Streptav*din

Streptavidin is a homotetrameric protein secreted by Streptomyces avidinii which binds firmly to biotin. Streptavidin is widely used in molecular biology because of its unique high affinity for biotin. The dissociation constant (Kd) of the biotin-streptavidin complex is about ca.10-15 mol/L. The strong affinity recognition of biotin and biotinylated molecules has made streptavidin one of the most important components in diagnostics and laboratory kits. The streptavidin/biotin system has one of the biggest free energies of association yet observed for noncovalent binding of a protein and small ligand in aqueous solution (K_assoc = 10-14 mol/L). The complexes are also extremely stable over a wide range of temperature and pH. The preparation contains an N- and C-terminal shortened variant (core streptavidin) with improved properties concerning homogeneity, solubility, resistance towards proteolytic degradation and accessibility of the biotin binding pocket as compared to native streptavidin.

Lyophilized from a sterile filtered solution in 50mM NaCl, pH 9.0.

Centrifuge vial prior to opening. Add sterile distilled water to the vial to fully solubilize the protein.

> 15.9 U/mg. 1 unit binds 1 ug biotin. Proteolytic activity is < 10-3 U/mg (24 hours at 25C and pH 8.0).