Mismatched base pair conformation?

[Maneesh Yadav <yadavm -8 at 8- scripps.edu>]

Hello all,
 We are trying to get a decent picture of the conformation of a duplex DNA
 string with a small internal reigon of mismatched base pairs, can anyone
 comment on some good tools/ways to do this?  I can run minimzations
 through insightII, but I don't think I can do a decent job with the
 forcefields that you can run minimizations with (if anyone would like to
 tell me other wise, please do).
 -Many Thanks,
 Maneesh Yadav