General Product Information: Streptavidin is produced by Streptomyces avidinii, which is affinity
purified from fermentation filtrates. It is supplied as an essentially salt-free lyophilized powder. The material is packaged by dry weight
(protein content: 95% ± 5%). The purified product is electrophoretically homogeneous with a pI = 7.0 ± 0.5. Biotin binding
activity is determined using the HABA assay method. One unit will bind 1 µg of d-biotin.
Streptavidin-HRP is supplied in
1 ml aliquots as a liquid in a stabilized buffer solution. The peroxidase content is standardized at 1 mg/ml as determined spectrophotometrically
at 403nm using an extinction coefficient of 18.6. HRP enzymatic activity is determined using pyrogallol. One unit will form 1 mg of purpurogallin
from pyrogallol in 20 seconds at pH 6.0, 20°C. Biotin binding is determined using the HABA assay method.
Streptavidin-Alkaline
Phosphatase is supplied in 1 ml aliquots as a liquid in a stabilized buffer solution. The alkaline phosphatase content is standardized at 1 mg/ml.
Enzymatic activity is determined using p-Nitrophenyl Phosphate as the substrate. One unit will hydrolyze 1 µmole of p-NPP per minute
at pH 9.8, 37°C.
The suggested dilutions for both enzyme conjugates are as follows:
Immunohistochemistry: 1:100 - 1:500
Immunoblotting: 1:500 - 1:5,000
ELISA: 1:1,000 - 1:10,000
Catalog No. S1214 (Part No. 90240) - Streptavidin, affinity purified
Purity: ≥ 99% by HPLC
Activity (biotin binding): ≥ 14.6 units/mg solid
Catalog No. S1521 (Part No. 90425) - Streptavidin, alkaline phosphatase conjugated
Activity (enzymatic): 2,300 ± 300 units/ml solution
Activity (biotin binding): 10 ± 1 units/ml solution
Catalog No. S1621 (Part No. 90426) - Streptavidin, horseradish peroxidase conjugated
Activity (enzymatic): 120 ± 30 units/ml solution
Activity (biotin binding): 3 ± 1 units/ml solution
The fermentation of Streptomyces avidinii results in the production of this biotin binding protein. Each molecule consists of four subunits, each of which binds one biotin molecule. Streptavidin and biotin are routinely conjugated to indicator enzymes such as horseradish peroxidase (HRP), alkaline phosphatase, and beta-galactosidase for use in diagnostic kit development and manufacturing. Unlike its counterpart, egg white avidin, streptavidin does not contain a carbohydrate moiety and, thus, possesses a lower isoelectric point (approximate pI = 7.0). As a result, streptavidin has lower non-specific binding characteristics than that of avidin, making streptavidin / biotin complexes more useful than avidin / biotin complexes in applications where low non-specific binding is crucial. Scripps Laboratories also offers Egg White Avidin, as well as reagents for biotin labeling proteins.