Oh, the other thing I noticed, when I made 5-bromo-uracil (5BU), was that elbow.builder failed to put in planar restraints at the bottom of the cif file. I had to do this manually, or the ring looked puckered. Fortunately it was fairly easy to do: loop_ _chem_comp_plane_atom.comp_id _chem_comp_plane_atom.plane_id _chem_comp_plane_atom.atom_id _chem_comp_plane_atom.dist_esd 5BU plan N1 0.020 5BU plan C2 0.020 5BU plan O2 0.020 5BU plan N3 0.020 5BU plan C4 0.020 5BU plan O4 0.020 5BU plan C5 0.020 5BU plan C6 0.020 5BU plan C1* 0.020 5BU plan H3 0.020 5BU plan BR 0.020 5BU plan H6 0.020 This keeps the six membered ring and the exocyclic functional groups (two keto oxygens and one Br atom) constrained to a plane. Claudia Scotti wrote:
Dear list,
I've refined a protein at 2.0 A resolution with its ligand, a small molecule which includes a phenyl group. For this, I used elbow to generate the cif file, and in this file the atoms of the phenyl ring are correctly defined as "aromatic". However, the pdb output of the refinement shows a boat configuration for the 6 carbon atoms ring, with a very nice fit to the electron density. This would suggest a flexible cyclohexyl- substituent instead of the expected, typically planar phenyl ring.
As my chemistry is poor, I'd really need some suggestions on where I'm wrong: did I give the wrong cif file or does phenix recognise a better fitting in a boat structure, indicating that my ligand phenyl moiety has been reduced somehow to a cyclohexyl one? Or is the aromatic ring of the phenyl group not so planar as I've supposed it to be until now?
Any help would be very appreciated.
Many many thanks,
Claudia
Claudia Scotti Dipartimento di Medicina Sperimentale Sezione di Patologia Generale Universita' di Pavia Piazza Botta, 10 27100 Pavia Italia Tel. 0039 0382 986335/8/1 Facs 0039 0382 303673
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