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Strep-Tactin Magnetic Beads

For efficient micro-scale purification of Strep-tagged proteins
  • Strep-tagged protein purification, especially from eukaryotic cell lysates
  • Facilitated detection due to small elution volumes
Strep-Tactin Magnetic Beads enable efficient micro-scale purification of recombinant proteins carrying the short Strep-tag affinity tag epitope. The small Strep-tag II can be used to purify active, native conformation proteins to high purity. In addition, it can be used in combination with the His tag for a standardized two-step purification procedure.

Strep-Tactin Magnetic Beads are intended for molecular biology applications. These products are not intended for the diagnosis, prevention, or treatment of a disease.

Highly specific detection of Strep-tagged proteins in any expression system.
Purified Strep-tagged thioredoxin (10 ng) was mixed with crude cell lysate from mammalian (NIH-3T3), insect (Sf9), and bacterial (E. coli) cells (each 10 µg total protein). After electrophoresis and western transfer, the Strep-tagged protein was detected using the Strep-tag Antibody and chemiluminescent detection.

Micro-scale purification of high purity Strep-tagged proteins.
The indicated tRNA synthestase was purifed from E. coli cell lysate using Strep-Tactin Magnetic Beads. L: cleared cell lysate; F: flow-through fraction; E: elution fractions.
Binding of Strep-tagged proteins to Strep-Tactin and elution using desthiobiotin.

In one experiment, a tRNA synthetase was purified from E. coli cell lysate using Strep-Tactin Magnetic Beads (see figure Micro-scale purification of high purity Strep-tagged proteins). Highly specific detection is possible with Strep-Tactin Magnetic Beads (see figure  Highly specific detection of Strep-tagged proteins in any expression system)


Strep -tagged proteins bind with high affinity and specificity to Strep-Tactin, an engineered form of streptavidin. After washing, proteins are eluted using low concentrations of biotin (the natural ligand of streptavidin) or desthiobiotin (a stable, reversibly binding biotin analog) (see figure Binding of Strep-tagged proteins to Strep-Tactin and elution using desthiobiotin). Labeling proteins with the small Strep-tag II enables efficient, standardized purification of recombinant proteins expressed in prokaryotic systems, and delivers highly pure proteins. In addition, the Strep-Tag II is the system of choice in situations where other tags may be unsuitable, e.g., when buffer additives such as EDTA may interfere with the Ni-NTA/His-tag interaction.


Strep-tagged proteins are expressed using the pQE TriSystem Strep Vector and obtained at very high purity from eukaryotic cell lysates using Strep-Tactin affinity purification procedures. The C-terminal location of the tag ensures that only full-length proteins are purified. Strep-Tactin Magnetic Beads can be used to purify 200–300 µg Strep-tagged protein per ml of bead suspension. The beads are added to cell lysate, incubated, washed, and Strep-tagged protein is eluted using a buffer containing biotin. Monoclonal Strep-tag antibodies are used to detect Strep-tagged proteins in immunodetection procedures with high sensitivity and specificity.  


Reagents compatible with the Strep-tag/Strep-Tactin interaction
Nonionic Detergents Ionic and Zwitterionic Detergents Reducing Agents Others Salts
2% Triton X-100 2% N-lauryl-sarcosine 50 mM DTT 25% Glycerol 5 M NaCl
2% Tween 20 0.1% SDS 50 mM β-mercaptoethanol 250 mM Imidazole 2 M Ammonium sulfate
2% N-octyl-β-D-glucopyranoside 1.3% N-octyl-2-hydroxy-ethylsulfoxide   50 mM EDTA 1 M Calcium chloride
2% Igepal CA-630 (Nonidet P40) 0.1% N-dodecyl-N,N-dimethylamine-N-oxide   1 M Guanidine  
      1 mM PMSF  



Strep-Tactin Magnetic Beads can be used for efficient and reproducible purification of Strep-tagged proteins, especially from eukaryotic cell lysates. Purified proteins can be used for functional or interaction studies.
Applications Proteomics
Binding capacity 200–300 µg/ml
Processing Manual/automated
Scale Micro scale
Start material Cell lysate
Support/matrix Magnetic agarose beads
Tag Strep tag
Yield Depends on cell type
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