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Hi, I am new to Chimera, so perhaps someone could give me a hand. I have used Robetta for predicting the structure of a protein I am interested in and it gave back models for different parts of the protein. I would like to join them, so I am trying to join two models by a C-N peptide bond. I have selected the corresponding atoms in the last amino acid in one of the proteins and in the first amino acid of the other protein I want to join. With both atoms selected I took the "Join Models" option in "Build Structure" with the "C-N peptide bond" selected. And the "Apply" button does not activate. (See the screen shot attached) I have gone through the manual and I do not see what I am missing or what I am doing wrong. Any help is welcome. Thank you very much in advance. Kind regards, Miguel