Streptavidin (AP)

Streptavidin (MW ~66kD) binds specifically with biotin (244D). It is derived from the bacterium Streptomyces avidinii and bears a remarkable similarity to chicken egg-white avidin both in three-dimensional structure and its ability to bind biotin with extremely high affinity (Kd=10e-15M). It is a tetrameric protein capable of binding up to 4 biotin molecules. Unlike avidin, Streptavidin is non-glycosylated and is essentially neutral in charge, whereas avidin (pH 10.5) is basic at neutral pH. Because of this, streptavidin has considerably less non-specific binding resulting in less background. It has replaced avidin as the reagent of choice for most applications where protein interactions may cause background. Applications: Suitable for use in ELISA, Immunohistochemistry, Immunocytochemistry and Western Blot. Other applications not tested. Recommended Dilution: ELISA: 1:1,000-1:2,500, Western Blot (chromogenic): 1:500-1:1,250, Western Blot (chemiluminescence) : 1:1,000-1:2,500, Immunohistochemistry:1:100 -1:300, Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4°C before opening. DO NOT FREEZE! Stable at 4°C as an undiluted liquid. Dilute only prior to immediate use. Stable for at least 6 months. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. Freezing alkaline phosphatase conjugates will result in a substantial loss of enzymatic activity.