Mal-Cyclohexyl-PEG3-Biotin is a PEG linker that includes a maleimide moiety and a biotin group. The maleimide specifically reacts with thiols at a pH between 6.5 and 7.5, forming a stable thioether bond. Biotinylation can occur with amine molecules in the presence of activators like EDC or HATU. The PEG linkage, attached to biotin, creates an extended spacer arm, facilitating biotin's access to protein binding sites. Additionally, the PEG component enhances the solubility of the biotin-PEG conjugate significantly.