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SPR analysis with Strep-Tactin®XT and Twin-Strep-tag®

Surface plasmon resonance (SPR) is a commonly used technology to study protein:protein interactions. It requires an efficient binding of the ligand to the immobilized capturing molecule.
The Twin-Strep-tag® Capture Kit is intended for reversible high affinity capturing of Twin-Strep-tag® fusion proteins on carboxyl-derivatized sensor chips using Biacore SPR systems. The Kit consists of Strep-Tactin®XT as capture molecule, a Control protein, Immobilization- and Regeneration buffer.


Key benefits of Strep-Tactin®XT and Twin-Strep-tag® for SPR experiments

  • Indirect immobilization of the ligand prevents the ligand to be inactivated or influenced by the immobilization procedure. In addition, no chemical modification of the ligand is required.
  • High affinity enables measurements over a long time (high affinity in low pM range; T1/2 = 13 h)
  • Chip can be regenerated easily by an established procedure – cost effective
  • Ligands can be captured directly from complex samples due to the high affinity and specificity of the Twin-Strep-tag®:Strep-Tactin®XT interaction and therefore save the additional purification of the ligand.

Products for SPR measurements

Product Contents Cat.no Price   Order
Twin-Strep-tag® Capture Kit 1 Kit 2-4370-000 USD 603.00  

Twin-Strep-tag® Capture Kit is intended for site-directed, reversible capture of Twin-Strep-tag® fusion proteins for biomolecular interaction analysis using surface plasmon resonance (SPR) devices. The kit provides Strep-Tactin®XT, SPR Immobilization Buffer, Regeneration Buffer and GFP-Twin-Strep-tag® as control protein. It enables the highly stable immobilization of the ligand based on the unique Strep-Tactin®XT:Twin-Strep-tag® technology, due to the pM affinity of ...

Further details, manuals, data sheets, related products and more

Application data for Strep-Tactin®XT in SPR

Reproducible coupling of Strep-Tactin®XT on CM5

Test of reproducibility for Strep-Tactin®XT on CM5 chips
BIAcore sensorgram of repetitive SPR measurements


We recommend to use the following conditions for optimal Strep-Tactin®XT coupling:

  • 20-50 µg/ml Strep-Tactin®XT
  • max. 20 mM acetate, pH 4.5

Using these conditions for Strep-Tactin®XT coupling, efficient and reproducible coupling results can be obtained, see also figure.

Evaluation of optimal regeneration conditions

Three different regeneration conditions were tested on Strep-Tactin®XT CM5 sensorchips:

  • 10 mM NaOH / 500 mM NaCl
  • 3 M MgCl2
  • 3 M GuHCl

for three different Twin-Strep-tag® fusion proteins:

  • mCherry-Twin-Strep-tag®
  • GAPDH-Twin-Strep-tag®
  • mAb-Twin-Strep-tag®

We recommend to use 3 M GuHCl for optimal regeneration conditions. However this is dependent on the protein of interest.

SPR measurements with membrane protein

SPR measurement with Strep-Tactin®XT and Twin-Strep-tag® fused to the membrane protein CB2
Data was published in A. Yeliseev et al., 2017 Protein Expression
and Purification 131 (2017) 109-118


The membrane protein CB2 was fused with Twin-Strep-tag® and then immobilized on a CM4 sensor chip coated with Strep-Tactin®XT.

Used conditions:

  • 50 mM Tris pH 7.5, 100 mM NaCl
  • 10 % glycerol, 0.1 % DDM, 0.5 % CHAPS, 0.1 % CHS


Develop your own assay

Strep-Tactin®XT has a high binding affinity with Twin-Strep-tag® in low picomolar range. Therefore it is highly suitable for screening for therapeutic proteins and industrial enzymes as well assay development. For assay development we offer unconjugated Strep-Tactin®XT. Please use this form for requests.