We investigated the redox properties of copper complexes with Aβ(4-16), which is a good model peptide for Aβ (4-42). On the basis of cyclic and square wave voltammograms as well as computational studies we investigated Cu(II) oxidation to Cu(III) and the influence of the tyrosine moiety on this process. On CVs recorded with lower scan rates (0.1 Vs -1 ) only the anodic peak for Cu(II)/Cu(III) appeared over the entire range of studied pH (from 5 to 9). The oxidation process Cu(II)/Cu(III) in a complex with Aβ(4-x) appears irreversible due to subsequent chemical reduction. However, a significant increase in the scan rate to 5 Vs -1 and higher, revealed the cathodic peak associated with the Cu(III)/Cu(II) process. We performed square wave voltammetry measurements and simulations based on the recorded CVs to determine the rate of charge transfer reaction between Cu(III) and tyrosine. This process is pH sensitive because with increasing pH the Cu(III)/Cu(II) cathode peak disappears, suggesting that the deprotonation of tyrosine increases the rate of charge transfer between the metal centre and this redox active amino acid. Our findings shed new light on the relevance of the tyrosine moiety in the redox process that may occur when neurodegenerative diseases such as Alzheimer's or Parkinson's disease are developing.