Resolution improvement in NMR spectra: application and significance of chemical shift upscaling in multidimensional NMR experiments

An analysis of resolution in nuclear magnetic resonance (NMR) spectra in terms of separation, linewidth, and limited digitization capability is presented. The effect of scaling up of frequencies on resolution is considered, and criteria useful for determining whether two peaks are resolvable in continuous-wave and digitized spectra are derived. Finally, a new pulse sequence based on upscaling of chemical shifts is described for resolution improvement along the F1 dimension in heteronuclear correlation NMR spectra. The performance of the sequence is demonstrated by experimental data on large proteins, and simulations are performed for its optimization