Separation and suppression of coherent transfer effects in two-dimensional NOE and chemical exchange spectroscopy

A new method for the separation of coherent and incoherent magnetization transfer in two-dimensional (2D) NOE and chemical exchange spectroscopy is described. The new experiment differs from previous 2D exchange experiments, in that the mixing time τ_m is incremented systematically together with the evolution time t₁. This permits the distinction of the different orders of multiple-quantum coherence during the mixing time and allows the separation of coherent and incoherent transfer processes. The resulting clarification of chemical exchange and 2D NOE spectra is illustrated with experiments on small molecules and on a globular protein, the basic pancreatic trypsin inhibitor.