

Dear Ronald,

you could try surfnet 
http://www.biochem.ucl.ac.uk/~roman/surfnet/surfnet.html
that comes free for academic users (as far as i remember) or,

icm, 
http://www.molsoft.com

a (very good) commercial solution for your problem.

best Regards,
Fuad
Fuad Abdallah
Max-Planck-Institut fuer Zuechtungsforschung / ZWDV
Tel.: 0221/5062-739 / Priv: 0221/584563
--------------------------------------------------------------