supercoiled plasmid DNA

[jahaley]

Is plasmid DNA naturally supercoiled or "relaxed"?

[aftabac]

Hi and welcome to forum
as there is expression from the genes on the plasmid DNA, that could only be possible if it is in normal coiling not in supercoiling form, so the Plasmid DNA naturally occurs in normal form. only when there is replication of plasmid DNA then there is supercoiling in DNA and that is for very short time and that is removed by cutting the DNA by specific enzymes, this is part of DNA replication mechinary.
regards
aftab

[jahaley]

Thanks for the reply and the warm welcome. I am studying DNA and polymer interactions for gene delivery and we are intersted in seeing what happens with supercoiled DNA (in addition to long linear DNA as well as short oligonucleotides). So I was trying to figure out if the plasmid DNA that I buy or obtain from a collaborator would be supercoiled, or if there are just particular strains that would be supercoiled. Any suggestions would be greatly appreciated!

[aftabac]

well
its very interesting study and a sort of novel work to figure out execlty that wheather DNA Polymerase has interaction with supercoiled DNA or not. but i think as the interaction of DNA polymearase is very specific with DNA in its normal form, so it may not interact and transcribe the supercoiled DNA, as we know that Topoisomerase (DNA Gyrase) work to make the DNA in its normal configuration before the Replication could occur of that DNA. so DNA might intearct with supercoild DNA but might not transcribe it. anyhow the result will be interesting and it will be nice that we will see you results at forum
best of luck for your work
regards
aftab