1-Isothiocyanato-PEG4-alcohol(CAT: I016564) is a heterobifunctional polyethylene glycol linker featuring a reactive isothiocyanate group and a terminal hydroxyl group. The isothiocyanate moiety enables stable conjugation to primary amines on proteins, peptides, or other biomolecules through thiourea bond formation, while the hydroxyl group offers flexibility for further chemical modification or derivatization. The PEG4 spacer provides enhanced solubility, reduced steric hindrance, and improved biocompatibility, making it a valuable tool for bioconjugation, drug delivery, and surface modification applications. This reagent is widely used in biomedical research, diagnostics, and material science where controlled and versatile molecular linking strategies are required