X-gal 20 mg/mL recipe
The substrate that turns insert-less colonies blue in blue/white screening; 40 µg/mL in plates.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| X-gal (5-bromo-4-chloro-3-indolyl-β-D-galactoside) | 200 mg | 20 mg/mL |
| DMF (dimethylformamide) or DMSO | to final volume |
Steps
- Dissolve in DMF (use glass or polypropylene tubes).
- Do not filter (DMF dissolves some filter membranes).
- Wrap in foil and store at −20 °C.
Good to know
- Add 2 mL per litre of plate medium, or spread 40 µL on a finished plate.
- A stock that has turned pink has degraded.
⚠ Safety DMF is toxic and absorbed through skin — use a fume hood and gloves.
FAQ
My colonies are pale blue.
Small in-frame inserts can leave partial lacZα activity; a few hours at 4 °C enhances the colour difference.
This is a widely used standard composition. Amounts depend on the hydrate form and purity of your reagents — check the formula weight (FW) on the bottle and follow your institution's safety rules and the manufacturers' instructions.