Hey,

I have a phagemid vector with ColE1 origin (pCMV-miR) normally my vector is 6.2kb and when I ligate it with a miRNA precurser it became 7kb.

My problem is during electrophoresis, I got an intact band at 1.9kb, the more also a band higher than 10kb. I am not sure that the band higher than 10kb can be genomic DNA because these kits never gave genomic DNA contamination in other samples.

I repeat the experiment with 3 different plasmid isolation kit. ( Qiagen midi, qiagen mini as well as MN mini). The results are the same. When I try a different plasmid with the same kits I got normal results.

The more, my mock vector gives band about 5kb marker so as a super coiled DNA 6.2 kb can be shown at 5kb. Mock vector is fine.

Can my vector becomes single strand with the addition of insert? Or can a super-super coiled form gives a band at 1.9kb?

I will also cut my plasmid with xhoi(one site) I will get the result tomorrow.

Thanks in advance.