HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Structure and Dynamics of Self-Assembled Thermo-Associative PNIPAM–PDMA-PNIPAM Triblock Copolymers of High Molar Mass
No full textInternational audienceABA triblock copolymers with thermosensitive poly(N-isopropylacrylamide) (PNIPAM) side blocks and high molar mass (>500 kg/mol) poly(N,N-dimethylacrylamide) (PDMA) central blocks were characterized in aqueous solution. Rheological studies revealed that using a large PDMA central block allows thermo-induced gelation at concentrations as low as 1 wt % and temperatures ranging from 28 to 38 °C in pure water, depending on PNIPAM concentration. Their temperature-induced self-assembly process was studied by static light scattering. In the dilute regime, the copolymers formed flower-like micelles. At higher concentrations, they formed 1D flower necklaces, which percolated when the semidilute regime was reached. This loose network structure gave rise to viscoelastic liquid behaviors at temperatures close to the sol–gel transition in the unentangled semidilute regime, with gradually increasing relaxation times as temperature was increased
Complementary pathways in C–H functionalization of furfural derivatives with cobalt-hydride catalysis
No full textInternational audienceThis study presents a cobalt-catalysed C–H functionalization of furfural derivatives, unveiling substrate-dependent reactivity. Furfurylimines undergo selective C5-alkenylation, while free aldehydes engage in decarbonylative C2-alkenylation
Distinct functions of cardiac β-adrenergic receptors in the T-tubule vs. outer surface membrane
No full textInternational audienceβ-adrenoceptors (β-ARs) regulate cardiac function during sympathetic nerve stimulation. β-ARs are present in both the cardiac T-tubule (TTM) and outer surface membrane (OSM), but how their location impacts their function is unknown. Here, we developed a technology based on size exclusion to explore the function of β-ARs located in the OSM. We synthetized a PEG-Iso molecule by covalently linking isoprenaline (Iso) to a 5000 Da PolyEthylene-Glycol (PEG) chain to increase the size of the β-AR agonist and prevent it from accessing the T-tubule network. The affinity of PEG-Iso and Iso on β1- and β2-ARs was measured using radioligand binding. Molecular dynamics simulation was used to assess PEG-Iso conformation and visualise the accessibility of the Iso moiety to water. Using confocal microscopy, we show that PEGylation constrains molecules outside the T-tubule network of adult rat ventricular myocytes (ARVMs) due to the presence of the extracellular glycocalyx. β-AR activation in OSM with PEG-Iso produced a lower stimulation of [cAMP]i than Iso but a larger stimulation of cytosolic PKA at equivalent levels of [cAMP]I and similar effects on excitation-contraction coupling parameters. However, PEG-Iso produced a much lower stimulation of nuclear cAMP and PKA than Iso. Thus, OSM β-ARs in ARVMs control mainly cytosolic cAMP/PKA pathway and contractility, while TTM β-ARs control mainly nuclear cAMP, PKA and consequent nuclear protein phosphorylation. Size exclusion strategy using ligand PEGylation provides a unique approach to evaluate the respective contribution of T-tubule vs. outer surface membrane proteins in cardiac cells
Prospects of Nanoscience with Nanocrystals: 2025 Edition
No full textInternational audienceNanocrystals (NCs) of various compositions have made important contributions to science and technology, with their impact recognized by the 2023 Nobel Prize in Chemistry for the discovery and synthesis of semiconductor quantum dots (QDs). Over four decades of research into NCs has led to numerous advancements in diverse fields, such as optoelectronics, catalysis, energy, medicine, and recently, quantum information and computing. The last 10 years since the predecessor perspective “Prospect of Nanoscience with Nanocrystals” was published in ACS Nano have seen NC research continuously evolve, yielding critical advances in fundamental understanding and practical applications. Mechanistic insights into NC formation have translated into precision control over NC size, shape, and composition. Emerging synthesis techniques have broadened the landscape of compounds obtainable in colloidal NC form. Sophistication in surface chemistry, jointly bolstered by theoretical models and experimental findings, has facilitated refined control over NC properties and represents a trusted gateway to enhanced NC stability and processability. The assembly of NCs into superlattices, along with two-dimensional (2D) photolithography and three-dimensional (3D) printing, has expanded their utility in creating materials with tailored properties. Applications of NCs are also flourishing, consolidating progress in fields targeted early on, such as optoelectronics and catalysis, and extending into areas ranging from quantum technology to phase-change memories. In this perspective, we review the extensive progress in research on NCs over the past decade and highlight key areas where future research may bring further breakthroughs
Crystal growth at a liquid–liquid interface upon drop impact
No full textInternational audienceThe crystallisation that occurs when a drop is in contact with a cold surface is a particularly challenging phenomenon to capture experimentally and describe theoretically. The situation of a liquid–liquid interface, where crystals appear on a mobile interface is scarcely studied although it provides a defect-free interface. In this paper, we quantify the dynamics of crystals appearing upon the impact of a drop on a cool liquid bath. We rationalise our observations with a model considering that crystals appear at a constant rate depending on the thermal shock on the expanding interface. This model provides dimensionless curves on the number and the surface area of crystals that we compare with our experimental measurements
Evaluation of Ligand Influence on Gold(I)-Alkyne Complexes Using (Threshold) Collision Induced Dissociation
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Stress distributions in soft particle glasses: Insights from a thermodynamic model
No full textInternational audienceJammed suspensions of soft particle glasses (SPGs) exhibit intriguing rheological response under different shear flows, such as stress overshoot in start-up shear and Herschel–Bulkley behavior in steady shear. However, the fundamental link between microscopic processes and macroscopic (bulk) behavior remains elusive. To address this, we employ large-scale 3D simulations of model SPGs to study the impact of shear-induced microstructural rearrangements on particle stress distributions. These rearrangements cause significant changes in stress distribution, consequently influencing the overall stress and bulk rheology of the system. The characteristics of stress distribution, including its width and peak, are found to be influenced by factors such as particle volume fraction, applied shear rate, and system history. Building upon previous works, we introduce a thermodynamic model that offers insights into the particle stress distribution in SPGs, providing a microscopic basis for understanding bulk rheology. Furthermore, we present a self-consistent model based on the advection–diffusion equation, which describes the evolution of particle stress distribution in SPGs under steady shear. Our findings emphasize the importance of stress distributions in elucidating bulk rheology and highlight the utility of thermodynamics as a valuable tool for modeling these complex materials
