Precision bioconjugation techniques are essential for constructing well-defined protein-based therapeutics such as antibody-drug conjugates (ADCs). Among native amino acids, cysteine is particularly attractive for site-selective modification due to its high nucleophilicity and low natural abundance. However, most proteins contain multiple free cysteines, making it challenging to target specific residues without affecting protein structure or function.

NMR-based metabolomics is a robust analytical tool used to investigate the chemical phenotype of biofluids. The relationships between its components and human health has the potential to alter clinical practices, including treatment efficacy and disease prognosis. As an intrinsically quantitative, highly reproducible and non-destructive technique, often requiring little sample preparation, NMR is ideal for metabolomics.