Supplementary Figure 6: 2D 13C-13C correlation spectra indicate intermolecular packing of the glucagon β-strands along the fibril axis.
From: The peptide hormone glucagon forms amyloid fibrils with two coexisting β-strand conformations
a, PDSD spectrum of mixed sample 11 and 12 with 1.0 s 13C spin diffusion. Intermolecular T5–L26, T5–M27, S11–A19, and S11–Q20 cross peaks are observed (assigned in purple), indicating antiparallel packing of the β-strands. b, 500 ms 2D 13C SD spectrum of sample 9c. In addition to sequential correlations, R18-K12, A19-K12, S11-A19, S11-R18 and R17-L14 cross peaks between conformers I and II are observed, supporting antiparallel β-strand packing. c, 500 ms sample 2 spectrum shows multiple H1-T29 correlations, indicating that the antiparallel packing spans the entire peptide sequence. d, 500 ms SD spectrum of sample 7c shows multiple sequential and long-range cross peaks of W25, which constrain the indole conformation. e, 200 μs 1H SD CHHC spectrum of sample 7c. f, 200 μs 1H SD CHHC spectrum of sample 9c. Cα–Cα cross peaks are observed for residue numbers that add up to 31 (for example Q3–N28, M27–G4, T5–L26, K12–A19, and Y13–R18), indicating that the β-strands are hydrogen-bonded in antiparallel. The cross peaks occur between conformers I and II, indicating that the two conformers alternate along the fibril axis.
