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multiplying bands in gel purification

William Coetzee coetzeew at is2.nyu.edu
Wed Feb 19 14:19:50 EST 1997

John G. Luz wrote:
> Folks--I'm tearing my hair out.  I cut a nice clean tight band out of a
> gel, and purified it with the qiagen gel extraction kit.  But when I ran
> the gel-purified band out on a gel to check my yield, I got two bands,
> both about equimolar.  One band looked about the right size.  The other
> looked about 1kb smaller.  The band I gel-purified was 5.4 kb and cut
> with NdeI and Xho.  What's going on?--John

We also had some strange results with the Qiagen gel extraction kit. See
my post "Subject: DNA recovery by phenol/chloroform extraction or
GeneClean". Repeated here for convenience:

    We observed something strange recently. We restricted a vector with 
    NcoI/BamHI and then gel-purified a fragment of about 3kb (GTG
    agarose/TBA followed by Qiagen Gel column purification. A subsequent
    mini-gel showed a strong 6kb band and a faint 3 kb band. Why? Is it
    possible that spontaneous ligation occurred?

William Coetzee

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