Impact of pH on the Stability and the Cross-Reactivity of Ochratoxin A and Citrinin

Mycotoxins are secondary metabolites produced by several fungi contaminating crops. In several countries, the maximum permitted levels of mycotoxins are found in foodstuffs and feedstuffs. The common strategy of mycotoxin analysis involves extraction, clean-up and quantification by chromatography. In this paper, we analyzed the reasons of underestimation of ochratoxin A (OTA) content in wine, and overestimation of OTA in wheat, depending on the pH of the clean-up step and the simultaneous presence of citrinin (CIT). We demonstrated that the increase of pH by adding polyethylene glycol (PEG) to wine led to an underestimation of OTA by conversion of OTA into open ring ochratoxin A OP-OA. In comparing three methods of extraction and clean-up for the determination of OTA and CIT in wheat—(i) an inter-laboratory validated method for OTA in cereals using immunoaffinity column clean-up (IAC) and extraction by acetonitrile/water; (ii) a validated method using IAC and extraction with 1% bicarbonate Na; and (iii) an in-house validated method based on acid liquid/liquid extraction—we observed an overestimation of OTA after immunoaffinity clean-up when CIT is also present in the sample, whereas an underestimation was observed when OTA was alone. Under neutral and alkaline conditions, CIT was partially recognized by OTA antibodie

The checkpoint Saccharomyces cerevisiae Rad9 protein contains a tandem tudor domain that recognizes DNA.

International audienceDNA damage checkpoints are signal transduction pathways that are activated after genotoxic insults to protect genomic integrity. At the site of DNA damage, 'mediator' proteins are in charge of recruiting 'signal transducers' to molecules 'sensing' the damage. Budding yeast Rad9, fission yeast Crb2 and metazoan 53BP1 are presented as mediators involved in the activation of checkpoint kinases. Here we show that, despite low sequence conservation, Rad9 exhibits a tandem tudor domain structurally close to those found in human/mouse 53BP1 and fission yeast Crb2. Moreover, this region is important for the resistance of Saccharomyces cerevisiae to different genotoxic stresses. It does not mediate direct binding to a histone H3 peptide dimethylated on K79, nor to a histone H4 peptide dimethylated on lysine 20, as was demonstrated for 53BP1. However, the tandem tudor region of Rad9 directly interacts with single-stranded DNA and double-stranded DNAs of various lengths and sequences through a positively charged region absent from 53BP1 and Crb2 but present in several yeast Rad9 homologs. Our results argue that the tandem tudor domains of Rad9, Crb2 and 53BP1 mediate chromatin binding next to double-strand breaks. However, their modes of chromatin recognition are different, suggesting that the corresponding interactions are differently regulated

