Nitrogen-15 nuclear magnetic resonance spectroscopy (nitrogen-15 NMR spectroscopy, or just simply N NMR) is a version of nuclear magnetic resonance spectroscopy that examines samples containing the N nucleus. N NMR differs in several ways from the more common C and H NMR. To circumvent the difficulties associated with measurement of the quadrupolar, spin-1 N nuclide, N NMR is employed in samples for detection since it has a ground-state spin of ½.  SinceN is 99.64% abundant, incorporation of N into samples often requires novel synthetic techniques.
Nitrogen-15 is frequently used in nuclear magnetic resonance spectroscopy (NMR), because unlike the more abundant nitrogen-14, that has an integer nuclear spin and thus a quadrupole moment, N has a fractional nuclear spin of one-half, which offers advantages for NMR like narrower line width. Proteins can be isotopically labeled by cultivating them in a medium containing nitrogen-15 as the only source of nitrogen. In addition, nitrogen-15 is used to label proteins in quantitative proteomics (e.g. SILAC).