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DNA precitipitation - DNA.....ethanol versus isopropanol (Oct/08/2005 )

Hi all
I wish to know that why we use isopropanol in precipitating DNA when it can be done with ethanol.
Waiting for a swift reply.
Amit Kumar

-Amit Kumar-

You generally need less isopropanol (< 1 volume) than ethanol (2 to 4 volumes) to precipitate DNA. Isopropanol will also efficently precipitate DNA at room temperature, whereas ethanol precipitation was always thought to work best at -20ÂșC (not sure if this is true -- I think EtOH works fine at RT, too).

But, isopropanol has it's own problems -- it's less volitile than ethanol (thus harder to remove), produces a glassy pellet (thus harder to see), and the pellet is usually less adherent than one precipitated with ethanol (thus more risk of loss).


Isopropanol can be done with 0.7 volumes, thus you can use a smaller tube. A limitation is that more salts precipitate with isopropanol, thus you need to still do a wash with 70% EtOH