Rapid acquisition of NOE difference spectra. The relative merits of transient versus driven experimental protocols

The effect of substantial reduction in the preparatory waiting period employed in the collection of nuclear Overhauser effect spectra has been examined experimentally for systems near the extreme narrowing limit with particular emphasis on the truncated driven and selective inversion-recovery techniques which do not require a long evolution period. Over short evolution periods the NOE buildup rate should be directly proportional to the cross-relaxation rate by either method. The transient NOE experiment still provides accurate ratios of cross-relaxation rates even when the waiting time is less than T₁. Comparisons of fractional enhancement data for prostaglandin F₂α and four other prostanoids obtained by standard (long waiting time) and rapid acquisition protocols indicate that the rapid acquisition method can, with the proper choice of integration standards, be used for quantitative studies.