Streptavidin

Description
Streptavidin is a non-glycosylated, 52.8 kDa, tetrameric bacterial protein isolated from Streptomyces avidinii with a very high affinity for biotin. Streptavidin-biotin bond is the strongest known non-covalent interaction with Kd ~10-15 M. Because streptavidin lacks any carbohydrate modification and has a near-neutral pI, it has the advantage of much lower nonspecific binding than avidin. The binding of streptavidin to biotin provides several further advantages in addition to the strength of the interaction:

Highly specific

Rapid on-rate

Resistant to changes in temperature or pH

Can withstand the presence of organic solvents and denaturing agents

Streptavidin is used extensively in a wide range of laboratory applications, and there are many ways in which their strong biological interaction can be exploited.

Applications

Immunoassays

Histochemistry

FISH (Fluorescence In Situ Hybridization)

Flow cytometry

Microarrays and blot analysis

Source
E. coli

Purity
> 95 % as determined by SDS-PAGE

Unit Definition
One unit is defined as the amount of streptavidin required to bind 1.0 µg of D-Biotin at pH 7.0.

Specific Activity
15.5 U/mg by biotin titration method

Storage
Store vial at 4° C prior to restoration. For extended storage aliquot contents and freeze at -20° C or below.  Avoid cycles of freezing and thawing.