Long-Range 1H−15N Heteronuclear Shift Correlation at Natural Abundance

2000-03-18T00:00:00Z (GMT) by Gary E. Martin Chad E. Hadden
Despite the inherently low sensitivity of 15N NMR because of its low gyromagnetic ratio (γN) and its relatively low natural abundance (0.37%), this important nuclide still has useful potential as a structural probe even at natural abundance. Inverse-detected NMR methods coupled with major advances in NMR probe designs have made it possible to acquire long-range 1H−15N heteronuclear shift correlation data on samples as small as a micromole overnight. Chemical shift referencing schemes for 15N and the range of 15N shifts are discussed, followed by a discussion of the currently available pulse sequences, pulse calibration, parametrization and processing of long-range 1H−15N data, and the implications of probe selection. These topics are followed by a review of the applications contained in the literature that have utilized 1H−15N heteronuclear shift correlation experiments at natural abundance, with emphasis placed on the observed long-range coupling pathways.