Homo- and heteronuclear two-dimensional covariance solid-state NMRspectroscopy with a dual-receiver system

Abstract

Two-dimensional (2D) covariance NMR spectroscopy, which has originally been established to extract homonuclear correlations (HOMCOR), is extended to include heteronuclear correlations (HETCOR). In a ¹³C/¹⁵N 2D chemical shift correlation experiment, ¹³C and ¹⁵N signals of a polycrystalline sample of ¹³C, ¹⁵N-labeled amino acid are acquired simultaneously using a dual-receiver NMR system. The data sets are rearranged for the covariance data processing, and the ¹³C–¹⁵N heteronuclear correlations are obtained together with the ¹³C–¹³C and ¹⁵N–¹⁵N homonuclear correlations. The present approach retains the favorable feature of the original covariance HOMCOR that the spectral resolution along the indirect dimension is given by that of the detection dimension. As a result, much fewer amounts of data are required to obtain a well-resolved 2D spectrum compared to the case of the conventional 2D Fourier-Transformation (FT) scheme. Hence, one can significantly save the experimental time, or enhance the sensitivity by increasing the number of signal averaging within a given measurement time.