PROJECT SUMMARY The Biological Science Imaging Resource (BSIR) at Florida State University is the focal point for cryogenic electron microscopy (cryo-EM) in the state of Florida and the Southeast. No other University facility in the region has a comparable emphasis or facilities. This application requests funds to replace an ageing conventional transmission electron microscope (TEM) called a CM120 that was built in 1997 is no longer supported by service contract and no longer has parts available for repair. We will replace the CM120 with a ThermoFisher Glacios cryo-EM. The Glacios will serve two purposes: efficient specimen screening and high-resolution data collection, especially for low molecular weight samples. The Glacios will support the needs of 5 major users and 2 minor users. The Glacios is a 200 keV TEM with a field emission gun (FEG). It is equipped with an autoloader that can robotically load up to 12 samples at a time. The autoloader specimen carriers (cartridges) are compatible with the existing high-end Titan Krios at FSU making the Glacios and ideal screening microscope. The Glacios will be equipped with a Direct Electron (DE) Apollo electron detector. The Apollo will be the primary data collection camera for the microscope. We have the first commercial Apollo equipped on our Titan Krios, and it has produced the highest resolution 3D reconstruction at FSU. The Apollo is the fastest detector on the market which makes it ideal for screening. The combination of the FEG and the Apollo make the Glacios a good data collection instrument as well as a screening instrument. The study of frozen-hydrated specimens by electron tomography and single particle methods is a large and growing research emphasis worldwide. The robotic capabilities of the Titan-Krios with its ability to run state of the art automated EM software, such as Leginon, are well adapted to this need, but ultimately, efficient utilization of the Titan Krios requires preparation of quality specimens that have been prescreened. The Glacios will support NIH and NSF funded research of the major users which encompasses the atomic resolution imaging of muscle filaments, which has health relevence to cardiac muscle function; ribosome modification and CRISPR structure & function, the mechanisms of vesicle trafficking sulfur metabolism, amyloid structural biology, and automated structure determination.