Yale researchers map atomic structure of toxic Alzheimer's peptide

Researchers at Yale School of Medicine have resolved the atomic structure of oligomeric amyloid beta, a short, rod-like peptide assembly about 65 nanometers long that differs from the long filaments of plaque amyloid beta. The study, published July 22 in Nature Communications, marks the first characterization of this intermediate form isolated directly from human Alzheimer's brain tissue.

Amyloid beta occurs naturally in healthy brains, but in Alzheimer's disease it misfolds and aggregates. For over a century, large plaques have been a hallmark of the disease, yet whether they cause damage or are merely a byproduct has been debated. Emerging evidence points to the intermediate oligomeric form as the primary driver of neuronal injury, but its structure remained unknown because the peptides bind tightly to neuronal receptors and are scarce in unbound form.

To overcome this, the team led by Stephen Strittmatter, chair of the Department of Neuroscience, treated Alzheimer's-affected human brain tissue with a drug that displaced oligomeric amyloid beta from its receptors. They then purified the peptides and confirmed their toxicity by adding them to cultured human neurons, which became damaged. Multiple microscopy methods revealed the distinct short-rod architecture and specific atomic arrangements that separate oligomers from plaque filaments.

The researchers also found that oligomeric amyloid beta can seed the formation of additional toxic peptides, with polymerization biased against forming long filaments. This self-propagating property may amplify damage in the brain.

Two FDA-approved antibody therapies, lecanemab and donanemab, reduce overall amyloid beta and slow disease progression by roughly 30%, but they carry risks of brain inflammation and bleeding. These drugs target both plaque and oligomeric forms, and their toxicities are thought to stem largely from plaque clearance. Knowing the precise atomic differences between the forms opens the possibility of designing agents that selectively neutralize the toxic oligomers while leaving nonpathogenic amyloid beta untouched.

Strittmatter said the atomic-resolution view of the harmful species provides a structural basis for developing more specific treatments. The work was supported by Yale University and published in Nature Communications (DOI: 10.1038/s41467-026-75895-9).