Biotin and Streptavidin
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The biotin-streptavidin complex is one of the most popular tagging systems for the conjugation of biomolecules, such as proteins, lipids and nucleic acids, as well as that of synthetic molecules, such as fluorescent labels. It has found strong success in the area of sample preparation as a core part of many purification systems and plays a critical role in many detection systems for instruments such as microscopy and flow cytometry.
The widespread adoption of the biotin-streptavidin conjugation system is primarily due to two factors. The first is the relatively small size of the biotin and streptavidin molecules themselves, which allows for extensive binding to biologically active macromolecules, such as antibodies, without impedance to their functions (i.e. an antibody’s binding site). The second is the specificity with which biotin and streptavidin bind to each other, as well as the strength of the subsequent bond, which allows for powerful, stream-lined bioassay applications.
AAT Bioquest offers one of the most comprehensive catalogs of biotin and streptavidin products, their derivatives and their conjugates. We also have a wide range of kits which have been designed to take advantage of the strengths of the biotin-streptavidin conjugation system and optimized to improve user convenience and workflow.
To learn more, please see the information below.
Biotin, a 244 dalton vitamin, is present in trace amounts in all living cells. Besides having a strong affinity for streptavidin, biotin exhibits two characteristics that make it ideal for bioconjugate development. First, is biotin’s relatively small size. This minimizes any significant hindrance with the protein or antibody’s biological reactivity, and permits the labeling of multiple biotin tags to a single macromolecule for maximum detection by streptavidin and its conjugates.
Second, is the valeric acid side chain of the biotin molecule. This chain can be derivatized to incorporate various reactive groups used to biotinylate (i.e. label) proteins without altering its binding affinity for streptavidin. This feature is critical as it allows for the development of various biotinylated reagents. These include, amine-reactive biotin succinimidyl ester and thiol-reactive biotin maleimide, as well as, AAT Bioquest’s ReadiView™ reactive biotins and ReadiLink™ Protein Biotinylation Kit which enable researchers to chemically label proteins, nucleic acids and other molecules in order make custom assay probes.
Biotinylated proteins are routinely used in conjunction with streptavidin conjugates. Together, they form a sophisticated detection platform that is readily adaptable to a broad range of applications. A large factor that contributes to the versatility of the biotin-streptavidin system is the ability to conjugate streptavidin to a variety of reporter tags. For example, enzyme conjugates of streptavidin, such as HRP-streptavidin or AP-streptavidin, are commonly used in immunoblotting, ELISA and in situ hybridization imaging applications. While fluorescently labeled streptavidin , such as iFluor™-streptavidin, are widely used in cell surface labeling, fluorescence activated cell sorting (FACs) and other fluroescence imaging applications.
Advantage of the Biotin-Streptavidin System
A key benefit of the biotin-streptavidin system is its ability to improve the detection sensitivity of any assay. This in large part is due to the tetrameric conformation of streptavidin, which enables streptavidin to bind four biotins per molecule with high affinity and selectivity. This multiplicity allows for amplification of weak signals, allowing for improved experimental results when testing for medium- to low- abundance targets in mammalian cells or tissues.
Table 1. Product ordering information for biotin, biotin derivatives, biotin conjugates and biotin kits.
Table 2. Product ordering information streptavidin conjugates.