Used in bioconjugation and click chemistry, Iodo-PEG4-N3 serves as a heterobifunctional linker for attaching molecules like peptides, proteins, or drugs to various surfaces or biomolecules. The iodo group enables conjugation to thiol-containing molecules via nucleophilic substitution, while the azide group facilitates efficient reactions with alkynes through copper-catalyzed azide-alkyne cycloaddition (CuAAC). This dual functionality makes it valuable in drug delivery systems, diagnostic probes, and material science. The PEG4 spacer enhances solubility and reduces steric hindrance, improving the performance of conjugated compounds in biological applications.