Decreased Water Mobility Contributes To Increased α‐Synuclein Aggregation**

The solvation shell is essential for the folding and function of proteins, but how it contributes to protein misfolding aggregation has still be elucidated. We show that mobility H2O molecules influences rate amyloid α-synuclein (αSyn), a associated with Parkinson's disease. When within reduced by presence NaCl, αSyn increases. Conversely, in CsI increased reduced. Changing solvent from D2O leads rates, indicating driven effect. not directly due change structural conformations αSyn, also influenced reduction both mobility. propose promoting intermolecular interactions.