Are you growing it in appropriate selective medium before doing your plasmid extraction?

Also, have you tried a control plasmid alongside o make sure your mini prep procedure is working well?

Michael J. Benedik

Thank you so much for responding

Yes I am growing E.coli from stock in LB broth with ampicillin. After 16 hours of growth, I use it for extraction.

Same with the control

But I haven't done mini prep. Just midiprep.

Since the midi-prep is not working, try minipreps so you can see if it is a strain issue or a kit issue.

Michael J. Benedik

Thank you so much

I will try this