HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Probing the colloidal behavior of a cell wall polysaccharides-degrading enzyme in a highly constrained model system
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Photodétecteurs hybrides plasmoniques nanobâtonnets/VO2 sensibles aux photons infrarouges à ondes courtes avec une réponse rapide
No full textInternational audienceThermal detectors, such as bolometers functioning by detecting the radiation‐induced temperature changes, represent a promising route to achieve infrared detection and imaging. In this context, vanadium dioxide (VO2 ), a narrow bandgap ( Eg ) semiconductor ( Eg ≈0.6–0.7 eV) with a unique near‐room‐temperature reversible metal‐to‐insulator transition (MIT), has emerged as one of the key materials for uncooled bolometer‐type short‐wave infrared (SWIR) photodetectors. In this work, photodetectors sensitive to the SWIR spectrum are fabricated to function at room‐temperature by coupling solution‐processed tungsten (W 6+ )‐doped VO2 thin films to colloidal plasmonic gold (Au) nanorods (NRs). Due to the dual beneficial roles of the NRs as both the photothermal heating and plasmonic antenna effects, the hybrid Au NR/VO2 devices exhibit significant advantages in terms of photosensitivity and detection range in comparison to the control devices without plasmonics. Together with the low external DC bias required (0.5 V) and the fast response speed ( t rise down to 14 ms), the present hybrid plasmonic‐VO2 thin film devices suggest a viable approach toward the development of future cost‐effective SWIR photodetectors
Unveiling Phase Transition Dynamics Using Cryogenic Optical Microscopy in a Charge-Transfer Fe 2 Co 2 Switchable Molecular Material
No full textInternational audienceUnderstanding the phase transition mechanism in switchable materials is crucial for optimizing their properties. In this study, we present the thermal electron transfer -coupled spin transition (ETCST) mechanism, revealed through the cryogenic optical microscopy (OM) measurements on a cyanide-bridged square complex:where Tp is tris(pyrazolyl)borate and vbik, bis(1vinylimidazolyl)ketone. A one-step thermal ETCST of 1•ClO4 is observed using conventional techniques such as single crystal X-ray diffraction (SC-XRD) and bulk sample magnetic measurements. The ETCST is cooperative, with slightly different transition temperatures for the single crystal (T1/2↑ = 251.5 K for heating and T1/2↓ = 243.5 K) and the bulk sample (T1/2↑ = 273 K and T1/2↓ = 255 K). In contrast, the direct visualization of the thermal ETCST in the single crystal of 1•ClO4 through OM and the subsequent image analysis disclose, for the first time, a phase transition of unexpected complexity. The ETCST progresses in three steps along the a, b and c axes, respectively: i) Initially, strip domains form and rapidly extend along the a-axis. ii) These domains then gradually widen in the b-axis covering the entire ab layer. iii) The final step involves a layerby-layer extension of ETCST along the c-axis. Structural analysis of 1•ClO4 reveals that two types of intermolecular interactions govern the two preferential propagation directions of ETCST. The first type, mediated by ClO4⁻ anion, drives the rapid propagation of ETCST along the a axis, occurring so rapidly that the conventional methods like magnetometry and SC-XRD are unable to detect it. The second type, along the b axis, involves the π-π stackings of vbik ligands, which contribute to the slower ETCST propagation in this direction. This mechanistic insight into the anisotropic propagation patterns of ETCST in 1•ClO4 underscores the role of intermolecular interactions in modulating the dynamics of molecular switching
Fabrication of microcompartments with controlled size and shape for encapsulating active matter
No full textInternational audienceIn all living systems, the cytoplasm is separated from the external environment by membranes. This confinement imposes spatial constraints on the self-organization of internal components, filaments and organelles. While reconstituted systems are instrumental for understanding fundamental biological principles, traditional experiments often utilize volumes vastly larger than actual cells. In recent studies, water-in-oil droplets or giant unilamellar vesicles have been widely used to impose confinement. However, these compartments present imaging challenges and make precise protein content control difficult. To address these limitations, we have developed versatile microwells that are straightforward to implement, compatible with different types of imaging and suitable for long-term experiments. These microwells are compatible with several surface treatments and a wide range of experimental techniques making them a powerful tool for answering key questions in cell biology. We present here a detailed protocol of the fabrication of the microwells as well as characterization of the method to ensure quality throughout the manufacturing process. These microwells support various cytoskeleton-based processes including actin polymerization, dynamic steady-state actin networks, and composite actin-microtubule networks. More broadly, they can be used to encapsulate and study over time any kind of active matter
