Biotinylation, Biotin-labeling is commonly used for non-radioactive labeling and purification of proteins and other target molecules. Biotin labeling takes advantage of the exceptionally strong interaction between biotin (vitamin H) and either avidin or streptavidin. The affinity of biotin to avidin or streptavidin is one of the strongest known non-covalent interactions of a protein and ligand, exhibiting a dissociation constant (Kd) around 10-15. Furthermore, this interaction is resistant to high or low pH, high salt concentrations, temperature extremes, and denaturants. These properties of the biotin-avidin interaction make it useful for purifying and/or detecting proteins of interest. BPS has a number of proteins that have been biotin-labeled via chemical methods through various reaction groups as well as enzymatically using AviTagTM technology.
In addition to our biotinylated proteins, we also offer a number of reagents that can be used to meet your specific biotinylation needs. There are a number of things to consider when selecting the appropriate biotinylation reagent:
Solubility – Modifications can be made to the biotinylation reagent to increase the solubility, thereby allowing access to hydrophobic or hydrophilic regions within the target protein. In addition, these modifications also increase the solubility of the resulting biotinylated protein. The most common method used to increase solubility of the biotinylation reagent is to add a poly(ethylene glycol) (PEG) spacer arm. The solubility of the biotinylation reagent increases with the number of PEG groups that have been added. BPS offers a variety of PEGylated biotinylation-reagents to meet all of your needs.
Spacer Arm Length – The ability of biotin to bind to avidin/streptavidin is dependent on the availability of biotin. The spacer arm length is defined as the distance between the conjugated amino acid and the biotin molecule. This length is varied by adding or removing chemical structures in between biotin and the reaction moiety. Increasing this length can increase the availability of biotin for binding to avidin/streptavidin.
Cleavable/Reversible Biotin Reagents – This refers to the ability of the biotin label to be either cleaved, or removed, from the protein or to reverse the biotin-avidin/streptavidin interaction. The former is done by adding spacer arms that include di-sulfide bonds. These disulfide bonds can easily be cleaved under denaturing conditions. The latter is accomplished using modified forms of biotin or avidin/streptavidin that exhibit a lower binding affinity.
Reactive Moiety/Enzymatic Addition – The reactive moiety within a biotinylation reagent determines the specific functional group or amino acid within a protein that will be labeled. Different reactive moieties are available to label primary amines, sulfhydryls, carboxyls, and carbonyls. Additionally, biotin can be enzymatically attached to a protein of interest by using AviTagTM technology. Here, a specific sequence, or AviTagTM, is added to the protein of interest. When this protein is co-expressed with the biotin ligase, BirA, or incubated with BirA under the appropriate conditions in vitro, biotin is site-specifically added to the AviTagTM.
BPS’ portfolio of biotinylation products includes reagents for labeling primary and secondary amines, alkyne groups, thiols, carboxyl groups, and phosphate groups with various numbers of PEG groups. This flexibility allows researchers to meet all of their biotinylation needs.