HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Binding mechanism of oligopeptides on solid surface: assessing the significance of single-molecule approach
No full textInternational audienceThis paper addresses the complementarity and potential disparities between single-molecule and ensemble-average approaches to probe the binding mechanism of oligopeptides on inorganic solids. Specifically, we explore the peptide/gold interface owing to its significance in various topics and its suitability to perform experiments both in model and real conditions. Experimental results show that the studied peptide adopts a lying configuration upon adsorption on the gold surface and interacts through its peptidic links and deprotonated thiolate extremities, in agreement with theoretical predictions. Single-molecule force spectroscopy (SMFS) measurements revealed the existence of a wide panel of adhesion forces, resulting from the interaction between individual peptide moieties and the abundant surface sites. We therefore propose methodological developments for sorting the events of interest to understand the peptide adsorption mechanism. Thermodynamic and kinetic aspects of the peptide adsorption are probed using both static and dynamic force spectroscopy measurements. Specifically, we show the possibility of providing a reasonable estimate of the peptide free energy of adsorption ΔadsG° by exploring the fluctuations of the adhesion work, based on the Jarzynski equality, and by using a parametric Gamma estimator. The proposed approach offers a relevant method for studying the different factors influencing the peptide adsorption and evaluating their impact on ΔadsG° as an alternative to exploring adhesion forces that may lead to misinterpretations. This is illustrated by the comparison of the adsorption of two peptides with specific amino acids substitution. Our method provides insights into the overall mechanism by which peptides interact with the surface and allows an integration of the single-molecule versus ensemble-average points of view
Chromosome mis-segregation triggers cell cycle arrest through a mechanosensitive nuclear envelope checkpoint
No full textInternational audienc
Dynamically Deforming Single Jointed Diver Models Reduce Pinch off Depth
No full textDivers reduce visible splash and earn higher scores by performing the rip entry. The diver impacts the water perpendicular to the free surface then roll forward in a somersault as they pass through the interface. This active shape change separates divers from previously studied entry bodies. This paper investigates how this type of dynamic shape change affects the splash production with a single jointed geometrically simplified diver model that turns after impact with the free surface. The impact and splash development is captured with a high speed camera and analyzed for underwater trajectory, pinch off depth, and splash production. The results show that the dynamic shape deformation after impact reduces pinch off depth by nearly half compared to fixed diver models. We demonstrate how their dynamic deformation causes the air cavity to re-attach to the legs of the model. This changes the shape of the trailing cavity from a wedge to an hourglass, and the cavity collapse occurs at the thinnest point. A non-dimensional pinch off depth based on the arm length of the hinged model and the body length of the fixed model shows collapse of the data for all models. Our results illustrate how dynamic deformation during entry changes the essential length for cavity collapse
Turning without Fins: How Snakes Achieve High Maneuverability While Swimming
No full textThe agile turning maneuvers of anguilliform swimmers remain one of the least studied aspects of aquatic locomotion, despite being crucial for survival in underwater environments. Turning is a difficult engineering problem because to change direction animals must minimize their moment of inertia while maximizing torque -two mathematical opposites. Anguilliform swimmers such as snakes are highly maneuverable and accomplish this goal without the aid of limbs or pectoral fins. In this study we explore how snakes manipulate their body position to change swimming direction by analyzing five turns by five individuals (four Natrix maura and one Nerodia rhombifer). We show that snakes curl their body inwards to shift their center of mass and reduce their moment of inertia when turning. We report a volumetric wake measurement for one turn which, together with the kinematics, allows us to quantify the timing between its change in moment of inertia and vortex shedding. Our results show that the snake only sheds vortices after it has minimized its moment of inertia. These results help explain how elongated anguilliform swimmers like snakes change swimming direction. They widen our understanding of how animals use transient maneuvers to navigate aquatic environments, with implications for both natural swimmers and underwater robots
Incidence and duration of human papillomavirus infections in young women: insights from a bimonthly follow-up cohort
