Figure 2
![Figure 2](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40035-019-0181-9/MediaObjects/40035_2019_181_Fig2_HTML.png)
Proposed models for the aggregation pathway. a Established schematic view for the pathway of aggregation of natively unfolded proteins [40]. According to this model, from an unfolded protein (UN) is formed an intermediate (I), which further aggregates into protofibrils (P) and eventually into fibrils (F). b The extended model we propose takes into account the possibility that a population of strains are produced, together with off-pathway oligomers that do not show the ability to form α-synuclein fibrils. Intermediate forms marked as I1 to In, each of them may produce a different protofibrillar form, marked as P1-n to Pn-n (the protofibril P1 derived from the intermediate I1 until the protofibril Pn derived from the intermediate In). It is noteworthy to state that the process may be in equilibrium between the aggregation of the intermediates and the rupture of protofibrillar forms. Further aggregation will cause the collapse into a limited number of fibrillar structures