The key pathological marker in Alzheimer’s disease (AD), the most common neurodegenerative disorder, is the formation of plaques primarily consisting of aggregated Amyloid-beta (Aβ) peptides. In addition to AD, Aβ plaques also form in other neurodegenerative diseases, such as dementia with Lewy bodies (DLB) and Parkinson’s disease (PD). It is generally believed that Aβ species with distinct structural features contribute differently to the pathology of the diseases. However, the specific structural properties of Aβ species related to its toxicity in different diseases remain largely unknown. To address this critical question, we propose to investigate the structure, propagation, and toxicity of Aβ species derived from brain tissues with AD, PD, and DLB with AD. The team of researchers, Drs. Ivanova, Ramamoorthy and Wang, have unique, and yet, complementary sets of technical skills in structure biology, biochemistry, biophysics and cell biology, which allow in depth investigations of the structure and toxicity of Aβ species associated with different neurodegenerative diseases. Using biophysical and biochemical tools, the Ivanova lab has successfully isolated and propagated alpha-synuclein species from brain tissues with multiple system atrophy (MSA). The Ramamoorthy lab has the expertise in characterizing the structures of tissue-derived Aβ oligomers and fibrils by NMR and other biophysical methods. The Wang lab has established cell-based assays to test Aβ toxicities on the structure and function of intracellular membrane organelles such as the Golgi apparatus, which will be essential for characterizing the cytotoxicity of the tissue-derived species. With this multidisciplinary approach, we expect to reveal molecular determinants of Aβ species and toxicities, which are disease specific, moving us closer to achieving the long-term objective of developing therapies that target the species associated with distinct disease phenotypes.