Electrochemical Detection of Interaction between Copper(II) and Peptides Related to Pathological α-Synuclein Mutants

We present a proof of concept study for electrochemical detection of the metal-binding site of α-synuclein (α-syn). Parkinson's disease (PD) is associated with the aggregation and misfolding of α-syn in dopaminergic neurons. Because copper homeostasis is deregulated in PD, it is of great significance to study the metal-binding site of wild-type α-syn (48-53, VVHGVA) and its pathological mutants (H50Q and G51D). Cyclic voltammetry and electrochemical impedance spectroscopy were used to monitor the formation of a peptide-PEG mixed layer on gold surfaces. Differential pulse voltammetry was used to detect and evaluate the interaction of copper(II) with the peptide layer. X-ray photoelectron spectroscopy was used to characterize the formation and attachment of the peptide layer on gold surfaces. Isothermal titration calorimetry was also utilized to evaluate the binding characteristics of the peptides with copper(II) ions. Our results indicated that the effect of a single amino acid mutation on the peptides drastically influenced their ability to interact with copper(II) ions. These results demonstrated that our electrochemical approach provided a rapid and cost-effective platform to study the strong interaction between α-syn and copper(II), which is implicated as one of the factors inducing structural changes in α-syn toward the progression of PD.