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A Dual Homeostatic Regulation of Dry Mass and Volume Defines a Target Density in Proliferating Mammalian Cells
No full textThe concentration of macromolecules, especially proteins, is vital for cellular function and is influenced not only by synthesis and degradation but also by the total cell volume. While we understand various growth regulation mechanisms, the coupling of dry mass and volume in growing mammalian cells remains unclear. Here we show that two independent mechanisms acting in single cells -one regulating volume through biophysical modulation and the other controlling protein biosynthesis-work together to maintain macromolecular dry mass density and restore it following perturbations. These mechanisms ensure that proliferating cells remain within a specific range around a target density, providing density homeostasis at the population level. Although the target density appears consistent across different cell types, it is disrupted around cell division, upon perturbations of growth pathways and in senescent cells. It may represent an optimal value for cellular processes, ensuring the efficiency of essential intracellular functions.</div
Proteins and Water Control the Stability of the Intracellular Amorphous Calcium Carbonate Inclusions Formed by Cyanobacteria
No full textInternational audienc
Characterizing the chemical composition of red coloring matter samples from the Altamira cave using synchrotron µXRF imaging
No full textrapport annuelInternational audiencePalaeolithic cave art remains mysterious, but through chemical analysis of the pigments new insights can be gained into its creation abd purpose. Red pigments contain poorly crystallized iron oxides whose crystallographic phases are not specific enough to discriminate between them. Trace element fingerprinting by means of highly sensitive, non-invasive analyses is essential to characterise chemical markers of the cave art pigments. Synchrotron induced X-ray fluorescence analysis on micro-samples from different figures of the Altamira cave was successful to define characteristic elemental patterns, allowing for instance an objective comparison of red Palaeolithic figures between them
Sustainable Chitosan-Based Composite Materials for the Photodegradation of Wastewater Contaminants
No full textInternational audienceSustainable Chitosan-Based Composite Materials for the Photodegradation of Wastewater Contaminant
Cyclopropyl‐Substituted Trialkoxysilanes and their Related Bis(catecholato)silicates: Preparation, Characterization and Reactivity
No full textInternational audienceHerein, we report a direct route for the synthesis of TMS‐ or ethyl ester‐cyclopropyl trialkoxysilanes and their transformation in bis(catecholato)silicates. Structural analysis of these hypercoodinated λ5 Si‐silicate species was achieved by 1H, 13C, and 29Si NMR, cyclic voltammetry as well as X‐ray diffraction analysis. Their ability to act as a potential cyclopropyl radical precursors was examined experimentally by single electron transfer oxidation via photoredox catalysis. Density functional theory calculations were performed to gain mechanistic insights into their lack of reactivity
Targeted fluorescent lipid microparticles for quantitative measurement of phagosomal pH
No full textInternational audienceABSTRACT Phagosomal acidification plays a pivotal role in pathogen destruction and immune signaling, yet tools capable of reporting these biochemical changes with spatial and mechanistic precision remain scarce. A modular biosensing strategy is presented in which BODIPY-derived hydrophilic fluorophores are conjugated to phospholipids and incorporated at the surface of targeted lipid microparticles. These soft and biomimetic particles combine receptor-specific uptake with ratiometric fluorescence readouts, enabled by pairing pH-responsive dyes at the interface with a pH-invariant reference probe in the core. Following Fcγ receptor-mediated internalization by macrophages, the particles deliver real-time insight into the onset and progression of phagosomal acidification. This versatile platform provides a direct means to couple defined surface recognition events to intracellular pH measurements, offering new opportunities to unravel how particle identity and ligand presentation modulate phagosomal physiology
Probing the role of isoelectric point in charge storage mechanisms of functionalized carbon by electrochemical quartz crystal microbalance (EQCM)
