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Mn 2+ Bispidine Complexes as Potential Magnetic Resonance Imaging Agents : Noncoordinating Peripheral Functional Groups Affect Structural, Kinetic, and Relaxation Properties
No full textInternational audienceMn 2+ bispidine complexes combine unprecedented kinetic inertness with high relaxivity and are under scrutiny as potential magnetic resonance imaging (MRI) probes. This study demonstrates that, beyond the rigid, preorganized bispidine structure and the first coordination sphere of the Mn 2+ ion, peripheral functional groups also play a role in enhancing those kinetic and relaxation properties. Three pentadentate ligands have been designed, synthesized, and their Mn 2+ complexes investigated in order to elucidate the effect of noncoordinating carboxylate and amine pendants on the bispidine scaffold. While thermodynamic stability is not influenced by these variations in the peripheral structure, kinetic inertness is increased two‐threefold when the ligand bears both carboxylate and amine functions. The synergistic effect of these groups could be related to the formation of a relatively stable dinuclear Mn L Zn complex, which can slow down transmetallation with Zn 2+ , the most important competitor of Mn 2+ in vivo. Water exchange rate on these monohydrated chelates remains unaffected by variations in the complex charge. On the other hand, the simultaneous presence of deprotonated carboxylate and protonated amine functions enhances proton relaxivity, likely via reorganization of the second sphere water shell. These insights into structure–activity relationships help fine‐tune the safety and the efficacy of MRI agents based on Mn 2+ ‐bispidines
Spatio-temporal learning from molecular dynamics simulations for protein–ligand binding affinity prediction
No full textInternational audienceMotivation The field of protein–ligand binding affinity prediction continues to face significant challenges. While deep learning (DL) models can leverage 3D structural information of protein–ligand complexes, they perform well only on heavily biased test sets containing information leaked from training sets. This lack of generalization arises from the limited availability of training data and the models’ inability to effectively learn from protein–ligand interactions. Since these interactions are inherently time-dependent, molecular dynamics (MD) simulations offer a potential solution by incorporating conformational sampling and providing interaction rich information. Results We have developed MDbind, a dataset comprising 63 000 simulations of protein–ligand interactions, along with novel neural networks capable of learning from these simulations to predict binding affinity. By utilizing MD as data augmentation, our models achieved state-of-the-art performance on the PDBbind v.2016 core set and an external test set, the free energy perturbation (FEP) dataset. Additionally, when trained on the full MD simulations, the models demonstrated less biased predictions. Availability and implementation The code for neural networks is available at https://github.com/ICOA-SBC/MD_DL_BA. The models, the results and the training/validation/test sets are available for download at https://zenodo.org/records/10390550. The MDbind trajectories are being transferred to the MDDB: https://mmb-dev.mddbr.eu/#/browse? option=mdbind
Combination of Bayesian and artificial neuronal networks to quantify uncertainty of the short- and long-term behavior of Callovo-Oxfordian claystone
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Multi-strain SIS dynamics with coinfection across heterogeneous patches
No full textAbstract We study a Susceptible-Infected-Susceptible (SIS) model with coinfection and multiple interacting strains where hosts move between a set of inter-connected patches. Under strain similarity and slow migration, we obtain a discrete model, following the corresponding continuous space model derived in (Le and Madec, 2023). In this model, the fast variables are total prevalence of susceptibles, single-infected and co-infected hosts in each patch ( S, I, D ). The slow variables are strain frequencies ( z ) in each patch. These local strain frequencies in each patch are governed by a replicator-like equation, where an additional contribution arises from migration, scaled explicitly by emergent patch heterogeneity. In our model, the strains can vary epidemiologically within- and between-patches along several traits, including transmission rates, clearance rates, priority effects and pairwise susceptibilities to coinfection; a complexity that totally defies straightforward prediction of their ecological outcome. However, harnessing the analytical advantage of this model reduction, we can investigate several key scenarios for the outcome of the coupled P-patch N-strain system. We focus on the global and local factors that promote or hinder coexistence, and on regimes that favour spatial segregation of strains, or ultimately competitive exclusion. The analytical tractability of this meta-population model, illustrated with several examples for N = 2 strains and 2-3 patches, makes it a useful framework for application to general multi-species co-colonization systems with migration across heterogeneous environments
« Comment le XIXe siècle a réinventé les fêtes populaires, des cafés-concerts aux bals masqués »
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Cryogenic bosch process using CF<sub>4</sub> plasma in deposition regime
No full textInternational audienceIn plasma cryogenic etching, the substrate is cooled to a temperature generally below -90°C, considerably increases surface residence time of adsorbed species. This enhances mechanisms such as passivation, physisorption, condensation or contributes to reduce plasmainduced damage as well chamber wall contamination. This is beneficial for applications like deep etching, damage-free etching of low-k materials or atomic layer etching. In this presentation, running the Bosch process at cryogenic temperature will be discussed. This process is usually performed at room temperature where SF6 etching plasma is alternated with C4F8 polymerizing plasma to achieve anisotropic features in silicon. It is shown that the deposition of the fluoropolymer layer, which controls profile anisotropy, is significantly enhanced at cryogenic temperature. Therefore, a lower C4F8 flow is required and, since polymerization is restricted to cold surfaces, chamber wall contamination is reduced [1]. However, C4F8 remains a highly polymerizing gas because of its low F/C ratio [2]. Chamber wall contamination could be further decreased by using a gas with a higher F/C ratio, such as CF4 which is in etching regime at room temperature. It is shown by means of UV absorption spectroscopy that CF radicals produced in a CF4 plasma physisorb more efficiently on a surface cooled at cryogenic temperature [3]. Therefore, a CF4 plasma is expected to turn to deposition regime at such a low substrate temperature and could be used as a passivation step instead of C4F8 in a Bosch-like process with barely no contamination at the chamber walls. This has been successfully demonstrated by running such a Bosch process over 200 cycles. The resulting profiles are mostly isotropic at room temperature whereas the are anisotropic at cryogenic temperature. This clearly confirms that the CF4 plasma switches from an etch regime to a deposition regime by lowering the substrate temperature.[1] J. Nos, R. Dussart, T. Tillocher, P. Lefaucheux, M. Boufnichel, J. Micromech. Microeng., 34 (2024), 10, 105011 [2] J. W. Coburn and H. F. Winters, J Vac Sci Technol 16 (1979), 391. [3] J. Nos, S. Iséni, M. Kogelschatz, G. Cunge, P. Lefaucheux, R. Dussart, T. Tillocher, E. Despiau-Pujo, Appl. Phys. Lett, 126 (2025) 031602
Faire et défaire envoûtements et maléfices. Savoirs, pratiques et représentations
No full textThe articles in this dossier are the result of a study day on the program "Divination, Magic, and Repression in the Late Middle Ages", funded by the Centre-Val de Loire Region. They explore, using a variety of sources, the different facets of the power to bind and unbind, for good or evil, vested in healers, magicians, and other sorcerers and witches in the late Middle Ages and the Renaissance.Les articles de ce dossier sont issus d’une journée d’étude du programme "Divination, magie et répression à la fin du Moyen Âge" financé par la Région Centre-Val de Loire, organisée à l’Université d’Orléans en 2024. Ils explorent, dans des sources de natures diverses, les différentes facettes du pouvoir de lier et de délier, tant en bien qu’en mal, dont sont investis les guérisseurs, magiciens et autres sorciers et sorcières aux derniers siècles du Moyen Âge et à la Renaissance
