300 keV FEG Electron Cryo Microscope for Single Particle Analyses and Tomography

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The recent technological developments in cryo-electron microscopy (cryo-EM) have led to a dramatic breakthrough with respect to improved resolution and, therefore, in its applicability. Using the novel direct electron detectors the two main applications of cryo-EM, single particle analysis and cryo-tomography, now routinely reach resolutions around 3 Å and 10 Å, respectively. This makes single particle cryo-EM the method of choice for a broad range of questions in structural biology that have usually been addressed by X-ray crystallography. In the case of cryo-tomography the improved resolution allows for the identification of individual macromolecular complexes in their native cellular environment and, after sub-tomogram averaging, the recognition of nucleic acid and protein secondary structure. As a result, this development has led to an explosion in the demand for data collection time, in particular, since increasingly smaller particles and also native, non-abundant complexes can be successfully subjected to structure determination. However, the currently available equipment at the Gene Center cannot satisfy this demand: firstly, the capacity of one high-end microscope is insufficient as to meet the increasing needs. Secondly, the existing equipment is optimized for fully automated high-through-put data collection of large particles. Consequently, data with optimal quality cannot be collected for smaller particles or for cryo-tomography. Therefore, we apply to purchase a second high-end cryo-microscope, which, in general, is expected to increase available data collection options and time. More specifically, the proposed microscope is planned to be equipped with a phase plate, an energy filter and a direct detector, thus allowing analysis of small particles as well as cryo-tomography applications.