HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Voltammetric techniques for low-cost on-site routine analysis of thymol in the medicinal plant Ocimum gratissimum
No full textInternational audienceThe composition of essential oils varies according to culture conditions and climate, which induces a need for simple and inexpensive characterization methods close to the place of extraction. This appears particularly important for developing countries. Herein, we develop an analytical strategy to determine the thymol content in Ocimum Gratissimum, a medicinal plant from Benin. The protocol is based on electrochemical techniques (cyclic and square wave voltammetry) implemented with a low cost potentiostat. Thymol is a phenol derivative and was directly oxidized at the electrode surface. We had to resort to submillimolar concentrations (25–300 μM) in order to minimize production of phenol oligomers that passivate the electrode. We worked first on two essential oils and realized that in one of them the thymol concentration was below our detection method. These results were confirmed by gas chromatography – mass spectrometry. Furthermore, we optimized the detection protocol to analyze an infusion made directly from the leaves of the plant. Finally, we studied whether the cost of the electrochemical cell may also be minimized by using pencil lead as working and counter electrodes
Lys716 in the transmembrane domain of yeast mitofusin Fzo1 modulates anchoring and fusion
No full textInternational audienceOuter mitochondrial membrane fusion, a vital cellular process, is mediated by mitofusins. However, the underlying molecular mechanism remains elusive. We have performed extensive multiscale molecular dynamics simulations to predict a model of the transmembrane (TM) domain of the yeast mitofusin Fzo1. Coarse-grained simulations of the two TM domain helices, TM1 and TM2, reveal a stable interface, which is controlled by the charge status of residue Lys716. Atomistic replica-exchange simulations further tune our model, which is confirmed by a remarkable agreement with an independent AlphaFold2 (AF2) prediction of Fzo1 in complex with its fusion partner Ugo1. Furthermore, the presence of the TM domain destabilizes the membrane, even more if Lys716 is charged, which can be an asset for initiating fusion. The functional role of Lys716 was confirmed with yeast experiments, which show that mutating Lys716 to a hydrophobic residue prevents mitochondrial fusion.La fusion de la membrane mitochondriale externe, un processus cellulaire vital, est médiée par les mitofusines. Cependant, le mécanisme moléculaire sous-jacent reste encore obscur. Nous avons réalisé des simulations de dynamique moléculaire multiéchelles étendues pour prédire un modèle du domaine transmembranaire (TM) de la mitofusine de levure Fzo1. Les simulations en gros grain des deux hélices du domaine transmembranaire, TM1 et TM2, révèlent une interface stable, contrôlée par l'état de charge du résidu Lys716. Des simulations par échange de répliques au niveau tout atome affinent davantage notre modèle, qui est confirmé par une correspondance remarquable avec une prédiction indépendante d'AlphaFold2 (AF2) de Fzo1 en complexe avec son partenaire de fusion Ugo1. De plus, la présence du domaine transmembranaire déstabilise la membrane, encore plus si Lys716 est chargé, ce qui peut être un atout pour initier la fusion. Le rôle fonctionnel de Lys716 a été confirmé par des expériences sur la levure, qui montrent que muter Lys716 en un résidu hydrophobe empêche la fusion mitochondriale
Design of Biocompatible and Biodegradable Composite Shape-morphing Hydrogels
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Simultaneous observation of the anomerization and reaction rates of enzymatic dehydrogenation of glucose-6-phosphate by dissolution-DNP
No full textInternational audienceThe hyperpolarization of biological samples using dissolution-dynamic nuclear polarization (dDNP) has become an attractive method for the monitoring of fast chemical and enzymatic reactions using NMR by taking advantage of large signal increase. This approach is actively developing, but still needs key methodological breakthroughs to be used as an analytical method for the monitoring of complex networks of simultaneous metabolic pathways. In this article, we use the deceptively simple example of glucose-6-phosphate (G6P) oxidation reaction by the enzyme G6P dehydrogenase (G6PDH) to discuss some important methodological aspects of dDNP kinetic experiments, such as its robustness and its ability to provide repeatable results, as well as the capacity of this time resolved methodology to test kinetic models and hypotheses, and to provide reliable parameter estimates. To illustrate the potential of our approach, we report the first direct and quantitative evidence of selectivity of G6PDH towards the β anomer of G6P
Comportement critique des nanofils supraconducteurs
No full textSingle-photon detectors based on low-temperature superconducting nanowires have already demonstrated excellent properties and remarkable performance in various applications below 1K, ranging from quantum information to integrated circuit testing. In this context, the idea of creating such a detector based on high-temperature superconductors operating around 40 K is highly appealing. However, the task is proving challenging not only due to technological barriers associated with the manufacture of ultra-thin nanowires but also because of the distinct nature of superconductivity in these materials.This work is divided into two parts: an experimental study of the transport characteristics of YBCO nanowires, and a numerical study of the influence of vortex motion on the transport characteristics of superconducting nanostripes.In the experimental part, we present the fabrication of superconducting nanowires using the ion irradiation technique. Their characterisation by DC and RF transport has