I have extracted genomic DNA from soil but the yield is very low (about 30 ng per microliter in 30 microliters per sample), so I want to put together some samples and concentrate the DNA in a smaller volume of water. What's the better method to do this?
By the way, I didn't know about glycogen precipitation, but now I've found a detailed protocol. I paste it here in case it may be useful for someone:
http://agctsequencing.wordpress.com/2012/07/06/protocol-alternative-method-for-sodium-acetate-to-ethanol-precipitate-dna/
Add Na acetate pH 5,2, 0.3M (0,7% of the DNA volume) and 100% ethanol (4 times the DNA volume).
Keep it at -20C overnight.
Centrifuge at 14.000 rpm for 10.
Remove supernatant and dry out at room temperature or with vacuum.
Dissolve again the DNA with distilled sterile water to the desired volume.
(This is for DNA solved in water or TE.If you have another buffer, you should adjust the concentration of Na acetate to achieve correct final concentration of salts)
Better not to precipitate DNA, or if you have to precipitate it use glycogen, instead of NA acetate. However, I recommand you instead DNA precipitation to use regenerated cellulose microcon concentrators (0,5 ml) from Millipore, or similar, optimised for DNA. For buffer exchange you can concentrate-dilute several times. The minimum volume is 10 ul.
Dear collage Angelov, why do you advice not to use Na acetate for precipitation?
Many thanks in advance for the information.
By the way, I didn't know about glycogen precipitation, but now I've found a detailed protocol. I paste it here in case it may be useful for someone:
http://agctsequencing.wordpress.com/2012/07/06/protocol-alternative-method-for-sodium-acetate-to-ethanol-precipitate-dna/
The most important is to avoid DNA precipitation as much as you can. It is risky for the homogeneity of the dissolved DNA. Sometimes, a DNA pellet, especially salt-precipitated DNA, when quite dry, cannot dissolve well. You need extensive washing with room T°C 70% ethanol to remove the salt and break any salt-induced DNA aggregates. As a rule, using precipitated DNA in fine biochemical experiments, is almost as horrible as using TCA precipitated proteins. Of course, precipitated DNA is OK for routine, molecular biology – cloning into vectors etc., experiments.
@Paula Garcia-Fraile Thanks for link but this link is not working anymore please upload corrected link or protocol in pdf.
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