Protocol Online logo
Top : Forum Archives: : Molecular Biology

Best way to precipitate/concentrate genomic DNA? - (Jun/28/2006 )

Hi, would .8 volumes of isopropanol for 30 minutes be sufficient to precipitate genomic DNA? or is 2 volumes of ice-cold 100% ethanol overnight recommended? Is it necessary to add a concentrated salt solution like sodium acetate or sodium chloride?


The difference between isopropanol and ethanol has been discussed in the forum a few days ago.
Personally, I always use sodium acetate because it helps the precipitation. Some people also use glycogen that works fine as well


i would add butanol. You add butanol (2-3 vols, but the more the better (as it's quicker) and swirl gentle. Spin 2' 1000g.
Upper phase should be removed in appropriate solvents garbage.
Repeat the operation.
By doing this, you'll see the lower phase will go smaller, and finally no longer exists. That wll fix the washing (70%etOH start). Gentle spin will not destroy your DNA.


I thinks both (isoprop and ethanol) work well. As dnafactory says, it was discussed before, you should check it.
If you have an small amount of DNA, you should use a salt (Na acetate 3 M, for example) or glucogen (I discovered few time ago, thanks to Fred_33, by the way). I personally prefer glucogen, because you see pellet clearly. If the amount of DNA is not very small, salt or glucogen is not necessary!!

-aztecan princess-

2/3 (0.6) volume of isopropanol works just fine and you should leave your sample to precipatate for a while (overnight)and then spin at a low temperature at high centrifigation..