difference between Qiaex and Qiaquick gel extraction kits - (Nov/16/2007 )
What is the difference between Qiagen's Qiaquick and Qiaex II gel extraction kits? Under what conditions should you prefer to use one over the other?
Qiaquick is more convient. With it, the only thing you do is mix yours samples with its buffer and then load and centrifuge. While there is no column in the Qiaex II, it is a bit inconvient, however, it could be scale up or down as you desire.
As the chaotropic buffers of the two kits are different, the recovery rate of the shorter moleculars are different between the two kits. Another thing is as said in their manual instruction: the largest fragment for Qiaquick<=10 kb, Qiaex II<=50 kb.
I tried Qiaex II yesterday to isolate DNA from silver stained acrylamide gel. I tried 3 samples but recover DNa from just one of them. It is my first trial with that kit so there may be some personal errors. But at the end ne of them worked means all the rest can work. It needs Whatman GC/F filter or glass wool to remove residual gel pieces after first icubation but kit does not supply that filter. you have to design it or find something else which can do the same job. And you need to prepare a DB(diffusion buffer) which needs ammonium acetate EDTA magnesium acetate and SDS to use the kit. I think without a kit with this diffusion buffer one can continue isolating DNA because the rest is simple NaOAc and EtOH precipitation.
best
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if you just like to reamplify the bands from acrylamide gels it is most of the time enough to cut out the bands from the gels, add some water (50 -100 µl), disrupt the gel piece (best way is to do that using a mixer mill), shake the mixture at 10 °C for 30 - 45 min, centrifuge the gel pieces down and use the supernatant directly for PCR (1-2 µl of the supernatant). I have done it successfully many times. Of course, you can also use the ammonium acetate buffer described above instead of adding water to the gel piece and precipitate with NaOAc and EtOH afterwards.
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if you just like to reamplify the bands from acrylamide gels it is most of the time enough to cut out the bands from the gels, add some water (50 -100 µl), disrupt the gel piece (best way is to do that using a mixer mill), shake the mixture at 10 °C for 30 - 45 min, centrifuge the gel pieces down and use the supernatant directly for PCR (1-2 µl of the supernatant). I have done it successfully many times. Of course, you can also use the ammonium acetate buffer described above instead of adding water to the gel piece and precipitate with NaOAc and EtOH afterwards.
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I tried this with TE buffer and water but it doesnt work. I try to quantify the amount of DNA with spectrophotometric techniques (nonodrop has ability to detect 2ng/ul) but i do not see ny peaks at 260nm. Even i tried PCR but I do not get any amplified bands when I checked in 2% agarose gel. My acrylamide gel is so dried that it is not dissolved in water. It is not dissolved even in ammonium acetate.
I tried this with TE buffer and water but it doesnt work. I try to quantify the amount of DNA with spectrophotometric techniques (nonodrop has ability to detect 2ng/ul) but i do not see ny peaks at 260nm. Even i tried PCR but I do not get any amplified bands when I checked in 2% agarose gel. My acrylamide gel is so dried that it is not dissolved in water. It is not dissolved even in ammonium acetate.
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I used this method with fresh gels only (mainly SYBR-Green staining) and did not try to extract DNA from dried acrylamide gels. When using fresh gels I always had the feeling that a good disruption of the gel is important for effective elution of the DNA (thats why I use a mixer mill / bead beater). I could readily measure DNA concentrations of about 10 ng / µl using the nanodrop.