L' esthétique du jeu dans les Alice de Lewis Carroll

Cette thèse consiste en l analyse du jeu dans les deux œuvres littéraires majeures de Lewis Carroll, Alice s Adventures in Wonderland et Through the Looking-Glass, œuvres qui accordent la part belle au jeu, tant au niveau diégétique, narratologique que stylistique et linguistique. Il en ressort qu une tension entre liberté et règle (entre paidia, l expression impulsive d un instinct de jeu, et ludus, le besoin de créer des règles et de s y plier, pour utiliser les termes de Caillois) traverse les Alice. L étude des jeux et jouets, des macro- et micro-structures, du style et des intertextes, permet d affirmer que ces deux volumes sont résolument ludiques, car ils reposent sur une légaliberté, une liberté dans et par une légalité (Duflo). Ils jouent avec et contre les attentes, la langue et les connaissances du lecteur de sens commun. Toutefois, dans le même temps, le champ d action du lecteur virtuel est considérablement restreint : ses facultés d idéation sont orientées par l imbrication du texte et des illustrations, et sa participation à la construction du texte carrollien se borne à compléter les blancs textuels, tel que Eco les définit, c est-à-dire à faire ressurgir les déjà-dits qui ont été effacés. Les œuvres carrolliennes sont ainsi caractérisées par ce paradoxe : alors que la diégèse et l économie textuelle semblent promouvoir le jeu, le rôle du Lecteur Modèle prévu par le texte est extrêmement réduit. Cependant, il est possible pour le lecteur réel, interpellé par le texte carrollien et son Auteur, d endosser le rôle de Lecteur Imposteur, de les contre-interpeller, et de devenir, par ce processus de subjectivation, un lecteur pleinement joueur. Il s avère alors que la légaliberté permet non seulement de saisir l esthétique du jeu, mais aussi la formation des sujets (personnages, auteurs, lecteurs) à l œuvre dans les Alice.This thesis consists in an analysis of play and game(s) in Lewis Carroll s two major literary works, Alice s Adventures in Wonderland and Through the Looking-Glass, in which diegetic, narratological, stylistic and linguistic games play a significant part. It shows that a tension is at work throughout the Alice books, between freedom and rules (between paidia, the impulsive manifestation of a play instinct, and ludus, the need to invent rules and to abide by them, to state this in Caillois s terms). The study of games and toys, of the macro- and micro-structures, of the style and the intertexts reveals the playfulness of these texts, as they rely on legafreedom , freedom in, and made possible by legality (Duflo). They play with and against the reader s commonsensical expectations, language and knowledge. Yet, at the same time, the virtual reader s playing field is considerably limited: his or her faculties of ideation are directed by the interweaving of text and illustrations, and his or her participation (involvement?) in constructing the Carrollian text is restricted to filling in the textual blanks, as defined by Eco, i.e. making the already said that has been erased reappear. Carroll s works are, therefore, characterized by this paradoxical idea: while the diegesis and the textual economy seem to promote play, the role of the Model Reader as mapped out by the text is extremely circumscribed. However, the real reader, interpellated by the Carrollian text and its Author, can take on the role of the Impostor Reader, counter-interpellate them, and become, thanks to this process of subjectification, a consummate playing reader. As such, legafreedom makes it possible to understand not only the aesthetics of play, but also the formation of subjects (characters, authors, readers) in the Alice books.NANTERRE-BU PARIS10 (920502102) / SudocSudocFranceF

Nanocasting, templated syntheses and structural studies of manganese oxide nanoparticles nucleated in the pores of ordered mesoporous silicas (SBA-15)

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The effect of mating system on invasiveness: some genetic load may be advantageous when invading new environments

The role of adaptation in determining invasion success has been acknowledged recently, notably through the accumulation of case studies of rapid evolution during bioinvasions. Despite this growing body of empirical evidence, there is still a need to develop the theoretical background of invasions with adaptation.Specifically,thei mpact of mating system on the dynamics of adaptation during invasion of a new environment remains only partially understood. Here, we analyze a simulation demo-genetic model of bioinvasion accounting for partial asexuality rates. We simulate two levels of recurrent immigration from a source population at mutation–drift–selection equilibrium to a new empty environment with a different adaptive landscape (black-holesink). Adaptation relies on a quantitative trait coded explicitly by10 lociunder mutation, selection and genetic drift. Using this model, we confirm previous results on the positive effects on invasiveness of migration, mutation and similarity of local phenotypic optima. We further show how the invasion dynamics of the introduced population is affected by the rate of asexuality. Purely asexual species have lower invasion success in terms of probability and time to invasion than species with other matingsystems. Among species with mixed mating systems, the greatest invasiveness is observed for species with high asexual rates. We suggest that this pattern is due to inflated genetic variance in the source population through the Hill-Robertson effect (i.e., clonal interference). An interesting consequence is that species with the highest genetic load in their source environment have greatest invasiveness in the new environment

Investigation of Methanol Oxidation over Au/Catalysts Using Operando IR Spectroscopy: Determination of the Active Sites, Intermediate/Spectator Species, and Reaction Mechanism

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Investigation of Methanol Oxidation over Au/Catalysts Using Operando IR Spectroscopy: Determination of the Active Sites, Intermediate/Spectator Species, and Reaction Mechanism

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Un kapâla trouvé en Loire

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