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From protein purification to analytical applications with Strep-Tactin®XT

Strep-Tactin®XT is the high affinity variant for the purification of strep-tagged fusion proteins, providing binding affinities in the picomolar range for Twin-Strep-tag® while still maintaining binding reversibility and mild recovery of immobilized proteins. It is suitable for efficient protein purification independent of protein class and size, including challenging proteins as well as low abundant proteins.

Protein purification

Fused to magnetic beads, MagStrep® Strep-Tactin®XT, is the ideal tool for complex identification via pull-downs and fast small-scale batch purification in reaction tubes or 96-well plates.

In particular, Strep-Tactin®XT 4Flow® high capacity provides superior performance for the purification of strep-tagged proteins from diluted cell extracts and allows for intensive wash procedures with large volumes of wash buffer. Strep-Tactin®XT 4Flow® high capacity resin is stable over a wide range of pH and compatible with various buffer conditions, and can be reused at least 100 times without losing performance. Due to this frequent reusability, experimental costs can be significantly reduced.

Analytical applications

The near covalent affinity of Strep-Tactin®XT to Twin- Strep-tag® expands the range of use towards analytical applications such as high throughput screening, assay development and protein kinetic studies. 

You can obtain Strep-Tactin®XT conjugated to microplates, fluorophores, or chips. Strep-Tactin®XT coated microplates ensure convenient diagnostic assays and high-throughput screenings with high stability and antibody-free protein immobilization. Moreover, immobilized biomolecules are presented to interaction partners in a uniform manner, which results in reliable and highly reproducible assay formats. The picomolar affinity is particularly valuable for surface plasmon resonance (SPR) analysis and bio-layer interferometry (BLI) and supports measurements with long dissociation times and slow off-rates. Moreover, Strep-Tactin®XT biosensors can be easily regenerated.

Key features of protein purification and analysis with Strep-Tactin®XT

  • Highly selective binding properties leading to unparalleled protein purity (> 95 %)
  • Exceptionally high affinity to Twin-Strep-tag® enables reliable use in analytic applications
  • Bioactive target proteins due to rapid one-step purification under target specific conditions
  • Variability in buffer conditions, e.g. high salts, detergents, metal ions, chelators or reducing agents
  • Favorable for protein-protein interaction studies due to mild elution conditions that preserve natural protein structure
  • Products covering the entire workflow from cloning, purification to analytical applications (ELISA, FACS, SPR, Microscopy, Western Blot, etc.)

Strep-Tactin®XT also ensures sharp elution profiles, achieving high concentration of the target protein. Strep-Tactin®XT even tolerates a wide pH range in addition to various detergents and additives, contributing to the universal usability of the system.

Strep-Tactin®XT purification cycle

Protein purification with Strep-Tactin®XT is very simple and fast, since the purification cycle for each target protein (Strep-tag®II or Twin-Strep-tag®) is the same. However, if a target protein needs a specific buffer composition, e.g. PBS, HEPES or no chelating agents, like EDTA, the buffers can be easily adapted without the need of changing the purification cycle. Strep-Tactin®XT resin accept various buffer compositions, reagents and additives. Find a list of compatible reagents for Strep-Tactin®XT here.

Strep-Tactin®XT protein purification cycle


 Binding affinity

 Strep-tag® II : nM range
 Twin-Strep-tag®: pM range


 Elution with Buffer BXT
 (50 mM Biotin)


 Regeneration with 100 mM NaOH or 3 M MgCL2

Find out more about Strep-tag® protein purification

Here, we have grouped links to make it easier to find more information about Strep-tag® technology for protein purification. In our web shop, you can find the protein purification products  that fit your research needs. Read the comprehensive comparison of the most used tag systems, Strep-tag® vs. His-tag. Browse through application examples and frequently asked questions about Strep-tag® purification system or download application notes in our download area.