Utrecht University Cryo-Electron Microscopy Facility for Life Sciences

Traditionally transmission electron microscopy (TEM) uses ultra-thin sections of chemically fixed and plastic-embedded cells or tissues to observe the subcellular structure and membrane dynamics of organelles. Chemical fixation of samples does not perfectly preserve the ultrastructure of organelles. To circumvent this limitation, physical immobilization approaches (vitrification by high pressure freezing or plunging) have been developed. Cryo-electron microscopy tomography (cryo-ET) is becoming a mainstream technology for studying membrane architecture and high-order macromolecular complexes in their close to native cellular environment at nm resolution. The major advantage of the physical fixation method is that it immobilizes cellular structures within milliseconds, which is much faster than conventional chemical fixation procedures. In addition, over the past decade real-time imaging and 3D electron tomography have increasingly replaced classical static light microscopy imaging and 2D electron microscopy. In our hotel approaches are being developed to combine light microscopy with high-resolution (cryo) electron tomography (Correlative Light and Electron Microscopy, CLEM). CLEM utilizes complementary visual techniques that allow capturing dynamic cellular processes by (immuno) fluorescence and then zooms in on these events to identify their ultrastructure by EM tomography. 3D reconstruction techniques allow snap-frozen structures to be reassembled visually into 3D models thereby providing detailed z-axis information. The Cryo-Electron Microscopy Unit harbors the latest instrumentation in FIB-SEM, cryo-EM and tomography technology, 3D reconstruction software and data analysis, all serving the needs of strategic themes in life sciences, including the analyses of biomolecules at the atomic level.