Long-Range <sup>1</sup>H−<sup>15</sup>N 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 <sup>15</sup>N NMR because of its low gyromagnetic ratio (γ<sub>N</sub>) 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 <sup>1</sup>H−<sup>15</sup>N heteronuclear shift correlation data on samples as small as a micromole overnight. Chemical shift referencing schemes for <sup>15</sup>N and the range of <sup>15</sup>N shifts are discussed, followed by a discussion of the currently available pulse sequences, pulse calibration, parametrization and processing of long-range <sup>1</sup>H−<sup>15</sup>N data, and the implications of probe selection. These topics are followed by a review of the applications contained in the literature that have utilized <sup>1</sup>H−<sup>15</sup>N heteronuclear shift correlation experiments at natural abundance, with emphasis placed on the observed long-range coupling pathways.