A 4D TROSY-based pulse scheme for correlating 1HNi,15Ni,13Calphai,13C'i-1 chemical shifts in high molecular weight, 15N,13C, 2H labeled proteins.

A 4D TROSY-based triple resonance experiment, 4D-HNCO(i-1)CA(i), is presented which correlates intra-residue (1)HN, (15)N, (13) C(alpha) chemical shifts with the carbonyl ((13)C') shift of the preceding residue. The experiment is best used in concert with recently described 4D TROSY-HNCOCA and -HNCACO experiments [Yang, D. and Kay, L.E. (1999) J. Am. Chem. Soc., 121, 2571-2575]. In cases where degeneracy of ((1)HN,(15)N) spin pairs precludes assignment using the HNCOCA and HNCACO, the HNCO(i-1)CA(i) often allows resolution of the ambiguity by linking the (13)C(alpha) and (13)C' spins surrounding the ((1)HN,(15)N) pair. The experiment is demonstrated on a sample of (15)N, (13)C, (2) H labeled maltose binding protein in complex with beta-cyclodextrin that tumbles with a correlation time of 46 ns.