Amyloid · Self-assembly
Two amyloid peptides share a solution, form separate fibrils, and still affect each other
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Short answer
Aβ40 and Aβ42 form separate homomolecular fibrils in mixtures, with weak cross-seeding but a genuine acceleration of Aβ40 nucleation by Aβ42 monomers.
What happened
Cukalevski and colleagues combined thioflavin T kinetics, circular dichroism, isotope-resolved mass spectrometry and NMR, cryo-electron microscopy pitch measurements and self- versus cross-seeding experiments. Below about 10 µM the mixtures showed two transitions, with the first fibrils being Aβ42 and containing under 13% Aβ40. Helical half-pitch was 162 nm for Aβ40 and 31 nm for Aβ42. Cross-seeding was weak relative to self-seeding, but Aβ42 monomers accelerated Aβ40 primary nucleation.
Why it matters
Whether the two peptides co-assemble determines what an in vitro aggregation assay with both of them is actually measuring. The answer here is specific: they build separate structures, so the products are not mixed, while one still influences the other's nucleation — an interaction visible only in the kinetics, not in the end product.
Evidence
- Study type
- Multi-technique aggregation kinetics with isotope-resolved composition analysis and seeding experiments
- Sample
- Binary peptide mixtures across concentrations below and above ~10 µM
- Journal
- Chemical Science · peer reviewed
- Replication
- Not assessed in this corpus
- Limitations
- Purified peptide biophysics in vitro. Atomic structures of mixed oligomers were not determined, and no patient material was studied.
What this connects to
Sources
The one study this explanation is built from, by the role each plays. Every source links to PaperFren’s explanation of it and to the original paper.
Primary study
- Aβ40 and Aβ42 make separate fibrils after mixed nuclei
In mixtures, Aβ42 fibrillizes first; elongation and secondary nucleation stay homospecific, so each peptide builds its own fibrils.
What it does not showLimitations
Atomic mixed-oligomer structures are not solved; disease relevance is inferred from peptide biophysics, not patients.
PaperFren explanationStudy with cards and a quizOriginal paper (DOI)cc by
Before
Mixtures of the two principal amyloid-β peptides were often treated as co-assembling into common fibrils, so aggregation assays were read as reporting on a blended species.
Now
The products are separate and structurally distinguishable, while a kinetic interaction persists at the nucleation step. Atomic structures of mixed oligomers are not solved, and disease relevance is inferred from peptide biophysics rather than from patients.