Dansyl acid is widely used as a fluorescent labeling reagent in biochemistry and molecular biology. It is particularly valuable for tagging amino acids, peptides, and proteins to study their structure, function, and interactions. The strong fluorescence of dansyl acid allows for sensitive detection and analysis in techniques like fluorescence spectroscopy and microscopy. Additionally, it is employed in chromatography as a derivatizing agent to enhance the detection of compounds that are otherwise difficult to analyze. Its applications also extend to the study of enzyme kinetics and the identification of biomolecules in complex mixtures.