Dear Chimera developers: I want to assign Gasteiger charges for a ligand, as a preparative step for docking. The ligand is GTP, extracted from a protein complex structure. I wanted to add the Gasteiger partial charge, and explicitly chose to have a total charge of ³-4² on the ligand molecule. However, the program assigned partial charges that sum to total charge of ³-2² instead of ³-4². Any idea why the program assigned the Gasteiger partial charges incorrectly, ignoring the input total charge on the ligand. Thanks in advance for your help. Regards, Ibrahim -- Ibrahim M. Moustafa, Ph.D. Biochemistry and Molecular Biology Dept. 201 Althouse Lab., University Park, Pennsylvania State University PA 16802 Tel. (814) 863-8703 Fax (814) 865-7927