Figure 2

Monitoring dityrosine and tyrosine fluorescence during Aβ42 assembly. Freshly prepared Aβ42 (20 μM) was incubated in the presence of Cu²⁺/H₂O₂ and monitored by fluorescence over three days (a) and compared to Aβ42 alone (b). Dityrosine fluorescence was monitored (Ex. 320 nm, Em. 410–420 nm) and a) oxidized Aβ42 shows a strong signal at 24 hours incubation compared to no signal in b) control Aβ42 sample. The development of the dityrosine signal was monitored at earlier time points (c) using the addition of EDTA and the spectrum shows a signal at 420 nm following only 10 mins incubation. Tyrosine fluorescence (Ex. 280 nm, Em. 305 nm) was used to follow assembly with time (d). The intensity at 305 nm is plotted against time. Both conditions show a decrease in fluorescence signal over time for tyrosine, but oxidized Aβ42 shows a significant reduction after 24 hours, compared to a slow reduction in tyrosine fluorescence that accompanies assembly for control Aβ42.