Hi gromacs guru! Does any know a clever way on how to convert QM charges to group charges as in shown in the residue topology file? Ciao, Luciano Dr. Luciano Triguero College of Art and Science Department of Chemistry Cox Science Building 1301 Memorial Drive, Room 146 P.O Box 249118 Coral Gables, FL 33124-0431 Cellular: 305-904-2419 Office: 305-284-3938