DNA extraction - white precipitate? - DNA extraction contamination (Jun/15/2005 )

Hi,
I was wondering if anyone has had this problem. I used a SEPAGENE kit for DNA extraction. Its basically a chloroform extraction method followed by precipitation in isopropanol.

I got DNA pellets, resuspended in TE, then went on to do an additional salt precipitation using 4M NaCl. I used a protocol from a friend for this that I had never used before. She has used it previously, with good results.

Anyway, after adding the NaCl sol and then the ethanol I got a white precipitate. It dissolves in ddH20, but if I try to reprecipitate the DNA using ethanol or isopropanol the precipitate comes back.

ANy ideas?

thanks

Hi


The whit precipitate is DNA. What you are doing with NaCL and then ethanol is the classicl way to precipitate DNA, if you add again ethanol or isopropapnol you are reprecipitating your DNA. THe classical way to extract DNA is with phenol:chloroform(v:v) and then choroform, and finalley the precipitation with NaCL + ethanol. You don't need to reprecipitate your DNA.

Good luck!!!


Baobabs

Hi and thanks!

I had never seen DNA a white precipitate like that, only very small greyish blobs.

Thanks and will try and PCR it now.

cheers
Syd

A white precipitate could indicate a high salt content co-precipitated with your DNA and may affect downstream applications. You could try and precipitate in a larger volume to reduce the amount of salt precipitating with the DNA or running the solution through a G50 sephadex column. If salt is none of your worry then I wouldn't worry about it.

Nick

thanks! PCR didn't look good but that may be for other reasons....