Аннотация:Alzheimer’s disease (AD) is the most prevalent neurological disorder affecting tens of millions of people worldwide. According to the amyloid cascade hypothesis, the key event of the AD pathology is a transition of amyloid-β (Aβ, the 39–42 amino acid long peptide) from the monomeric to the aggregated state, which triggers a chain of adverse molecular events [1]. Various biophysical and biochemical techniques are currently employed to study Aβ peptide, its isoforms and their aggregation in vitro in a search for a cure for AD. Among them, the direct electrochemistry appears to present itself as a rapid and cost-effective approach [2]. It is generally accepted that Aβ electroactivity is determined by oxidation of three types of amino acid residues: Tyr-10, His (His-6, -13 and -14), and Met-35 [3]. The oxidation of Aβ via Tyr-10 at 0.6–0.7 V (vs. Ag/AgCl) commonly utilizes for Aβ detection and for monitoring Aβ aggregation. Thus, the electrochemical approach for studying Aβ seems to be limited to the Tyr-containing peptides. However, as been shown by our group, nearly all proteinogenic amino acids (with a single exception of Glu) exhibit the site-specific electrooxidation in amperometric flow injection analysis (FIA) at a constant potential (0.95 V) on carbon screen printed electrodes (SPE) [4]. Furthermore, Prussian Blue (PB) was found to catalyzed this electrooxidation [4]. For 20 amino acids out of 21 tested, the electrogenerated Berlin Green (BG) has been reduced back to PB by amino acids, forming a catalytic cycle that resulted in an enhancement of oxidation signals. The most effective catalysis – the 54-, 31-, and 11-fold current enhancement – was observed for Gln, Ser, and His, respectively. The significant catalytic effect of electrogenerated BG on their oxidation has been observed for various proteins as well [4]. The aim of this work was to evaluate the effect of PB on the electrochemical oxidation of peptides of various lengths and amino acid sequences. For this purpose, a set of Aβ peptides and its isoforms / mutants was tested on bare and PB modified carbon SPE by cyclic voltammetry and FIA. To our surprise, a pronounced catalytic effect of PB (about a 20-fold current increase) was found for peptides lacking the Tyr residue, viz. Aβ7-D7H, rat Aβ16, and Aβ16-Y10A, while practically no effect of PB was observed for Aβ16-D7H, Aβ16-H6R, and Aβ16-E11A mutants. Only a 1.5-fold current enhancement was observed for Aβ16 oxidation on SPE/PB, compared to bare SPE, by FIA. Apparently, this reflects the fact that no significant catalytic effect of PB was found for Tyr [4]. Therefore, the combination of FIA and SPE/PB opens a new avenue for electrochemical monitoring of aggregation of Aβ isoforms / mutants containing no Tyr residues as well as other peptides of interest, lacking intrinsically electroactive residues.This work was financially supported by the Russian Science Foundation, grant 19-74-30007.References: 1J. Hardy, N. Bogdanovic, B. Winblad, E. Portelius, N. Andreasen, A. Cedazo-Minguez and H. Zetterberg, J. Intern. Med., 2014, 275, 296-303.2A. Veloso, K. Kerman, Anal. Bioanal. Chem., 2013, 405, 5725-5741.3E.V. Suprun, S.A. Khmeleva, S.P. Radko, S.A. Kozin, A.I. Archakov and V.V. Shumyantseva, Electrochem. Commun., 2016, 65, 53-56.4E.V. Suprun, E.V. Karpova, S.P. Radko and A.A. Karyakin, Electrochim. Acta, 2020, 331, 135289.
