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Specifications of Strep-tag® Protein Purification Resins 

There are several resin versions available for the purification of strep-tagged target proteins. All resins differ in their properties and suitability for applications. Learn more about the different resin matrices in order to know when to use which resin.
Ligand Strep-Tactin®  Strep-Tactin®XT
Matrix 4Flow® high capacity 4Flow® 4Flow® high capacity MagStrep® Strep-Tactin®XT beads
Binding capacity 20 mg/ml resin* 11 mg/ml resin* 31 mg/ml resin* 25.5 µg/µl resin**
Bead structure 4% agarose, highly crosslinked 4% agarose, highly crosslinked 4% agarose, highly crosslinked magnetic core covered with 6% agarose, crosslinked
Bead size 50-150 µm, spherical 50-150 µm, spherical 50-150 µm, spherical 30 μm (average), spherical
Exclusion limit 3 x 107 Da 3 x 107 Da 3 x 107 Da not specified 
Recommended  formats Gravity flow, FPLC Gravity Flow, FPLC Gravity Flow, FPLC Batch purification
pH range for protein binding 7-8 4-10 4-10 6-10
Max pressure 3.5 bar 3.5 bar 3.5 bar  
Storage 2-8 °C, do not freeze 2-8 °C, do not freeze 2-8 °C, do not freeze 2-8 °C, do not freeze
Shipping RT RT RT RT
Eluent desthiobiotin
biotin biotin biotin
Regeneration buffer 100 mM NaOH Buffer XT-R
100 mM NaOH
Buffer XT-R
100 mM NaOH
100 mM NaOH
Activity Test Buffer R (HABA) Buffer R (HABA) Buffer R (HABA)  
Features and recommendations
  • Strep-Tactin® 4Flow® high capacity combines a low percentage agarose and pressure stability
  • For proteins that are hard to elute from Strep-Tactin®XT resins, like proteins with multiple tags or multimers
  • Applicable for proteins of all types and sizes

  • Strep-Tactin®XT 4Flow® is recommended for first time users of the Strep-tag® system 
  • Applicable for all protein types and sizes, especially low abundant and challenging proteins
  • Strep-Tactin®XT 4Flow® high capacity binds three to five times more target protein compared to Strep-Tactin®XT 4Flow®
  • Recommended for the purification of well-expressed proteins or in large-scale purification
  • Optimized for Batch purification
  • Beads can be separated with a magnetic device, no centrifugation necessary
  • Suitable for high-throughput purification in 96-well plates

*determined with a 52 kDa Twin-Strep-tag® fusion protein

**determined with a 30 kDa Twin-Strep-tag® fusion protein

What is the difference between Sepharose®, Superflow® and 4Flow®?

The underlying matrix of many protein purification resins are porous agarose beads. The characteristics of these agarose beads determine for which proteins and for which applications the resin is most suitable. IBA’s Sepharose® resin consists of a 4% cross-linked agarose and is therefore suitable not only for small, but also for large proteins. However, a disadvantage of Sepharose® is that it is not pressure stable and consequently not suitable for automated applications such as FPLC. In contrast, IBA’s Superflow® products work well for FPLC. The disadvantage of Superflow® is that it consists of a 6% cross-linked agarose. This means that the pores are smaller and not accessible for larger proteins, resulting into low yields.
4Flow® combines the advantageous characteristics of Sepharose® and Superflow®. It is a 4% cross-linked agarose, and it is pressure stable, making it a universal matrix for small and large proteins as well as for different applications such as FPLC.

Resin reuse

Strep-Tactin® and Strep-Tactin®XT resins for protein purification can be regenerated and reused >10 times without loss in performance. The proper regeneration of the column and resin activation can easily be checked with HABA. The yellow HABA solution turns red (Strep-Tactin®) or orange (Strep-Tactin®XT) upon binding  to the engineered biotin binding pockets of Strep-Tactin® and Strep-Tactin®XT clearly indicating that the resin is fully regenerated. Afterwards, HABA can be removed by washing with 1x Buffer W. Once the red color has disappeared the column can be reused.  If the biotin binding pocket is blocked or damaged no color shift occurs and the resin cannot be reused.

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. Browser through application examples and frequently asked questions about Strep-tag® purification system or download application notes in our download area.