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[GUAN <grj@pewdc.ibp.ac.cn>]

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Dear all:
when I refine my structure, I can definitely see a cis peptide
bond between proline and histidine. (it is very obvious from the 
2fo-fc.map at R=17.1% and Rf=19.1%). This is a non-proline cis
peptide because it is formed by CO of proline and NH of histidine.

I am using CNS to refine the structure, and I changed the name of
proline and defined the bond and dihedral parameters in the toppar
files for this peptide bond, but it seems not successful in the map.
It has not put the N atom to the density it should be.
 
Does anyone have experiences on the refinement of non-proline cis
peptide bond, or know how to deal with it? And where can I find the
bond and dihedral parameters for non-proline cis peptide bond?

Thanks in advance.
Rong-Jin guan