A NEW 3D HN(CA)HA EXPERIMENT FOR OBTAINING FINGERPRINT H(N)-H-ALPHA CROSS PEAKS IN N-15-LABELED AND C-13-LABELED PROTEINS

A new 3D H-1-N-15-C-13 triple resonance experiment is presented that p rovides in-phase absorptive cross peaks between amide protons and alph a-protons of the same and the sequentially preceding residue. The expe riment yields similar connectivities as those described previously by Montelione and Wagner (1990a) [J. Magn. Reson., 87, 183-188] and Kay e t al. (1991) [J. Magn. Reson., 91, 84-92]. However, the pulse sequence was designed to minimize the time that transverse coherence of the C- 13(alpha) nucleus is present, since this nucleus has the shortest tran sverse relaxation time of all the nuclei involved in these experiments . This is achieved by using a coherence transfer pathway from H-1(N) t o N-15, C-13(alpha), H-1(alpha) and back to the H-1(N). In the sequenc e described, transverse C-13(alpha) coherence is present only for a le ngth of ca. I/1J(C(alpha)-H(alpha). This reduces loss of signal due to transverse relaxation. We tested the technique on uniformly N-15- and C-13-enriched T4 lysozyme.