DL-Phenylalanine-15N is primarily used in research and scientific studies as a stable isotope-labeled compound. It serves as a tracer in metabolic studies to track the pathways and mechanisms of phenylalanine metabolism in biological systems. This labeled form is particularly valuable in nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry, where it helps in identifying and quantifying metabolic intermediates. Additionally, it is employed in nutritional research to investigate amino acid utilization and protein synthesis in humans and animals. Its use in these applications provides critical insights into metabolic disorders, dietary effects, and the development of therapeutic strategies.