enabled demonstrating the role of the vortex dynamics on critical superconducting properties.The experimental observations are supported by our numerical study, developed specifically for the geometry of our system and devoted to the effects of Abrikosov vortex motion on the transport properties. Within the framework of the time-dependent Ginzburg-Landau theory, we have confirmed the signatures of vortex synchronisation leading to the appearance of fractional Shapiro steps. Moreover, in a specific disorder landscape, this synchronisation can create dynamic metastable states, leading to phenomena experimentally observed in the studied nanowires.Les détecteurs de photons uniques basés sur des nanofils supraconducteurs à basse température ont déjà démontré d'excellentes propriétés et des performances remarquables dans diverses applications en dessous de 1K, allant de l'information quantique au test de circuits intégrés. Dans ce contexte, l'idée de créer un tel détecteur basé sur des supraconducteurs à haute température fonctionnant autour de 40 K est très séduisante. Cependant, la tâche s'avère difficile, non seulement en raison des obstacles technologiques liés à la fabrication de nanofils ultraminces, mais aussi en raison de la nature distincte de la supraconductivité dans ces matériaux.Ce travail est divisé en deux parties : une étude expérimentale des caractéristiques de transport des nanofils YBCO et une étude numérique de l'influence du mouvement vortex sur les caractéristiques de transport des nanorubans supraconducteurs.Dans la partie expérimentale, nous présentons la fabrication de nanofils supraconducteurs à l'aide de la technique d'irradiation ionique. Leur caractérisation par transport DC et RF a permis de démontrer le rôle de la dynamique des vortex sur les propriétés supraconductrices critiques.Les observations expérimentales sont soutenues par notre étude numérique, développée spécifiquement pour la géométrie de notre système et consacrée aux effets du mouvement vortex d'Abrikosov sur les propriétés de transport. Dans le cadre de la théorie de Ginzburg-Landau dépendante du temps, nous avons confirmé les signatures de la synchronisation des vortex conduisant à l'apparition de marches de Shapiro fractionnaires et, dans un paysage de désordre spécifique, cette synchronisation peut créer des états métastables dynamiques, observés dans nos nanofils supraconducteurs
Spin-orbit induced splitting in two-dimensional Dirac Cones in single and double antimony layers on Au(111)
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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
Shedding Light on Stakeholders' Perspectives for Sorbent-based Carbon Capture
No full textInternational audienceReducing CO 2 emissions requires urgently deploying large-scale carbon capture technologies, amongst other strategies. The quest for optimum technologies is a multiobjective problem involving various stakeholders. Today's research follows a sequential approach, with chemists focusing first on material design and engineers subsequently seeking the optimal process. Eventually, this combination of materials and processes should operate at a scale that significantly impacts the economy and the environment.Understanding these impacts requires assessing factors such as greenhouse gas emissions over the lifetime of the capture plant, which usually constitutes one of the final steps. In this work, we present the PrISMa (Process-Informed design of tailormade Sorbent Materials) platform, which seamlessly connects materials, process design, techno-economics, and life-cycle assessment. We compare over sixty Case Studies in which CO 2 is captured from different sources in five world regions with different technologies. These studies demonstrate how the platform simultaneously informs various stakeholders: identifying the most cost-effective technology and optimal process configuration, revealing the molecular characteristics of top-performing sorbents, determining the best locations, and informing on environmental impacts, co-benefits, and trade-offs. Our platform brings together all stakeholders at an early stage of research, which is essential to accelerate innovations at a time when they are most needed.</div
Topological Insulator Nanowires Made by AFM Nanopatterning: Fabrication Process and Ultra Low‐Temperature Transport Properties
No full textInternational audienceAbstract Topological insulator nanostructures became an essential platform for studying novel fundamental effects emerging at the nanoscale. However, conventional nanopatterning techniques, based on electron beam lithography and reactive ion etching of films, have inherent limitations of edge precision, resolution, and modification of surface properties, all of which are critical factors for topological insulator materials. In this study, an alternative approach for the fabrication of ultrathin Bi 2 Se 3 nanoribbons is introduced by utilizing a diamond tip of an atomic force microscope (AFM) to cut atomically thin exfoliated films. This study includes an investigation of the magnetotransport properties of ultrathin Bi 2 Se 3 topological insulator nanoribbons with controlled cross‐sections at ultra‐low 14 mK) temperatures. Current‐dependent magnetoresistance oscillations are observed with the weak antilocalization effect, confirming the coherent propagation of 2D electrons around the nanoribbon surface's perimeter and the robustness of topologically protected surface states. In contrast to conventional lithography methods, this approach does not require a highly controlled clean room environment and can be executed under ambient conditions. Importantly, this method facilitates the precise patterning and can be applied to a wide range of 2D materials
Multilayer Bolometric Structures for Efficient Wideband Communication Signal Reception
No full textInternational audienceIt is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures