HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Structural insights into nanofibers formed by templated polymerization-induced self-assembly through combined SANS and AFM characterizations
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Hippocampal microstructural changes following electroconvulsive therapy in severe depression
No full textInternational audienceIntroductionElectroconvulsive therapy (ECT) induces an increase in hippocampal volume presumed to reflect neurogenesis in severely depressed patients. We hypothesized that Neurite Orientation Dispersion and Density Imaging (NODDI) provides in vivo evidence of hippocampal neurogenesis following ECT.MethodsThis prospective longitudinal study included 43 depressed patients treated by ECT. Three sequential evaluations (V1: baseline, V2: at 2 weeks into ECT, V3: 14 days within completing ECT) included a 3T MR-scan with 3D T1-weighted and multi-shell diffusion (b = 200/1500/2500 s/mm2, 30/45/60 directions) sequences and clinical assessment with depression scales. Q-ball, Diffusion Tensor and NODDI models provided the following metrics: axial (AD), radial (RD) and mean diffusivity (MD), fractional anisotropy (FA) and generalized FA (GFA), neurite density index (NDI), isotropic fraction (Fiso), neurite orientation and dispersion index (ODI). FreeSurfer was used to extract whole hippocampal and subfields volumes from T1-weighted images. A linear mixed-effect model assessed the changes over time in hippocampal volumes and mean diffusion metrics, and their relationship with clinical response was analyzed with ANOVA. Bonferroni corrections were applied.Results107 MRI were obtained at V1 (n = 43), V2 (n = 34) and V3 (n = 30) from 43 patients. Mean (± SD) interval between V1-V3 was 70 ± 25 days. Diffusion metrics in the hippocampus were: at V2, a decrease in left GFA, right AD, bilateral Fiso, and a bilateral ODI increase. Additionally, at V3, we observed a left MD decrease, bilateral AD decrease, right NDI increase, and bilateral ODI increase. Notably, NDI and Fiso changes were localized to the dentate gyrus but not to the hippocampal tail. ECT-responders showed a significant right hippocampus volume increase at 2 weeks into ECT.ConclusionAfter ECT, the observed increase in hippocampal volume is accompanied by bilateral changes in NODDI parameters, consistent with hippocampal neuroplasticity
Mono-excitonic lasing of colloidal semiconductor nanocrystals in polymeric parabolic microcavities
No full textColloidal semiconductor nanocrystals constitute materials of choice to realize microlasers, thanks to the fine control of their optical and electronic properties, and to their solution processability. However so far, lasing has mostly been obtained under high excitation, in the biexciton regime. Here, we demonstrate instead that, in high-quality cavities, lasing naturally occurs in the single exciton regime. We describe the facile fabrication of nanocrystal-coated polymeric microcavities and study their lasing characteristics. We show that the lasing threshold lies in the sub-monoexcitonic excitation regime for CdS/CdSe/CdS quantum shells in particular, thanks to the high quality factor of the cavities and high transition cross sections of the quantum shells. We explain these results using a comprehensive model of nanocrystal optical properties. The model correctly reproduces lasing characteristics near and above the threshold. In this regime, in contrast to previous studies, the performance of the microlasers relies mostly on the transition cross section and the Stokes shift, not on biexciton recombination or exciton-biexciton splitting. This improved understanding will enable rational design of colloidal nanocrystals for low-threshold lasing applications
Self-assemblies of cell-penetrating peptides and ferrocifens: design and biological evaluation of an innovative platform for lung cancer treatment
