Figure 1.

(a-d) ¹³C CPMAS spectra of protein crystals for (a, b) lysozyme and (c, d) ubiquitin prepared in D₂O obtained (a, c) with and (b, d) without 10mM Cu-EDTA at ¹³C NMR frequency of 100.6 MHz. The recycle delays were set to (a) 0.5 s, (b) 1.1 s, (c) 1.0 s, and (d) 2.5 s. The spectra were acquired at a spinning speed of 10 kHz under ¹H TPPM decoupling of (a, b) 71 kHz and (c, d) 90 kHz. Signals were accumulated during acquisition periods of 10 ms with (a) 28160, (b) 12800, (c) 14336, and (d) 5736 scans in a common total experimental time of 4 hours. During the CP period of 1.0 ms, ¹³C RF field was swept (a, b) from 56 kHz to 76 kHz and (c, d) from 52 kHz to 72 kHz, while ¹H RF field was kept at (a, b) 76 kHz and (c, d) 72 kHz. All the spectra were processed with Gaussian line broadening of 25 Hz. At the right of the spectra in (a-d), microscope images of the corresponding protein micro/nano-crystals used for the NMR experiments are displayed in (e-h). The images were obtained at 32× magnification.