Maleimide-PEG-NTA

Maleimide-PEG-NTA is a heterobifunctional polyethylene glycol (PEG) linker functionalized with a maleimide group at one terminus and a nitrilotriacetic acid (NTA) group at the other. It is specifically designed for site-specific conjugation to proteins or surfaces containing free thiol groups (via the maleimide) while enabling reversible, high-affinity binding to polyhistidine (His-tag) sequences through metal coordination (typically with Ni²⁺ or Co²⁺ ions). The maleimide moiety allows selective and efficient covalent attachment to cysteine residues under mild conditions. The NTA group, once charged with divalent metal ions, forms a stable complex with 6xHis or other His-tags, commonly used for oriented immobilization or labeling of recombinant proteins. The PEG spacer provides excellent water solubility, reduces non-specific binding, and offers steric flexibility. This reagent is widely employed in protein engineering, surface functionalization, biosensor development, and the construction of protein–nanoparticle or protein–surface conjugates where controlled orientation and minimal steric hindrance are required.