Recombinant Core Streptavidin 3 (r-cSA3 )

Streptavidin (SA) has a strong affinity with biotin. The affinity constant Kd can generally be as high as 10-15 M. Active SA usually exists as a tetramer. Because SA does not contain sugar groups, SA has a lower level of non-specific binding than avidin in detection applications. It has been widely used in enzyme-linked immunosorbent assay, immunohistochemistry, time-resolved immunofluorescence technology (TRFIA), quantitative PCR, single-stranded DNA preparation, biomolecule-purification, preparation of monoclonal antibodies and other biotechnology fields.

However, the very high affinity of SA and biotin generally makes it difficult to separate the combined SA from biotin by a gentle method. Conditions that can be separated generally render SA inactive, as well as biotin-labeled antibodies and antigens. Therefore, it is generally considered that the combination of SA and biotin is irreversible. Recombinant central streptavidin 3 (r-cSA3) is modified from native streptavidin at the molecular level by removing the binding force to form tetramers. r-cSA3 is an active monomer, but its affinity for biotin is strongly weakened (Kd≈10-7M), achieving reversible binding and dissociation. It can be used for gentle separation and purification of proteins, antibodies, nucleic acids and other biotinylated materials.