Cutting Qiagen miniprebs??

[Bjoern Voldborg]

Hello out there,

I am having serious problems cutting plasmids (pBlueskript) prepared with the Qiagen minipreb kit. The plasmid comes from a Xblue MRF' strain and contains an insert of aprox. 3.8kb.PCR product. I have tryed cutting it with SacI , with negative results, then I tried to Phenol extract it followed by Ethanol precipitation, with the same negative result. As a positive controle, I am cutting the original pBluescript as it came from the supplier, that works out fine. 
Is there anybody that has experienced the same thing, why is it happening, and how do I solve it.

Thanks in advance
Bjorn Voldborg
voldborg at biobase.dk