Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 100: Poster Session I
AKB 100.11: Poster
Samstag, 5. März 2005, 16:45–18:45, Poster TU D
Helium vs. Nitrogen cooling of biological samples for Cryo Electron Tomography — •Gabriele Schweikert1, Guenter Pfeifer1, Uwe Luecken2, Stephan Nickell1, Wolfgang Baumeister 1, and Juergen Plitzko1 — 1Max-Planck-Institute of Biochemistry, Struktural Biology, 82152 Martinsried, Germany — 2FEI Company, 5600 KA Eindhoven, The Netherlands
In the life sciences, cryo electron microscopy is used increasingly due to its power to reveal the structure of single protein complexes within their cellular context. The radiation-sensitivity of biological specimens, however, sets a limit to the possible examination using highly energetic electrons. We will present our findings concerning radiation damage and cryo-protection at L-He temperature in comparison to L-N2, especially with regard to the application of cryo electron tomography. We have obtained dose series of vitrified specimens of a crystalline surface layer (HPI-layer) at L-N2 and L-He temperature and analysed them by means of Fourier shell correlation. Additionally, we determined the relative mass loss during exposure using the log-ratio-technique. To assess the differences in ice density, we have measured the inelastic mean free path (MFP) of the electrons in low-density amorphous ice at L-N2 and high-density amorphous ice at L-He temperature at 300 kV accelerating voltage with an FEI Tecnai F30 instrument equipped with a Gatan imaging filter.