The influence of coordination mode on the redox properties of copper complexes with Aβ(3-16) and its pyroglutamate counterpart pAβ(3-16)

Senile plaques are a hallmark of Alzheimer’s disease. The plaques are mainly composed of small peptides from the β-amyloid (Aβ) family which differ in how they bind copper ions and thus in their properties. pAβ(3-42) species and its Aβ(3-42) precursor are found in significant proportion in the plaques, however, their complexes with copper ions are hardly explored. The electrochemical response of the copper complexes with N-truncated Aβ(3-16) and its pyroglutamate counterpart pAβ(3-16) was investigated using cyclic voltammetry. Results obtained in physiological pH (pH ~ 7.4) show that Cu(II) ions in in these peptides undergo reduction Cu(II)/Cu(I) at a potential (Ef)~0.05 V which in other peptides have been shown to enhance production of reactive oxygen species. Detailed voltammetric study, performed at pH below and above 7.4, revealed the effects of coordination modes on the observed redox processes. The conclusions are important for a better understanding of the pathogenesis of Alzheimer's disease.