Hi David, Currently you cannot form a bond between two different models, i.e. structures opened from two different files (or separated with MODEL/ ENDMDL records in a single file). You need to first put the coordinates for both structures in the same PDB file, without MODEL/ ENDMDL records. There may be an issue of duplicate residue numbers; if so, you'd need to renumber to avoid the problem. For example, if one structure has residues 1-10 and another has residues 1-50, the coordinates should be concatenated into one file and renumbered so that no two residues have the same number (1-60 is one possibility; 1-10, 100-150 is another). Hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html On Oct 25, 2005, at 12:31 AM, David Chenoweth wrote:

Hi!

I am trying to pull up two molecules in chimera and link them by forming a covalent bond between a N and C atom. I am selecting only the N of one molecule and the C of the other. When I go to command line and use the bond sel command I get the following error message.

Type error: Cannot form covalent bond joining two molecules.

Does anyone know how to get around this.

Thanks, David C.

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