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Avidin, Biotin, Streptavidin

Avidin, Biotin, and Streptavidin Overview



Rockland offers avidin, biotin and streptavidin in unconjugated and conjugated forms for common immunoassays including ELISA, western blotting, immunohistochemistry. The avidin-biotin system is a simple yet elegant system to link proteins in immunoassays by exploiting the very high affinity of hen egg white avidin for biotin (vitamin B7). Streptavidin, isolated from bacteria, binds biotin equally well but lacks the glycoprotein portion found on avidin and therefore shows lower non-specific binding. In immunoassays antibodies and reporters like fluorochromes or enzymes that are used to localize or quantitate analytes are often coupled via an avidin-biotin bridge.



Avidin and Conjugates



Avidin, a tetrameric biotin binding protein that shows high sequence homology in birds, reptiles and amphibians, is deposited in the egg white. Hen egg white avidin is a tetrameric protein composed of four identical subunits, each with the ability to bind biotin with high affinity and specificity (Kd ~ 1015 M). In biotechnology, the functional consequence of tetrameric biotin binding is signal amplification. Biotin-avidin bridging is a great way to increase signal strength while maintaining specificity. Avidin is a glycoprotein with a molecular weight of approximately 62.4 kDa.





Applications (if applicable)Avidin Conjugates


Avidin Peroxidase Conjugate for western blotting


Avidin Fluorescein Conjugate for immunofluorescence miscroscopy


Avidin Alkaline Phosphatase Conjugate for ELISA





Biotin and Conjugates



In biotechnology biotin is most often conjugated to antibodies. Other proteins, including enzymes, are often coupled to biotin. By exploiting the tetravalent binding of avidin, a biotin-avidin-biotin complex, can be formed. By example, a biotinylated antibody can be indirectly linked to a biotin conjugated beta Galactosidase through avidin resulting in signal amplification as an intended consequence of biotin-avidin bridging.



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Applications (if applicable) Biotin Conjugates



Biotin Peroxidase Conjugate for western blotting 


Biotin Beta Galactosidase Conjugate for molecular biology 


Biotin Glucose Oxidase Conjugate for ELISA





Streptavidin and Conjugates



Streptavidin has identical biotin binding properties compared with avidin, but lacks the glycoprotein portion of the molecule and therefore shows less non-specific binding. Streptavidin is a slightly smaller molecule with a molecular weight of approximately 53.6 kDa. The sequence of avidin only shows 30% homology with streptavidin, and anti-avidin and anti-streptavidin antibodies are not immunologically cross reactive. Rockland offers streptavidin conjugated to a wide variety of enzymes and fluorochromes, including ATTO, DyLight™ and Cy™ dyes.



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Applications (if applicable) streptavidin dylight 488



Streptavidin Peroxidase Conjugate for western blotting


Streptavidin Cy5™ for immunofluorescence microscopy


Streptavidin DyLight™ 800 Conjugated for fluorescent western blotting





Biotin, Avidin Streptavidin: Technical Tips for Success



Reference Rockland Bucket



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