Streptavidin is a 55 kDa (subunit MW 14 kDa) biotin-binding protein isolated from Streptomyces avidini. Streptavidin is superior to avidin, because it does not contain carbohydrate like avidin and has no net charge at neutral pH. Streptavidin~biotin system is routinely used in Immunohistochemistry (IHC). Extinction Coefficient 1% A280=32.0; Eletrophoretically homogenous, single band. Protein content: > 95%; One mg of Streptavidin is conjugated with FITC, unconjugated Streptavidin is removed. This conjugate of streptavidin is recommended for use with Biotin~conjugated antibodies. Avidin~Biotin conjugated reagents are stable, sensitive and give less background. Fluorophore: Fluorescein isothiocyanate A max=492nm; E=520nm; Fluorophore/Protein: A492nm/A280nm=~1