I suspect that your question is CNS-related. Easy is relative, but what you need to do is to uncomment the appropriate DIHEDRAL statements (assuming that used xplo2d, they will be there but mostly commented out). Just figure out what values you need for particular angles. If it is wise to fix ligand conformation is a different question altogether. On Fri, 2009-08-28 at 00:44 +0530, sajid akthar wrote: > Dear All > > Is there any easy to way write topology and parameter file for a cofactor with specific conformation. > > Thanks a lot > > Sajid > > > > Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com --