TFB2 (RbCl competent-cell buffer 2) recipe
The second RbCl-method buffer in which cells are resuspended and frozen: 10 mM MOPS pH 6.5, 75 mM CaCl₂, 10 mM RbCl, 15% glycerol.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| MOPS (free acid) | 209 mg | 10 mM |
| CaCl₂·2H₂O | 1.103 g | 75 mM |
| RbCl | 121 mg | 10 mM |
| Glycerol | 15 mL | 15% |
| Water (distilled) | to final volume |
Steps
- Dissolve in about 80% of the final volume of water.
- Adjust to pH 6.5 with KOH.
- Bring to the final volume with water.
- Filter-sterilise through 0.22 µm. Store at 4 °C.
Good to know
- Resuspend cells in TFB2, aliquot 50–100 µL on ice, snap-freeze and store at −80 °C.
FAQ
How do I check efficiency?
Transform 10 pg–1 ng of a plasmid such as pUC19 and compute colonies per µg (good preps give 10⁷–10⁸/µg).
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.