Fast and Cost-Efficient O-Isotopic Labeling of Carboxylic Groups in Biomolecules: From Free Amino Acids to Peptide Chains.

O NMR spectroscopy is a powerful technique, which can provide unique information regarding the structure and reactivity of biomolecules. However, the low natural abundance of O (0.04 %) generally requires working with enriched samples, which are not easily accessible.