No full textInternational audienceChemotherapy currently used for lung cancer treatment often consists in a combination of drugs, with a moderate efficacy and severe side effects. A major drawback of the classical inorganic drugs used is their hydrophobicity, leading to a very low blood availability and a weak efficacy. To overcome this constraint, a nanoplatform was set up in order to vectorize a ferrocifen drug, an organometallic tamoxifen derivative known for its really potent in vitro activity, but as well for its poor water solubility. Two different ferrocifens were tested: P54 and P819. The covalent conjugation of a cell-penetrating peptide (CPP) to the ferrocifen was performed, leading to an amphiphilic prodrug, potentially able to self-assemble. The CPP used in this study are polyarginines and RLW. Moreover, in order to bring stealth and mucopenetration properties, polyethylene glycol (PEG) was incorporated into the nanostructure. The co-nanoprecipitation of CPP-ferrocifen and PEG-ferrocifen was investigated to obtain self-assemblies. A comparison of the biological activity of the different suspensions was assessed in vitro on a healthy cell line and on two different lung cancer cell lines. The biological activity of P54 was increased by a factor 9 with the Arg9-P54 suspension, by increasing the cell internalization. Moreover, the P54 based-self-assemblies were chosen to test their in vivo activity on mice bearing lung tumor. The results showed that the intratracheal nebulization of Arg9-P54/PEG-P54 or of Arg9-P54 suspensions slowed up significantly the evolution of lung cancer in mice: the suspension with PEG bringing an additional comfort to the animal at the administration
Commutation moléculaire multivoie dans des réseaux hexagonaux 2D : une stratégie d'ingénierie moléculaire pour la conception de matériaux bistables à température ambiante
No full textInternational audienceMagnetic materials exhibiting bistability at ambient condition are appealing for application in high-density memory, data storage, sensing and switches devices. Octacyanometallates have been extensively studied as building blocks for constructing novel molecular magnetic materials with exciting physical properties. Here, we have designed and synthesized two cyanide bridged 2D hexagonal networks using octacyanotungstate(V) building block where {[W(CN)8]2[Co(V-im)4]3}n(1) undergoes a single-crystal to single-crystal (SC-SC) structural transformation to form {[W(CN)8]2[Co(V-im)4]2[Co(V-im)2(DMF)2].4H2O}n (2). Complex 1 exhibits reversible thermo-induced metal-to-metal electron transfer (MMET) (T1/2 = 176 K) with a 12 K thermal hysteresis width while complex 2 exhibits near ambient temperature two-step MMET (heating: T1/2(1) 324 K, T1/2(2) 340 K; cooling: T1/2(1) 286 K, T1/2(2) 232 K) with a hysteresis width of 4 and 15 K respectively. Interestingly, light-induced reversible ON/OFF MMET has also been observed for both complexes (1 and 2) using 808 nm and 900 nm lights (ON mode) and 405 and 635 (OFF mode) respectively, converting the low-temperature diamagnetic {WIVLS-CN-CoIIILS} ground-state into the metastable paramagnetic {WVLS-CN-CoIIHS} phase and vice-versa . X-ray absorption spectroscopy was performed in order to investigate the local electronic structure and magnetization associated with the MMET between the W and Co metal centres.Les matériaux magnétiques bistables en conditions ambiantes sont prometteurs pour les applications dans les mémoires haute densité, le stockage de données, les capteurs et les commutateurs. Les octacyanométallates ont été largement étudiés comme éléments constitutifs de nouveaux matériaux magnétiques moléculaires aux propriétés physiques intéressantes. Nous avons conçu et synthétisé ici deux réseaux hexagonaux 2D pontés au cyanure en utilisant l'élément constitutif octacyanotungstate(V) où {[W(CN)8]2[Co(V-im)4]3}n(1) subit une transformation structurale monocristalline-monocristalline (SC-SC) pour former {[W(CN)8]2[Co(V-im)4]2[Co(V-im)2(DMF)2].4H2O}n(2). Le complexe 1 présente un transfert d'électrons métal-métal (MMET) thermo-induit réversible (T1/2 = 176 K) avec une largeur d'hystérésis thermique de 12 K tandis que le complexe 2 présente un MMET en deux étapes à température ambiante (chauffage : T1/2(1) 324 K, T1/2(2) 340 K ; refroidissement : T1/2(1) 286 K, T1/2(2) 232 K) avec une largeur d'hystérésis de 4 et 15 K respectivement. Il est intéressant de noter qu'un MMET ON/OFF réversible induit par la lumière a également été observé pour les deux complexes (1 et 2) en utilisant des lumières de 808 nm et 900 nm (mode ON) et de 405 et 635 (mode OFF) respectivement, convertissant l'état fondamental diamagnétique à basse température {WIVLS-CN-CoIIILS} en phase paramagnétique métastable {WVLS-CN-CoIIHS} et vice-versa. Une spectroscopie d'absorption des rayons X a été réalisée afin d'étudier la structure électronique locale et la magnétisation associées au MMET entre les centres métalliques W et Co
Crystal structures of monomeric BsmI restriction endonuclease reveal coordinated sequential cleavage of two DNA strands
