Distant echoes of the accordion: Reduced dimensionality, GFT-NMR, and projection-reconstruction of multidimensional spectra

Multidimensional NMR spectroscopy can be speeded up appreciably by techniques that reduce the number of evolution periods examined independently. This review charts the evolution of the "reduced dimensionality" concept starting with the accordion experiment, and showing how it gradually developed into GFT-NMR and projection-reconstruction (PR-NMR), which collects plane projections at different orientations and uses them to reconstruct the full multidimensional spectrum. While the data-gathering stages of GFT-NMR and PR-NMR are similar, the processing stages are radically different. The methods described here are generally applicable to the standard multidimensional NMR sequences, and they offer comparable sensitivity and resolution, and a similar advantage in speed. By adopting a method related to the inverse Radon transform, PR-NMR can also be applied to situations of only marginal sensitivity. (C) 2004 Wiley Periodicals, Inc.