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SUMMARY:Liquid-Liquid Crystalline Phase Separation of Amyloid Fibrils - Pr
 of. Raffaele Mezzenga\, ETH Zurich
DTSTART:20220316T100000Z
DTEND:20220316T110000Z
UID:TALK171536@talks.cam.ac.uk
CONTACT:Alyssa Miller
DESCRIPTION:Liquid-Liquid phase separation of macromolecules is ubiquitous
  in nature and implies\, in the most common form\, the demining of a macro
 molecule rich-phase (often as droplets) from a macromolecules-depleted con
 tinuous phase. Liquid-liquid phase separation in the context of biomacromo
 lecules has been shown to be at the center of important cellular processes
  and is involved in the formation of the so-called membraneless organelles
 . In the case of filamentous colloids\, the process is similar in the outc
 ome\, but fundamentally different in the ruling physics since the interact
 ions among the biomacromolecules are essentially of liquid crystalline nat
 ure. We call this Liquid-Liquid Crystalline Phase Separation (LLCPS). In t
 his talk I will discuss our recent work on amyloid liquid-liquid crystalli
 ne phase separation\, including the discovery of cholesteric phases in amy
 loids fibrils and the new implications that this brings to the fields of l
 iquid crystals and liquid-liquid phase separation in general. By selecting
  amyloid fibrils as model filamentous chiral colloids\, an unprecedented b
 readth of liquid crystalline morphologies is observed\, where up to six di
 stinct configurations of the nematic field are observed under identical co
 nditions. Amyloid-rich droplets -also known as tactoids- nucleating from a
 n isotropic phase via liquid-liquid phase separation show homogeneous\, bi
 polar\, radial\, uniaxial chiral and radial chiral nematic fields\, with a
 dditional parabolic focal conics in bulk. Furthermore\, tactoids of differ
 ent symmetry undergo order–order transitions by flow-induced deformation
 s of their shape. Tactoids align under extensional flow\, undergoing extre
 me deformation into highly elongated prolate shapes\, with the cholesteric
  pitch decreasing as an inverse power-law of the tactoids aspect ratio. Va
 riational and scaling theories allow rationalizing the experimental eviden
 ce as a subtle interplay between surface and bulk energies and to debate o
 n the thermodynamic nature of theses transitions. I will conclude the talk
  discussing the implications that LLCPS may have in the field of amyloid-b
 ased neurodegenerative diseases. \nReferences:\n\n# G Nyström\, M Arcari\
 , R Mezzenga\, Nature Nanotechnology 13\, 330 (2018)\n# M Bagnani\, G Nyst
 röm\, C De Michele\, R Mezzenga\, ACS Nano 13\, 591 (2019)\n# M Bagnani\
 , P Azzari\, S Assenza\, R Mezzenga\, Scientific Reports 9\, 1-9 (2019)\n#
  H Almohammadi\, M Bagnani & R Mezzenga\, Nature Communications 11\, 5416 
 (2020)\n# P Azzari\, M Bagnani\, R Mezzenga\, Soft Matter\, 17\, 6627 (202
 1)\n
LOCATION:https://zoom.us/j/95370222402
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