For highly sensitive and specific detection of Strep-tagged proteins
Monoclonal mouse Strep-tag antibodies are used to detect recombinant proteins carrying the short Strep-tag affinity tag epitope with high specificity and sensitivity. Like all QIAGEN mouse monoclonal antibodies, they are prepared under serum-free conditions — guaranteeing absence of viruses, mycoplasma, and contaminating immunoglobulins.
The Strep-tag Antibody allows highly sensitive detection of proteins (see figures Highly sensitive detection of proteins carrying a Strep-tag and Ultrapure protein in two steps)
The Two-Step Affinity Purification System, which is based on the proven 6xHis tag and the short Strep-tag II, enables simple and highly efficient purification of ultrapure proteins in a fast and standardized procedure. Recombinant proteins carrying both tags are purified sequentially on Ni-NTA and Strep-Tactin matrices (see figure Ultrapure protein in two steps). The two simple affinity purifications provide fully active, full-length, ultrapure protein, suitable for any downstream application.
Recombinant proteins that carry two small affinity tags (the 6xHis tag and Strep-tag II) are efficiently expressed in E. coli, insect, or mammalian cells using pQE-TriSystem His·Strep vectors. After cell lysis and clearing of the lysate, proteins are initially purified using an immobilized-metal affinity chromatography procedure that is based on the proven 6xHis-tag-Ni-NTA interaction. After elution from the Ni-NTA matrix using imidazole, recombinant proteins (which also carry the Strep-tag II epitope) are loaded directly onto a Strep-Tactin matrix. No buffer exchange is required. Protein is eluted from the Strep-Tactin matrix using either biotin or desthiobiotin. This two-step affinity purification delivers ultrapure (>98% pure) protein (see figure Two-step affinity purification procedure). The order of purifications can be reversed (i.e., Strep-Tactin followed by Ni- NTA purification). Proteins can be detected with high specificity and sensitivity using mouse monoclonal Strep-tag or Anti·His antibodies.
The two-step affinity purification system, using the Strep-tag Antibody for detection, is highly suited for applications where high purity is at a premium or is difficult to achieve. The standardized purification procedure also increases throughput by eliminating the need for protein-specific purification protocol development and optimization. The ultrahigh purity and convenience provided by the two-step affinity purification system make it the method of choice for:
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