CV results were supported also by SWV experiments in order to investigate both oxidation and reduction processes at fast switching time and determine the rate of the following chemical step of EEC process. We have additionally performed SWV at different frequencies (from 5 up to 25 Hz) (SI Figure .1) in order to determine the rate of the following chemical step, which is an internal electron-transfer from the Cu(III) ion to the Tyr • . As the frequency decreases, the cathodic peak during the reverse current step gradually disappears. The slope in the voltammogram makes it hard to determine the exact frequency when the peak disappears, but it lies between 10 and 15 Hz. This critical frequency is dependent on the rate of the following homogeneous step in an EC reaction mechanism, which in our case corresponds to 30-45 s -1 . This is somewhat higher than found in the CV simulations (15 s -1 ). As the pH increases, the reduction peak disappears. This is likely due to the increase in the amount of deprotonated Tyr, which as discussed above, significantly increases the rate for the intramolecular electron transfer. The SWV results corroborate the CV data that the oxidation of Aβ(416)-Cu(II) complexes is an EEC mechanism, with the rate of the chemical step dependent on the amount of deprotonated tyrosine available.