Used in bioconjugation processes, particularly in antibody-drug conjugate (ADC) development, due to its ability to selectively react with thiol groups under mild conditions. Its water-soluble nature enhances reaction efficiency in aqueous buffers, making it suitable for labeling proteins and peptides without the need for organic co-solvents. Commonly employed in the preparation of diagnostic probes and targeted therapeutics where controlled conjugation is critical. The sulfo group improves solubility and reduces aggregation, supporting higher yields in conjugation reactions.