Relaxation Editing Using Long-Lived States and Coherences for Analysis of Mixtures

Nuclear magnetic resonance (NMR) is a powerful tool for structural and dynamical studies of molecules. Although widely applicable, the search for novel spectral editing methods that facilitate spectral assignment of peaks in high-resolution NMR is highly desirable. Earlier, the sensitivity of lifetime of spin states (spin-lattice relaxation time, T1) and coherences (spin-spin relaxation time, T2) to the immediate environment was utilized for spectral editing in solution NMR. Long-lived states (LLS) and coherences (LLCs) were recently uncovered to have longer and more domain sensitive lifetime than other type of states and coherences. Herein, this longevity and increased sensitivity of LLS and LLC lifetime is utilized for more enhanced dispersion in relaxation editing in NMR. The generality of the method as a powerful tool in spectral editing is confirmed with molecules containing a mixture of strongly and weakly coupled spin systems and finally with metabolomic mixture. Extension to insensitive nuclei enhanced by polarization transfer (INEPT), correlation spectroscopy (COSY), and heteronuclear single quantum coherence (HSQC) are also demonstrated.