Biotinylation

Because of its especially high affinity and binding specificity, the biotin-avidin (or biotin-streptavidin) interaction has been used for several decades as the basis of many laboratory research techniques to label, detect and purify peptide, proteins and other biomolecules. The biotin moiety has a very strong affinity for streptavidin (K_d<10^-10 M) and biotinylation of peptides is therefore an efficient method to specifically bind peptides to streptavidin coated surfaces.

Peptide biotinylation can be performed either at the N- or C-terminus. Biotinylation at the N-terminus can be performed directly to the primary-terminal amino group, whereas biotinylation is usually performed at the ε-amino group of an (extra) C-terminal lysine. An important consideration when making a biotinylated peptide is to ensure there is a sufficient spacer arm between the biotin group and the amino acids in the peptide which are expected to interact with a macromolecule (such as an antibody). To avoid sterical hindrance, a linker can be inserted between biotin and the peptide sequence. A hydrophobic straight chain spacer such as the 6-carbon ε-aminohexanoic (Ahx) is frequently applied or a hydrophilic tetrapeptide such as -SGSG- can be inserted. Multiple other spacers and linkers are available and can be applied to meet your specific requirements.

One limitation of the biotin-(strept)avidin interaction in purification applications is that it is essentially irreversible under physiological conditions. Binding is resistant to pH and/or temperature changes, organic solutions and denaturing reagents. Therefore in case a reversible interaction to (strept)avidin is desired, the use of biotin analogs is recommended.

Iminobiotin is an analog of biotin, in which the upper ring structure of D-biotin is replaced with a 2-imino-imidazole structure, causing moderated interaction with the avidin or streptavidin binding sites. This biotin analog can be therefore be used in situations requiring mild dissociation of the (strept)avidin-biotin complex.

Similarly desthiobiotin, a non-sulfur containing biotin analog, can be used. Desthiobiotin binds less tightly to avidin and streptavidin than biotin but nonetheless provides a high level of specificity. Moreover it is less prone to oxidation.

Pepscan routinely synthesizes peptides with the above biotin tags, but also offers custom peptides with a range of other tags. For a listing of frequently incorporated tags, go to Tagged Peptides.