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Errors in peptide synthesis are a source of discrepancies in Aβ42 studies

Matulewska-Sobczuk, K.; Bernfur, K.; Thacker, D.; Wallerstein, J.; Stemme, E.; Dear, A.; Lindblom, N.; Andrzejewska, E.; Sneideriene, G.; Knowles, T. P. J.; Gouras, G.; Olsson, U.; Linse, S.; Ortigosa-Pascual, L.

2026-07-31 biochemistry
10.64898/2026.07.30.741826 bioRxiv
Show abstract

Amyloid-{beta}42 (A{beta}42) aggregation is highly sensitive to experimental conditions, making reproducibility a persistent challenge in Alzheimers disease research. Among the many variables that influence aggregation, the impact of peptide production remains poorly understood. Direct comparison of recombinant and chemically synthesised A{beta}42 prepared under carefully controlled conditions reveals that, despite following similar aggregation mechanism and forming the same predominant fibril structures, synthetic A{beta}42 aggregates more slowly and exhibits reduced seeding efficiency. Consequently, synthetic A{beta}42 produces fewer oligomeric species and displays lower cellular toxicity. Mass spectrometric analyses identify low-abundance sequence imperfections introduced during peptide synthesis as the origin of these differences. By linking synthesis-derived imperfections to variations in A{beta}42 behaviour, this work reveals a previously underappreciated source of discrepancies in amyloid studies. In addition, we provide a framework for evaluating the impact of sequence impurities on biophysical studies that are sensitive to peptide composition.

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