Used extensively in biological research for fluorescence labeling of proteins, peptides, and other biomolecules. It is particularly valuable in fluorescence microscopy and flow cytometry, enabling the visualization and tracking of cellular components and processes. Its bright red fluorescence and high photostability make it ideal for multi-color imaging studies. Additionally, it is employed in immunohistochemistry to detect specific antigens in tissue samples, aiding in disease diagnosis and research. The isothiocyanate group allows for covalent bonding to amino groups, ensuring stable and specific labeling of target molecules.