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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260302T110000
DTEND;TZID=Europe/Paris:20260302T120000
DTSTAMP:20260515T101547
CREATED:20260227T094612Z
LAST-MODIFIED:20260227T094814Z
UID:10000077-1772449200-1772452800@sfp-alpes.fr
SUMMARY:Moritz SENGER (Université d’Uppsala\, Département de chimie pour les sciences de la vie\, Suède)
DESCRIPTION:From Catalysis to Sensing : Proton Transfer in [FeFe]-hydrogenases\nRésumé : \nEnzymes are natures catalysts enabling challenging reactions at ambient conditions and at low overpotentials. In particular\, [FeFe]-hydrogenases which catalyse bidirectional H2 turnover (2e- + 2H+ <-> H2) at high turnover numbers raise interest for their application in a green hydrogen economy. In [FeFe]-hydrogenases catalysis takes place at a unique diiron cofactor that is equipped with carbon monoxide (CO) and cyanide (CN) ligands. They serve as intrinsic infrared active probes sensitive to redox changes located directly at the centre of the catalytic reaction. This in isolation inactive di-iron cofactor becomes efficient H2 catalyst when incorporated into the [FeFe]-hydrogenase protein scaffold. More recently H2 sensing [FeFe]-hydrogenases have been characterised using the identical cofactor but for H2 sensing. The fundamental design principles of the protein scaffolds to selectively tune cofactor function either to efficient H2 catalyst or to H2 sensor remain unknown.Here we use organic dyes to artificially activate catalytic [1-2] and sensory [3-5] [FeFe]-hydrogenases photochemically and investigate them via in situ ATR-FTIR spectroscopy. Following changes of the cofactor CO and CN ligands\, single carboxylic acid residues and collective amide I modes\, we show that protein scaffold differences are not limited to the cofactor second coordination sphere but extend through the whole protein via proton transfer pathways\, secondary structure changes and most likely dimerization events. More general\, our results give a first idea how protein scaffolds can tune cofactor functions. \nReferences :[1] M. Senger\, V. Eichmann\, K. Laun\, J. Duan\, F. Wittkamp\, G. Knor\, U. P. Apfel\, T. Happe\, M. Winkler\, J. Heberle and S. T. Stripp*J Am Chem Soc\, 2019\, 141\, 17394-17403.[2] M. Lorenzi\, M. T. Gamache\, H. J. Redman\, H. Land\, M. Senger* and G. Berggren*ACS Sustain Chem Eng\, 2022\, 10\, 10760-10767.[3] I. Voloshyn\, C. Schumann\, P. R. Cabotaje\, A. Zamader\, H. Land and M. Senger*Chem Commun (Camb)\, 2024\, 60\, 10914-10917[4] M. Senger*\, C. Schumann\, P. R. Cabotaje\, A. Zamader\, P. Huang\, H. Land and G. Berggren*Phys Chem Chem Phys\, 2025\, 27 (18)\, 9864-9875 [5] Cabotaje\, P. R. ; Sekretareva\, A. ; Senger\, M. ; Huang\, P. ; Walter\, K. ; Redman\, H. J. ; Croy\, N. ; Stripp\, S. T. ; Land\, H. ; Berggren\, G.J Am Chem Soc 2025\, 147 (5)\, 4654-4666. \nContact : ibs.seminaires@ibs.fr
URL:https://sfp-alpes.fr/event/moritz-senger-universite-duppsala-departement-de-chimie-pour-les-sciences-de-la-vie-suede/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Séminaire
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260302T110000
DTEND;TZID=Europe/Paris:20260302T120000
DTSTAMP:20260515T101547
CREATED:20260227T102022Z
LAST-MODIFIED:20260227T102040Z
UID:10000083-1772449200-1772452800@sfp-alpes.fr
SUMMARY:Matteo MILANI (ESPCI Paris)
DESCRIPTION:Rheofluidics: single-drop oscillatory rheology with microfluidics\nRésumé : \nThe measurement of frequency-dependent viscoelastic moduli is of paramount importance in many fields\, from material science to biology\, and is typically accomplished in bulk materials using commercial rheometers. The trend towards miniaturization in the biotechnology\, manufacturing and chemical processing industries has motivated the extension of viscoelastic measurements to microscopic objects with well-defined shape and size such as droplets\, vesicles\, microcapsules\, or even single cells. For instance\, local mechanical probes such as AFM nanoindentation can be used to probe single-cell stiffness\, and micropipette aspiration probes the interfacial properties of droplets and vesicles. Despite their versatility\, these techniques are characterized by complex deformation geometries and a relatively low throughput\, which makes them unfit to sample highly heterogeneous populations such as those typical of biological samples. To this end\, novel microfluidic approaches have been recently developed to measure the stiffness of cells and droplets flowing through narrow channels. These approaches are well-suited for applications requiring a high throughput\, but they lack the fine control of stress and strain required by quantitative mechanical measurements. Here\, we present a novel technique called Rheofluidics\, which combines the high throughput of microfluidics with the versatility of traditional rheological probes. Like a stress-controlled rheometer\, Rheofluidics measures the time-dependent deformation of droplets subject to a well-defined hydrodynamic stress\, whose time evolution is controlled by the shape of the microfluidic channel in which the droplets are flowing. To validate this approach and to demonstrate the power of this technique\, we study the linear and nonlinear rheology of oil droplets\, hydrogel beads and lipid vesicles\, extracting their viscoelastic properties with a throughput more than 1000 times higher than that of standard rheology. \nContact : gwennou.coupier@univ-grenoble-alpes.fr
URL:https://sfp-alpes.fr/event/matteo-milani-espci-paris/
LOCATION:LiPhy\, Salle de Conférence\, 140 rue de la Physique\, St Martin d'Hères\, 38400
CATEGORIES:Séminaire
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260302T140000
DTEND;TZID=Europe/Paris:20260302T150000
DTSTAMP:20260515T101547
CREATED:20260206T095950Z
LAST-MODIFIED:20260206T095958Z
UID:10000056-1772460000-1772463600@sfp-alpes.fr
SUMMARY:Ran TAO  (Institut Néel)
DESCRIPTION:Magnetic excitations in LuFe2Ge2\nRésumé : \nThe iron-based superconductor YFe2Ge2 (Tc ~ 1.8 K)[1] has attracted interest due to strong electronic correlations[2] and shows enhanced magnetic fluctuations in neutron scattering[3]. Its isoelectronic and isostructural sister compound LuFe2Ge2 orders antiferromagnetically below TN ~ 6.8 K\, and in clean crystals shows a resistive superconducting transition below 1 K. We present recent inelastic neutron scattering experiments on LuFe2Ge2 in the ordered and paramagnetic phases. The excitations are modelled with linear spin wave theory\, and we note some similarities to previous results in paramagnetic YFe2Ge2. \n[1] J. Chen et al.\, Phys. Rev. Lett. 125\, 237002 (2020).\n[2] J. Baglo et al. Phys. Rev. Lett. 129\, 046402 (2022). B. Xu et al.\, Proc. Natl. Acad. Sci. U. S. A. 121\, e2401430121 (2024).\n[3] H. Wo et al.\, Phys. Rev. Lett. 122\, 217003 (2019). \n_ \nContact : andrew.fefferman@neel.cnrs.fr
URL:https://sfp-alpes.fr/event/ran-tao-institut-neel/
LOCATION:CNRS – Salle Louis Weil (E424)\, CNRS - Institut Néel 25 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Séminaire
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