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

A 4D TROSY-based triple resonance experiment, 4D-HNCO(i-1)CA(i), is present ed which correlates intra-residue (HN)-H-1, N-15, C-13(alpha) chemical shif ts with the carbonyl (C-13') shift of the preceding residue. The experiment is best used in concert with recently described 4D TROSY-HNCOCA and -HNCAC O experiments [Yang, D. and Kay, L.E. (1999) J. Am. Chem. Soc., 121, 2571-2 575]. In cases where degeneracy of ((HN)-H-1,N-15) spin pairs precludes ass ignment using the HNCOCA and HNCACO, the HNCO(i-1)CA(i) often allows resolu tion of the ambiguity by linking the C-13(alpha) and C-13' spins surroundin g the ((HN)-H-1,N-15) pair. The experiment is demonstrated on a sample of N -15, C-13, H-2 labeled maltose binding protein in complex with beta-cyclode xtrin that tumbles with a correlation time of 46 ns.