Spectroscopy
2D IR indexing maps hIAPP helix-to-sheet kinetics
Open access · cc by · source: Europe PMC
Paired 13C18O labels report dihedral angles: monomeric hIAPP is partly helical at L12A13, then oligomers lose helix and fibers form β-sheets.
Study at a glance
- Design
- Other — 13C18O isotope-edited 2D IR of hIAPP secondary structure during aggregation
- N
- Biophysical spectroscopy of peptide aggregation — no cohort N
- Population
- Human islet amyloid polypeptide (hIAPP) monomers/oligomers
- Outcome
- Site-specific helix vs sheet coupling and aggregation kinetics
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Helix coupling is +8.3 cm–1 vs +2.5 cm–1 in a β-sheet. Monomers are ~20–38% helical at L12A13; oligomers lack detectable helix; L12A13 shows three-state kinetics unlike two-state A13.
Methodology
Authors 13C18O double-labelled neighbouring residues, calibrated couplings in SDS micelles, and recorded time-resolved 2D IR during aggregation versus singly labelled controls.
Limitations
The leucine-rich-repeat oligomer model is postulated, not a high-resolution oligomer structure; only two labelled sites were tracked.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Isotope-edited 2D IR can separate helix from sheet at a chosen pair of residues. Neighbouring ¹³C¹⁸O labels give a helix coupling of +8.3 cm⁻¹ versus +2.5 cm⁻¹ in a β-sheet. hIAPP monomers are ~20–38% helical at L12A13; oligomers lack detectable helix; L12A13 shows three-state kinetics unlike two-state A13. Only two labelled sites were tracked; the leucine-rich-repeat oligomer model is postulated, not a high-resolution structure.
Evidence for the claim as stated.
Site-specific 2D IR couplings and a bulk epoxy FTIR trace are not the same vibrational experiment. +8.3 versus +2.5 cm⁻¹ reports secondary structure at L12A13; 906 and 1687 cm⁻¹ report consumption of epoxy and appearance of amide in a thermoset. One is a labelled peptide kinetic; the other is a cure fingerprint. Calling both 'we ran IR' hides that.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Site-specific 2D IR couplings and a bulk epoxy FTIR trace are not the same vibrational experiment. +8.3 versus +2.5 cm⁻¹ reports secondary structure at L12A13; 906 and 1687 cm⁻¹ report consumption of epoxy and appearance of amide in a thermoset. One is a labelled peptide kinetic; the other is a cure fingerprint. Calling both 'we ran IR' hides that.
Related papers in this topic
Same topic cluster — not a recommendation engine.