Figure 4. 3D HNCO spectra for Ubiquitin at 14.1 T (600 MHz for ¹H).

¹³C/¹H planar cross-sections at a ¹H frequency of 8.14 ppm. The one-dimensional cross-sections through the plots are of the ¹³C row at the weakest peak (¹⁵N frequency of 120.5 ppm), scaled so that the highest and lowest amplitudes are aligned. A) Using a full dataset, 6656 data samples, processed using LP extrapolation in each indirect dimension, shifted sine-bell apodization, and DFT; this data set required 36 hours of data collection B) using 100 uniformly-sampled data points (10 increments in each indirect dimension); this data requires 25 minutes of data collection. The spectrum was computed by LP extrapolation in each indirect dimension, apodization using a shifted sine-bell, and DFT. C) using NUS, with 100 random samples selected according to an exponentially weighted distribution, reconstructed using MaxEnt; this data also requires 25 minutes of data collection. D) Same as C), except using nuDFT instead of MaxEnt. The weak peak near the center of the ¹³C trace in A is the “tail” of a peak at a nearby ¹H frequency; this disappears because of the narrower peaks in C.