Avidin and Streptavidin Reagents

Avidin and Streptavidin are vital tools in biotechnological and diagnostic applications due to their high-affinity binding to biotin. These proteins are frequently employed in molecular biology, immunology, and other life science fields to facilitate the detection, isolation, and purification of biotinylated molecules.

Explore our complete catalog of avidin and streptavidin reagents to find the right solution for your research needs.

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Understanding Avidin Reagent

Avidin, a glycoprotein derived from egg whites, exhibits an extraordinarily high affinity for biotin, with a dissociation constant (Kd) in the order of 10^-15 M. This remarkable affinity makes Avidin ideal for applications requiring robust and stable biotin binding. Avidin's natural form is a tetramer, meaning it can bind up to four biotin molecules simultaneously. The glycosylation of Avidin contributes to its stability and solubility but can also lead to non-specific binding in certain applications, necessitating careful consideration during experimental design.

Key Applications:

• Immunoassays - Avidin-biotin complex formation enhances signal detection in ELISA, Western blotting, and immunohistochemistry.
• Affinity Chromatography - Avidin can be immobilized on a solid matrix to purify biotinylated proteins or nucleic acids with high specificity.
• Biosensors - The Avidin-biotin interaction is employed in the development of biosensors to detect various analytes.

Figure 1. Schematic diagram of avidin/biotin amplification^[1].

Understanding Streptavidin Reagents

Streptavidin, a biotin-binding protein derived from Streptomyces avidinii, shares structural and functional similarities with Avidin but offers distinct advantages. Unlike Avidin, Streptavidin is non-glycosylated, resulting in lower non-specific binding. Streptavidin also has a near-neutral isoelectric point (pI), further reducing background interference in various assays. This makes Streptavidin particularly suitable for applications where specificity and low background noise are critical.

Key Applications:

• Protein Labeling - Streptavidin conjugated to enzymes, fluorophores, or other detection molecules is commonly used to detect biotinylated targets in various assays.
• Cell Sorting and Imaging - Biotinylated antibodies can be employed in flow cytometry or microscopy with Streptavidin-conjugated markers for precise cell population identification and analysis.
• Molecular Diagnostics - Streptavidin's strong and specific binding to biotinylated probes is instrumental in nucleic acid detection and amplification techniques, such as PCR and DNA microarrays.

Figure 2. (a) Avidin/biotin and streptavidin/biotin complex formation. (b) Interaction between avidin/biotin and streptavidin/biotin^[2].

Choosing Between Avidin and Streptavidin

The choice between Avidin and Streptavidin depends on the specific requirements of the application. Avidin's glycosylation can be advantageous in some cases, providing enhanced stability, while Streptavidin's lower non-specific binding and neutral pI make it preferable for sensitive assays. Both reagents are available in various forms, including native, conjugated to enzymes or fluorophores, and immobilized on solid supports, providing flexibility in experimental design.

References:

1. Guerin CJ; et al. Using Antibodies in Microscopy: A Guide to Immunohistochemistry. Part 2: IHC Staining Protocols. Microscopy Today. 2023, 31(3): 34-39.
2. Haque ST; et al. Strategies to Assemble Therapeutic and Imaging Molecules into Inorganic Nanocarriers. Frontiers of Materials Science. 2022, 16: 220604.

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