Used in bioconjugation to selectively label thiol groups in proteins and peptides. The iodoacetate group reacts with cysteine residues, forming a stable thioether bond, while the NHS ester enables coupling to primary amines on biomolecules or surfaces. Commonly applied in preparing fluorescent or biotinylated probes for assays like Western blotting, flow cytometry, and immunoassays. Also utilized in crosslinking studies and drug delivery systems where controlled attachment of molecules is required. Its dual reactivity allows stepwise modification of biomolecules under mild conditions.