what i think is we use to precipitate DNA in Ethanol... i never dissolved it ... you could go for centrifugation..

You can use speed vac

Ethanol Wash

Ethanol washes are performed after salt/EtOH precipitations to remove any residual salt from the nucleic acid pellet. The wash employs 70-80% EtOH which will solubilize salts but not nucleic acids.

Do

Add 70 - 80% EtOH to the nucleic acid pellet. The volume should be sufficient to at least cover the pellet and wet the sides of the tube when vortexed (there is no volume too large). Vortex the sample for 1 minute; the pellet should come loose from the tube and be broken up in the EtOH. Centrifuge the sample 10 - 30 minutes, to recollect the pellet. Aspirate off the EtOH.

Don't

Don't just add the EtOH and immediately decant. The pellet should be vortexed so that the EtOH can penetrate the sample and solubilize salt.

Don't forget to respin! The pellet must be firmly reaffixed to the tube so that it is not lost during aspiration

If you decide to centrifuge without precipitating (that is if you didn't precipitate in the first place:

I would also add 10% volume of 3M sodium acetate if centrifugation does not yield a DNA pellet. Then I would recentrifuge the solution. I don't know if that will work, but it is worth a try. If you had previously precipitated the pellet with the salt and 100% ethanol the DNA will already be precipitated and so centrifuging without adding the salt should work.

I just realized something important. 70% Ethanol is 30% water, so add .3 X 7ml to get the volume of water in the DNA/70% solution, then add 3M salt to precipitate the DNA:

so 0.3 X 7 ml = 2.1 ml of water in the disolved DNA in 70% EtOH. So add one tenth of 3 M sodium Acetate using 2.1 ml as your guide:

so 2.1 X 0.1 = 0.21 ml, add 0.21 ml of 3 M sodium acetate to the DNA in 70 % EtOH and put in -20 degrees for some period of time to cool down the solution for preciptation. Then centrifuge as you normally would.

DNA is insoluble in 70% EtOH in the presence of salt (NaCl, NaAC...). 70% EtOH is used to wash DNA pellets (after precipitation/centrifugation) because the 30% of water will solubilize the excess of salts used for precipitation while maintaining the DNA insoluble (for precipitating DNA you add 2 - 2.2 volumes of absolute ethanol to your volume of DNA so that the final concentration of EtOH is !70%!). So add some salt (as above) and if the concentration of your DNA is very low (i.e. less than 1 ug/ml) try adding some carrier as well. tRNA or molecular biology grade glycogen will do it.

"(for precipitating DNA you add 2 - 2.2 volumes of absolute ethanol to your volume of DNA so that the final concentration of EtOH is !70%!)"

I was going to say you only need to add an additional 0,5 ml of 100% ethanol.

" Margaret Mchenney · 22.58 · 38.55 · Eli Lilly

"I just realized something important. 70% Ethanol is 30% water, so add .3 X 7ml to get the volume of water in the DNA/70% solution, then add 3M salt to precipitate the DNA:

so 0.3 X 7 ml = 2.1 ml of water in the disolved DNA in 70% EtOH. So add one tenth of 3 M sodium Acetate using 2.1 ml as your guide:

so 2.1 X 0.1 = 0.21 ml, add 0.21 ml of 3 M sodium acetate to the DNA in 70 % EtOH and put in -20 degrees for some period of time to cool down the solution for preciptation. Then centrifuge as you normally would."

You needn't add any absolute EtOH in this case to achieve 70% EtOH because:

2.1 plus 0.21 = 2.3 ml and" 2 X 2.3 ml as suggested above" =4.6. The total is 6.9 ml so you have an extra 0.1 ml 100% EtOH in your solution, making the EtOH content between 2 and 2.2 times the total aqueous starting point.

I'd suggest using Ammonium acetate rather than sodium - easier to clean up at the end

Grant,

"I'd suggest using Ammonium acetate rather than sodium - easier to clean up at the end"

How so?

Please explain, I have never used ammonium acetate to ppt DNA.javascript:

Just add few extra amount of 99% ethanol so that the final volumes become the same.