Ion Mobility Spectrometry Reveals the Mechanism of Amyloid Formation of Aβ(25-35) and Its Modulation by Inhibitors at the Molecular Level: Epigallocatechin Gallate and Scyllo-inositol

Amyloid cascades leading to peptide beta-sheet fibrils and plaques are central to many important diseases. Recently, intermediate assemblies of these cascades were identified as the toxic agents that interact with the cellular machinery. The relationship between the transformation from natively unstructured assembly to the beta-sheet oligomers to disease is important in understanding disease onset and the development of therapeutic agents. Research on this early oligomeric region has largely been unsuccessful since traditional techniques measure only ensemble average oligomer properties. Here, ion mobility methods are utilized to deduce the modulation of peptide self-assembly pathways in the amyloid-beta protein fragment A beta(25-35) by two amyloid inhibitors (epigallocatechin gallate and scyllo-inositol) that are currently in clinical trials for Alzheimer's Disease. We provide evidence that suppression of beta-extended oligomers from the onset of the conversion into beta-oligomer conformations is essential for effective attenuation of beta-structured amyloid oligomeric species often associated with oligomer toxicity. Furthermore, we demonstrate the ease with which ion mobility spectrometry mass spectrometry can guide the development of therapeutic agents and drug evaluation by providing molecular level insight into the amyloid formation process and its modulation by small molecule assembly modulators.