Nuclear magnetic resonance (NMR)

NMR is an analytical technique that is used to measure organic and some inorganic compounds inside biological samples (as solid tissue or extracted metabolite). When a sample is exposed to a magnetic field and radio frequency (rf) pulse, the nuclei absorb and re-emit this electromagnetic radiation. The energy that is emitted has a specific resonating frequency, which depends on several factors including the magnetic properties of the atoms’ isotopes and the strength of the magnetic field (usually referred to as chemical shifts). In the case of metabolomics, proton atoms from small molecules are usually investigated (1H-NMR). For more on NMR concepts check the Royal Society of Chemistry analytical chemistry introduction (5).

NMR-based metabolomics is a non-invasive and non-destructive technique with high reproducibility, making it a powerful tool for searching new and novel biomarkers. For NMR, we measure the resulting signal from small molecules’ protons resonating within a magnetic field. One of the first usages of NMR was to detect metabolites in unmodified biological samples (6).