PROJECT SUMMARY Structural biology has played a key role in defining the molecular architecture of life, leading to fundamental insights into the function and biology of macromolecules. Within our Ohio Valley consortium, consisting of the University of Cincinnati, Cincinnati's Children's Hospital Medical Center, Miami University, and University of Kentucky, all have well-established programs in structural biology, with a major focus on X-ray crystallography. This has provided an outstanding training environment for graduate students and postdoctoral fellows to learn modern structural biology approaches to address fundamental questions around biomedically important macromolecules. However, in recent years, cryogenic electron microscopy (cryo-EM) has emerged as an indispensable technique for structural analysis of proteins and molecular complexes due to the fact that it can produce atom-resolution structures without drawbacks inherent to crystallization. Thus, our consortium structural biologists have been actively working to incorporate this technology into their research programs, primarily through collaboration and attempts to access instruments at other institutions. As a result of these efforts, we now have a critical mass of investigators that strongly justifies bringing this technology to our region. The University of Cincinnati has committed to laying the groundwork for this initiative by purchasing a Talos L120C instrument for negative stain analysis and a Vitrobot to prepare grids with a vitrified sample. These investments will allow users the ability to ascertain the quality of biological samples for further cryo-EM analysis. To take us to the next level, we are requesting NIH funding for a Glacios 200 kV microscope with Falcon 4 detector and autoloader, which will be housed in a newly developing cryo-EM facility at the University of Cincinnati. The Glacios will allow us to further optimize samples for structural analysis in house, or provide the justification for use of advanced cryo-EM instrumentation available at other institutions or NIH consortia for higher resolution studies. Collectively, the acquisition of the Glacios will directly benefit over 30 NIH funded investigators working in the focus areas of Cardiovascular, Cancer, Infectious Disease, and Neuroscience.