Iron(III) hydroxide suspensions were prepared by diluting 18 mM iron(III) nitrate (Sigma-Aldrich) in deionized water and subsequently neutralizing to pH 7 with 1 M NaOH, giving an iron concentration of 440 µM. Suspensions containing both 440 µM iron(III) and 440 µM aluminium(III) at pH 7 were created from 18 mM iron(III) nitrate, and 37 mM aluminium(III) nitrate (Perkin-Elmer) in a similar manner as described above, with aluminium(III) nitrate being added after the iron(III) nitrate. All suspensions were sonicated for 5 min prior to Aβ addition to encourage a homogeneous metal distribution.
Frozen Aβ(1–42) was thawed and dissolved in 0.1 M NaOH to create a 1 mg ml−1 (220 µM) Aβ stock. This Aβ stock was allowed to sit for 30 min to ensure complete peptide dissolution before being added to the previously prepared metal suspensions. Aβ/metal suspensions were again neutralized to pH 7 following the addition of the Aβ stock, via the addition of 0.1 M hydrochloric acid (HCl). Final Aβ and metal concentrations were 35 and 370 µM, respectively. Amyloid-free iron suspensions were created in the same manner as above with the substitution of deionized water in place of Aβ. All Aβ/iron suspensions and amyloid-free controls were incubated at 37°C over a period of 144 h.
Frozen Aβ(1–42) was thawed and dissolved in 0.1 M NaOH to create a 1 mg ml−1 (220 µM) Aβ stock. This Aβ stock was allowed to sit for 30 min to ensure complete peptide dissolution before being added to the previously prepared metal suspensions. Aβ/metal suspensions were again neutralized to pH 7 following the addition of the Aβ stock, via the addition of 0.1 M hydrochloric acid (HCl). Final Aβ and metal concentrations were 35 and 370 µM, respectively. Amyloid-free iron suspensions were created in the same manner as above with the substitution of deionized water in place of Aβ. All Aβ/iron suspensions and amyloid-free controls were incubated at 37°C over a period of 144 h.