300 kV transmission electron microscope for cryo applications

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A key aspect in all of the projects to be realized with the envisaged instrument is the determination of threedimensional structures of large, flexible, multi -factorial biomacromolecular and supramolecular complexes. The large size, flexible nature and low stability of these complexes limit possibilities to determine their structures by X-ray crystallography or NMR, leaving single particle cryo-EM as the only viable alternative. Near-atomic resolution cryo-EM maps (i.e. around 3.5 Å or better) are required to model the structures de novo, to model the portions of these structures that are not contained in available high-resolution structures of component subcomplexes or to accurately model different conformational states. To enter these resolution regimes, a 300 kV cryo-EM instrument with phase plate, energy filter and direct electron detector is required. Additionally, a capability for automated data collection is required to enable acquisition of a large number of micrographs - only with enough particle images, subsequent conformational sorting will provide enough images in each class for high-resolution structure analysis of all conformational states. Such structures would allow give rise to detailed hypotheses regarding the molecular mechanisms or modes of regulation of the molecular machineries involved, and would provide a basis for designing interfering mutations to directly test the putative mechanisms.