Biotin peptide is a valuable labeling reagent used in immunodetection, purification and cell-based studies. It is a versatile labeling tool that can be applied to many macromolecules, including protein and nucleotide ligands.
Biotin has a strong affinity for avidin, which is why it is often used to detect and purify proteins or ligands. It is also a useful tool for identifying protein-protein interactions because it can be attached to multiple proteins and binds avidin with high specificity.
However, it is important to note that biotinylation interferes with the function of some proteins and may lead to false-positive staining, particularly after heat antigen retrieval treatment. Therefore, it is crucial to identify the exact residue modified by biotinylation.
Several approaches can be utilized to determine the exact residue modified by biotinylation. These include the HABA assay and various click chemistry techniques.
In the case of HABA, a dye is bound to avidin or streptavidin. When introduced into the sample, the biotinylated protein displaces the dye and changes its absorbance at 500 nm. This change is proportional to the amount of biotinylated protein and allows a quantitative determination of the extent of biotinylation.
The biotinylation of proteins is often carried out in a series of steps. The first step is synthesis of the peptide. This can be performed using a solid phase synthesis system such as Fmoc or via post synthesis chemical cleavage of the peptide. The peptide can be linked to biotin via the side chain thiol of a cysteine residue during synthesis or via a thiol group on the N-terminus of the peptide after synthesis.