Strep-TactinXT is a streptavidin variant, which binds to the Strep-tagII and Twin-Strep-tag with high affinity and specificity. It is available as conjugate with fluorescent dyes (DY-488, DY-549, DY-649) for fast and directed detection of N-terminally, C-terminally as well as internally tagged Strep-tagII or Twin-Strep-tag fusion proteins in applications like ELISA, FACS, immunohistochemistry, and immunocytochemistry. The absorption/emission maxima of the fluorescent dyes are: • DY-488: 493/518 nm • DY-549: 550-560/575 nm • DY-649: 655/676 nm