Another band after plasmid purificaiton - ran the plasmid DNA on a gel (Oct/22/2009 )

Dear all,
I have got a problem about plasmid purificaiton. After the plasmid purificaiton, I ran plasmid DNA on a gel , but there is an another band before super colied plasmid .
I do not know what happened . Do you have any suggestions? Thanks a lot!

I'm assuming it is uncut plasmid? In which case it is probably your plasmid in another conformational state, like relaxed circular.......which runs slower than the supercoiled.

leelee on Oct 22 2009, 02:04 PM said:

Dear leelee,
maybe I do not explain this problem clearly. so I edit my photo, and the stranger band, I have marked it with asterisk.. I do not digest the plasmid with any enzyme, there should be no band! so I do not know what happened!