Tribochimie du laminage à froid : étude par ToF-SIMS de la chimisorption sur la tôle des additifs du lubrifiant : Tribologie de la mise en forme des métaux

International audienceLa chimisorption des additifs de lubrifiant de laminage à froid sur un acier et un alliage d'aluminium est étudiée par spectrométrie de masse ToF-SIMS. L'étude préparatoire de l'adsorption des divers additifs permet de mettre en évidence leur rôle individuel, les compétitions d'adsorption, les seuils thermiques de désorption ou de décomposition. Ces résultats sont validés par des essais sur laminoir pilote = The chemisorption of cold rolling oil additives on steel and aluminium surfaces is studied with a mass spectrometry technique, ToF-SIMS. Preliminary experiments underline adsorption competition, and thermal threshold for desorption or decomposition. This results fit well with experimental cold rolling results

La rétinite ponctuée albescente (aspects cliniques, paracliniques et évolution)

La rétinite ponctuée albescente (RPA) est une forme de rétinite pigmentaire caractérisée par des ponctuations blanches au fond d'oeil et une héméralopie débutant dans la petite enfance. C'est une maladie génétique rare de transmission autosomique récessive due à des mutations dans le gène RLBP 1. Ce gène code pour la protéine CRALBP qui est un acteur clé du cycle visuel. Tout d'abord un rappel sur les connaissances actuelles sur cette pathologie a été réalisé. Les différents diagnostics différentiels ont été évoqués avec notamment une attention plus particulière sur le fundus albipunctatus (FA) dont la présentation est très proche de la RPA. De plus une étude de cas a été menée chez 6 patients atteints de FA provenant du centre national référent des affections sensorielles génétiques de Montpellier. En deuxième partie, la dégénérescence fovéale précoce dans la RPA a été étudiée chez 11 patients du centre référent. Une diminution significative de l'épaisseur rétinienne en OCT a été retrouvée au niveau du centre de la fovéa, au niveau de la fovéa, et dans l'anneau maculaire de 3 mm de diamètre dans les quatre quadrants. Cependant cette diminution au niveau de la fovéa et au centre de la fovéa est indépendante de l'âge alors qu'elle est corrélée de façon significative avec l'âge dans l'anneau maculaire de 3 et de 6 mm de diamètre. L'analyse de la mosaïque des cônes retrouve une diminution du nombre de cônes fovéaux, à part chez un sujet jeune de 13 ans. Au total, on retrouve un degré variable de mort des cônes fovéaux chez les sujets atteints de RPA même à un stade précoce. Ces données ont des implications pour des futurs traitements notamment la thérapie géniqueMONTPELLIER-BU Médecine UPM (341722108) / SudocSudocFranceF

Evaluation de l’exposition professionnelle des prothésistes ongulaires aux méthacrylates

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Kinetic study of the "living" cationic polymerization of a galactose carrying vinyl ether. MALDI-TOF MS analysis of the resulting glycopolymers

The "living" cationic polymerization of a new saccharidic monomer, namely 1,2:3,4-di-O-isopropylidene-6-O-(2-vinyloxyethyl)-D-galactopyranose (GVE) has been investigated using acetaldehyde diethyl acetal/trimethylsilyl iodide as the initiating system in the presence of ZnCl2 as co-initiator. To determine if the process is living, the conversion was followed by dilatometry or by regularly withdrawing samples and analyzing them by H-1 NMR. Fast polymerization occurred together with a nonlinear ln([M](0)/[M](t)) = f(t) plot indicating an apparent loss of active centers. Nevertheless, the H-1 NMR- and SEC-determined molecular weights proved the absence of termination and transfer reactions during the polymerization process. MALDI-TOF mass spectrometry confirmed the absence of such side reactions and indicated a parallel initiation consecutive to the presence of water traces in the trimethylsilyl. iodide solution. The nonlinear ln([M](0)/[M](t)) = f(t) plot was attributed to specific interactions between the saccharidic rings and ZnCl2 and/or the growing carbocations

Specific photoaffinity-labeling of Tyr-50 on heavy chain and of Tyr-32 on the light chain in the steroid combining site of a mouse monoclonal anti-estradiol antibody using C3-, C6-, and C7-linked 5-azido-2-nitrobenzoylamidoestradiol photoreagents

