Figure 3.

a, b) ATR-FTIR spectra of Lys^RA (a) and Lys fibrils (b), shown in black, with the contributions obtained by curve fitting colored as follows: red: β sheet, green: random/α helix, blue: turns and loops, gray: side chains. c) SDS-PAGE of fibril samples isolated by ultracentrifugation during proteolysis. d) Positions of cleavage sites indicated on the polypeptide chain; rectangles and arrows indicate the location of the native α helices and β strands. The protease-resistant region of Lys^RA fibrils encompasses residues 29–108; almost exactly the same region (32–108) was found to be protease-resistant in early aggregates of Lys,[24] but maturation progressively transforms these species into fibrils protected from proteolysis (E. Frare, personal communication). e) Disaggregation by GdnHCl of fibrils formed by Lys^RA (gray) and Lys (black). f) Effect of fibrils formed by Lys^RA (gray) and Lys (black) on SH-SY5Y cells evaluated by the calcein viability assay; the mean and the 95 % confidence interval after three experiments are reported. g) Normalized aggregation propensity of the human proteome as a function of cellular localization and of the presence of disulfide bonds. The numbers in white represent the number of sequences belonging to each class.