Caractérisation du peptide fluoré LX2 pour le développement d'un nouveau canal ionique membranaire

Dans le but de développer un canal ionique membranaire à visée nanochimiothérapeutique, ce mémoire présente la synthèse et la caractérisation des peptides fluorés LX2 et LX2 acétylé lorsqu'ils interagissent avec des modèles de membranes cellulaires. Ces peptides s'inspirent du peptide LS2 (LSLLLSL)3, un polypeptide de 21 acides aminés composé de résidus leucine et sérine, qui a été développé et caractérisé par le groupe du Pr W.F. DeGrado. Dans le cas du LX2 (LXLLLXL)3, les sérines ont été remplacées par des acides 2-amino-4,4,4-trifluorobutyrique. Des études de modélisation antérieures suggèrent que ce peptide membranaire s'auto-assemble en tétramère dans des membranes phospholipidiques. Différentes techniques ont été utilisées pour caractériser le LX2 et sa forme acétylée, ainsi que leurs interactions avec des membranes modèles de type eucaryote formées de POPC et de cholestérol. Le dichroïsme circulaire et la spectroscopie infrarouge ont permis de déterminer la structure secondaire des peptides en solution et au sein des membranes. La spectroscopie infrarouge et la résonance magnétique nucléaire ont donné de l'information sur les perturbations induites par les peptides sur les membranes. La séquence CODEX utilisée en spectroscopie RMN des solides a constitué une première étape afin de mettre en évidence l'oligomérisation des peptides

Membrane assembly and ion transport ability of a fluorinated nanopore

A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fd-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures

Trypan Blue Dye Enters Viable Cells Incubated with the Pore-Forming Toxin HlyII of Bacillus cereus

Trypan blue is a dye that has been widely used for selective staining of dead tissues or cells. Here, we show that the pore-forming toxin HlyII of Bacillus cereus allows trypan blue staining of macrophage cells, despite the cells remaining viable and metabolically active. These findings suggest that the dye enters viable cells through the pores. To our knowledge, this is the first demonstration that trypan blue may enter viable cells. Consequently, the use of trypan blue staining as a marker of vital status should be interpreted with caution. The blue coloration does not necessarily indicate cell lysis, but may rather indicate pore formation in the cell membranes and more generally increased membrane permeability

Genetic landscape of a large cohort of Primary Ovarian Insufficiency : New genes and pathways and implications for personalized medicine

Background Primary Ovarian Insufficiency (POI), a public health problem, affects 1-3.7% of women under 40 yield-ing infertility and a shorter lifespan. Most causes are unknown. Recently, genetic causes were identified, mostly in single families. We studied an unprecedented large cohort of POI to unravel its molecular pathophysiology.Methods 375 patients with 70 families were studied using targeted (88 genes) or whole exome sequencing with pathogenic/likely-pathogenic variant selection. Mitomycin-induced chromosome breakages were studied in patients' lymphocytes if necessary. Findings A high-yield of 29.3% supports a clinical genetic diagnosis of POI. In addition, we found strong evidence of pathogenicity for nine genes not previously related to a Mendelian phenotype or POI: ELAVL2, NLRP11, CENPE, SPATA33, CCDC150, CCDC185, including DNA repair genes: C17orf53(HROB), HELQ, SWI5 yielding high chromo-somal fragility. We confirmed the causal role of BRCA2, FANCM, BNC1, ERCC6, MSH4, BMPR1A, BMPR1B, BMPR2, ESR2, CAV1, SPIDR, RCBTB1 and ATG7 previously reported in isolated patients/families. In 8.5% of cases, POI is the only symptom of a multi-organ genetic disease. New pathways were identified: NF-kB, post-translational regulation, and mitophagy (mitochondrial autophagy), providing future therapeutic targets. Three new genes have been shown to affect the age of natural menopause supporting a genetic link.Interpretation We have developed high-performance genetic diagnostic of POI, dissecting the molecular pathogene-sis of POI and enabling personalized medicine to i) prevent/cure comorbidities for tumour/cancer susceptibility genes that could affect life-expectancy (37.4% of cases), or for genetically-revealed syndromic POI (8.5% of cases), ii) predict residual ovarian reserve (60.5% of cases). Genetic diagnosis could help to identify patients who may benefit from the promising in vitro activation-IVA technique in the near future, greatly improving its success in treating infertility.Funding Universite? Paris Saclay, Agence Nationale de Biome?decine.Copyright (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer reviewe

French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

Could conservative iron chelation lead to neuroprotection in amyotrophic lateral sclerosis?

Iron accumulation has been observed in mouse models and both sporadic and familial forms of Amyotrophic lateral sclerosis. Iron chelation could reduce iron accumulation and the related excess of oxidative stress in the motor pathways. However, classical iron chelation would induce systemic iron depletion. We assess the safety and efficacy of conservative iron chelation (i.e. chelation with low risk of iron depletion) in a murine preclinical model and pilot clinical trial. In Sod1G86R mice, deferiprone increased the mean life span as compared with placebo. The safety was good, without anemia after 12 months of deferiprone in the 23 ALS patients enrolled in the clinical trial. The decreases in the ALS Functional Rating Scale and the body mass index (BMI) were significantly smaller for the first 3 months of deferiprone treatment (30 mg/kg/day) than for the first treatment-free period. Iron levels in the cervical spinal cord, medulla oblongata and motor cortex (according to MRI), as well as cerebrospinal fluid levels of oxidative stress and neurofilament light chains were lower after deferiprone treatment. Our observation leads to the hypothesis that moderate iron chelation regimen that avoids changes in systemic iron levels may constitute a novel therapeutic modality of neuroprotection for ALS

L’expertise dans le champ des sciences du langage sur des terrains sensibles : un point de vue épistémologique

International audienc

Superstructure stability (top row) and typical equilibrated structures (bottom row) of the LX2 trimer, tetramer, pentamer and hexamer.

<p>Surrounding lipids are not shown for clarity. The pentamer and hexamer starting structures are not completely symmetric following energy minimization. Internal diameters (I.D.) are averaged values along the complete pore lumen. The color code is the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166587#pone.0166587.g005" target="_blank">Fig 5</a>.</p

Averages of the fluorine-fluorine surface of contact in Ų.

<p>Averages of the fluorine-fluorine surface of contact in Ų.</p