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Structure and properties of lead silicate glasses
No full textInternational audienceGiven their specific properties, glasses containing lead oxide have a very broad field of application. This extends from crystal glasses, enamels and glazes, to optical glasses with high refractive index, passing through glasses absorbing ionizing radiation and glasses for low-temperature welding of metals, ceramics or glasses. This chapter focuses first of all on the chemistry of lead, and more specifically on the properties and stereochemistry of the Pb ion (species under which lead is present in oxide glasses), the nature of the Pb-O chemical bond and the crystalline structure of pure PbO oxide (stereochemistry and mode of connection of the polyhedrons). Then, since the lead-based oxide glasses of interest are overwhelmingly silicate glasses, the focus is on how the Pb ions get inserted in the glassy network of silica and modify its structure, first of all in the case of the simple binary SiO2-PbO system (for which the evolution of the structure of the binary crystalline phases will also be approached depending on their PbO content compared to glasses), then in the case of more complex systems such as the ternary SiO-PbO-RO (R: alkaline) and SiO-PbO-AlO systems
Multivalent interactions of the disordered regions of XLF and XRCC4 foster robust cellular NHEJ and drive the formation of ligation-boosting condensates in vitro
No full textInternational audienceIn mammalian cells, DNA double-strand breaks are predominantly repaired by non-homologous end joining (NHEJ). During repair, the Ku70-Ku80 heterodimer (Ku), X-ray repair cross complementing 4 (XRCC4) in complex with DNA ligase 4 (X4L4) and XRCC4-like factor (XLF) form a flexible scaffold that holds the broken DNA ends together. Insights into the architectural organization of the NHEJ scaffold and its regulation by the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) were recently obtained by single-particle cryo-electron microscopy analysis. However, several regions, especially the C-terminal regions (CTRs) of the XRCC4 and XLF scaffolding proteins, have largely remained unresolved in experimental structures, which hampers the understanding of their functions. Here we used magnetic resonance techniques and biochemical assays to comprehensively characterize the interactions and dynamics of the XRCC4 and XLF CTRs at residue resolution. We show that the CTRs of XRCC4 and XLF are intrinsically disordered and form a network of multivalent heterotypic and homotypic interactions that promotes robust cellular NHEJ activity. Importantly, we demonstrate that the multivalent interactions of these CTRs lead to the formation of XLF and X4L4 condensates in vitro, which can recruit relevant effectors and critically stimulate DNA end ligation. Our work highlights the role of disordered regions in the mechanism and dynamics of NHEJ and lays the groundwork for the investigation of NHEJ protein disorder and its associated condensates inside cells with implications in cancer biology, immunology and the development of genome-editing strategies
A Versatile, Functional Group‐Tolerant, and Bench‐Stable Iron Precatalyst for Building Arene and Triazine Rings by [2+2+2] Cycloadditions
No full textInternational audienceAbstract We report an efficient iron‐catalyzed cycloaddition procedure leading to the construction of (hetero)aromatic rings by alkyne [2+2+2] cycloisomerization. This method relies on the use of an air‐stable ( N , N )Fe(II) precursor easily prepared from a commercially available ligand derived from 1,10‐phenanthroline, reduced in situ into a catalytically active non‐innocent ( N , N ⋅ − ) 2 Fe(II) species. This system displays a large scope application, operates under mild conditions and at low catalytic charges (25 cycloadducts formed, up to 1.5 mol% catalyst). Moreover, this method also enables access to 29 cycloadducts by cross‐cycloisomerization between 1,6‐ or 1,7‐diynes and alkynes in near‐equimolar conditions. 1,3,5‐Triazines can also be prepared with this procedure starting from the corresponding cyanamides. Scale‐up reactions and post‐functionalization of several cycloadducts also show that this [2+2+2] cycloaddition can be used in multistep sequences
Développements méthodologiques pour la simulation de l'adsorption des gaz simples dans les matériaux nanoporeux
No full textGas separation and purification is a crucial industrial issue, which is technologically addressed by fine-tuning the gas specificity of adsorbents. However, the experimental development of new adsorbents is a costly process, hence the need for preliminary computer simulations to test only the most promising candidates.These simulation techniques remain costly in themselves. In order to improve their performance, this thesis proposes and explores new methodological options across the different steps of the simulation. In particular, new algorithms and tools are presented to tackle the identification of the topology of crystalline materials, the location of cations in zeolitic frameworks, and the adsorption capacity of a gas in porous materials. The simulation results are then used to feed a database, which allows using a statistical approach to provide coarse but ultra-fast predictions of adsorption isotherms, paving the way for high-performance screening stratgies of nanoporous materials.La séparation et purification des gaz est un enjeu industriel majeur, qui nécessite l'emploi d'adsorbants spécifiques à certaines espèces moléculaires. Afin d'accélérer le développements de nouveaux adsorbants d'intérêt, il peut être utile d'avoir recours à des méthodes de simulations numériques permettant d'identifier des candidats potentiels.Ces méthodes restent cependant coûteuses en temps et en énergie. Pour tenter d'améliorer leurs performances, cette thèse propose et explore plusieurs avancées méthodologiques sur les différentes étapes de la simulation. En particulier, de nouveaux algorithmes et outils sont présentés pour l'identification de la topologie des matériaux cristallins, pour localiser les cations dans les charpentes zéolitiques, et pour déterminer la capacité d'adsorption d'un gaz dans un matériau poreux. Les résultats de simulation alimentent une base de donnée qui est aussi exploitée pour proposer une prédiction approximative mais ultra-rapide d'isothermes d'adsorption, ouvrant la voie à des stratégies de criblage de matériaux nanoporeux à haute performance
