low plasmid concentration - (Nov/02/2015 )

Hi,

I've recently cloned an insert the size of 1800bp. However, my plasmid yield is only 70ng/ul. I'm using DH5@ competent cells for trasnformation.

I need the plasmid  for transfection in mammalian cell line to generate stable cells lines. Thus I require higher concentration of plasmid for transfection. I usually transfect 3ug of plasmid for transfection to generate stable cell lines.

I don't know why the yield is so low. I've used the same miniprep on different plasmids in the past and never had trouble with the plasmid concentration.  Shall I try midiprerp instead of miniprep to increase my concentration or shall I try a different type of competent cells?

Many thanks

This is not, in my experience, an unusually low concentration.  A larger prep will certainly help.