No full textInternational audienceBackground. We studied the duration of HPV detection and risk of (re-) detection for 25 HPV genotypes in a cohort of 132 women followed every eight weeks for up to two years between 2016 and 2020. Participants were between 18 and 25 years old at inclusion and half of them were vaccinated against HPV. They were recruited near the University and the STI detection centre in Montpellier, France.Methods. We used genotype-specific longitudinal data to characterise the dynamics of HPV-detected episodes. We investigated the contribution of viral and host factors to the variations in the duration of HPV detection, and the time before (re-)detection of the same genotype using multivariate Cox regression models with frailty at the patient level.Findings. We detected at least one HPV episode in 74% of the participants and re-detected the same genotype in 47% of them. Covariates related to socio-economic difficulties were associated with a lower risk of detectability loss (hazard ratio 0.45 with a 95% confidence interval, CI, from 0.21 to 0.97).The number of lifetime sexual partners was strongly associated with an increased risk of new positive detection (hazard ratio 2.40 with a 95%CI from 1.07 to 5.39). In contrast, vaccination was associated with a lower risk of displaying incident infections (hazard ratio of 0.64 with a 95%CI from 0.43 to 0.96).Conclusion.In the short term, vaccination shows clear signs of protection against new HPV detections, including for some genotypes not targeted by the vaccine, such as HPV31 and HPV51.</p
One-way catalysis in a solvable lattice model
No full textInternational audienceCatalysts speed up chemical reactions with no energy input and without being transformed in the process, therefore leaving equilibrium constants unchanged. Some catalysts, however, are much more efficient at accelerating one direction of a reaction. Is it possible for catalysis to be strictly unidirectional, accelerating only one direction of a reaction? Can we observe directional catalysis by analyzing the microscopic trajectory of a single reactant undergoing conversions between a substrate and a product state? We use the framework of a simple but exactly solvable lattice model to study these questions. The model provides examples of strictly one-way catalysts and illustrates a mathematical relationship between the asymmetric transition rates that underlie directional catalysis and the symmetric transition fluxes that underlie chemical equilibrium. The degree of directionality generally depends on the catalytic mechanism and we compare different mechanisms to show how they can obey different scaling laws
Covalent POM-Ir hybrid assemblies: tuning redox properties for light-driven multiple charge accumulation
No full textInternational audienceThis study reports the synthesis, electrochemical characterization, and photophysical properties of two novel photoactive polyoxometalate (POM)-Ir photosensitizer hybrid assemblies. Under visible light irradiation in the presence of triethylamine and trifluoroacetic acid, the polyoxomolybdate-based dyad photoaccumulates the electrons via an efficient intramolecular photoinduced electron transfer process
Intelligent soft matter: towards embodied intelligence
No full textInternational audienceIntelligent soft matter lies at the intersection of materials science, physics, and cognitive science, promising to change how we design and interact with materials. This transformative field aims to create materials with life-like capabilities, such as perception, learning, memory, and adaptive behavior. Unlike traditional materials, which typically perform static or predefined functions, intelligent soft matter can dynamically interact with its environment, integrating multiple sensory inputs, retaining past experiences, and making decisions to optimize its responses. Inspired by biological systems, these materials leverage the inherent properties of soft matter such as flexibility, adaptability, and responsiveness to perform functions that mimic cognitive processes. By synthesizing current research trends and projecting their evolution, we present a forward-looking perspective on how intelligent soft matter could be constructed, with the aim of inspiring innovations in areas such as biomedical devices, adaptive robotics, and beyond. We highlight new pathways for integrating sensing, memory and actuation with low-power internal operations, and we discuss key challenges in realizing materials that exhibit truly “intelligent behavior”. These approaches outline a path toward more robust, versatile, and scalable materials that can potentially act, compute, and “think” through their inherent intrinsic material properties—moving beyond traditional smart technologies that rely on external control
Fluoroscopy-guided high-intensity focused ultrasound ablation of the lumbar medial branch nerves: dose escalation study and comparison with radiofrequency ablation in a porcine model
No full textInternational audienceBackground Radiofrequency ablation (RFA) is a common method for alleviating chronic back pain by targeting and ablating of facet joint sensory nerves. High-intensity focused ultrasound (HIFU) is an emerging, non-invasive, image-guided technology capable of providing thermal tissue ablation. While HIFU shows promise as a potentially superior option for ablating sensory nerves, its efficacy needs validation and comparison with existing methods. Methods Nine adult pigs underwent fluoroscopy-guided HIFU ablation of eight lumbar medial branch nerves, with varying acoustic energy levels: 1000 (N=3), 1500 (N=3), or 2000 (N=3) joules (J). An additional three animals underwent standard RFA (two 90 s long lesions at 80°C) of the same eight nerves. Following 2 days of neurobehavioral observation, all 12 animals were sacrificed. The targeted tissue was excised and subjected to macropathology and micropathology, with a primary focus on the medial branch nerves. Results The percentage of ablated nerves with HIFU was 71%, 86%, and 96% for 1000 J, 1500 J, and 2000 J, respectively. In contrast, RFA achieved a 50% ablation rate. No significant adverse events occurred during the procedure or follow-up period. Conclusions These findings suggest that HIFU may be more effective than RFA in inducing thermal necrosis of the nerve