Used as a reactive fluorescent dye in bioconjugation applications, particularly for labeling proteins, antibodies, and nucleic acids. Its sulfonate groups enhance water solubility and reduce nonspecific binding, making it suitable for use in biological assays such as fluorescence microscopy, flow cytometry, and immunoassays. The N-hydroxysuccinimide (NHS) ester groups react efficiently with primary amines on biomolecules to form stable amide bonds, enabling covalent attachment. The compound’s benzoxazolium backbone provides strong absorption and bright emission in the red to near-infrared range, allowing for high-sensitivity detection with minimal background autofluorescence. Commonly employed in multiplex labeling experiments due to its distinct spectral properties and compatibility with common biological buffers.