DNA Nucleic Acid Precipitation

[Dionisia]

Hi, would someone be able to explain why alcohol and low temperatures are used to precipitate DNA and other nucleic acids?

Also why in specific ethanol or isopropanol?
thank you

[kmunson779]

There are some answers but no references in this [Only registered users see links. ].

[biochemistry0408]

About this question, I have some idea but I'm not sure whether it is correct.
Therefore, I'm also would like to know the real answer of this question.
Unfortunately, I can't get open the blog introduced by kmunson779. Could anyone tell me the answer by posting the message to here or sending me personal message? Thanks!:-)

[swaroopsk]

Originally Posted by Dionisia

Hi, would someone be able to explain why alcohol and low temperatures are used to precipitate DNA and other nucleic acids?

Also why in specific ethanol or isopropanol?
thank you

Basic principle is Di-electric constant.
at low temp the dielectric constant of water reduces
once the ethanol os isopropanol is added it further reduces the value and makes DNA not soluble in water and hence the DNA ppts......

[ChinoMGV]

Adding to what swaroopsk said:
The use of Ethanol or isopropanol is for the low content of water in them, especifically in isopropanol with is water free

[swaroopsk]

i dont think so thats a exact reason cos for preparation of ethanol water is needed i suppose...
water actually reduces the di-electric constant..
and the NaOH which is added dissolves with competition with DNA and hence DNA ppts out......
agreeeee......??

[gel]

swaroopsk,

Water has a high dielectric constant, ethanol has a much lower constant. Therefore, when you add ethanol to water, the overall dielectric constant of the solution is lowered. What this does is lower the strength of hydration shells around polar molecules "dissolved" in solution. When you add cations (Li, Na, etc) they will ionically bond to the negatively charged phosphate backbone of DNA (because the hydration shells created by water are weakened due to addition of ethanol), thus precipitating the molecule out of solution.

Hope this helps.