Streptavidin, Alexa Fluor™ 568 conjugate - FAQs

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3 个常见问题解答

How many binding sites does the streptavidin within the Streptavidin, Alexa Fluor 568 conjugate (Cat. No S11226) have and what is its molecular weight?

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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I am planning to use a fluorescent streptavidin labeled conjugate. What are the storage conditions and shelf life for the lyophilized powder and reconstituted solution?

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.

I am planning to use a fluorescent streptavidin labeled conjugate. How should I prepare the working solution of the conjugate?

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).