Dear all, I am working with some chemically modified residues. For consistency with MMTK, I have to move non-natural atoms in the ATOM list of the pdb. I would like to do that directly from chimera and not editing the pdbfile. I thought that I could alter the heteroatom value of chimera's residues to get there. But whether this is not the right attribute or I miss something. What I do is: build my system, select the atoms of the non-natural and natural part of the residue. Make a new residue and then, having selected it: atoms=chimera.selection.currentAtoms() for a in atoms: a.residue.isHet=False This indeed changes the isHet attribute but when saving the pdb, the residue is in the HETATM field. Any pointer? Best, JD **************************** Dr. Jean-Didier Maréchal Associate Professor The Computational Biotechnological Chemistry Team Departament de Química Universitat Autònoma de Barcelona Edifici C.n. 08193 Cerdanyola (Barcelona) Tel: +34.935814936 e-mail: JeanDidier.Marechal@uab.es www: http://g <http://asklipio.qf.uab.es>ent.uab.cat/jdidier<http://ent.uab.es/jdidier>