Dear Mr/Ms, Good morning. My name is Tommy from San Diego Biomedical Research Institute. I am currently learning to use the chimera software. Great work in creating a program for protein and DNA visualization. I have one question to ask regarding the subject above. Is there a way to manually add sugar component onto an existing pdb file? To be precise, I am currently working with HIV-1 envelope. I have the pdb files that features the structure of HIV-1 trimer Env. I wanted to add glycan at specific sites to show steric hindrance to antibody binding. Another question. Is there a way to superimpose 2 pdb files into one image? For example, I have one pdb file for HIV-1 Env and another pdb file for antibody. Can I "merge" these two pdb files as one image? Also, assuming that it is possible to "merge" two different pdb into one image, is there a way to rotate one protein without affect the orientation of the other protein? Any advice/tip is greatly appreciated. Thank you. Sincerely, Tommy