Rapid aggregation and assembly in aqueous solution of A beta (25-35) peptide

The highly toxic Aβ(25-35) is a peculiar peptide that differs from all the other commonly studied β-amyloid peptides because of its extremely rapid aggregation properties and enhanced neurotoxicity. We investigated Aβ(25-35) aggregation in H2O at pH 3.0 and at pH 7.4 by means of in-solution analyses. Adopting UV spectroscopy, Congo red spectrophotometry and thiofl avin T fl uorimetry, we were able to quantify, in water, the very fast assembling time necessary for Aβ(25-35) to form stable insoluble aggregates and their ability to seed or not seed fi bril growth. Our quantitative results, which confi rm a very rapid assembly leading to stable insoluble aggregates of Aβ(25-35) only when incubated at pH 7.4, might be helpful for designing novel aggregation inhibitors and to shed light on the in vivo environment in which fi bril formation takes place