In vitro monitoring of amyloid β-peptide oligomerization by Electrospray differential mobility analysis: An alternative tool to evaluate Alzheimer's disease drug candidates.

Alzheimer's disease (AD) is a neurodegenerative disorder linked to protein aggregation, like more than twenty other human pathologies. One major protein incriminated in AD is the 42-residue amyloid-β peptide (Aβ1-42 ) which aggregates to form neurotoxic oligomers and fibrils. While, low molecular weight oligomers have been evidenced as neurotoxic species, only scarce methods raise the challenge to monitor the beginning of the aggregation process, called oligomerization. We propose here an innovative and fast monitoring of the time-dependent Aβ1-42 oligomerization pattern by electrospray differential mobility analysis (ES-DMA). We developed a non-denaturing method based on ES-DMA to afford a real-time and direct characterization of the early, metastable and neurotoxic species. This technique provided their size distribution over time. At the beginning of the in vitro oligomerization process of Aβ1-42 , the size distribution is characterized by two populations with modal diameters around 3.5 and 4nm, corresponding to Monomer and Small oligomers. After few hours, larger species around 10nm are observed. The results were correlated to those obtained by capillary electrophoresis. We also demonstrated the ability of our method to evaluate Aβ1-42 kinetics modulators. Thereby, ES-DMA provides new insights on Aβ1-42 oligomerization in the presence of sugar-based peptidomimetic analogs which were recently described as modulators of Aβ1-42 self-assembly and neurotoxicity inhibitors.