Figure 5.

Chemical shift differences plotted for each residue in the LC8 sample doped with 5 mM Cu(II)-EDTA, for the following atom types: ¹³C_a (A, D), ¹⁵N (B, E), and ¹³C_b (C, F). The left panel (A–C) is the difference of chemical shifts between two 3D NCACB uniformly sampled spectra. The right panel (D–F) is the difference of chemical shifts between two 3D NCACB spectra, one acquired by non-uniform sampling in both indirect dimensions and another- by uniform sampling. The US spectrum used as the reference dataset in both the left and right panel was acquired as a 32×32 point hypercomplex matrix in two indirect dimensions; the total evolution time is 12.4 ms and 6.9 ms in the indirect ¹⁵N (t₁) and ¹³C (t₂) dimensions, respectively. The second US data used for chemical shift comparison has shorter evolution time in N and CA dimensions (50% of evolution time in N dimension, and 37.5% of evolution time in CA dimension). The NUS spectrum was acquired using a 3D NUS schedule consisting of 25% points of the corresponding reference US dataset and using the same spectral width and the same evolution time in all dimensions. Note that the chemical shift differences between the NUS and US spectra are small and below 0.2 ppm for the overwhelming majority of the residues. On the other hand, the two US spectra exhibit significantly higher chemical shift deviations.