Robustesse des approches chimiométriques pour la reconstruction de profils moléculaires

Ce papier traite des approches chimiométriques pour la reconstruction de profils moléculaires. La quantification de protéines du sang est réalisée à partir du traitement par analyse factorielle de spectrogrammes issus d'une chaîne d'analyse contenant une colonne de nano-chromatographie et un spectromètre de masse. Nous nous intéressons plus particulièrement à la comparaison de la robustesse des méthodes de régression de type Unfold-PLS, N-PLS et PARAFAC vis-à-vis du problème de décalage temporel des pics contenus dans les spectrogrammes. Les méthodes multidimensionnelles type N-PLS et PARAFAC fournissent de meilleurs résultats ce qui permet d'envisager une quantification des protéines avec une plus grande tolérance sur le recalage des pics en temps de rétention

Reconstruction bayésienne de profils moléculaires

L'étude des protéines laisse entrevoir de grands espoirs pour la médecine de demain. Cependant pour répondre à ces promesses, les méthodes actuelles doivent gagner en sensibilité, en spécificité et en robustesse. Dans cette optique, le CEA développe un laboratoire sur puce et des méthodes de traitement numérique dédiées aux analyses protéomiques par LC-MS. Nous présentons dans cet article une approche bayésienne pour la reconstruction des profils de concentrations de protéines. Dans un premier temps nous proposons un modèle pour le dispositif de mesure complet. Puis nous décrivons une méthode d'estimation des concentrations de protéines présentes, les paramètres instrumentaux étant fixés. Enfin nous estimons conjointement les concentrations et les paramètres instrumentaux

Evolution of porosity in carbide-derived carbon aerogels

Carbide-derived carbon (CDC) aerogel monoliths with very high porosity are synthesized starting from polymeric precursors. Cross-linking by platinum-catalyzed hydrosilylation of polycarbosilanes followed by supercritical drying yields preceramic aerogels. After ceramic conversion and silicon extraction in hot chlorine gas, hierarchically porous carbon materials with specific surface areas as high as 2122 m² g⁻¹ and outstanding total pore volumes close to 9 cm³ g⁻¹ are obtained. Their pore structure is controllable by the applied synthesis temperature as shown by combined nitrogen (-196 °C) and carbon dioxide (0 °C) measurements coupled with electron microscopic methods. The combination of large micropore volumes and the aerogel-type pore system leads to advanced adsorption properties due to a combination of large storage capacities and effective materials transport in comparison with purely microporous reference materials as shown by thermal response measurements

Die Spaltung von Arylether-Bindungen durch initiale Dioxygenierung: Grundlage des bakteriellen Dioxinabbaus

Bei der Untersuchung des bakteriellen Abbaus von Arylether-Modellsubstraten wie 2-Alkoxybenzoat, Carboxybiphenylether und Dibenzofuran wurde ein grundlegender Mechanismus für die Spaltung von Aryletherbindungen aufgedeckt. Demnach bewirken Dioxygenase-Enzyme unter Einführung zweier Hydroxylgruppen die Überführung von Ether- in Hemiacetalbindungen. Diese instabilen Hemiacetale reagieren unter Rearomatisierung zu aliphatischen Alkoholen und/oder Phenolverbindungen ab. Enzyme dieses Typs sind auch in der Lage, Dioxine zu spalten.During investigations on the bacterial metabolism of aryl ether model compounds like 2-alkoxybenzoates, carboxybiphenylethers and dibenzofuran, a basic mechanism for cleavage of aryl ether bonds was revealed. Accordingly dioxygenase enzymes insert two hydroxyl groups into ether compounds in such a way that stable ether bonds are transformed into labile hemiacetal bonds. The hemiacetal compounds with concomitant rearomatization rearrange to aliphatic alcohols and/or phenolics. Enzymes or this highly specialized type are also able to cleave ether bonds in dioxin structures

Nanomechanics of individual aerographite tetrapods

R.A., O.L. and K.S. would like to thank the German Research Foundation (DFG) for the financial support under schemes AD 183/17-1 and SFB 986-TP-B1, respectively, and the Graphene FET Flagship. R.M. and D.E. would like to thank for financial support from Latvian Council of Science, no. 549/2012. N.M.P. is supported by the European Research Council (ERC PoC 2015 SILKENE no. 693670) and by the European Commission H2020 under the Graphene Flagship (WP14 ‘Polymer Composites’, no. 696656) and under the FET Proactive (‘Neurofibres’ no. 732344). S.S. acknowledges support from SILKENE

Degradation of haloaromatic compounds

An ever increasing number of halogenated organic compounds has been produced by industry in the last few decades. These compounds are employed as biocides, for synthetic polymers, as solvents, and as synthetic intermediates. Production figures are often incomplete, and total production has frequently to be extrapolated from estimates for individual countries. Compounds of this type as a rule are highly persistent against biodegradation and belong, as "recalcitrant" chemicals, to the class of so-called xenobiotics. This term is used to characterise chemical substances which have no or limited structural analogy to natural compounds for which degradation pathways have evolved over billions of years. Xenobiotics frequently have some common features. e.g. high octanol/water partitioning coefficients and low water solubility which makes for a high accumulation ratio in the biosphere (bioaccumulation potential). Recalcitrant compounds therefore are found accumulated in mammals, especially in fat tissue, animal milk supplies and also in human milk. Highly sophisticated analytical techniques have been developed for the detection of organochlorines at the trace and ultratrace level