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.

doi:10.64898/2026.07.30.741826

bioRxiv · 10.64898/2026.07.30.741826

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.

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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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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. Errors in peptide synthesis are a source of discrepancies in Aβ42 studies. https://doi.org/10.64898/2026.07.30.741826

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