NITROGEN-15

'Nitrogen-15' is a stable, non-radioactive isotope of nitrogen. It is often used in agricultural and medical research. Nitrogen-15 is frequently used in nuclear magnetic resonance spectroscopy (NMR), because unlike the more abundant nitrogen-14, it has a nuclear spin of one half, which simplifies observation by NMR. Proteins can be isotopical labelled by cultivating them in a medium containing only nitrogen-15. In addition, nitrogen-15 is used to label proteins in quantitative proteomics (e.g. SILAC).
It is a product of oxygen-15 beta decay in stars.
₈O¹⁵ → ₇N¹⁵ + e⁺ + ν
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