No full textInternational audienceIn this work, we aim to explore the synergetic influence of the functionalization of the carbon electrode and that of the electrolyte pH on the charge storage mechanism by utilizing the technique of EQCM (Electrochemical Quartz Crystal Microbalance). A comparative analysis has been carried out on YP50 and o-YP50 (carbon with oxygen functionalities), which revealed crucial differences in the evolution of ionic contribution to charge storage under varying pH. A progression from anionic to cationic mechanism was observed with an increase in pH, depending on the isoelectric point of the carbon under study. A combination of TPD-MS (Temperature Programmed Desorption Mass Spectrometry) and EQCM was used to probe pH-dependent surface transformations occurring on the functionalized and non-functionalized carbon electrode during electrochemical cycling. The electrolyte pH governs the protonation state of the surface functional groups, which influences the charge on the electrode and hence the mechanism of charge storage
Bioorthogonal Post‐Labeling Reveals Nuclear Localization of a Highly Cytotoxic Half‐sandwich Ir(III) Tetrazine Complex in Live Cells
No full textInternational audienceIntracellular imaging of anticancer metallodrugs often relies on pre‐labeling with organic fluorophores, which significantly affects their physicochemical properties and intracellular distribution. On the other hand, the reported post‐labeling strategies based on click‐chemistry reactions require cell fixation and permeabilization. Here, we present a post‐labeling approach based on the catalyst‐free, inverse electron‐demand Diels‐Alder reaction (iEDDA) between a strained fluorescein‐tagged bicyclononyne derivative (BCN‐FAM) and half‐sandwich Ir(III) complexes containing bidentate ligands comprising a tetrazine (Tz‐R,R’) entity. Five half‐sandwich Ir(III) complexes with formula [Cp*Ir(Tz‐R,R’)Cl]0/+ have been synthesized and fully characterized, including the X‐ray crystal structures of three of the five derivatives. Investigations of their stability and their reactivity in aqueous solution and in a model iEDDA reaction revealed the strong influence of the tetrazine ligand structure on the chemical properties of the corresponding complexes. A highly cytotoxic metallodrug candidate (Ir‐C,NPh,Me) was identified from biological studies, and chemical reactivity studies disclosed an unusual preference for binding of methionine over cysteine. Post‐labeling of Ir‐C,NPh,Me in live HeLa cells highlighted its preferential accumulation within the nucleus, suggesting its retention through covalent modifications of nuclear proteins in good agreement with other half‐sandwich iridium(III) complexes
Electrodeposition and soft oxidation of nickel‑iron hydroxides: An efficient two-step approach for the synthesis of highly active and stable iron-rich NiFe-LDHs with controlled Ni/Fe composition for oxygen evolution reaction
No full textInternational audienceNickel‑iron layered double hydroxides (NiFe-LDHs) are promising low-cost and active electrocatalysts for the alkaline oxygen evolution reaction (OER), yet conventional synthesis methods face two key limitations: (i) poor control over the Ni/Fe atomic ratio and (ii) difficulty in producing active, stable iron-rich NiFe-LDHs due to the formation of inactive iron hydroxide phases. Given iron's higher abundance and lower cost compared to nickel, developing iron-rich NiFe-LDHs is highly desirable. In this study, we present a two-step synthesis approach to overcome these challenges: first, rapid cathodic electrodeposition (<1 min) of NiFe(OH)2 onto an electrode, followed by controlled ambient oxidation of Fe2+ to Fe3+, yielding phase-pure NiFe-LDH. By adjusting the electrodeposition potential, we achieve precise control of the Ni/Fe ratio in the film, matching the precursor solution composition. SEM-EDS analysis confirms this correlation for films electrodeposited at −2.0 V vs. Ag/AgCl (3 M KCl) across a broad Ni/Fe range. The oxidation step integrates iron (as Fe2+ and Fe3+) into the LDH lattice without forming inactive iron oxide phases. XPS analysis reveals a consistent M3+/M2+ ratio (∼1/3, M = Ni and Fe), consistent with the hydrotalcite (honessite) structure, indicating Fe oxidation is governed by the LDH structure. Electrochemical testing in 1 M aqueous KOH demonstrates outstanding performance: a NiFe-LDH with 35.1 ± 2.0 at. % Fe exhibits an overpotential of 167 ± 22 mV at 30 mA·cm−2, while a 76.6 ± 4.0 at. % Fe film requires 249 ± 10 mV. Both catalysts maintain stability over 100 h at 100 mA·cm−2, surpassing previously reported NiFe-LDHs with comparable Fe content in activity and durability. This work provides a scalable route to iron-rich NiFe-LDHs synthesis with controlled composition and high catalytic performance