Synthesis, Structure, and Electrochemistry of Crystallized Layered Chlorides, LiMCl 6 (M = Ta/Nb)
No full textInternational audienceA suitable solid electrolyte can turn the long‐standing dream of a safe commercial all‐solid‐statebattery into reality in the same way as appropriate liquid electrolytes kickstarted the first commercial lithium‐ion battery. Presently, halide‐based electrolytes despite their reactivity with lithium metal are extensively studied as they offer better processability, malleability, oxidative stability, and safety over sulfide‐based electrolytes. Particularly, LiMCl 6 (M = Ta/Nb) chloride‐based amorphous electrolytes are generating widespread interest with their high conductivities, comparable to liquid electrolytes. In this context, with synchrotron X‐ray and neutron powder diffraction techniques, well‐crystallized triclinic layered LiMCl 6 (M = Ta/Nb) chlorides with an hcp AB‐type stacking of chloride ions is reported. The hexagonally ordered NbCl 6 octahedra share edges with LiCl 6 octahedra forming a honeycomb pattern, whereas Li + is intermixed with M 5+ for M = Ta. Furthermore, it is found that crystalline LiTaCl 6 has an ionic conductivity of ≈10 −5 mS cm −1 , six orders of magnitude lower than that reported for superionic amorphous LiTaCl 6 . Nevertheless, crystalline LiTaCl 6 is utilized as an intercalation compound in an all‐solid‐state‐battery, uncovering a solid‐solution/two‐phase/conversion pathway for lithium‐insertion during the three distinct redox plateaus below 3 V versus Li + /Li°. Broadly, the findings give insights into the structure, ionic conduction, and intercalation in a new family of layered halides
Extraction de l'antimoine et du brome des plastiques de déchets électriques et électroniques (DEEE)
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Carbon/Titanium-based composite materials as negative electrodes for sodium-ion batteries
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Overlay databank unlocks data-driven analyses of biomolecules for all
No full textInternational audienceTools based on artificial intelligence (AI) are currently revolutionising many fields, yet their applications are often limited by the lack of suitable training data in programmatically accessible format. Here we propose an effective solution to make data scattered in various locations and formats accessible for data-driven and machine learning applications using the overlay databank format. To demonstrate the practical relevance of such approach, we present the NMRlipids Databank-a community-driven, open-for-all database featuring programmatic access to quality-evaluated atom-resolution molecular dynamics simulations of cellular membranes. Cellular membrane lipid composition is implicated in diseases and controls major biological functions, but membranes are difficult to study experimentally due to their intrinsic disorder and complex phase behaviour. While MD simulations have been useful in understanding membrane systems, they require significant computational resources and often suffer from inaccuracies in model parameters. Here, we demonstrate how programmable interface for flexible implementation of data-driven and machine learning applications, and rapid access to simulation data through a graphical user interface, unlock possibilities beyond current MD simulation and experimental studies to understand cellular membranes. The proposed overlay databank concept can be further applied to other biomolecules, as well as in other fields where similar barriers hinder the AI revolution. © 2024. The Author(s)
TS‐tools: Rapid and automated localization of transition states based on a textual reaction SMILES input
No full textInternational audienceHere, TS‐tools is presented, a Python package facilitating the automated localization of transition states (TS) based on a textual reaction SMILES input. TS searches can either be performed at xTB or DFT level of theory, with the former yielding guesses at marginal computational cost, and the latter directly yielding accurate structures at greater expense. On a benchmarking dataset of mono‐ and bimolecular reactions, TS‐tools reaches an excellent success rate of 95% already at xTB level of theory. For tri‐ and multimolecular reaction pathways ‐ which are typically not benchmarked when developing new automated TS search approaches, yet are relevant for various types of reactivity, cf. solvent‐ and autocatalysis and enzymatic reactivity ‐ TS‐tools retains its ability to identify TS geometries, though a DFT treatment becomes essential in many cases. Throughout the presented applications, a particular emphasis is placed on solvation‐induced mechanistic changes, another issue that received limited attention in the automated TS search literature so far
Visible Light‐promoted C( sp 3 )‐H α‐Carbamoylation of Cyclic Ethers with Isocyanides
No full textInternational audienceA protocol exploiting isocyanides as carbamoylating agents for the α‐C( sp 3 )‐H functionalization of cyclic ethers has been optimized via a combined visible light‐driven hydrogen atom transfer/Lewis acid‐catalyzed approach. The isocyanide substrate scope revealed an exquisite functional group compatibility (18 examples, with yields up to 99 %). Both radical and polar trapping, kinetic isotopic effect and real‐time NMR studies support the mechanistic hypothesis and provide insightful details for the design of new chemical processes involving the generation of oxocarbenium ions