Aβ40(Italian) monomer cross-seeding with Aβ(WT) and Aβ(Italian) fibrils. A, fibril formation of monomeric Aβ40(Italian) in presence of a range Aβ isoform fibril seeds (10 % w/w): No seed (black); Aβ40(WT) (blue); Aβ42(WT) (red); Aβ40(Italian) (purple); and Aβ42(Italian) (green). B, typical representative (median) single trace of Aβ40(Italian) in the absence and presence of different seeds, same colors. Empirical kinetic parameters: tlag (C), t50 (D), and kapp (E) of Aβ40(Italian) fibril formation, mean from n = 9 for each condition, error bars are standard deviation. Total Aβ is 10 μM at pH 7.4, Hepes buffer (30 mM) and NaCl (160 mM). Self-seeding with Aβ40(Italian) fibrils (in purple) most effectively nucleates fibril formation, with a large reduction in the lag-time. One-way ANOVA test, a comparison between unseeded and seeded kinetics, ∗∗∗∗p ≤ 0.0001, ∗∗∗p ≤ 0.001. Aβ, Amyloid-β.