Oxidative Footprinting of Fibrillar and Prefibrillar Oligomer Forms of Amyloid Beta

Abstract

The mechanism by which amyloid-β (Aβ) plaque accumulation contributes to neurodegeneration in Alzheimer's disease (AD) remains poorly understood. With biophysical, thermodynamic and kinetic characterization of the various Aβ structures involved in plaque development, we aim to identify connections between polymerization cascade events and AD pathogenesis. Herein, we present oxidative footprinting with mass spectrometry to probe the solvent accessibility of specific amino acid side chains in Aβ40 fibrils and oligomeric forms of Aβ40. These accessibilities are compared to those of a fully exposed reference state using hydroxyl radicals (∗OH) generated either by water radiolysis or by Fe(II)-EDTA reaction with peroxide. Using this information we distinguish topological relationships within the fibril to allow selection of the relevant tertiary structural model of fibrillar Aβ from those suggested by NMR and those by cryogenic electron microscopy. This work provides important steps towards correlating structure and morphology in Aβ fibrils -- essential for understanding the molecular pathogenesis of AD.