Hi Elaine, I am a PhD student studying interactions between carbohydrates and proteins and I am trying to add charges to a molecule that I have to use for a simulation. I have followed the guidelines that you give in: http://www.cgl.ucsf.edu/pipermail/chimera-dev/2004/000312.html But doesn't work as I want... My molecule is not a protein in this case but an oligosaccharide of ten residues long. I have written the pdb file using the server sweet II and now I am trying to add charges on the carboxylate groups present in the structures. I attach the pdb file and the attribute file that I have created in this mail. The atoms where I would like to add the charges are the OM atoms specified in the pdb file for each ADA residue. However, when I try to give the attribute to the atoms chimera replies: "Data line 1 or file either not selector/value or not tab-delimited" Please, can you help me to solve this problem and tell me what I wrong? Thanks in advance for your help. Cheers, Davide Davide Mercadante Ph.D. Department of Chemistry The University of Auckland, Auckland New Zealand