Magic minipreps--DNA don't cut

Anita Gould anita at
Thu Jan 13 18:10:58 EST 1994

In article <1994Jan13.171215.1 at> mrege at writes:

   Date: 13 Jan 94 17:12:15 WET
   Organization: C.N.Biotecnologia,  CSIC

   Has anybody had any problem with Promega's Wizard Minipreps?
   In my hands the DNA looks well, but it is difficult to cut.
   Does  anybody know how to overcome this? Maybe washing the column twice?


Yes, people in my group have had exactly this problem -- the DNA looks
great on a gel, but won't cut with certain enzymes (but will cut with
others).  It does not appear to be a problem with a particular lot --
the same bottle of resin (& other reagents) can yield both good and
bad preps.  At least, a prep that I made from a particular kit cut
fine with EcoRI, & one that one of our postdocs made didn't.  (NB: I
*think* the enzyme in question that we had both used was EcoRI, but I
can check for you if it's crucial.  I think the other enzyme he had
trouble with was NotI, altho again I'd have to check to make sure.)
He tried both phenol extracting & gel purifying the DNA, & it still
wouldn't cut, so he thinks it must be covalently modified somehow,
perhaps preferentially at certain bases or base combinations.

Anyway, sorry I don't have a solution for you, but I can tell you that
you're not alone!

                                   -Anita Gould
                                    anita at

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