Next, we studied the effect of pH on fibril stability. We prepared αSyn fibrils at pH 7.4 (neutral (N) polymorph) and 5.5 (acidic (H) polymorph) in the presence of 150 mM NaCl to mimic cytosolic and lysosomal pH, respectively . We characterized their morphology using AFM and found that the neutral polymorph has an average pitch length of 162 ± 47 nm and height of 5.2 ± 0.7 (Figure ). The morphology of acidic polymorph was difficult to assess due to the clumping of individual fibrils into amorphous-like large particles observed by AFM (Figure ). When depolymerized in their native conditions, the acidic polymorph was more stable compared to the neutral polymorph (Figure ).