Molecular rotors provide insight into the mechanism of formation and conversion of α-synuclein aggregates

α-synuclein is an intrinsically disordered protein forming amyloids in Parkinson's disease. Currently, detection methods predominantly report on the formation of mature amyloids but are poorly sensitive to the early-stage, toxic oligomers. Molecular rotors are fluorophores that sense changes in the viscosity of their local environment. Here, we monitor α-synuclein oligomer formation, based on fluorescence lifetime of molecular rotors. We detected oligomer formation and conversion into amyloids for wild type and two α-synuclein variants; the pathological mutant A30P and ΔP1 α-synuclein, which lacks a master regulator region of aggregation (residues 36-42). We report that A30P α-synuclein showed a similar rate of oligomer formation compared to wild type α-synuclein, whereas ΔP1 α-synuclein showed delayed oligomer formation. Additionally, both variants demonstrated a slower conversion of oligomers to amyloids. Our method provides a quantitative approach to unveiling the complex mechanism of α-synuclein aggregation which is key to understanding the pathology of Parkinson's disease.