parameters, such as mixing voltage and time, concentration of labeling solution and the length of the spacer plug were studied. The optimal conditions for in-capillary derivatization procedure were obtained using successive hydrodynamic injections (30mbar) of AAs for 2s, borate buffer for 4s and 10mM FMOC solution for 6s, followed by a mixing at 3kV for 72s and wait time of 1min. Moreover, a particular attention was paid to improve separation chemoselectivity. The effect on stereoselectivity and chemoselectivity of different factors, such as decrease of pH and tetraborate concentration and the addition of sodium dodecyl sulfate (SDS), was investigated using the in-capillary derivatization procedure. The best separation of a standard mixture of ten AA racemates was observed using a BGE containing 30mM beta-CD, 30mM OS-gamma-CD, 25mM SDS, 40mM sodium tetraborate and 17% IPA. [less ▲]

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See detailImpurity fingerprints for the identification of counterfeit medicines - a feasibility study
Sacré, Pierre-Yves ULg; Deconinck, Eric; Daszykowski, Michal et al

Poster (2011, September)

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See detailOptimization of micro-HPLC peak focusing for the detection and quantification of low hepcidin concentrations.
Mansion, François ULg; Chiap, Patrice ULg; Houbart, Virginie ULg et al

in Journal of Separation Science (2011), 34(15), 1820-1827

Micro-high-performance liquid chromatography is a miniaturized, economic and ecological chromatographic system allowing the use of reduced size chromatographic columns. Coupled with electrospray ... [more ▼]

Micro-high-performance liquid chromatography is a miniaturized, economic and ecological chromatographic system allowing the use of reduced size chromatographic columns. Coupled with electrospray ionization tandem mass spectrometry, this technique can be used to detect and quantify low concentrations of peptides. In this study, hepcidin was used as the model compound and analysed using octadecylsilica stationary phase by means of a gradient elution mode at a flow rate of 4 muL/min. Several parameters were studied to optimize peak focusing. Using the methodology of experimental design, the mobile-phase gradient conditions and the sample composition were optimized in order to maximize the sensitivity and minimize retention time. Stability of the target peptide in solution was also demonstrated. [less ▲]

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See detailImpurity fingerprints for the identification of counterfeit medicines - a feasibility study
Sacré, Pierre-Yves ULg; deconinck, Eric; Daszykowski, Michal et al

Poster (2011, June 22)

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