Fred Does the .gam have a final geometry? You'll need to check because performing a QM geometry minimisation is not straight forward. BTW. A PDB file is the lowest quality input format. It's recommended that you try for a most information rich input such as SMILES or mol2. Cheers Nigel --- Nigel W. Moriarty Building 33R0349, Physical Biosciences Division Lawrence Berkeley National Laboratory Berkeley, CA 94720-8235 Phone : 510-486-5709 Email : [email protected] Fax : 510-486-5909 Web : CCI.LBL.gov