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DTSTART;TZID=Europe/Paris:20260626T110000
DTEND;TZID=Europe/Paris:20260626T120000
DTSTAMP:20260604T145405Z
CREATED:20260604T145405Z
LAST-MODIFIED:20260604T145405Z
UID:10000191-1782471600-1782475200@sfp-alpes.fr
SUMMARY:Christophe MASSELON (CEA-Irig/BGE) et Vincent AGACHE (CEA-Leti/DTIS)
DESCRIPTION:Sensing Mass at the Nanoscale : Suspended Nanochannel Resonators and NEMS-MS for Biology\nRésumé : \n\nDetermining the mass of biological nanoparticles opens new avenues for characterizing biological systems at their own scale. In this joint seminar\, researchers from LETI and IRIG will present two complementary nanoresonator platforms : Suspended Nanochannel Resonators (SNR)\, which operate in solution\, and Nanoelectromechanical Mass Spectrometry (NEMS-MS)\, which operates in the gas phase. Together\, these technologies cover a range of biological particles\, from lipid nanoparticles and extracellular vesicles to viral particles. Beyond the technical principles underlying each platform\, selected applications will illustrate the potential of these approaches for the characterization of biological samples.​​​​​\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.\nPensez à vous munir d’une pièce d’identité le jour de votre visite.
URL:https://sfp-alpes.fr/event/christophe-masselon-cea-irig-bge-et-vincent-agache-cea-leti-dtis/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Séminaire
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260626T110000
DTEND;TZID=Europe/Paris:20260626T120000
DTSTAMP:20260618T094136Z
CREATED:20260618T094136Z
LAST-MODIFIED:20260618T094136Z
UID:10000199-1782471600-1782475200@sfp-alpes.fr
SUMMARY:Rémi AVRILLER
DESCRIPTION:Resonance energy transfer in molecular aggregates : a stochastic approach\nLe séminaire théorie est financé par la fédération de recherche Quantalps. \nRésumé : \nWe investigate theoretically how energy dissipates and migrates from one place to another in complex and bi-dimensional molecular aggregates. In this context\, a key role is played by resonance electronic energy transfer (RET) processes [1] through which an excitation initially stored onto a donor molecule (D) can be transferred to an acceptor molecule (A). Despite its long history\, the mechanism of RET is still not completely understood and is the object of intense research activities and debates [2].\nIn this presentation\, we address the question of how to describe collective and non-equilibrium effects in RET processes after all the donor molecules have been excited by a pump laser (see Fig). We predict that\, due to the dimensionality of the network\, the effective rate of RET scales as ^{\alpha}\, with the average distance between individual excited donors and their nearest-neighbor acceptor molecules\, and \alpha \in [-6\, -2] an exponent depending on the spatial distribution of molecular pairs in the 2D sample [3]. We show departures from this mean-field description arising from fluctuations and spatial correlations between several molecules involved in the RET process.\nThe relevance of such stochastic approaches is further investigated in order to capture the essential features of more recent experiments related to energy transfer in optical cavities [4]. In the latter case\, we show as preliminary results that the interaction between pairs of molecules inside cavity can be highly modified with consequences on the kinetics of RET processes inside cavity [5]. \nReferences :\n[1] T. Förster. “Transfer mechanisms of electronic excitation energy” (1960). \n[2] S. Jang\, M. D. Newton\, and R. J. Silbey. Phys. Rev. Lett. 92\, 218301 (2004). \n[3] R. Avriller\, A. Marché\, and G. Jonusauskas\, Phys. Rev. B 108\, 205419 (2023). \n[4] X. Zhong et al.\, Angewandte Chemie International Edition\, 56(31)\, 9034-9038 (2017). \n[5] K. Wu\, D. Hagenmüller et R. Avriller\, in preparation (2026). \n_ \nContact : jeanne.colbois@neel.cnrs.fr
URL:https://sfp-alpes.fr/event/remi-avriller/
LOCATION:LPMMC – salle Roger Maynard (G421)\, CNRS - LPMMC 25 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Séminaire
