– Amyloid-β (25-35) (Aβ (25-35)) is an 11-residue fragment of the Aβ protein that retains the physical and biological characteristics of the full length peptide. It forms fibrils that react to thioflavin T and Congo red and are organized in a cross-β arrangement of β-strands similar to Aβ (1-40) and Aβ (1-42) fibrils. Aggregated Aβ (25-35) decreases the viability of rat adrenal PC12 cells. It also decreases the viability of primary rat cortical neurons at concentrations ranging from 1 nM to 30 μM.