Steptavidin, a bacterial protein isolated from Streptomyces avidinii, is similar to egg-white avidin in its ability to bind biotin, and has been used as a replacement for egg-white avidin because of its more favorable chemical properties.
Conjugates of streptavidin are recommended for use with Biotin-SP-conjugated antibodies and Biotin-SP-conjugated ChromPure proteins.
Conjugate: Alexa Fluor® 594
Alexa Fluor® 594-conjugated antibodies absorb light maximally around 591 nm and fluoresce with a peak around 614 nm. They are brighter, more photostable, and more hydrophilic than Texas Red conjugates. Alexa Fluor® 594 conjugates are brighter than red-fluorescing conjugates, and they provide more color separation from green-fluorescing dyes than DyLight 549, Cy3, and TRITC conjugates. They are the best choice for immunofluorescence detection in the deep-red region of the visible spectrum.