Streptavidin is a protein isolated from the bacterium Streptomyces avidinii and has no carbohydrate moieties. It has a molecular weight of approximately 60,000 Daltons with an isoelectric point of 5. Streptavidin and avidin have a high affinity (Kd = 10 -15 M -1 ) to biotin and are the basis for the most widely used technique for amplification and detection in tissues or cells.
Although streptavidin and avidin are similar, each has distinct properties that should be taken into consideration when developing an assay. Streptavidin has physical properties that allow higher signal-to-noise ratios than is possible with the biotin-avidin complex. It is much less soluble in water than avidin thereby reducing nonspecific binding to cell surface antigens.
SeraCare offers a full line of KPL streptavidin labeled with alkaline phosphatase, horseradish peroxidase, fluorescein, rhodamine, Cy dyes, R-phycoerythrin and gold. We also offer enzyme labeled streptavidin in a variety of forms for specific applications. KPL streptavidin conjugates are prepared with molecular biology grade chemicals and dispensed into RNase/DNase-free sterile vials. HRP-and AP-labeled streptavidin are available in liquid form for nucleic acid detection assays. The liquid conjugates are provided at a concentration of 0.1 mg/mL.