text: The Strep-tag system offers a selective tool to purify proteins under physiological conditions. The proteins obtained are bioactive and display a very high purity (above 95%). Also, the Strep-tag system can be used for protein detection in various assays. Depending on the experimental circumstances, Strep-tag antibodies or Strep-Tactin, with an enzymatic (e.g.horseradish peroxidase (HRP), alkaline phosphatase (AP)) or fluorescence (e.g. green fluorescent protein (GFP)) marker. If high purity is required, the lysate can be purified by first using Strep-Tactin and then perform a second run using antibodies against Strep-tag. This reduces the contamination with unspecific bound proteins, which might occur in some rare scenarios.
  Following assays can be conducted using the Strep-tag detection system:
  * one-step affinity purification
  * Protein:protein interaction studies
  * Colony blot, dot blot, Western blot and ELISA
  * Screening for positive expression clones
  * Immunocytochemistry and Immunohistochemistry
  * Protein localization and targeting studies
  Because the Strep-tag is capable of isolating protein complexes, strategies for the study of protein-protein interactions can also be conducted. Another option is the immobilization of Strep-tag proteins with a specific high affinity antibody on microplates or biochips.
  Strep-Tag/StrepTactin system is also used in single-molecule optical tweezers and atomic force microscope experiments, showing high mechanical stability comparable to the strongest non-covalent linkages currently available.