Revealing Aβ peptide isoforms, including post-translationally modified species, through Cu(II)-mediated...

Amyloid-β (Aβ) peptides constitute key molecular signatures associated with Alzheimer's disease (AD), the most common neurodegenerative disorder. The high diversity of the Aβ peptide family, including N-terminal truncations and post-translational modifications, poses a major analytical challenge, as closely related Aβ variants may differ by a single amino acid yet exhibit distinct biochemical properties. In particular, modifications at the N-terminus influence redox behavior and processes linked to oxidative stress and aggregation. Here, we present an electrochemical fingerprinting strategy for discriminating Aβ peptides with physiologically relevant N-terminal truncations and modifications, based on the redox behavior of metal-peptide complexes, with Cu(II) used as a model redox-active ion. Differential pulse voltammetry (DPV) was performed using a dual-electrode set-up comprising glassy carbon and gold electrodes to generate multidimensional electrochemical profiles. The datasets were analyzed using chemometric methods, including principal component analysis (PCA) for exploratory data analysis and partial least squares discriminant analysis (PLS-DA) for classification. Distinct and reproducible fingerprints were obtained for a panel of model Aβ peptides (Aβ_1-16, Aβ_3-16, Aβ_pyr3-16, Aβ_4-16, Aβ_5-16, Aβ_11-16, and Aβ_pyr11-16), enabling reliable discrimination between closely related variants, both in single-component systems and in mixtures. Data fusion of signals from both electrodes significantly enhanced class separability, highlighting the benefit of a multi-sensor approach to electrochemical profiling. These results demonstrate that metal-mediated electrochemical fingerprints encode chemically meaningful information related to Aβ sequence and post-translational modifications. The presented strategy establishes a proof-of-concept analytical framework for electrochemical fingerprinting of model Aβ peptide systems, providing a foundation for future Alzheimer's disease-related studies.