HETERONUCLEAR NMR PULSE SEQUENCES APPLIED TO BIOMOLECULES

Current concepts in heteronuclear multidimensional NMR spectroscopy ar e reviewed. Methods to improve the sensitivity and the efficiency of d ata collection include constant time, compression through the overlap of chemical shift evolution and dephasing and rephasing periods, and d ual or time-shared evolution. Two classes of three-dimensional and fou r-dimensional triple-resonance experiments applied to proteins are con sidered. The first class correlates H-1, N-15, and C-13 signals of the protein backbone. The second class correlates both backbone and side- chain signals. Application of triple resonance to RNA is also discusse d. Heteronuclear cross polarization (HCP) is considered as an alternat ive to INEPT transfer, and its application to nucleic acids is present ed. Finally, two methods of employing pulsed field gradients (PFGs) ar e reviewed.