LJC

Partenaires

CNRS

Rechercher

Sur ce site

Sur le Web du CNRS

Accueil du site > Animations Scientifiques > Séminaires 2012 > Dominique Ploton - Targeted quantification of water and ions using correlative Cryo-Fluorescence and Analytical Scanning Transmission Electron Microscopy.

Dominique Ploton - Targeted quantification of water and ions using correlative Cryo-Fluorescence and Analytical Scanning Transmission Electron Microscopy.

Speaker : Dominique Ploton, Faculté de Médecine de Reims

When : Thursday 15 november at 11am

Where : Salle CO23 (grande salle de réunions du CBP rez-de-chaussée LR6)

Title : Targeted quantification of water and ions using correlative Cryo-Fluorescence and Analytical Scanning Transmission Electron Microscopy.

The cell is a heterogeneous crowded volume, with estimated mean mass concentrations of macromolecules and of water ranging from 7.5 to 45 % and 55 to 92.5 %, respectively. However, the concentrations of macromolecules, ions and water are unknown at the nanoscale within the various cell compartments. To address that point, we recently developed a new approach with physicists : Correlative Cryo- Fluorescence and Analytical Scanning Transmission Electron Microscopy. This approach allows a targeted quantification of ions and water contents at the nanoscale (using energy- Dispersive X-ray Spectrometry and Scanning Transmission Electron Microscopy dark field imaging) within domains previously identified on the same ultrathin cryosection by examination of specific GFP-tagged proteins. Thus, various elements (C, N, P and S) and ions (K+, Cl-, Mg2+ and Na+) can be quantified in mmol/l (and not in mmol/kg of dry matter as classically done). This new approach was used to quantify water, elements and ions in the cytosol, mitochondria, condensed chromatin, nucleoplasm and nucleolar components of control and stressed cancerous cells. The water content of control cells was between 60 and 83 % (in the mitochondria and nucleolar fibrillar centers, respectively). Potassium, the most abundant ion, was present at concentrations of 128 to 462 mmol/l in nucleolar fibrillar centers and condensed chromatin, respectively. The induction of nucleolar stress by treatment with a low dose of actinomycin-D to inhibit rRNA synthesis resulted in both an increase in water content and a decrease in the elements and ions content in all cell compartments.

Dans la même rubrique :