I am currently using ligandfit for virtual screening and for that I am docking a number of ligands into a particular cavity of the receptor. Suitable docked ligands for my study must have interaction with certain atoms in the receptor (say 3 atoms in this study). Can I fix those atoms by using interaction filters and if yes please inform me wht parameter should I fix in Minimum number of features. Pleas answer my question urgently. Thank you in advance.