The streptavidin variant Strep-Tactin® is available as conjugate with alkaline phosphatase (AP) for fast and directed detection of N-terminally, C-terminally, or internally tagged Strep-tag®II or Twin-Strep-tag®
fusion proteins transferred to a blotting membrane. The AP conjugate is suitable for chromogenic reaction.
Depending on the host organism, protein extracts may contain small amounts of biotinylated proteins, e.g., the biotin carboxyl carrier protein (BCCP, 22 kDa ) of E. coli. Biotin Blocking Buffer is recommended for blocking of such biotinylated proteins on western blots
prior to detection of Strep-tag®II or Twin-Strep-tag® fusion proteins with Strep-Tactin® AP to prevent the detection of false positive bands. For this purpose, Biotin Blocking Buffer contains the tetrameric biotin binding protein avidin, which selectively binds biotinylated proteins.