Used as a fluorescent labeling reagent in biological research, particularly for tagging proteins, peptides, and nucleic acids. Its high fluorescence intensity and stability make it suitable for sensitive detection in fluorescence microscopy, flow cytometry, and immunoassays. The succinimidyl ester group enables efficient conjugation to primary amines, ensuring precise labeling of biomolecules. Commonly applied in live-cell imaging and diagnostic assays due to its excellent photophysical properties and compatibility with aqueous environments.