Used in bioconjugation to label proteins, antibodies, peptides, nucleic acids, and enzymes for fluorescence detection. The NHS ester group reacts efficiently with primary amines (e.g., lysine residues) at pH 7–9. Enables imaging in techniques like fluorescence microscopy, flow cytometry, gel scanning, and microarray analysis due to strong near-infrared emission. Ideal for tracking biomolecules in live and fixed cells with minimal background autofluorescence. Commonly used in multiplex assays when combined with other fluorophores. Stable in physiological conditions, allowing long-term monitoring of biological processes.