Fig. 5.

An example showing removal of proton chemical shift degeneracy by addition of aliphatic carbon-13 dimension. In the standard 3D ¹³C^aro-edited NOESY-HSQC spectrum (top left panel) only two cross peaks are observed for Hζ proton of Phe 15. In the bottom left panel a cross section from 4D aliphatic–aromatic NOESY is presented, and one of the cross peaks splits into two. On the right panel the corresponding fragment of previously determined 3D structure of S100A1 E32Q (PDB code 2LHL) is shown. All three atoms giving rise to NOE contacts are close in space. For clarity only the E70 Hα–F15 Hζ and K27 Hα–F15 Hζ interactions were marked