Figure 6.

A comparison of 2D ¹³C/¹³C correlation SSNMR spectra of Cu²⁺-bound amyloid fibrils of Aβ(1-40) obtained at ¹H NMR frequencies of (a) 400 MHz with traditional scheme and at (b) 800 MHz with PACC scheme, together with (c) 1D slices. The total experimental times were (a) 32 h and (b) 1.9 h for (a) 2 mg and (b) 1 mg of the Aβ sample that was uniformly ¹³C- and ¹⁵N-labeled at selected residues Phe-4, Gly-9, Val-12, Leu-17, and Ala-21. The data in (a, b) were processed with Gaussian broadening of 1.0 ppm in both t₁ and t₂ periods. The data in (a) were acquired with the t₁ and t₂ periods of 4 ms and 8 ms, respectively on a Bruker Avance III 400 MHz spectrometer equipped with a homebuilt 2.5-mm CPMAS triple-resonance probe. For (a), a standard 2D ¹³C/¹³C correlation sequence was used under MAS at 20 kHz with high-power ¹H TPPM decoupling at the RF intensity of 90 kHz.⁴⁵ During the mixing period of 1.6 ms, the fpRFDR sequence⁴⁵ was applied with ¹³C π-pulses of 15-μs width. The data in (b) was acquired in the PACC scheme with the t₁ and t₂ periods of 2 ms and 8 ms, respectively on a Bruker Avance 800 MHz spectrometer equipped with a JEOL 1-mm double-resonance CPMAS probe. In (b), ¹H lpTPPM decoupling was applied at 12.5 kHz in the t₁ and t₂ periods, and the fpRFDR mixing was applied during the mixing period of 1.92 ms with ¹³C π-pulses of 7 μs widths.