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DTSTART;TZID=Europe/Paris:20260408T093000
DTEND;TZID=Europe/Paris:20260408T113000
DTSTAMP:20260405T184929
CREATED:20260402T160829Z
LAST-MODIFIED:20260402T160835Z
UID:10000120-1775640600-1775647800@sfp-alpes.fr
SUMMARY:Soutenance d'HDR de Marie-Aude MEASSON (Institut Néel\, équipe MagSup)
DESCRIPTION:Matériaux Quantiques en Conditions Extrêmes : Modes Collectifs et Ordres Quantiques Exotiques\nRésumé : A VENIR… \nPrésentation en français \n_ \nContact : marie-aude.measson@neel.cnrs.fr
URL:https://sfp-alpes.fr/event/soutenance-dhdr-de-marie-aude-measson-institut-neel-equipe-magsup/
LOCATION:CNRS – Bâtiment A\, CNRS - Institut Néel 25 avenue des Martyrs\, Grenoble\, 38054\, France
CATEGORIES:Soutenance,Soutenance HDR
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260421T140000
DTEND;TZID=Europe/Paris:20260421T160000
DTSTAMP:20260405T184929
CREATED:20260402T154628Z
LAST-MODIFIED:20260402T154831Z
UID:10000118-1776780000-1776787200@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Eymeline PAGEOT (IRIG / IBS)
DESCRIPTION:Decoding chaos : a cryo-em walk through physarum polycephalum heterogeneous cell extracts\nRésumé : \n\nCryo-electron microscopy (cryo-EM) has become a central method in structural biology for determining high-resolution structures of macromolecular assemblies. However\, most cryo-EM studies still rely on highly purified samples\, which limits the range of biological systems that can be investigated. In recent years\, the analysis of cell extracts by single particle cryo-EM has emerged as an alternative strategy to explore the structural diversity of cellular proteins directly from complex mixtures. Despite its potential\, this approach remains technically challenging due to the high level of heterogeneity present in such samples and the difficulty of identifying proteins without complementary techniques such as mass spectrometry.\n\n​ The work presented in this thesis investigates the feasibility of using cryo-EM as a primary discovery tool to determine and identify protein structures directly from fractionated cell extracts. The study focuses on the plasmodial slime mould Physarum polycephalum\, a non-model eukaryotic organism whose structural proteome is largely unexplored. In contrast to most previous studies in the field\, protein identification relied solely on structural information derived from cryo-EM reconstructions.\n\nCell extracts from P. polycephalum were fractionated using biochemical separation methods and analysed by cryo-EM. Because such samples contain a wide range of proteins with different sizes\, shapes\, and abundances\, dedicated image processing strategies were developed to address the challenges posed by particle heterogeneity and flexibility. Particular attention was given to 2D classification\, particle sorting\, and iterative particle picking strategies to improve the recovery of multiple particle orientations and increase the number of particles contributing to 3D reconstructions.\n\nUsing these approaches\, fourteen macromolecular assemblies were identified and solved directly from the heterogeneous samples. In cases where the cryo-EM maps reached sufficient resolution\, atomic models could be built ab initio. For lower-resolution structures\, identification relied on structural comparison with known protein folds and structures predicted by generative tools. This work demonstrates that protein identity and putative function can be inferred directly from the structural information\, opening the possibility of structure-based genome annotation in poorly characterised organisms.\n\nBeyond the individual structures determined in this study\, this work also outlines the methodological challenges associated with large-scale structural exploration of complex biological mixtures. The largely manual nature of several steps in the workflow currently limits the throughput of the approach. Strategies to automate key stages of the pipeline\, including particle classification\, initial model generation\, and structural identification\, are therefore discussed as important directions for future development.​\n\nFinally\, this work highlights the importance of community-driven analysis and open data sharing for the continued development of large-scale structural exploration approaches. Making both the raw cryo-EM data and the solved structures publicly available enables other researchers to further investigate the dataset\, potentially identifying additional structures and improving the analysis using new computational methods\, as well as enabling the development of the methods themselves. In the longer term\, combining such « shotgun » cryo-EM approaches with advances in computational modelling and high-throughput data analysis may contribute to the systematic structural characterisation of cellular proteomes.\n\n​​–\n\n\n\nLes séminaires et soutenances sont ouverts à tous\, notez toutefois que l’accès au campus EPN nécessite un avis de rendez-vous. Merci de remplir ce formulaire  et de l’adresser\, plus de 48h à l’avance\, à ce contact. Pensez à vous munir d’une pièce d’identité le jour de votre visite.
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-eymeline-pageot-irig-ibs/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260423T140000
DTEND;TZID=Europe/Paris:20260423T160000
DTSTAMP:20260405T184929
CREATED:20260402T155914Z
LAST-MODIFIED:20260402T155920Z
UID:10000119-1776952800-1776960000@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Moritz KIRCHNER (IRIG / IBS)
DESCRIPTION:Molecular bases of a multiprotein assembly linking membrane biology to stress adaptation in enterobacteria\nRésumé : \n\nEnteric bacteria encounter a variety of stress factors when infecting their host. This includes but is not limited to acid stress\, oxygen limitation and antibiotic stress. Bacteria counteract such stressors using various stress response systems. A central factor in the stress adaptation of enterobacteria is their cell envelope\, in particular their cell membrane. A system of proteins which has been demonstrated to be involved in multiple stress adaptation pathways is the RavA-ViaA-LdcI triad in Escherichia coli. RavA and ViaA are two proteins with as of yet unknown function that have been shown to sensitise E. coli to aminoglycoside antibiotics under anaerobic conditions. RavA forms a large complex with LdcI\, an inducible lysine decarboxylase which is one of the central enzymes involved in acid stress response of E. coli. Both RavA and ViaA have been shown to bind specific anionic lipids and their lipid binding capacity is strongly linked to their sensitising effect to aminoglycosides.\n​This thesis presents the exploration of the connections these three proteins have to each other and their other binding partners by optical and electron microscopy in order to elucidate how their action leads to antibiotic sensitisation and what role their connection to the cell membrane and acid stress might play in this regard. It is shown that LdcI prefers to localise to the cell periphery to efficiently counteract acid stress and that mutations of its active site lead to large domain movements which might play a crucial role in its enzymatic activity. Furthermore\, an investigation of liposome decoration by RavA and ViaA is presented\, demonstrating the effect they have on membrane shape. In addition\, the first cryo-EM structure of ViaA is presented using helical repeat proteins to stabilise the protein. Finally\, predictions of RavA and ViaA protein-protein interactions in the inner E. coli membrane reveal possible functional targets of the proteins and the implications of these new possible avenues for action are discussed with regard of the microscopy investigations.\n\n—\n​​\n\n\nLes séminaires et soutenances sont ouverts à tous\, notez toutefois que l’accès au campus EPN nécessite un avis de rendez-vous. Merci de remplir ce formulaire  et de l’adresser\, plus de 48h à l’avance\, à ce contact. Pensez à vous munir d’une pièce d’identité le jour de votre visite.
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-moritz-kirchner-irig-ibs/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs
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