Biotinylated peptides are very useful in immunodetection studies, for example to link the peptide to avidin coated microtitre plates.
Biotin can be linked to the N-terminus of peptides or to the side chains of lysine (Lys) or glutamic acid (Glu) during Fmoc solid phase synthesis. Post synthesis biotinylation can be carried out using the side chain thiol of a cysteine (Cys) residue. This is particularly useful when a cysteine-containing peptide has been synthesised for conjugation to a carrier protein for antibody production.
The incorporation of a spacer between biotin and the peptide is useful to reduce steric hindrance in the subsequent binding of biotin to avidin. This can be a hydrocarbon chain (provided for example by aminohexanoic acid) or polyethylene oxide. The latter has the added advantage of improving the solubility of the reagent and biotinylated peptide.