Br-PEG4-THP（Cat No.:I044637）is a bifunctional polyethylene glycol (PEG) derivative featuring a terminal bromo group and a tetrahydropyranyl (THP)-protected hydroxyl, connected by a four-unit PEG spacer. The bromo group serves as a reactive handle for nucleophilic substitution with thiols, amines, or other nucleophiles, allowing for covalent attachment to various molecules or surfaces. The THP group protects the hydroxyl moiety from undesired reactions and can be selectively removed under mild acidic conditions. The PEG4 spacer enhances solubility, reduces steric hindrance, and improves biocompatibility, making this reagent valuable for synthesis, bioconjugation, and material modification.