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DTSTART;TZID=Europe/Paris:20260626T140000
DTEND;TZID=Europe/Paris:20260626T160000
DTSTAMP:20260529T140307Z
CREATED:20260529T140204Z
LAST-MODIFIED:20260529T140307Z
UID:10000170-1782482400-1782489600@sfp-alpes.fr
SUMMARY:Soutenance de Thèse de Henri GRÖGER (Irig/IBS)
DESCRIPTION:Structural and functional characterisation of the vaccinia virus PLD- fold endonuclease K4\, telomere-binding protein i1 and the DNA polymerase complex E9A20D4\nRésumé : \n\nPoxviruses\, such as the vaccinia virus (VACV) and the monkeypox virus\, are large\, enveloped dsDNA viruses from the orthopoxvirus genus that replicate entirely within the host cytoplasm. The 2022 and 2024 outbreaks of mpox\, caused by clade IIb and Ib\, respectively\, have revealed the lack of efficient antivirals and underlined the urgency of understanding poxvirus biology. The poxvirus genome is flanked by short\, inverted complementary hairpin telomeres that feature mismatched bases and insertions essential for viral replication. ​\n​\nThis thesis presents the structural and functional characterisation of three proteins central to poxvirus DNA metabolism : the E9A20D4 DNA polymerase holoenzyme\, and two telomere-interacting proteins\, the PLD-fold nuclease K4 and I1. The project initially focused on the VACV polymerase holoenzyme\, but was reoriented towards the telomere-interacting proteins following the publication of numerous competing mpox polymerase structures. ​\n​\nHaving established that VACV polymerase activity requires K+ and is inhibited by Na+\, I undertook a structure determination of the E9A20D4 polymerase holoenzyme bound to template DNA\, primer and incoming nucleotide in the presence of K+\, using single-particle cryogenic electron microscopy (cryo-EM). I obtained both the structure of the complex E9exo−A20D4 as well as the structure of E9exo− alone bound to the primer-template DNA. The structures in the presence of K+ appear identical to published structures in the presence of Na+. However\, I identified an ion binding site in the exonuclease domain of E9. The thumb domain is disordered in the DNA-free structure\, partially disordered in DNA-bound E9 and ordered in the holoenzyme-DNA complex. SAXS data indicate conformational flexibility\, with more open conformations of E9A20D4 lacking an E9-D4 interface\, while mass photometry reveals partial dissociation of E9A20D4 at low concentrations\, even in the presence of substrate. ​\n​\nUsing cryo-EM\, I report the first structures of K4 in both apo and DNA-bound states\, revealing that the active site is occluded by an orthopoxvirus-specific C-terminal extension of the PLD fold that is displaced upon DNA binding. Biochemical characterisation demonstrates that K4 functions as a DNA-specific endonuclease with a preference for single-stranded DNA and hairpin loops. ​\n​\nI also report the first cryo-EM structure of I1 bound to DNA. I1 is known to bind to viral telomeres and is essential for virion maturation. Cryo-EM data showed the presence of dimers where the head domains 2 and 3 of I1 interact with the DNA duplex through electrostatic interactions\, while the N-terminal domain predicted to be α-helical remains disordered. In solution\, isolated I1 or I1 bound to DNA forms higher-order assemblies\, predominantly tetramers\, but also octamers. ​\n​\n​ Altogether\, these findings substantially advance the molecular understanding of poxvirus biology\, providing a foundation for future mechanistic studies and the rational development of antiviral strategies against emerging orthopoxvirus infections.\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 ibs.seminaires@ibs.fr. Pensez à vous munir d’une pièce d’identité le jour de votre visite.\n\n  \n  \n  \n  \n  \n 
URL:https://sfp-alpes.fr/event/soutenance-de-these-de-henri-groger-irig-ibs/
LOCATION:Salle des séminaires du CIBB\, EPN Campus - 71 avenue des Martyrs\, Grenoble\, 38000\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IRIG - CEA":MAILTO:odile.rossignol@cea.fr
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