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UID:0-690@lptms.universite-paris-saclay.fr
DTSTART:20191121T143000Z
DTEND:20191121T170000Z
DTSTAMP:20191024T123711Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/soutenance-de-the
 se-luca-barberi/
SUMMARY:Soutenance de thèse: Luca Barberi - Petit amphi\, bâtiment Pascal
  n° 530 - 21 Nov 19 14:30
DESCRIPTION:Soutenance de thèse:\nInferring forces from geometry in biolog
 y\npar\n\nLuca Barberi\n&nbsp\;\n\nJury:\n\nRudolf Podgornik\, University 
 of Ljubljana (Slovenia) and Chinese Academy of Sciences (Beijing\, China)\
 n\nAnđela Šarić\, University College London (United Kingdom)\n\nClémen
 t Campillo\, Université d'Évry Val d'Essonne (France)\n\nAntonio De Simo
 ne\, Scuola Internazionale Superiore di Studi Avanzati (Trieste\, Italy)\n
 \nAurélien Roux\, Université de Genève (Suisse)\n\nPierre Sens\, Instit
 ut Curie (Paris\, France)\n\nMartin Lenz\, CNRS and Université Paris-Sud 
 (France)\n\n&nbsp\;\n\nRésumé :\n\nInter-molecular forces on which we ha
 ve poor prior knowledge are often essential for the stability and evolutio
 n of biological assemblies. In this thesis\, we focus on two such forces t
 hat are critically involved in the deformation of either biopolymers or me
 mbranes. We infer these forces by reconciling the geometry of such deforma
 tion with simple mechanical models.\n\nIn the first part of the thesis\, w
 e consider the attractive force between DNA molecules mediated by multival
 ent cations. This attraction is required to compensate DNA bending rigidit
 y when packaging large quantities of DNA in comparatively small environmen
 ts\, such as the nuclei of sperm cells. In vitro\, multivalent cations dri
 ve DNA condensation into dense toroidal bundles. Geometrical data on DNA t
 oroidal bundles give access to the competition between inter-helical attra
 ction and DNA bending rigidity. From these data\, we infer inter-helical f
 orces and argue that the toroid curvature weakens the adhesion between DNA
  molecules.\n\nIn the second part of the thesis\, we turn to the binding f
 orce of a membrane remodeling protein complex\, ESCRT-III\, to cellular me
 mbranes. ESCRT-III proteins assemble into membrane-remodeling polymers dur
 ing many cellular processes\, ranging from HIV budding to cytokinesis. The
  mechanism by which ESCRT-III polymers deform membranes is still unclear. 
 In vitro\, ESCRT-III polymers can reshape spherical membrane vesicles into
  helical tubes. We argue that helical tubes result from the peculiar posit
 ioning of membrane-binding sites on the surface of ESCRT-III polymers. Fur
 thermore\, we infer the binding force between ESCRT-III and membrane from 
 the geometry of helical tubes.\n\n&nbsp\;
CATEGORIES:seminars
LOCATION:Petit amphi\, bâtiment Pascal n° 530\, rue André Rivière\, Ors
 ay\, 91405\, France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=rue André Rivière\, Orsay
 \, 91405\, France;X-APPLE-RADIUS=100;X-TITLE=Petit amphi\, bâtiment Pasca
 l n° 530:geo:0,0
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