Fig. 4.

Problematics in resonance assignment with 3D H^α-detected experiments can be resolved with 4D HACACON and 4D (HACA)CONCAHA experiments. The upper row of 2D planes from 3D HA(CA)CON and iHA(CA)NCO spectra shows that the sequential walk from ⁹⁷Ala to ⁹⁶Glu is ambiguous because the ⁹⁷Ala Ha, C′ shift pair observed in the HA(CA)CON can be found in several planes of the iHA(CA)NCO and is overlapping with other peaks. While there is overlap in the 4D spectra also, the planes are far more easily interpreted and allow for unambiguous assignment of ⁹⁸Ala-⁹⁷Ala-⁹⁶Glu. Grey labels mark peaks with maximum in adjacent ¹⁵N or ¹³C planes