Synthesis, Characterization and Stability of {Mo 132 }-type Capsules Containing Phosphorus Oxo Anion Ligands
No full textInternational audienceThis article deals with a set of {Mo 132 }-type capsules containing phosphorus oxo anions as ligands.Two of them, with hypophosphite and phosphate ligands, respectively, were prepared and characterized by IR spectroscopy and X-ray diffraction in Bielefeld more than two decades ago. We extended this pioneering work to phosphite and methylphosphonate ligands. All these capsules were prepared by ligand exchange in the acetate-containing {Mo 132 } capsule and some of them contain residual acetate, depending on the incoming ligand and the pH of the reaction mixture. All of them were characterized by 1 H and 31 P NMR spectroscopy in D 2 O and one by single-crystal X-ray diffraction. These studies showed that side reactions occur. On the one hand, degradation of the {Mo 132 } framework leads to the release of fragments that can be trapped as {MoO 3 H} + units by the ligands inside capsules. This was known for phosphate and is also observed for methylphosphonate.On the other hand, monitoring by NMR spectroscopy revealed that capsules slightly transform over time in solution as well as in the solid state, as evidenced by growth of characteristic signals of R. T. Deceased on December 5, 2022 2 Strandberg-type complexes and reduced Keggin-type molybdophosphates. Decomposition, however, remains fairly low over a few months. 2-, IUPAC name H-phosphonate, noted HPhos), methylphosphonate (MePO 3 2-, noted MePhos) and phosphate (HPO 4 2-, noted Phos). {Mo 132 }-type porous capsules, which Müller proposed to name Keplerates, 1 consist of 12 pentagonal {(Mo VI )Mo VI 5 O 21 (H 2 O) 6 } 6-units positioned at the vertices of an icosahedron while being connected by 30 {Mo V 2 O 4 } 2+ linkers. One of their most noteworthy features is the presence of 20 well-defined and flexible {Mo 9 O 9 } pores (diameter ca. 0.35 nm) allowing controlled matter exchange between the inside and the outside. 2 They most often incorporate 30 internal bidentate anionic ligands that are weakly bound 3 to the inner surface of the {Mo 132 O 372 (H 2 O) 72 } 12-shell and are readily replaced by other ligands. Compounds 1 1,4 and 2 5 ({Mo 132 (OAc)} and {Mo 132 (SO 4 )}, respectively, in simplified notations; see formulae in Table 1) are two representative examples. Though {Mo 132 (hypo)} (3) 4,6 and {Mo 132 (Phos)} (4a and 4b) 7 capsules were prepared very early from 1 by substituting hypophosphite or phosphate for acetate, they have since received little attention in comparison to other members of the {Mo 132 } family, specifically 2. 2Recent reports yet focused on encapsulation of Gd 3+ 8 and first-row transition metals (M = Mn 2+ , Co 2+ , Fe 2+ ) 9 in 4b, with views to assess the potential of the resulting host-guest systems as MRI contrast agents 8 and to develop catalytic and photocatalytic reactions in confined space. 9 For our part we have extended the {Mo 132 (POA)} set of capsules to {Mo 132 (HPhos)} (5) and {Mo 132 (MePhos)} (6). We report herein their synthesis, the single-crystal X-ray diffraction characterization of one of them (6b'), and a set of solution 1 H and 31 P NMR studies related to synthesis monitoring and characterization of 3, 4, 5 and 6 while providing insight in their stability, which is a crucial issue from the perspective of possible applications
Noninvasive characterization of oocyte deformability in microconstrictions
No full textL.B., R.B., M.-H.V., C.C., and M.-E.T. are inventors on patent application EP23166408.7 submitted by Université PSL that covers “microfluidic device for use in a system for measuring at least one biomarker of at least one oocyte.” The other authors declare that they have no competing interests.International audienceOocytes naturally present mechanical defects that hinder their development after fertilization. Thus, in the context of assisted reproduction, oocyte selection based on their mechanical properties has great potential to improve the quality of the resulting embryos and the success rate of these procedures. However, using mechanical properties as a quantifiable selective criterion requires robust and nondestructive measurement tools. This study developed a constriction-based microfluidic device that monitors the deformation of mouse oocytes under controlled pressure. The device can distinguish mechanically aberrant oocyte groups from healthy control ones. On the basis of a mathematical model, we propose that deformability measurements infer both oocyte tension and elasticity, elasticity being the most discriminating factor in our geometry. Despite force transmission during oocyte deformation, no long-term damage was observed. This noninvasive characterization of mouse oocyte deformability in microconstrictions allows for a substantial advance in assessing the mechanical properties of mammalian oocytes and has potential application as a quantifiable selective criterion in medically assisted reproduction
The Soap Opera of Metal Catalysis in Epoxy-Acid Vitrimers
