Dérivés ambiphiles : chimie de coordination d'un phosphine-alane, synthèse et réactivité de phosphine-boréniums

Ce travail porte sur la chimie des dérivés ambiphiles combinant une base et un acide de Lewis de type PE (E = B, Al). Le premier chapitre aborde l'étude d'adduits phosphine-boranes et phosphine-boréniums dans lesquels le phosphore et le bore sont en positions peri d'un noyau naphthalène. Dans une première partie, l'influence du squelette carboné ainsi que des substituants portés par le bore sur l'interaction donneur-accepteur PB au sein d'une famille de phosphine-boranes a été étudiée par des méthodes expérimentales et théoriques. Dans une deuxième partie, ce système a été étendu à la préparation de boréniums stabilisés intramoléculairement par la phosphine. L'acidité de ces espèces cationiques du bore a été estimée par différentes méthodes expérimentales et leur réactivité vis-à-vis de petites molécules a été étudiée. Le deuxième chapitre porte sur l'étude en coordination d'un ligand monophosphine-alane à espaceur Csp2 vis-à-vis des métaux chlorures des groupes 9 à 11. L'influence de la géométrie du fragment métallique et de la nature des co-ligands sur le mode de coordination du ligand ambiphile ont été étudiées. Une attention particulière a été portée sur la chimie de coordination à l'or(I) qui a permis d'accéder à un complexe actif en cycloisomérisation catalytique. Le troisième chapitre explore plus avant la chimie de coordination du ligand monophosphine-alane et se concentre sur le comportement de type Z d'un tel ligand. La capacité de l'aluminium à accepter un transfert de densité électronique de la part de l'or(I) et du platine(0) a été étudiée par des méthodes expérimentales et théoriques. Dans le cas des complexes d'or, la nature du co-ligand a été variée et son influence sur la force de l'interaction a été étudiée. Finalement, le complexe de platine(0) a fait l'objet d'une étude en réactivité vis-à-vis du dihydrogène.This work deals with the chemistry of ambiphilic derivatives that combine a Lewis base and a Lewis acid of general formula PE (E = B, Al). The first chapter deals with the study of phosphine-borane and phosphine-borenium adducts in peri position on a naphthalene backbone. First, the influence of the naphthyl backbone and the substituents at boron on the PB donor-acceptor interaction was studied with different analytical methods. This system was then applied to the prepration of boreniums stabilized intramolecularly by the phosphorus. The Lewis acidity as well as the reactivity of such species toward small molecules were studied. The second chapter focuses on the coordination chemistry of a phosphine-alane ambiphilic ligand containing a Csp2 linker toward M-Cl bonds in transition metal fragments of groups 9 to 11. The gold chemistry has been studied particularly in detail as well as the capability of the resulting complexes to promote cycloisomerisation processes catalytically. The third chapter further explores the coordination chemistry of the phosphine-alane ligand and focuses on its ability to behave as a Z-type ligand. The propensity of the aluminum atom to accept electron density from the isoelectronic gold(I) and platinum(0) has been assessed by experimental and computational means. The influence of the organic co-ligand on the strength of the interaction was also investigated. Finally, the reactivity of the platinum complex toward dihydrogen has been studied

Etude de la compression transversale du lamellé-collé

Depuis que la méthode d'essais pour la résistance en compression perpendiculaire a été modifiée, les valeurs de résistance pour les bois résineux selon la norme EN 338 ont été sensiblement réduites. De ce fait, un changement de l'Eurocode V était nécessaire pour assurer un niveau de résistance équivalent en compression perpendiculaire au fil. Des résultats expérimentaux sur des éprouvettes de laboratoires sont présentés ici. De ces essais nous pouvons conclure que le modèle de l'Eurocode V surestime la résistance perpendiculaire au fil. Un modèle non-linéaire par les éléments finis a été effectué et a prouvé que la résistance en compression transversale dépend des caractéristiques mécaniques du bois, de ses dimensions et des conditions de chargement

Effect of Bacillus subtilis Strains on Intestinal Barrier Function and Inflammatory Response

Strong tight junctions and curtailed inflammatory responses under stressful conditions are key for optimal digestive health. Bacillus-based probiotics are increasingly being used to maintain broilers' health, but their mode of action is often not well-defined. In the present study we used Caco-2 cells as a model for intestinal epithelia and assessed the effect of three Bacillus-based probiotics on intestinal barrier function and intestinal inflammation. Experimental results showed that one of the three tested strains, Bs 29784, significantly reinforced intestinal barrier integrity under basal conditions through an up-regulation of the expression of tight junction's proteins, whereas the others had no or detrimental effects. When Caco-2 cells were pre-treated with Bacillus subtilis strains, the subsequent IL-8 release to various pro-inflammatory signals (IL-1β, deoxynivalenol, or flagellin) was blunted compared to cells that had not been pretreated, but to a different extent depending on the strain of Bacillus used. Bs 29784, was able to significantly decrease IL-8 production in all stressed conditions tested. Mechanistically, Bs 29784 appeared to limit nuclear translocation of NF-κB during IL-1β exposure by preventing IκB degradation. The effects of Bs 29784 were observed independently with supernatant and cells but in a lesser extent than with the combination, indicating that they can thus likely be attributed to both secreted metabolites and cell-associated compounds. Moreover, under inflammatory conditions, Bs 29784 significantly reduced the upregulation of iNOS protein levels further underlining its intestinal anti-inflammatory potential. Our data show that Bacillus-based probiotics may indeed improve digestive health by strengthening intestinal barrier and limiting inflammatory responses and that these properties are strain-dependent

Meta-analysis of SHANK Mutations in Autism Spectrum Disorders: A Gradient of Severity in Cognitive Impairments.

