Fig. 4.

Predictions of αS aggregation kinetics at low concentrations by nucleation–conversion–polmerization models. After fitting to the available kinetic data, both unimolecular (Fig. 3) and bimolecular (SI Appendix, Fig. S12) conversion models were used to predict how the concentrations of low-FRET efficiency oligomers and high-FRET efficiency oligomers vary over time at low initial monomer concentrations; the fitting was carried out by considering only the total concentration of oligomers at these low monomer concentrations. As the fitting was carried out over a reaction time of 33 h and overlaid over 54 h, a similar time range was used for the predictions. From the first two columns, it is clear that a unimolecular conversion model alone predicts similar concentrations of both types of oligomers and furthermore predicts a ratio of concentrations that is very stable with changing initial monomer concentration. These predictions are consistent with the single-peak FRET histograms at low concentrations shown in Fig. 2B.