How to achieve unparalleled purification factors The
Strep-tag® purification system is based on the highly selective and easily controllable interaction between the
Strep-tag II peptide and specially engineered streptavidin called
Strep-Tactin. The binding affinity of
Strep-tag II to
Strep-Tactin is nearly 100 times higher than to streptavidin. The tagged protein binds to immobilized
Strep-Tactin during affinity purification. Physiological buffers like PBS in combination with wide range of additives can be used. After a short washing step, gentle elution of purified recombinant protein is performed by addition of desthiobiotin (2.5 mM) to the same buffer. Desthiobiotin is an inexpensive, reversibly binding and stable analog of biotin – the natural ligand of streptavidin. This competitive elution is the second step conferring specificity thus enabling unparalleled purification factors. The system is safe and easy to use; column regeneration and activity status are visualized by a colour change on the purification column.
Convenient detection of
Strep-tag fusion proteins can be performed in Western blots, ELISA, electron or fluorescence microscopy. Appropriate
Strep-Tactin enzyme conjugates and monoclonal antibodies against
Strep-tag II are available along with new products for protein immobilization and protein:protein interaction studies.
Strep-tag® II has negligible effects on the proteinThe short peptide tag (8 amino acids) has negligible effect on the recombinant protein due to its chemically balanced amino acid composition (WSHPQFEK). The tag can be placed at the C- or N-terminus. A two amino acid spacer between the protein and tag is recommended to ensure accessibility of the tag. Generally, it does not interfere with folding or bioactivity, does not react with heavy metal ion buffer impurities, has no exchange properties and does not induce protein aggregation. Thus, there is no need for removing the tag.
Strep-Tactin®: long lasting affinity columnsStrep-Tactin is a streptavidin derivative which is one of the most stable proteins known. Streptavidin is stable to treatment with 8 M urea or guanidine, 0,5 M NaOH as well as 50% formamide (t=1h ; T=37˚C). Proteases (proteinase K, pepsin, papain, subtilisin, thermolysin, elastase) do not cleave streptavidin during a 2 h incubation at 1:50 w/w ratio and 37˚C. In the presense of SDS streptavidin begins to break up into monomers only at a temperature above 60˚C. As far as tested, we have been able to confirm these extraordinary properties for
Strep-Tactin, a basis for long-affinity columns which can be re-used 3-5 times. Furthermore, the neutral pl of
Strep-Tactin minimizes non-specific proteins or nucleic acid binding.
Read more about the different products hereBenefits:
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Purification of bioactive recombinant proteins
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Physiological purification using desthiobiotin elution
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Protein aggregation is avoided
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Broad range of detergents, chelators, salt or redox conditions allowed
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Avoids interaction with heavy metal ions which are toxic and may catalyze protein oxidation