International audienceSHANK genes code for scaffold proteins located at the post-synaptic density of glutamatergic synapses. In neurons, SHANK2 and SHANK3 have a positive effect on the induction and maturation of dendritic spines, whereas SHANK1 induces the enlargement of spine heads. Mutations in SHANK genes have been associated with autism spectrum disorders (ASD), but their prevalence and clinical relevance remain to be determined. Here, we performed a new screen and a meta-analysis of SHANK copy-number and coding-sequence variants in ASD. Copy-number variants were analyzed in 5,657 patients and 19,163 controls, coding-sequence variants were ascertained in 760 to 2,147 patients and 492 to 1,090 controls (depending on the gene), and, individuals carrying de novo or truncating SHANK mutations underwent an extensive clinical investigation. Copy-number variants and truncating mutations in SHANK genes were present in ∼1% of patients with ASD: mutations in SHANK1 were rare (0.04%) and present in males with normal IQ and autism; mutations in SHANK2 were present in 0.17% of patients with ASD and mild intellectual disability; mutations in SHANK3 were present in 0.69% of patients with ASD and up to 2.12% of the cases with moderate to profound intellectual disability. In summary, mutations of the SHANK genes were detected in the whole spectrum of autism with a gradient of severity in cognitive impairment. Given the rare frequency of SHANK1 and SHANK2 deleterious mutations, the clinical relevance of these genes remains to be ascertained. In contrast, the frequency and the penetrance of SHANK3 mutations in individuals with ASD and intellectual disability-more than 1 in 50-warrant its consideration for mutation screening in clinical practice

A common statement on anthropogenic hybridization of the European wildcat (Felis silvestris)

Preserving natural genetic diversity and ecological function of wild species is a central goal in conservation biology. As such, anthropogenic hybridization is considered a threat to wild populations, as it can lead to changes in the genetic makeup of wild species and even to the extinction of wild genomes. In European wildcats, the genetic and ecological impacts of gene flow from domestic cats are mostly unknown at the species scale. However, in small and isolated populations, it is known to include genetic swamping of wild genomes. In this context, it is crucial to better understand the dynamics of hybridization across the species range, to inform and implement management measures that maintain the genetic diversity and integrity of the European wildcat. In the present paper, we aim to provide an overview of the current scientific understanding of anthropogenic hybridization in European wildcats, to clarify important aspects regarding the evaluation of hybridization given the available methodologies, and to propose guidelines for management and research priorities

The Chemistry of Multibonded Organoboron Compounds

International audienceMultiply bonded boron species are fascinating objects of study addressing concerns about the chemical bonding. Although mostly exemplified with light p‐block elements, the use of Group 6–10 transition metals as models to more clearly understand and rationalize the bonding in this family of compounds has also proved successful. In this prospect, the interplay between experiment and theory pushes forward the frontiers of the analysis based on the metric parameters, and it clearly appears that the notion of doubly or triply bonded boron in such species must be qualified. The bond orders are more often partial involving more or less polarized bonds responsible for the chemical reactivity. These features are developed in this chapter starting with the nearest neighbors of boron and finishing with the case of transition metals

HMPA-Free Synthesis of TMS-Substituted Alkynes

International audienceTMS-substituted alkynes are versatile building blocks in organic synthesis. Traditional synthesis involves alkyne deprotonation and the reaction with TMSCl. Recently, TMS-acetylene has become an increasingly inexpensive bulk chemical, offering an attractive alternative to accessing TMS-substituted alkynes, especially when the alkyne is expensive or not commercially available. However, this route has been established with carcinogenic HMPA as a cosolvent. In this work, we disclose optimized conditions utilizing DMPU as a substitute for HMPA

A computational study of the interplay of steric and electronic effects in the stabilization of 1,3-(diamino)oxyallyls

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Stable dicationic dioxoliums and fate of their dioxolyl radicals

International audienceStable dicationic dioxolium salts featuring an ancillary vinamidinium pattern were synthesized and characterized. Although highly reactive, they were found otherwise easy to handle under inert atmosphere. This offered the opportunity to generate and study the fate of unknown 1,3-dioxolyl radicals. Depending on substituents, reduction led to the formation of dimers of either dioxolyl or cyclohexadienyl radicals, stemming from a process that is related to the Surzur-Tanner rearrangement. The cyclohexadienyl radical could be characterized in the case of a tri(tert-butyl)phenyl group, which prevents dimerization processes

Synthesis of Photochromic Phosphines by Pd-Catalyzed Annulation Reaction of Alkynes bearing Phosphinyl Substituent with a Silacyclopropene

International audienceThe synthesis of phosphines with light controlled basicity is presented in this study. A methodological approach for the preparation of these unconventional photochromic phosphines based on a dithienylethene organic moiety is reported. It relies on the palladium-catalyzed annulation of alkynyl phosphines in the presence of a 2,3-Dithienylsilacyclopropene. Accordingly, a diphenyphosphino moiety is connected to the organic photochrome thanks to different linkers. Their influence on the photochromism and on the phosphinyl group basicity is studied and evaluated based on experimental an NMR descriptor as well as DFT calculations