The research focus of the Southworth Lab is to determine the structural and mechanistic basis of protein quality control systems in protein folding and neurodegeneration in aging. Dr. Southworth’s lab has contributed more than 35 structures of macromolecular protein complexes solved by cryo-EM to the Protein Data Bank. The group recently solved cryo-EM structures of tau filaments from Alzheimer’s Disease brain bound to a diagnostic PET tracer ligand revealing novel a small molecule binding mechanism for targeting disease amyloids9. As discussed above, with the recent Beckman Instrumentation grant for the development of new focused-ion beam milling (FIB-SEM) methods with cryo-electron tomography (cryo-ET), Dr. Southworth acquired a newly-developed plasma FIB-SEM (Helios Hydra) with advanced capability in high-volume plasma milling and high-resolution SEM imaging, essential advancements for preparing and imaging human tissue samples. With their recently developed imaging pipeline they are now poised to begin studying disease filaments in human tissues as outlined in this proposal. The work proposed here, therefore, represents new research directions for the lab and does not overlap with existing supported research. By contributing these advanced resources and expertise, the Southworth lab will be an integral member and collaborator on this proposed project to accelerate understanding of age-related diseases. The proposed research is distinct from previously funded research in the Southworth lab, since it investigates for the first time tau structures in cell based models and fresh human tissue, in a novel collaboration with the co-investigators.