Help! I cannot find the supercoil form!

Qunfeng Dong qfdong at
Wed Apr 12 16:38:17 EST 1995


  Please help me, I have wasted two weeks to do the simple work, and I still
cannot do it.  I was trying to isolate a plasmid vector(8.4 kb) from DH5a
host cells. and I run a gel(1%) with the plasmid and with the linear form (I
cut the plasmid with a unique RE). the linear form run into the exact the
same band of 8.4 kb, but in the vector alone lane I cannot see any band corresponding to the
supercoil form of the plasmid, there was a major band a litter upper than the linear
form.  I selected 10 colonies to do the miniprep, and all got the same
result.  I called the technique service, and they don't think it's because
of the dimerization. 

  I isolated a recombinant plasmid (total about 10 kb) from the same vector
above before. and I didn't see this result. 

  I am looking forward to any suggestion, please help!

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