Fig. 4.

A 2D NHHC spectrum of AS fibrils (A form) grown from U-[¹³C,¹⁵N\K,V] AS diluted 1:2 with natural abundance AS. The spectrum was recorded at a static magnetic field of 18.8 T with a spinning speed of 11 kHz at a temperature of -13°C. The maximum t₁ evolution time was 4 ms, and the total experiment time was 113 h. The spectrum was processed with exponential multiplication with a line-broadening factor of 50 Hz in both dimensions. Red circles represent Nⁱ⁺¹C^αi cross-correlations for amino acids involved in β-strands according to chemical-shift analysis, including also Nⁱ⁺¹C^α(V)ⁱ cross-peaks due to residual carbon labeling in V residues. Red squares represent Nⁱ⁺¹C^αi cross-correlations for amino acids not involved in β-strands according to their chemical shift. Blue squares represent intraresidue N-C^α correlation for Gly residues. For several correlations, sequential residue numbers are given.