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Cat. No.: DFSA-1 (for 1mg)

Cat. No.: DFSA-5 (for 5mg)

Description

DNA-Free Streptavidin is a protein with similar biological properties to avidin, synthesized by Streptomyces avidinii. Its molecular weight and ability to bind biotin are similar to those of avidin found in egg whites. Streptavidin has an isoelectric point of 6.0 and nearly no net charge at neutral pH, and it lacks carbohydrate side chains, resulting in much lower nonspecific binding compared to avidin. Streptavidin is a tetrameric protein with a size of 66 kDa. Each molecule of streptavidin can specifically bind four molecules of biotin with an exceptionally strong affinity, with a dissociation constant in the range of 10^-14 to 10^-15 M, which is one of the strongest known non-covalent interactions in nature. Streptavidin is soluble up to 1 mg/ml in water and up to 5 mg/ml in 100 mM NaCl. The extinction coefficient of a 1 mg/ml streptavidin solution at 280 nm is 3.2.

A full SA peptide chain contains 159 amino acid residues with a molecular weight of 16,450. Streptavidin consists of four identical peptide chains, with a high content of glycine and alanine. The active site for biotin binding is the tryptophan residue within the peptide chain. Under protease action, streptavidin can cleave between the N-terminal 10-12 residues and the C-terminal 19-21 residues. The resulting core streptavidin still retains its full biotin-binding capability, with the core structure consisting of 127 amino acids responsible for biotin binding. According to international standards, its specific activity ranges from 12-15 IU/mg, with a maximum activity of 18 U/mg.

The streptavidin-biotin complex is highly resistant to organic solvents, denaturants (such as guanidine hydrochloride), detergents (such as SDS and Triton), proteolytic enzymes, and extreme temperatures and pH. This property, combined with biotin-conjugated antigen/antibody detection techniques, makes it widely used in immunology for signal amplification in ELISA assays. Additionally, it can be used for surface coating of immunoassay plates, immunochromatography nitrocellulose membranes, gene chips, and protein chips, facilitating the rapid immobilization of biotinylated antigens, antibodies, nucleic acids, and other substances. It is also suitable for coupling to NHS magnetic beads, resin microspheres, and applications in luminescent diagnostics, biotinylated substance separation, and magnetic strip immunochromatography.

Streptavidin can be conjugated with horseradish peroxidase, alkaline phosphatase, fluorescent groups, and other molecules, participating in signal amplification in immunoassays. It is widely used in chemiluminescence, IHC, WB, IF, ISH, flow cytometry, nucleic acid extraction, protein purification, and the preparation of affinity chromatography media, biosensors, and biochips.

Our DNA-Free Streptavidins are all recombinant proteins and purified through multiple steps, devoid of genomic and plasmid DNA from the production strain, with a specific activity >11 U/mg.

Unit Definition

One unit is defined as the amount of streptavidin required to bind 1 μg of biotin (Green, N.M., Biochem.J., 89:599,1963).

Features

• Completely free from bacterial DNA.
• Recombinant streptavidin expression.
• Solution formulation for ease of use.
• Includes His-tag.

Applications

• Enrichment of biomolecules using nickel columns.

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