HELP ! get DNA (< 500bp) out of gel

sujoy ghosh sujoy_ghosh at
Thu Jun 27 12:58:00 EST 1996

I have used Qiagen's Qiaex DNA extraction kit for routinely isolating
small (100-500 bp) fragments from regular agarose gels and they have
worked great for me. You may want to try them. The Promega kit is not good
for small DNAs.

In article <4puiqs$h8g at>, N.P.Dantuma at (Nico
Dantuma) wrote:

> ez026048 at (Hong Lin) wrote:
> >I had problem of isolating small DNA fragments from gel. I had tried 
> >promega "Wizard" DNA purification system and Bio 101 Geneclean product.
> >Both did not end up satisfied result. I have no problem, however, in 
> >isolating longer DNA fragment (eg >1000 bp) using the same methods above. 
> >I did slightly modify the procedure; for example, add 5 ul of 10% of 
> >acetic acid for each ml of NaI in Bio-101 geneclean kit, or incubation 
> >DNA samples before elute it out. I guess, I can only get less than 20 % 
> >of recovery from gel.
> >Can anyone provide any information or advice for eluting small bp DNA out of 
> >gel with satisfied recovery. Or other alternative methods (I had tried 
> >dialysis method too). Thanks in advance
> Why do you think the poor recovery of the small fragment is due to
> elution from the gel. I would assume that it is mainly caused by a
> substantial loss of the DNA during precipitations, as you do not have
> poor recoveries with the larger fragments, which are more difficult to
> elute but easier to precipitate. The poor precipitation of small DNA
> fragments is a well known problem, that can be solved by precipitating
> the fragments in the presence of carrier molecules, for example
> linearized acrylamide. I think that protocols can be found in standard
> manuals.
> Nico Dantuma

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