Iodoacetamide-PEG3-azide is widely used in bioconjugation and chemical biology research. Its primary application is in the modification of proteins, peptides, and other biomolecules. The iodoacetamide group selectively reacts with thiol groups (-SH) in cysteine residues, enabling site-specific labeling. The PEG3 spacer enhances solubility and reduces steric hindrance, while the azide group allows for further functionalization via click chemistry, such as copper-catalyzed azide-alkyne cycloaddition (CuAAC). This makes it a valuable tool for creating fluorescent probes, affinity tags, or drug conjugates for studying protein interactions, cellular imaging, or targeted drug delivery systems.