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TZID:Europe/Paris
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BEGIN:VEVENT
UID:1-202@lptms.universite-paris-saclay.fr
DTSTART:20140411T140000Z
DTEND:20140411T150000Z
DTSTAMP:20140401T124227Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/physics-biology-i
 nterface-seminar-gijsje-koenderink/
SUMMARY:Physics-Biology interface seminar: Gijsje Koenderink - Amphi BLANDI
 N du LPS de la Faculté des Sciences d’Orsay (Bâtiment 510) - 11 Avr 14
  14:00
DESCRIPTION:Living soft matter\nGijsje Koenderink (FOM Institute AMOLF)\nOn
 e of the defining qualities of soft matter is that it is readily driven fa
 r from thermodynamic equilibrium by external stress. Driving forces such a
 s those due to an electric field or shear can drive colloidal suspensions 
 and polymer networks into fascinating non-equilibrium patterns\, such as b
 anded or ordered steady states. By contrast\, living cells naturally exhib
 it a unique form of internal driving in the form of chemomechanical activi
 ty. A prominent example is the cytoskeleton\, a meshwork of protein polyme
 rs and force-generating motor proteins that constitutes the scaffold of ce
 lls. The cytoskeleton is responsible for driving vital cellular functions 
 such as growth\, division\, and movement. In this talk\, I will present tw
 o examples of our research on active cytoskeletal polymer gels. The first 
 example concerns active contractility of the actin cortex\, which lies und
 erneath the cell membrane and drives shape changes by means of myosin moto
 rs. By reconstituting a simple model system composed of purified proteins\
 , we could show how myosin motors and actin filaments collectively self-or
 ganize into force-generating arrays. We discovered that motors contract ac
 tin networks only above a sharp threshold in crosslink density\, correspon
 ding to a connectivity percolation transition. Surprisingly\, the motors t
 end to drive initially well-connected networks robustly to this critical p
 oint. The second example I will discuss concerns cell shape polarization d
 irected by interactions of actin filaments with microtubules. I will show 
 that active force generation by growing and shrinking microtubules leads t
 o feedback between the organization of the actin filaments and microtubule
 s\, explaining earlier observations made in living cells.
LOCATION:Amphi BLANDIN du LPS de la Faculté des Sciences d’Orsay (Bâtim
 ent 510)\, 15 Rue Georges Clemenceau\, orsay\, France
GEO:48.698187;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
  orsay\, France;X-APPLE-RADIUS=100;X-TITLE=Amphi BLANDIN du LPS de la Facu
 lté des Sciences d’Orsay (Bâtiment 510):geo:48.698187,2.181768
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