I have a circular peptide structure solved from Xtal. The peptide is actually a circular peptide that has the N terminal and C terminal joined together by a peptide bond. When refining the structure, I had a problem getting the C-N terminal (between G34 and S2) joined together by the peptide bond. I even made a link between the C terminal carbon atom and N terminal N atom in coot and used this model as the input model to do the refinement using Phenix.refine. It seemed that the program didn't consider the link made in coot as a valid bond and intentionally avoid forming a bond between the C atom and the N atom. So, how can I solve this problem?

Thank you,

Best regards,

Jiang 

Lin Chen Lab

University of Southern California

After refinement