Fig. 7. Impact of alcohol concentration on the aggregation behavior of αS. (A) Fraction of antiparallel aggregates found in the plateau phase of aggregation reactions of 100 μM αS in PBS pH 7.4 (37 °C) in the presence of different MeOH concentrations as derived from IR deconvolution (black dots) or pyrene E/M ratio (grey dots) analysis. For the pyrene data, error bars show the standard deviation of triplicate experiments, while for the IR data the uncertainty obtained from the global spectra fitting was 0.02 (see ESI and Methods in ESI†). The stability of parallel (generated at 10% MeOH) and antiparallel (generated at 35% MeOH) β-sheet aggregates under conditions at which the other type of aggregates is preferentially formed was analyzed (marked as blue and orange points and arrows, respectively). (B) Stability of the aggregates indicated in panel A by IR spectra.