Used as a stable isotope-labeled tracer in metabolic studies to track the flow of carbon through biochemical pathways, particularly in amino acid metabolism and the citric acid cycle. Enables precise measurement of metabolic fluxes in cells, tissues, or whole organisms using techniques like mass spectrometry or nuclear magnetic resonance (NMR). Commonly applied in research on neurological disorders, energy metabolism, and cancer metabolism due to aspartate's role in neurotransmission and anaplerotic reactions. Also used in the development and validation of quantitative assays for amino acids in biological samples.