An integrated Rheo-NMR platform for real-time, site-specific kinetic analysis of amyloid formation
Amyloid fibrils are protein aggregates associated with neurodegenerative diseases. Their formation proceeds through protein- and condition-dependent microscopic pathways that can generate structurally and biologically distinct aggregates, yet these pathways are inferred from ensemble-averaged measurements. Amyloid formation is often slow under quiescent conditions, prompting agitation. However, conventional agitation precludes simultaneous high-resolution solution nuclear magnetic resonance (NMR) spectroscopy, limiting site-specific kinetic analysis of microscopic aggregation pathways. Here we present an integrated Rheo-NMR platform combining controlled shear flow, time-resolved NMR spectroscopy and mechanistic kinetic modeling to quantify site-specific amyloid-formation kinetics in a single, continuously monitored reaction. Applied to -synuclein under dilute and polyethylene glycol (PEG)-induced liquid-liquid phase separation (LLPS) conditions, the method revealed environment-dependent redistribution of kinetic signatures associated with primary nucleation-elongation and secondary nucleation-elongation pathways across the sequence. The platform distinguishes changes in overall aggregation rates from differences in residue-specific kinetic profiles, providing a quantitative framework for dissecting environment-dependent amyloid formation.