1. Measure the volume of nucleic acid containing sample. If the volume is less than 450 ul, place it in a 1.5 ml eppendorf tube. If the volume is between 450 ul and 4.5 ml, place it in a 15 ml baked siliconized Corex tube. If the volume is between 4.5 ml and 9 ml, place it in a 30 ml Corex tube.

2. Add 0.1 times the volume of 3M NaAc pH 5.2 *. Mix. Calculate the new volume, then add 2 volumes of cold ethanol. Seal the tube tightly with parafilm. Mix.

* It is usually preferable to use ammonium acetate(1/2 volume of 7.5M) instead of NaOAc as the salt. It is more volatile, and leaves behind more protein. However, the larger volume may be inconvenient.

3. Place the sample at -20deg. (If there is a lot of DNA, you can proceed almost immediately. If there is only a few hundred nanograms, it is best to wait at least one hour or overnight) or at -70deg. for 1 hr. For dilute samples, better recovery is obtained at -20deg. O/N.

4. If the precipitation is being done in a microfuge tube, spin at least 15 minutes in the TOMY at 4deg. (For 15 ml or 30ml Conical tubes, spin 20 minutes in the Sorvall in swinging bucket rotor). IT IS IMPERATIVE THAT YOU ARE READY TO TAKE THE TUBES IMMEDIATELY AFTER THE SPIN STOPS. If the machine has stopped for even a minute by the time you get to it, turn it back on for an additional 5 minutes. Otherwise, you run a great risk of the pellet becoming dislodged and being dumped out. Don't try to precipitate too many tubes at once. It will take too long to deal with them all, and you may lose the last few pellets. 5. Dump off the ethanol and tap the tube (upside down) on a paper towel to remove as much EtOH as possible. Keep the tube upside down. Quickly dry off the inside of the tube with a Q-tip, but don't touch the pellet. Put the tube into an upright position, and dry in Speed-Vac for 5 minutes.

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