Hi everyone,

           Following Chandrika's question, what should I do if one peptide 
chain crosses a two-fold crystallographic symmetry axis?
The peptide is not symmetric and the sidechain of one Se-Met (two after CS 
operation) is determined and conformed by MAD.

           Your sincerely
        De-Feng Li
        lidef...@moon.ibp.ac.cn
          2009-04-29

Defeng Li, Dr.,
Email: lidef...@moon.ibp.ac.cn
National Laboratory of Biomacromolecules,
Institute of Biophysics, Chinese Academy of Sciences,
15 Datun Road, Chaoyang District,
Beijing 100101, China


======= 2009-04-29 17:02:00 You writed in your letter:=======

>Hello everyone,
>
>My protein crystallised in the spacegroup P6522 with one protein molecule in 
>the asymmetric unit. I have a PEG molecule from the crystallization condition 
>which crosses a two-fold crystallographic symmetry axis. PEG is symmetric 
>hence this does not violate the crystal symmetry. However, this situation 
>causes two problems which I need to solve :
>
>First, How can I refine this structure ? I am using Phenix. Is there a way to 
>remove van der Waals repulsion between one half occupancy PEG and its 
>crystallographic symmetry mate ?
>
>Second, how do I submit this structure to PDB ? Do I include a full PEG 
>molecule at half occupancy even though one half is related to the other via 
>crystallographic symmetry ?
>
>Thanks,
>Chandrika

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