A problem in topology

[Ed Beaty]

I was wondering if anyone had a good way to completely convert a batch of
double-stranded, unnicked plasmid to single-stranded, unlinked closed circles?
I assume that if you heat a ds unnicked plasmid to denature it, the two 
ss circles remained linked, and quickly reanneal upon cooling. 
 
The catch is, I can't use a phagemid vector to directly make ss circular 
DNA in this case.  If anyone knows a good way to unlink two linked circles 
(using a topoisomerase, maybe?) I'd be extremely thankful to hear it.

thanks,
Edward Beaty
Pierce Chemical Company