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dna extraction question

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#1 claritylight



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Posted 09 May 2011 - 05:29 AM

What is the difference in using phenol:chloroform:isoamyl alcohol at 25:24:1 v/v versus just using chloroform:isoamyl alcohol at 24:1 v/v?

I need to extract some DNA but seems there is only the phenol:chloroform:isoamyl alcohol left but the protocol just calls for chloroform:isoamyl alcohol so I am wondering what the difference would be?

#2 pDNA



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Posted 09 May 2011 - 07:12 AM

Chloroform helps to denature proteins as well as removing residual phenol (since phenol is not very soluble in chloroform) ...so it is not a really good idea to use phenol:chloroform instead.
You can try to find some chloroform without isoamylalcohol ...that would do the trick as well. The isoamylalcohol is not that essential.


#3 David C H

David C H


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Posted 10 May 2011 - 05:29 AM

In addition to denaturing protein, phenol also acts as a buffer and is used in RNA isolations to keep the pH acidic. Acidic phenol:chloroform is used for RNA isolation; at this pH DNA will be seperated into the interphase and RNA will be left in the aqueous phase. If the pH of your phenol:chloroform is below 7, you will lose DNA. I believe the isoamyl alcohol acts as a defoaming agent, probably allows the phases to mix more completely and efficiently.

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