I want to use it for biotinylation to protein.
I know the final concentration of biotin dissolve in DMSO, but I don't know how to prepare firstly the concentration of DMSO for the stock solution or directly use it.
I usually dissolve biotin in neat DMSO. It goes in easily up to about 50 mg/mL as a stable stock solution.
The same is true if you use NHS-biotin, which greatly simplifies the biotinylation reaction. ;-)
Hello, it depends on which “biotin” you’re using.
Plain biotin will not biotinylate proteins by itself (no reactive handle). It’s used for enzymatic ligation (BirA/biotin ligase + ATP) or as a nutrient. For chemical biotinylation of lysines, you need an activated ester: NHS-Biotin (hydrophobic): make a 10–50 mM stock in anhydrous DMSO, aliquot, −20 °C desiccated. During labeling, keep final DMSO ≤1–5% v/v to avoid protein denaturation. Sulfo-NHS-Biotin (water-soluble): dissolve fresh in water/PBS (no DMSO needed), use immediately (unstable in aqueous buffer).
Typical workflow (amine labeling): Buffer: PBS or 50 mM sodium phosphate/borate, pH 7.4–8.5 (no primary amines like Tris during coupling). Add NHS-biotin (from DMSO stock) to reach desired molar excess (e.g., 5–20× over protein’s accessible lysines); keep final DMSO ≤1–2% if possible. React 30–60 min at RT (gentle mix, protect from moisture). Quench with Tris or glycine (50 mM). Remove excess reagent (desalting column, dialysis, or spin filter).
If you really mean plain biotin + DMSO: it won’t label proteins chemically. Use BirA ligase (Avi-tagged protein) with biotin (aqueous) + ATP, or switch to an NHS-biotin reagent as above.
The answer to this question is provided by MedChemExpress Technical Support.
Well, actually you *can* label a protein using plain biotin if you use a carbodiimide protocol. That's how I had to do it in grad school, before Pierce introduced the NHS ester (and dinosaurs still roamed the earth).
Otherwise Lucian Miles is correct.
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