Steven W. Sparks

Detection of insensitive nuclei

Publisher Summary This chapter describes a number of 2D reverse-correlation experiments that yield high-sensitivity heteronuclear correlation spectra. The optimal pulse sequence depends on the particular application and on the spectrometer used. For example, for correlation through long-range coupling or through one-bond coupling, different pulse schemes have to be used. Certain pulse schemes provide better suppression of artifacts but yield poorer line shapes. These techniques then can be combined with NOESY and HOHAHA methods to obtain spectra of reduced complexity. Alternatively, three-dimensional NMR techniques that are based on combining HOHAHA or NOESY with heteronuclear correlation are expected to become of major practical relevance for nuclear magnetic resonance (NMR) analysis of proteins. Although the use of one-bond heteronuclear correlations is largely limited to solving assignment problems, the multiple-bond correlations also carry structural information since the intensities of the correlations reflect the size of the heteronuclear J couplings. For the methods discussed in this chapter, it is essential to have access to a so-called “inverse probehead,” with the 1 H observe coil close to the sample and the decoupler coil on the outside.