Influence of DiY-α-syn and other DiY species on the aggregation of α-syn. Kinetics of fibril formation of 25 μM non-irradiated WT α-syn in the presence of (black) 25 μM of non-irradiated WT α-syn, or in the presence of 25 μM of the indicated DiY species: (a) single Y-to-A mutants, (b) double/triple Y-to-A mutants, (c) quadruple tyrosine knockout mutant, DiY/tyrosine mix (prepared as DiY α-syn), and DiY-TauK18Δ280AA. Mean curves of triplicates are shown (with the exception of the black curve, which is the mean of 15 experiments), normalized by setting the highest fluorescence intensity in the aggregation reaction of non-irradiated WT α-syn to unity.