Iso-propanal precipitation - (May/14/2006 )
I wanted to know how does isopropanol precipitates salt during DNA precipitation? Does precipitating DNA with isopropanol at lower temperature increase the salt precipitation. Please anyone can tell me this.
Thanks in advance
it is said that the advantage of isopropanol for precipitation of DNA is that it is used usually at room temperature. therefore less salt is co-precipitated during the procedure. At lower temperature more salt will be precipitated as far as I know.
all alcoholic based precipitation precipitates salts too. So IprOH also precipitates.
The greater number of C, the greater amount of salts precipitated.
Moreover, at low temp, quantity of salts is greater too, which btw helps the nucleic acids precipitation.
Isopropanol precipitates the DNA by unhydrating it.
I guess that it can do the same to the salt.
Try using organic salts e.g. acetate salts. Thy will stay in the organic phase (isoopropanol or ethanol) when you wash the DNA.
In any case check for salts in your sample by A260/A230 it should be ~2.2
i wouldn't precipitate with isopropanol AND in -80 for example. I did it once and my DNA was completely in a capsule of salts. After that i could hardly get it in solution again.
For quick precipitations i use icecold 100% ethanol with NaAc together with a drop of glycogen.
Ethanol = -20C
Isopropanol = RT
Thanks for the feedbacks
well i mentionned -80 for detailing the mechanisms by which refreshing sample helps precipitation with ETHANOL. not to say use it with IprOH or BuOH...
sorry for confusion
I was told by my Postdoc to try ethanol ppt in RT. It has always worked for him. And it worked nicely when I tried. DNA recovery as in -20C ppt. and the 260/280 ratio is also fine.
i want to clear some points: the ethanole is more advantageos over isopropanole in that ethanole is more volatile than isopropanol so decreasing the time for drying your DNA prep.
but can anyone answer my question that tackle me alot. how can i choose between isprpop. and ethanol.?
is one for DNA ppt. and the other is for RNA Precipitation?what is the best?