It has been reported that fibrils formed in under conditions that simulate the acidic cellular compartments (lysosomes, endosomes) are destabilized when transferred to the neutral pH of the cytosolic environment . Our results agree with such observations and provide a quantitative view of this phenomenon. Aggregation of αSyn under acidic pH conditions is faster and the resulting fibrils (H) are slightly more stable compared to a neutral pH (Figure , Figure ; SI figure and). In contrast to the case above, the solubility differs between the fibril-forming conditions which explains the higher stability of fibrils at pH 5. However, the stability of H fibrils decreases upon transfer to physiological pH even below the stability of fibrils formed under such conditions. This indicates that a given fibril structure can be well-adapted to a given set of solution conditions, while a change in solution conditions can severely destabilize the structure. A change in pH can lead to a significant change in charge state of a protein and hence can lead to the emergence of additional unfavourable electrostatic interactions that render the given structure ill-adapted to the new solution environment.