Alexa Fluorr 647 Streptavidin, 1 mg

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® 647 Alexa Fluor® 647-conjugated antibodies absorb light maximally around 651 nm and fluoresce maximally around 667 nm. They are brighter than Cy5 and DyLight 650 in aqueous mounting media. Alexa Fluor® 647- and APC-conjugated secondary antibodies are the best choice for flow cytometry when secondary antibodies fluorescing at these wavelengths are desired. Alexa Fluor® 647 conjugates are the best choice of far red-emitting dyes for multiple-labeling detection with a confocal microscope. A significant advantage of using Alexa Fluor® 647 over lower wavelength-emitting dyes is the low autofluorescence of biological specimens in this region of the spectrum. However, because of its peak emission at 667 nm, Alexa Fluor® 647 cannot be seen well by eye, and it cannot be excited optimally with a mercury lamp. Therefore, Alexa Fluor® 647 is not recommended for use with conventional epifluorescent microscopes. It is most commonly visualized with a confocal microscope equipped with an appropriate laser for excitation and a far-red detector. Alexa Fluor® 647 conjugates are less expensive alternatives to allophycocyanin conjugates for flow cytometry.