Berlin 2012 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

BP: Fachverband Biologische Physik

BP 1: Proteins I

BP 1.7: Topical Talk

Montag, 26. März 2012, 11:30–12:00, H 1058

Cryo electron microscopy of biological materials — •Wolfgang Baumeister — Max-Planck-Institute of Biochemistry, Martinsried, Germany

Today, essentially all electron microscopy of biological materials aiming for molecular resolution is cryo electron microscopy. Samples are examined in a frozen-hydrated state to avoid artifacts resulting from dehydration or from chemical fixation and staining. Three different imaging modalities are used: Electron crystallography, which can provide atomic resolution structures but requires that the molecules under study form well-ordered two-dimensional crystals. Single particle analysis which is the method of choice for large multi subunit protein complexes; in conjunction with other methods (hybrid methods) it can provide structures with pseudo-atomic resolution. Electron tomography allows to study large (non-repetitive) structures, such as organelles or cells, and to analyze molecular structures in situ, i.e. in their unperturbed functional environments.

In cryo electron tomography the main challenges are sample preparation and the molecular interpretation of tomograms with a poor signal-to-noise ratio. Denoising, automated segmentation, pattern recognition, and subtomogram averaging are the key strategies in tomogram interpretation. Focused ion beam technology is an emerging tool in the micromachining of frozen-hydrated samples. In conjunction with correlative fluorescence microscopy allowing the navigation of complex samples, thin lamellae suitable for tomography can be produced in a targeted manner.