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Cryoelectron Microscopy

par douarche - publié le , mis à jour le


Cryo-TEM at LPS. (A) Cubosome (phytantriol/polymer/water). (B) Supra-crystal of gold nanoparticles. (C) Bacteriophage capsid containing a DNA molecule condensed into a toroid. (C) Liquid crystalline phase of nucleosomes. Scale bar 20 nm.

CryoEM let us visualize biological and soft matter objects while preserving their hydrated state and native ionic environment, to access their conformations and interactions. One major interest of the method is to be able to explore conformational changes of the macromolecular complexes under physicological conditions, in the aim to relate these changes to their functional activities.
We use both thin film cryoEM, to image macromolecular complexes and nano-objects in solution, and CEMOVIS (Cryo-Electron Microscopy Of VItreous Sections) to image biologiocal tissue and cells, or bulk liquid crystals.

The SOBIO team hosts the CRYO-LPS platform of the National facility METSA


JEOL 2010F-CRYO, 200kV FEG, equipped with a Gatan 626 cryo-holder and a Gatan Utrascan 4K



Two methodes are used to vitrify the samples at low temperature :
- The plunging method is used for small objects suspended in solution. The lab is equipped with 2 home made plunge-freezing devices and 1 Vitrobot Mark IV vitrification robot (Thermofischer).
- The « slam-freezing » method (an alternative to high pressure freezing) is used for entire cells and bulk samples. We use the Liquid Helium Cryovacublock device (Reichert).

  • Thin film vitrification  
    Freeze-plunging device (home-made) Vitrobot Mark IV (Thermofischer)
  • Bulk sample vitrification  
    Slam-freezing Cryovacublock



The CEMOVIS method, initially developped in the group of J. Dubochet (Lausanne), relies on the obtention of ultra-thin sections (40-100nm) of vitrified biological and soft matter samples.
Our cryo-microtome (Leica UC6/FC6) is installed in a temperature and humidity controlled room (RH <20%), and coupled to a fluorescence microscope to target Regions Of Interest.

We use CEMOVIS to explore a variety of systems : cultured eukaryotic cells and bacteria, unicellular eukaryotes (Paramecium, Euglena, yeast), tissues (Caenorhabditis elegans), polymers and colloids in concentrated solutions, lyotropic liquid crystals, ...




Freeze fracture is used to analyse the liquid crystalline phases of DNA and nucleosomes.

Freeze-fracture device (BALZERS BAF 400T)

Visualisation of DNA fragments in a layer of the columnar hexagonal phase, after vitrification of the sample and freeze-fracture.



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