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Revealing the unexpected: formal charge exchanges in collisional activation of cereulide ionized molecular species
No full textInternational audienceUnder positive electrospray desorption/ionization mass spectrometry (ESI-MS) conditions, a bacterial cyclodepsipeptide toxin, cereulide [ (D) Ala- (L)O Val- (L) Val- (D)O Leu]3, is mainly desorbed as ammonium adduct and alkalicationized species. In addition to the naturally occurring alkali cation (Li + /Na + /K + ), Rb + can be attached to the molecule after addition of its chlorine salt (RbCl) solution. Under non-resonant collision-induced dissociations (non-resonant CID) using a quadrupole time-of-flight (Qq/TOF) instrument, bare alkali cations were recently detected in non-resonant CID spectra. Investigation using energy-resolved mass spectrometry (ERMS) of cationized cereulide revealed coexistence of charge-solvated (CS) and protonated salt (PS) tautomers. Infusion of cereulide solution containing RbCl salt into the ion source led to the unexpected detection of 85 Rb + and 87 Rb + within their natural abundances when Rb-free species ([M+NH4] + , [M+Na] + or [M+K] + ) were selected for subsequent fragmentation. To elucidate the origin of these unexpected cations, ERMS of the various ionized cereulide species was carried out using an Orbitrap-based instrument. Curiously, in addition to the unexpected Rb + isotopique cations, Rb2Cl + isotopologues were abundantly detected in nonresonant CID spectra of [M+NH4] + , [M+Na] + , and [M+K] + , but not of [M+ 85 Rb] + . Additional calculations and ERMS logarithmic plots made it possible to rule out a possible endogenous origin of the Rb2Cl + and Rb + isotopologues. They are produced by ion/molecule reactions in the higher-energy collisional dissociation (HCD) cell between ionized cereulide (and b(12-n) ions), relaxed by the buffer gas, and neutral RbCl isotopologue salts present in gas phase. The latter are likely generated either during preliminary studies of RbnCl(n-1) + cluster dissociation in smaller cluster ions and neutral RbCl loss, or from the HCD cell surface by collisions with the buffer gas. Consequently, Rb2Cl + isotopologues are not precursors of 85 Rb + plus 87 Rb +
Unlocking self-discharge: Unveiling the mysteries of electrode-free Zn-MnO2 batteries with advanced in situ techniques in mild acid aqueous electrolytes
No full textInternational audienceWe introduce a novel approach to Zinc-MnO2 battery architecture utilizing a 3D network of carbon nanofibers as both current collector and electrode material, promising enhanced performance and longevity for large-scale energy storage. Employing mild aqueous electrolytes, we address the challenge of managing self-discharge, crucial for short-term energy storage.Advanced coupled characterization techniques, including in-situ EQCM (Electrochemical Quartz Crystal Microbalance) and high-resolution optical microscopy, elucidate self-discharge mechanisms across over multiple length scales. Findings reveal that the self-discharge is mainly at the zinc electrode due to concomitant dissolution of Zinc (corrosion) and HER (Hydrogen Evolution Reaction) phenomena. Interestingly, the corrosion current was estimated irrespective of charging protocol and remains consistent, indicating the independence of zinc corrosion kinetics from the length scale. Finally, the morphology of the zinc layer appears to be critical, suggesting that self-discharge is primarily a chemical process. This innovative design strategy offers the potential for high-performance Zinc-MnO2 batteries with extended cycle life to meet the requirements of large-scale energy storage applications
Cristallographie des figures de moiré quasi-périodiques dans des bicouches homophases tournées
No full textInternational audienceThis paper discusses the geometric properties and symmetries of general moiré patterns generated by homophase bilayers twisted by rotation 2δ. These patterns are generically quasiperiodic of rank 4 and result from the interferences between two basic periodicities incommensurate to each other, defined by the sites in the layers that are kept invariant through the symmetry operations of the structure. These invariant sites are distributed on the nodes of a set of lattices called Φ-lattices – where Φ runs on the rotation operations of the symmetry group of the monolayers – which are the centers of rotation 2δ + Φ transforming a lattice node of the first layer into a node of the second. It is demonstrated that when a coincidence lattice exists, it is the intersection of all the Φ-lattices of the structure.Cet article traite des propriétés géométriques et des symétries des figures de moiré générales engendrées par des bicouches homophases tournées d'une rotation de 2δ. De manière générique, ces figures sont quasi-périodiques de rang 4 et résultent d'interférences entre deux périodicités fondamentales incommensurables entre elles, définies par les sites des couches qui sont restés invariants sous l'action des opérations de symétrie de la structure. Ces sites invariants sont distribués sur les nœuds d'un ensemble de réseaux appelés réseaux Φ – où Φ représente les opérations de rotation du groupe de symétrie des monocouches – qui sont les centres de rotation 2δ + Φ transformant un nœud du réseau de la première couche en un nœud de la seconde. On démontre que lorsqu'un réseau de coïncidence existe, il s'agit de l'intersection de tous les réseaux Φ de la structure
A Single Tensile Test for TRIP–TWIP Mechanisms High-Throughput Mapping in a Compositionally Graded Ti–Nb Alloy
No full textInternational audienceCompositional boundaries of transformation induced plasticity and mechanical twinning (TRIP/TWIP) activity in the Ti-Nb system are determined on a 18-30 at.% Nb chemically graded sample prepared by diffusion couple. Deformation mechanisms triggered by a single tensile test are analyzed by EBSD and EDX. TRIP activity is resolved in the range 22-25 at.% Nb and TWIP activity in the range 23-28 at.% Nb, showing the possibility to chemically map deformation mechanisms with a single tensile test
