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Third generation Strep-tag® system

IBA’s third generation Strep-tag® system is based on the novel Strep-Tactin®XT Superflow® resin in combination with Twin-Strep-tag®. Due to a binding affinity of Strep-Tactin®XT to Twin-Strep-tag® in the low pM range (near covalent binding!), the system is superior to all other available affinity purification systems and can be used for a wide variety of approaches, e.g. protein purification and assay development.

Strep-Tactin®XT and Strep-Tactin® are engineered Streptavidins. The Strep-tag® is a peptid binding to the Biotin binding pocket of Streptavidin. The development of the Strep-tag® system is illustrated in the figure below.

Near covalent binding affinity

The Streptavidin:Biotin binding is the strongest noncovalent biological interaction known. With IBA's newly developed Strep-Tactin®XT in combination with Twin-Strep-tag®, this high binding affinity can be used for e.g. protein purification, protein interaction analysis or assays (e.g. BIAcore). Since Biotin is still binding strongly to Strep-Tactin®XT it can be used for elution of Twin-Strep-tag® fusion proteins.

Purification Procedure of Strep-Tactin®XT in comparison to Strep-Tactin®

The overall purification procedure of Strep-Tactin®XT and Strep-Tactin® is the same (see figure below). Only two changes were introduced:

  • Elution from Strep-Tactin®XT is done with biotin
  • Regeneration of Strep-Tactin®XT resin is done with 10 mM NaOH