Biotin-PEG-Alk (MW 10000) is a biotinylated polyethylene glycol (PEG) derivative featuring an alkyne group for click chemistry applications. This compound combines biotin, an enzyme co-factor used in protein labeling, with PEG, a hydrophilic, water-soluble, and low-toxicity polymer. The alkyne moiety facilitates copper-catalyzed azide-alkyne cycloaddition (CuAAC) with azido-containing molecules, enhancing the efficiency of targeting biotin-binding entities.