Abstract
Understanding the pathophysiology of Alzheimer disease has relied upon the use of amyloid peptides from a variety of sources, but most predominantly synthetic peptides produced using t-butyloxycarbonyl (Boc) or 9-fluorenylmethoxycarbonyl (Fmoc) chemistry. These synthetic methods can lead to minor impurities which can have profound effects on the biological activity of amyloid peptides. Here we used a combination of cytotoxicity assays, fibrillation assays and high resolution mass spectrometry (MS) to identify impurities in synthetic amyloid preparations that inhibit both cytotoxicity and aggregation. We identify the Aβ42Δ39 species as the major peptide contaminant responsible for limiting both cytotoxicity and fibrillation of the amyloid peptide. In addition, we demonstrate that the presence of this minor impurity inhibits the formation of a stable Aβ42 dimer observable by MS in very pure peptide samples. These results highlight the critical importance of purity and provenance of amyloid peptides in Alzheimer’s research in particular, and biological research in general.
Highlights
Since introduction of the amyloid hypothesis of AD over 20 years ago[1], an overwhelmingly large literature has accumulated, cementing the central importance of Aβ42 in the mechanism of the disease [2,3,4,5,6,7]
The concentration of each peptide sample was determined by BCA assay in a method that has been independently verified by SDS-PAGE, UV-Vis spectroscopy and amino acid analysis
Prior studies demonstrated the additional purification of synthetic Aβ42 could restore both aggregation kinetics and toxicity yet the nature of the inhibitory material in synthetic Aβ42 was not investigated[9]
Summary
Since introduction of the amyloid hypothesis of AD over 20 years ago[1], an overwhelmingly large literature has accumulated, cementing the central importance of Aβ42 in the mechanism of the disease [2,3,4,5,6,7]. We have validated those findings and extended the line of questioning to determine the identity of the contaminants which appear to inhibit the toxic activities of Aβ42 Through both discovery-oriented and candidate-based approaches, we have found that a failed valine-valine coupling at position 39–40 in Aβ42 produces a truncated peptide that co-purifies with full-length Aβ42 and is a potent inhibitor of its aggregation and cytotoxic activity. These results mandate that future assays using sAβ42 should ensure that this impurity is remove and we propose that this truncated Aβ derivative, and analogues thereof, merits further investigation in bioassays to characterize its potentially therapeutic properties for treating Alzheimer’s disease
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
