Non-uniform frequency domain for optimal exploitation of non-uniform sampling.

Random sampling of NMR signal, not limited by Nyquist Theorem, yields up to thousands-fold gain in the experiment time required to obtain desired spectral resolution. Discrete Fourier transform (DFT), that can be used for processing of randomly sampled datasets, provides rarely exploited possibility to introduce irregular frequency domain. Here we demonstrate how this feature opens an avenue to NMR techniques of ultra-high resolution and dimensionality. We present the application of high resolution 5D experiments for protein backbone assignment and measurements of coupling constants from the 4D E.COSY multiplets. Spectral data acquired with the use of proposed techniques allow easy assignment of protein backbone resonances and precise determination of coupling constants.