A modified protocol to prepare seed-free starting solutions of amyloid-β (Aβ)₁₋₄₀ and Aβ₁₋₄₂ from the corresponding depsipeptides.

Preparing reliable, seed-free stock solutions of the highly amyloidogenic peptides amyloid-β (Aβ) is difficult. Besides the formation of aggregates during synthesis and storage, dissolution of the peptide is a critical step because vortexing can induce aggregation. To overcome this, synthesis of the more water-soluble depsi-Aβ(1-42) peptide, from which the native sequence is easily obtained, has been suggested. We further refined this technique, including a cutoff filtration step and switching the depsipeptide in basic conditions, to stabilize the formed native peptide. The obtained solutions of native Aβ(1-40) and Aβ(1-42) peptides were homogeneous and aggregate free, as indicated by thioflavin T and circular dichroism analysis.