Hi all. I'm trying to use chimera in order remove bad contacts in my crystal structure using the Minimize Structure under Tools -> Structure Editing. I have a Magnesium ion in the active site of my protein and I need to keep it for further calculations. When I attempt to minimize the structure I get the following message in the reply log: AttributeError: '_chimera.Atom' object has no attribute 'gaffType' (see reply log for Python traceback info) Dock Prep runs with no problems and I'm able to save the mol2 file in which everything is OK, including hydrogen atoms, charges and Mg atom type and charge. If I remove the Mg ion from the structure, then the minimization runs with no problems. I think it is a problem while assigning amber atom type for Mg, Can anybody help me???? Thanks in advance for any help Yunierkis __________________________________________________________________ Servicio de Correos del Grupo de Redes. UCLV Participe en Universidad 2008 del 11 al 15 de febrero del 2008. Palacio de Convenciones. La Habana. Cuba. http: //www.universidad2008.cu