Rapid aggregation and assembly in aqueous solution of Aβ (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 thioflavin T fluorimetry, 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 fibril growth. Our quantitative results, which confirm 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 fibril formation takes place.