Étude des processus d'interaction laser de fibres naturelles par spectrométrie de masse : application à la validation expérimentale des critères de différenciation du cheveu

Not availableLe cheveu suscite l'intérêt de nombreux scientifiques, car il se comporte comme une bande enregistrant l'imprégnation de l'organisme par divers composes : drogues, médicaments, éléments minéraux... Cependant, comme le montre notre travail bibliographique, l'interprétation des résultats obtenus nécessite une connaissance approfondie du cheveu et des interactions avec son environnement. Les différentes techniques d'analyse du cheveu sont généralement longues à mettre en ?uvre et consommatrices en échantillon. C'est pourquoi, nous avons étudié dans ce mémoire une méthode de caractérisation des cheveux à l'aide des microsondes laser couplées à la spectrométrie de masse : LAMMA et FTMS. En effet, elles permettent une analyse rapide sur seulement quelques millimètres de tige pilaire. Les ions formés lors de l'ablation laser d'un cheveu témoin (irradiance = 5 10 [à la puissance]8 W/cm2, longueur d'onde = 266 nm) ont été caractérisés afin de faciliter l'interprétation des spectres de masse. Pour cela, nous avons travaillé sur des cheveux dopés en éléments minéraux ou lavée pour observer la matrice organique et, effectué des calibrations en haute résolution. Ces analyses montrent que l'empreinte « minérale » est due à l'agrégation des cations minéraux avec les anions organiques majoritaires (CN- et CNO-), tandis que l'empreinte organique est principalement liée à la fragmentation de la chaine polypeptidique des kératines. Enfin, nous exposons le protocole d'expertise discriminante des cheveux, tel qu'il a été développé dans notre laboratoire. Dans ce contexte, nous effectuons des analyses morphologiques et par spectrométrie de masse LAMMA. Nous augmentons ainsi le nombre de critères d'analyses, pour qu'une comparaison deux à deux des résultats de chaque cheveu, puisse exclure ou non l'appartenance à une seule et même personn

Next Challenges for the Comprehensive Molecular Characterization of Complex Organic Mixtures in the Field of Sustainable Energy

The conversion of lignocellulosic biomass by pyrolysis or hydrothermal liquefaction gives access to a wide variety of molecules that can be used as fuel or as building blocks in the chemical industry. For such purposes, it is necessary to obtain their detailed chemical composition to adapt the conversion process, including the upgrading steps. Petroleomics has emerged as an integral approach to cover a missing link in the investigation bio-oils and linked products. It relies on ultra-high-resolution mass spectrometry to attempt to unravel the contribution of many compounds in complex samples by a non-targeted approach. The most recent developments in petroleomics partially alter the discriminating nature of the non-targeted analyses. However, a peak referring to one chemical formula possibly hides a forest of isomeric compounds, which may present a large chemical diversity concerning the nature of the chemical functions. This identification of chemical functions is essential in the context of the upgrading of bio-oils. The latest developments dedicated to this analytical challenge will be reviewed and discussed, particularly by integrating ion source features and incorporating new steps in the analytical workflow. The representativeness of the data obtained by the petroleomic approach is still an important issue

Structural Organizations of Qβ and MS2 Phages Affect Capsid Protein Modifications by Oxidants Hypochlorous Acid and Peroxynitrite

International audiencePathogenic enteric viruses and bacteriophages such as Qβ and MS2 are transmitted through the fecal-oral route. However, oxidants such as peroxynitrite (ONOOH) and hypochlorous acid (HClO) can prevent new infection by inactivating infectious viruses. Their virucidal effect is well recognized, and yet predicting the effects of oxidants on viruses is currently impossible because the detailed mechanisms of viral inactivation remain unclear. Our data show that ONOOH and HClO cross-linked the capsid proteins and RNA genomes of Qβ and MS2 phages. Consistently, the capsids appeared intact by transmission electron microscopy (TEM) even when 99% of the phages were inactivated by oxidation. Moreover, a precise molecular study of the capsid proteins shows that ONOOH and HClO preferentially targeted capsid protein regions containing the oxidant-sensitive amino acid C, Y, or W. Interestingly, the interaction of these amino acids was a crucial parameter defining whether they would be modified by the addition of O, Cl, or NO2 or whether it induced the loss of the protein region detected by mass spectrometry, together suggesting potential sites for cross-link formation. Together, these data show that HClO and ONOOH consistently target oxidant-sensitive amino acids regardless of the structural organization of Qβ and MS2, even though the phenotypes change as a function of the interaction with adjacent proteins/RNA. These data also indicate a potential novel mechanism of viral inactivation in which cross-linking may impair infectivity

Study of the Size Distribution of Sulfur, Vanadium, and Nickel Compounds in Four Crude Oils and Their Distillation Cuts by Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry

The size distribution of sulfur, vanadium, and nickel was determined for four crude oils and their distillation cuts using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show a trimodal distribution of vanadium and nickel compounds in the crude oils, the atmospheric residues, and the vacuum residues and, for sulfur compounds, either a mono- or bimodal distribution depending upon the distillation cut considered. A correlation exists between the sulfur fraction retention times and the temperature cuts of the distillation for a temperature below 560 °C and also between the viscosity of the crude oils and the proportion of trapped sulfur compounds in a higher boiling temperature fraction. The thermic treatment applied for the distillation increases the aggregation of low- and medium-molecular-weight compounds of vanadium and nickel into higher molecular weight aggregates between the crude oil on the one hand and the atmospheric residue and vacuum residue on the other hand, especially when the crude oil has a high total sulfur content

Increased synthesis of a new oleanane-type saponin in hairy roots of marigold (<i>Calendula officinalis</i>) after treatment with jasmonic acid

<p>Native plant of marigold (<i>Calendula officinalis</i> L.) synthesizes oleanolic acid saponins classified as glucosides or glucuronides according to the first residue in sugar chain bound to C-3 hydroxyl group. Hairy root culture, obtained by transformation with <i>Agrobacterium rhizogenes</i> strain 15834, exhibit a potent ability of synthesis of oleanolic acid glycosides. The HPLC profile of saponin fraction obtained from <i>C</i>. <i>officinalis</i> hairy roots treated with plant stress hormone, jasmonic acid, showed the 10-times increase of the content of one particular compound, determined by NMR and MALDI TOF as a new bisdesmoside saponin, 3-<i>O</i>-β-d-glucuronopyranosyl-28-<i>O</i>-β-d-galactopyranosyl-oleanolic acid. Such a diglycoside does not occur in native <i>C. officinalis</i> plant<i>.</i> It is a glucuronide, whereas in the native plant glucuronides are mainly accumulated in flowers, while glucosides are the most abundant saponins in roots. Thus, our results revealed that the pathways of saponin biosynthesis, particularly reactions of glycosylation, are altered in <i>C. officinalis</i> hairy root culture.</p