nitrogen15

Nitrogen-15 (15N) is a stable isotope of nitrogen with mass number 15. It contains 7 protons and 8 neutrons, making it one of the two stable nitrogen isotopes, the other being nitrogen-14 (14N).

Natural abundance and stability: In nature, 15N accounts for about 0.366% of all nitrogen, with 14N comprising the remainder. Both isotopes are non-radioactive, so nitrogen has a stable isotopic composition over time. The small mass difference between 15N and 14N enables isotope labeling without introducing radioactivity.

Occurrence and production: 15N occurs naturally at low abundance and is enriched for research use through industrial isotope separation methods. Enriched 15N is delivered as labeled compounds such as 15NH4+, 15NO3−, or 15N-labeled organic molecules for experimental applications.

Applications: 15N is widely used as a tracer in biology, chemistry, and environmental science. In nuclear magnetic resonance (NMR) spectroscopy, labeling proteins, nucleic acids, and metabolites with 15N provides detailed structural and dynamic information because 15N has a nuclear spin of I = 1/2, which yields simpler spectra. In mass spectrometry and quantitative biology, 15N-labeled compounds enable precise tracking of nitrogen incorporation and metabolic flux. In environmental studies, the 15N/14N ratio (δ15N) helps identify nitrogen sources, study trophic levels, and investigate nitrogen cycling and fixation processes.

Notes: 15N is stable and non-radioactive, making it suitable for safe, long-term research applications. Its relatively low natural abundance is offset by readily available enrichment technologies for experimental needs.