No full textInternational audienceBsmI, a thermophilic Type IIS restriction endonuclease from Bacillus stearothermophilus, presents a unique structural composition, housing two distinct active sites within a single monomer. Recognition of the non-symmetrical 5'-GAATGC-3' sequence enables precise cleavage of the top and bottom DNA strands. Synthetic biology interventions have led to the transformation of BsmI into Nb.BsmI, a nicking endonuclease. Here we introduce Nt*.BsmI, tailored for top-strand cleavage, which is inactive on standard double-stranded DNA, but active on bottom-strand nicked DNA, suggesting a sequential cleavage mechanism. Crystallographic structures of pre- and post-reactive complexes with cognate DNA show one major conformational change, a retractable loop possibly governing sequential active site accessibility. The x-ray structures reveal the position of the divalent metal ions in the active sites and the DNA:protein interactions, while the models predicted by Alphafold3 are incorrect. This comprehensive structural and functional study lays a foundation for rational enzyme redesign and potential applications in biotechnology
On the shape of air bubbles trapped in ice
No full textInternational audienceWater usually contains dissolved gases, and because freezing is a purifying process these gases must be expelled for ice to form. Bubbles appear at the freezing front and are then trapped in ice, making pores. These pores come in a range of sizes from microns to millimeters and their shapes are peculiar; never spherical but elongated, and usually fore-aft asymmetric. We show that these remarkable shapes result of a delicate balance between freezing, capillarity, and mass diffusion. A nonlinear ordinary differential equation suffices to describe the bubbles, which features two nondimensional numbers representing the supersaturation and the freezing rate, and two additional parameters representing simultaneous freezing and nucleation treated as the initial condition. Our experiments provide us with a large variety of pictures of bubble shapes. We show that all of these bubbles have their rounded tip well described by an asymptotic regime of the differential equation and that most bubbles can have their full shape quantitatively matched by a full solution. This method enables the measurement of the freezing conditions of ice samples, and the design of freeze-cast porous materials. Furthermore, the equation exhibits a bifurcation that explains why some bubbles grow indefinitely and make long cylindrical “ice worms,” well known to glaciologists
Bioinorganic chemistry: where from and where to?
No full textInternational audienceBioinorganic chemistry is a multidisciplinary field that bridges the apparent divide between inorganic chemistry and biology. The very name "bioinorganic" is an intriguing oxymoron, as "inorganic" chemistry traditionally refers to the study of the inanimate world, while the "bio" prefix refers to living systems. Bioinorganic chemistry focuses on metallic systems within biological environments, with the dual aims of better understanding these natural systems and leveraging the solutions developed through evolution to design new industrial or therapeutic applications. As a close cousin of the field of metallomics, bioinorganic chemistry shares the fundamental principles that underpin metallomics' systemic analyses of metal-containing biomolecules. In this article, we trace the historical development of bioinorganic chemistry, highlighting its recent advancements and outlining future research challenges in this dynamic interdisciplinary area
AMOEBA Polarizable Molecular Dynamics Simulations of Guanine Quadruplexes: from the c-Kit Proto-oncogene to HIV-1
No full textInternational audienceLong oligomer sequences, rich in guanine and cytosine, such as c-kit1 and the HIV-1 LTR-III sequence, are prevalent in oncogenes and retroviruses and play crucial roles in cancer. Understanding the conformational dynamics of such guanine quadruplexes and identifying druggable regions are therefore essential for developing new inhibition strategies. In this study, we used extensive AMOEBA polarizable force field molecular dynamics simulations combined with data-driven adaptive sampling and clustering algorithms, reaching a cumulative simulation time of 7.5 μs for c-kit1. Such simulations identified novel structural motives and showcased the flexible loop dynamics, as well as the role of polarizable water in transient stabilization of the G-quadruplex. They also identified two druggable pockets in c-kit1. The 400 ns simulation of the HIV-1 LTR-III sequence confirmed its quadruplex stability and uncovered a potentially druggable cryptic pocket
