Sulfo-Cy5 amine, a dye derivative of Cyanine 5 (Cy5), includes an amine group and a sulfonate ion to enhance water solubility, making it ideal for aqueous solutions. This near-infrared fluorescent dye is extensively used in biolabeling and cell imaging, where its amine functionality can react with carboxyl groups to form covalent bonds, enabling attachment to biomolecules like proteins and antibodies for tracking their location and dynamic changes in biological samples.