Used for labeling thiol groups in proteins and peptides, particularly in fluorescence-based assays. Ideal for conjugating to cysteine residues due to the maleimide group, enabling site-specific labeling. The diSulfo-Cy3 fluorophore is water-soluble and exhibits strong red fluorescence, making it suitable for imaging, flow cytometry, and protein detection without requiring organic solvents. Commonly used in studying protein interactions, cellular localization, and biomolecule tracking in aqueous environments.