Product Description
Streptavidin is a biotin binding protein present in the fermentation broth of the bacterium Streptomyces avidinii. Each molecule of streptavidin can bind four molecules of biotin with a high affinity constant (Kd~10 -15). Unlike native avidin, streptavidin is not glycosylated and has a near neutral isoelectric point (pI ~ 5-6) vs a pI of 10 for native avidin.
Information
ConjugationUnconjugated.
Specifications
Storage BufferLyophilized in 10mM potassium phosphate buffer pH 6.5.
SourceEscherichia Coli. Streptomyces avidinii.
Purity / Grade>98% by SDS-PAGE and HPLC
Biotin-binding activity: >17 U/mg (Green’s modified assay)
SolubilityIt is recommended to reconstitute the lyophilized Streptavidin in sterile 18MΩ-cm H2O not less than 0.5mg/ml, which can then be further diluted to other aqueous solutions.
Misc Information
Storage InstructionThe lyophilized streptavidin is stable for at least one year when stored desicated at –20°C.
It is recommended to only reconstitute the amount required for use. However, any unused reconstituted streptavidin should be aliquoted in working volumes without diluting and stored at –20°C in a manual defrost freezer.
Avoid Repeated Freeze Thaw Cycles
Calculated Molecular Weight52kDa.
SequenceMAEAGITGTWYNQLGSTFIVTAGADGALTGTYESAVGNAESRYVLT
GRYDSAPATDGSGTALGWTVAWKNNYRNAHSATTWSGQYVGGA
EARINTQWLLTSGTTEANAWKSTLVGHDTFTKVKPSAAS.
NotesStreptavidin is lyophilized under slight alkaline conditions from deionized water. The final lyophilized protein contains approximately 10% NaCl. Therefore, the streptavidin concentration should be determined by measuring the absobance at A280 nm and calculated using the extinction coefficient.
ProtocolReconstitute in highly pure deionized water to 1-15 mg/ml. If buffering is required, add sufficient stock solution of 10-20X phosphate buffered saline (PBS) to bring the final concentration to 1X PBS. Do not reconstitute directly in PBS.