International audienceA mouse monoclonal anti-7-(O carboxymethyl)oximinoestradiol antibody 9D3, raised against the same immunogen as that employed for generating the reported anti-estradiol antibody 15H11 [Rousselot, P., et al. (1997) Biochemistry 36, 7860-7868], was found to exhibit an opposite specificity profile with a much stronger recognition of the D-ring than of the A-ring extremity of the steroid, but a similar lack of specificity for both 6- and 7-positions of the B-ring. This antibody was photoaffinity-labeled with five (5-azido-2-nitrobenzoyl)amido (ANBA) derivatives of [17 alpha-H-3]estradiol, synthesized from 3-aminoethyloxy, 3-(aniinoethylamido)carboxymethyloxy, 6 alpha- and 6 beta -amino, and 7-[O-(aminoethylamido)carboxymethyl]oximino precursors. After tryptic digestion, the radioactive peptides on L and H chains were immunopurified with the immobilized antibody 9D3, separated by reversed-phase liquid chromatography, sequenced, and characterized by mass spectrometry, including post-source decay-matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The long 3-(ANBA-ethylamido)carboxymethyl ether photoreagent was found to label TyrL-32 (on CDR L1), whereas no labeling was observed with the shorter 3-derivative, a result in agreement with a binding pocket large enough to explain the high crossreactivity with estradiol 3-conjugates. The two 6 alpha- and 6 beta -ANBA-estradiol isomers, as well as the 7-[O-(ANBA-ethylamido)carboxymethyl]oximinoestradioI photoreagent derived from the steroid hapten, labeled the same TyrL-32 residue. The 6 beta -ANBA epimer also labeled TyrH-50 (at the basis of CDR H2). These experiments indicate that TyrL-32 is freely accessible from the three C3, C6, and C7 positions, all presumed to be exposed to solvent, while TyrH-50 is probably located on the beta -face of estradiol. These results, obtained in solution, provide experimental data useful for molecular modeling of the steroid-antibody complex

An expeditious multigram-scale synthesis of lysine dendrigraft (DGL) polymers by aqueous N-carboxyanhydride polycondensation

International audienceThe synthesis and characterisation of new arborescent architectures Of poly(L-lysine), called lysine dendrigraft (DGL) polymers, are described. DGL polymers were prepared through a multiple-generation scheme (up to generation 5) in a weakly acidic aqueous medium by polycondensing N-epsilon-trifluoroacetyl-L-lysine-N-carboxyanhy-dride (Lys(Tfa)-NCA) onto the previous generation G(n-1) of DGL, which was used as a macroinitiator. The first generation employed spontaneous NCA polycondensation in water without a macroinitiator; this afforded low-molecular-weight, linear poly(L-lysine) G1 with a polymerisation degree of 8 and a polydispersity index of 1.2. The spontaneous precipitation of the growing N-epsilon-Tfa-protected polymer (GnP) ensures moderate control of the molecular weight (with unimodal distribution) and easy work-up. The subsequent alkaline removal of Tfa protecting groups afforded generation Gn of DGL as a free form (with 35-60% overall yield from NCA precursor, depending on the DGL generation) that was either used directly in the synthesis of the next generation (G(n+1)) or collected for other uses. Unprotected forms of DGL G1-G5 were characterised by size-exclusion chromatography, capillary electrophoresis and H-1 NMR spectroscopy. The latter technique allowed us to assess the branching density of DGL, the degree of which (ca. 25%) turned out to be intermediate between previously described dendritic graft poly(L-lysines) and lysine dendrimers. An optimised monomer (NCA) versus macroinitiator (DGL G(n-1)) ratio allowed Lis to obtain unimodal molecular weight distributions with polydispersity indexes ranging from 1.3 to 1.5. Together with the possibility of reaching high molecular weights (with a polymerisation degree of ca. 1000 for G5) within a few synthetic steps, this synthetic route to DGL provides an easy, cost-efficient, multigram-scale access to dendritic polylysines with various potential applications in biology and in other domains

Heat stability and degradation of thermally stable prepolymers in a controlled atmosphere: III. Thermal homopolymerization cycle of dicyanate monomers and physicochemical characterization of the crosslinked system

International audienceMonitoring the homopolymerization of cyanate monomers during heat treatment shows that triazine rings formed during the 180 degreesC step. Oligomers were composed of 1 to 15 triazine rings. Analysis of compounds formed before the gel point revealed the presence of side products containing terminal phenolic functions: the phenol-cyanate (M-0-OH) and oligomers with one or two hydroxyl functions (M-1.2,...-OH). Kinetic and mechanistic monitoring during treatment at 210 degreesC in the solid state allowed the determination of the structure of the final system and the detection and quantification of unreacted cyanate functions. Kinetic and thermal studies in the temperature range of 100 to 220 degreesC showed that the homopolymerization of hexafluorobisphenol A dicyanate starts at a lower temperature and is slower than that of bisphenol A dicyanate. Thermogravimetric data showed that residual monomers volatilized between 150 and 300 degreesC, while the degradation of crosslinked products occurred between 400 and 600 degreesC and involved two distinct steps