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 --------------------------------------------------------------