Streptavidin, Alexa Fluor™ 568 conjugate - FAQs

Each streptavidin molecule within the Streptavidin, Alexa Fluor 568 conjugate (Cat. No S11226) has 2-4 binding sites, which means that it can bind 2-4 dye molecules. However, the exact number of binding sites is lot-dependent and can be found on the lot-specific Certificate of Analysis. The molecular weight (MW) of streptavidin is 52.8 kDa and each Alexa Fluor 568 dye molecule has a MW of 679 Da, so the MW of the Streptavidin, Alexa Fluor 568 conjugate is in the range of 54.2-55.5 kDa.

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In the lyophilized powder form, the fluorescent streptavidin labeled conjugate is stable for six months when stored at -20 degrees C, desiccated, and protected from light. The reconstituted solution is stable for approximately six months when stored at 4 degrees C, protected from light, with the addition of sodium azide to a final concentration of 5 mM or thimerosal to 0.2 mM. For longer storage, we recommend dividing the solution into aliquots and freezing at -20 degrees C, protected from light. Avoid repeated freezing and thawing of the solution.

The fluorescent streptavidin labeled conjugate solution can be made by dissolving the powder in 0.5-1.0 mL of PBS or other suitable buffer. For details, please refer to page 4 of the "Streptavidin and Fluorescent Conjugates of Streptavidin" manual (https://assets.fishersci.com/TFS-Assets/LSG/manuals/mp00888.pdf).