Disulfide bonds preserve their conformation upon insulin fibrillation.

<p>Raman spectra of native insulin (red) and insulin fibrils (black) have a peak at 510 cm⁻¹, corresponding to the gauche-gauche-gauche (g-g-g) conformation of disulfide bonds (schematically represented in the inset).</p

Snapshots of insulin dimers from MD simulations.

<p>The β-sheet character of each structure is shown in parentheses.</p

Equilibrated structure of an insulin dimer from 150-ns MD simulations in aqueous solution.

<p>The A- and B-chain of the second monomer are labeled A` and B`, respectively. Intact disulfide bridges are shown in green.</p

The majority of H/D exchange-protected amino acids are located in the B-chain of insulin.

<p>The amino acids in the 3D structure (A) and primary sequence of insulin fibrillar monomer (B) are colored according to the following degree of H/D exchange protection: yellow, I_D2O/I_H2O≥0.75; red, 0.75>I_D2O/I_H2O≥0.675; and blue, 0.675>I_D2O/I_H2O≥0.60. Gray (in the 3D structure) and white colors (in the primary sequence) indicate unprotected (exchanged) amino acids. (C) 2D ¹H,¹H-TOCSY spectrum of insulin fibrillar monomer in DMSO and 0.05% TFA at 30°C after a 7-day D₂O exchange at room temperature. NMR data were acquired at room temperature on a Bruker Avance II 500 MHz NMR spectrometer equipped with a cryoprobe.</p

The α-helix and β-sheet character of simulated insulin monomer and dimer.

<p>The α-helix and β-sheet character of simulated insulin monomer and dimer.</p