Alkynyl Radicals, Myths and Realities
No full textInternational audienceThis Perspective deals with the organic chemistry of alkynyl radicals, a species that is ultimately still little known in the synthetic community. Starting with the first observations and characterizations of alkynyl radicals generated by various methodologies in the gas phase, we then particularly turned our attention to the implications of these highly reactive intermediates in organic synthesis and materials science. Mechanistic considerations have been provided, in particular, for the key steps of generating alkynyl radicals, which are mainly based on photochemical or thermal activation and single electron transfer processes. This Perspective should serve as a roadmap for the synthetic chemist in order to plan more reliably alkynylation reactions based on alkynyl radicals
Investigation of protonation induced metal-to-metal electron transfer in a cyano-bridged MnIII –FeIII dinuclear complex
No full textInternational audienceDinuclear MnIII (μ-NC)FeIII molecular Prussian blue analogue reported here exhibits field-induced SMM behavior with Ueff of 15.09 K and protonation induced metal to metal electron transfer in solution
Synthesis, Characterization, and Biological Evaluation of Iron(III)- N -Heterocyclic Carbene Complexes as Photosensitizers for Photodynamic Therapy and Chemotherapeutics against Cancer
No full textInternational audiencePhotodynamic therapy (PDT) is a promising strategy for cancer treatment, yet the reliance on rare, expensive, and potentially toxic heavy metals limits the practical application of many current photosensitizers. In this study, we synthesized and evaluated a series of iron(III)-N-heterocyclic carbene (Fe(III)-NHC) complexes (1–7) bearing diverse substituents to explore their potential as cost-effective alternatives for cancer therapy. While none of the complexes exhibited significant singlet oxygen generation under light excitation, several (particularly complexes 1, 2, 3, and 7) showed strong cytotoxicity toward cancer cells even in the absence of photodynamic activation. Structure–activity analysis revealed that hydrophobic or moderately electron-donating groups enhanced cellular uptake and bioactivity, while polar or bulky substituents reduced efficacy of cellular uptake, as confirmed by ICP-MS and confocal fluorescence microscopy. Further biological studies suggested that the cytotoxic effects of these compounds may stem from mitochondrial damage, potentially caused by disruption of mitochondrial membrane potential through iron-mediated redox processes. These findings highlight the promise of Fe(III)-NHC complexes as potential chemotherapeutic agents and underscore the importance of rational ligand design in modulating their biological activity
Synthesis and Biological Evaluation of Itraconazole Derivatives: Design in an Old Scaffold
No full textInternational audienceAntimicrobial resistance is a major global problem for public health, indicating the need for the development of new anti-infective drugs, among other actions (i.e., better stewardship, diagnostics, etc.). A common strategy in medicinal chemistry is to modify existing drugs with an organometallic moiety to enhance their efficacy or overcome resistance. One notable example is ferroquine, an organometallic derivative of chloroquine. Here, we describe the design, in-depth characterization, and in vitro evaluation of seven new derivatives of the antifungal drug itraconazole (ITZ) against parasitic and fungal pathogens. ITZ was selected as a privileged scaffold because it targets ergosterol biosynthesis, which is an essential component of cell membranes in fungi and trypanosomatid parasites. While none of the compounds were active against Trypanosoma cruzi and Leishmania infantum, the ferrocenyl derivatives proved to be 1.5- to 1.9-fold more potent than ITZ toward Trypanosoma brucei. Of particular interest, all of the compounds exhibited high antifungal activity against the azole-susceptible clinical isolates. Furthermore, the ferrocenyl-containing compound was the most active against Aspergillus. Despite showing 10-fold lower activity than ITZ, these organometallic derivatives constitute an interesting starting point for further pharmacomodulation since we confirmed that they blocked the ERG11 enzyme, the main target of azoles
Recent Advances in Synthetic Strategies of Glycans and their Pharmaceutical Applications
No full textInternational audienceThe understanding of glycans, the third life chain, is widely desired. Naturally, the glycoconjugates are found in heterogeneous forms due to the enzyme competition in the same process. As a result, the synthesis of homogeneous glycans has become one of the trending research topics. In this review, orthogonal protection strategies were summarized to overcome the difficulties, such as the numerous hydroxyl groups of oligosaccharides and stereoselectivities during glycosylations. A variety of synthetic glycomics, including glycoproteins, glycolipids, and newly discovered glycoRNAs, were also presented. Their applications were categorized by different diseases, which elucidated the great potential of glycans as drug candidates in the next generation
Synthesis of Na3SbS4 solid electrolyte from dimethyl sulfoxide solvent
No full textInternational audienceAs a more effective and scalable substitute for conventional solid-state syntheses, solution synthesis of electrolytes for all solid-state batteries attracts a lot of attention. Sodium tetrathioantimonate Na3SbS4 is a promising solid electrolyte (SE) for all-solid-state sodium ion batteries. Dimethyl sulfoxide solvent was used for the first time as a reaction medium. The Na3SbS4 powder is made of agglomerated irregular particles, and exhibits a Na-ionic conductivity at room temperature of 2.74·10−4 S/cm coupled with a low activation energy of 0.26 eV. The current route using dimethyl sulfoxide solvent would be an alternative approach for the production of high-performance solid electrolytes