No full textInternational audiencePrecipitation of bivalent metal carboxylates is a well-known issue in detergency, resulting in decreased efficiency and unwanted accumulation of lime soap on laundry. We demonstrate that the same phenomenon is occurring in formulations of metal-catalyzed epoxy-acid vitrimers. When for instance a Zn (II) salt and glutaric acid are allowed to meet each other in the same reaction feedstock, precipitation takes place, resulting in phase-separation of zinc glutarate and glutarate-poor polymer network, showing no vitrimer properties. We present a strategy to overcome this issue based on step addition at a single end of the dicarboxylic acid monomer, prior to contact with zinc. In this case, formation of crystalline zinc soap is completely avoided, and the network shows thermo-stimulated stress relaxation. This strategy is particularly appealing for the synthesis of polyhydroxyester networks showing high-Tg and fast relaxation.La précipitation des carboxylates métalliques bivalents est un problème bien connu en détergence, entraînant une diminution de l'efficacité et une accumulation indésirable de savon de calcium sur le linge. Nous démontrons que le même phénomène se produit dans les formulations de vitrimères époxy-acides catalysés par des métaux. Lorsque, par exemple, un sel de Zn (II) et de l'acide glutarique se rencontrent dans le même mélange réactif, une précipitation a lieu, entraînant une séparation de phase entre d'une part le glutarate de zinc et d'autre part un réseau polymère pauvre en glutarate, ne présentant aucune propriété vitrimère. Nous présentons une stratégie pour surmonter ce problème en faisant réagir avec l'époxy une seule extrémité du monomère d'acide dicarboxylique, avant le contact avec le zinc. Dans ce cas, la formation de savon de zinc cristallin est complètement évitée et le réseau présente une relaxation de contrainte thermo-stimulée. Cette stratégie est particulièrement intéressante pour la synthèse de réseaux de polyhydroxyesters présentant une Tg élevée et une relaxation rapide
Actualités de 2024 sur les troubles neurologiques du sommeil
No full textInternational audienceAt the annual French Sleep Congress, Laure Peter-Derex presented a review of impactful 2024 studies on neurological sleep disorders, focusing on the role of REM sleep behavior disorder (RBD) as an early marker of neurodegenerative diseases, the development of new RBD severity scales, and emerging biomarkers (e.g., language alterations) to predict progression toward Parkinson’s disease or dementia. She also emphasized that RBD can sometimes be linked to treatable autoimmune encephalitis, underscoring the importance of thorough etiological assessments. Finally, potential novel therapies such as acetyl-DL-leucine show preliminary promise for RBD prodromes, highlighting the need for clinical trials to assess their long-term efficacy and possible neuroprotective benefits.Au Congrès français du Sommeil, Laure Peter-Derex a présenté une revue des études marquantes de 2024 sur les troubles neurologiques du sommeil. Elle a notamment mis l’accent sur le rôle du trouble comportemental en sommeil paradoxal (TCSP) en tant que marqueur précoce de maladies neurodégénératives, sur l’élaboration de nouvelles échelles de sévérité spécifiques au TCSP ainsi que sur l’apparition de nouveaux biomarqueurs (par exemple, des altérations du langage) permettant de prédire la progression vers la maladie de Parkinson ou la démence. Elle a également souligné que le TCSP peut parfois être associé à des encéphalites auto-immunes potentiellement curables, soulignant ainsi l’importance d’une évaluation étiologique approfondie. Enfin, de nouvelles approches thérapeutiques, telles que l’acétyl-DL-leucine, semblent prometteuses dans le traitement des prodromes du TCSP, d’où la nécessité de mener des essais cliniques afin d’évaluer leur efficacité à long terme et leurs éventuels effets neuroprotecteurs
Actualités de 2024 sur les troubles du sommeil en pédiatrie
No full textInternational audienceFor this review, Benjamin Dudoignon selected articles from prestigious journals that directly impact patient clinical management. He structured his presentation around three main areas: respiratory conditions, neurological and psychiatric disorders, and finally, recommendations for the management of insomnia and the prescription of melatonin in neurotypical patients. This thematic approach provided a clear and coherent overview of relevant medical advances while highlighting the practical implications for clinicians.Pour ces actualités, Benjamin Dudoignon a sélectionné des articles issus de revues prestigieuses ayant un impact direct sur la prise en charge clinique des patients. Il a structuré sa présentation autour de trois axes principaux : les affections respiratoires, les troubles neurologiques et psychiatriques, et enfin, les recommandations concernant la prise en charge de l'insomnie ainsi que la prescription de mélatonine chez les patients neurotypiques. Cette approche thématique a permis d'offrir une vision claire et cohérente des avancées médicales pertinentes, tout en mettant en lumière les implications pratiques pour les cliniciens