Used as a stable isotope-labeled internal standard in mass spectrometry and metabolic studies to accurately quantify L-tyrosine and related metabolites in biological samples. Enables precise tracking of tyrosine metabolism in research on neurotransmitter synthesis, protein turnover, and metabolic disorders. Commonly applied in proteomics and metabolomics workflows where high specificity and sensitivity are required. Also utilized in tracer studies to investigate amino acid transport and utilization in cells and tissues.