Used as a stable isotope-labeled compound in metabolic studies and research to trace nitrogen pathways in biological systems. It aids in understanding amino acid metabolism, protein synthesis, and cellular processes. Applied in nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry for precise analysis of biochemical reactions. Also utilized in pharmaceutical development to study drug metabolism and in nutritional research to investigate the role of cysteine in health and disease. Its labeled nitrogen atom provides a reliable marker for tracking and analysis in complex biological systems.