Central Electron Microscopy Facility
The mission of the Central Facility Electron Microscopy is to provide access to the latest electron microscope (EM) technology for high resolution imaging. Over the last several years, especially the field of cryo-EM has undergone a revolution. The development of new detector hardware has led to a so-called „resolution revolution“ in cryo-electron microscopy.
The high-end cryo-electron microscopes of our facility are equipped with this new type of direct electron detectors and allow us to achieve high resolution structures of cryofixed proteins, protein complexes, cell organelles and cells in their native state.
In 2015 a new FEI Titan Krios EM was installed. This 300kV instrument is equipped with a corrector for spherical aberrations (Cs-corrector), a special field emission gun for higher beam brightness and lower energy spread (X-FEG) and a volta phase plate (VPP). The Titan Krios collects data automatically for up to 7 days with Gatan K2 (including QuantumLS energy filter) and FEI Falcon III direct electron detection cameras.
Beside the FEI Titan Krios the facility also enables the use of a 300kV cryo-EM JEOL JEM 3200FSC instrument to collect high resolution data. This microscope is equipped with a field emission gun, in-column omega energy filter and a TVIPS F416 4K-camera.
For high-throughput screening of negative stained and cryofixed samples two 120kV EM are available in the facility: The JEOL JEM 1400 EM (with additional high tilt holder for tomography) and a FEI Tecnai Spirit EM. Data acquisition is performed on both instruments with a TVIPS F416 4K camera.
Imaging capabilities of the facility are supported by a complete pipeline of cryo-sample preparation equipment: Vitrification is performed by automated plunge freezing (FEI Vitrobot and Gatan Cp3 cryoplunger) or by high pressure freezing (LEICA HPM100). Cryo-ultramicrotomy is done with the help of a Leica FC6 cryo-ultramicrotome.
In addition to these cryo-techniques the facility offers a broad range of electron microscopical methods for the examination of chemical fixed specimen, e.g. resin embedding of whole cells, cell organelles or tissues. Correlative light and electron microscopy is performed with the diaminobenzidine (DAB)-photobleaching method: Fluorescently marked macromolecules (e.g. proteins fused with GFP-derivates) are detected in the fluorescence light microscope. After photobleaching in the presence of DAB the fluorescent signal is transformed into an electron dense signal that can be localized with nanometer resolution within the ultrastructural context using the EM.