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2D IR indexing maps hIAPP helix-to-sheet kinetics
Paired 13C18O labels report dihedral angles: monomeric hIAPP is partly helical at L12A13, then oligomers lose helix and fibers form β-sheets.
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What is 2D IR dihedral indexing?
Labelling two neighbouring residues so vibrational coupling reports dihedral angles.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
What helix vs sheet coupling constants are used?
+8.3 cm–1 (helix) versus +2.5 cm–1 (β-sheet nearest neighbours).
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
How large is the 13C18O shift?
About 65 cm–1, giving small background.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
How helical is monomeric hIAPP at L12A13?
About 20–38% in buffer.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
Is helix detected in the oligomer?
No helix at L12A13 or L16V17 in the oligomeric state.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
What kinetics does L12A13 show?
Three-state: monomer → oligomer dihedral change → fiber β-sheets.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
What do singly labelled A13 kinetics show?
Two-state fiber β-sheet formation; isotope and 1620 cm–1 traces match.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
Where is L16V17 in the NMR structure?
L16 at the helix end and V17 at a disordered turn—not a helix pair.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
What SDS control established the helix fingerprint?
hIAPP in 100 mM SDS, compared to PDB 2L86.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
How fast is a 2D IR spectrum collected?
424 ms at 1 kHz repetition rate.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified
What oligomer-seeding analogy is proposed?
Helical monomers seed oligomers like leucine-rich repeat proteins.
Source: Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP · DOI · quote verified