[phenixbb] Refining sucrose

Priit Eek priit.eek at gmail.com
Mon May 23 07:15:41 PDT 2011


I couldn't find this (probably basic knowledge) in the manual or here, so...

I have a problem with refining a sucrose ligand. It is not covalently bound to the protein – just electrostatic interaction. The density isn't the best, but it's still obvious it must be there. LigandFit can find the blob and fits the sucrose in there quite well, but when I run phenix.refine it distorts the geometry of the molecule and complains about it later in MolProbity - Basic Geometry validation in almost every possible way.

How can I apply more stringent restraints to the ligand so its geometry wouldn't get so twisted?

This might not be the most appropriate list for my second question, but the problem is the same and somebody probably knows: how to manually modify that sucrose in Coot (eg rotate only one ring or a -CH2OH group) or perform real space refinement? Right now I can only rotate/translate the whole sucrose and trying to perform a real space refinement results in an error ("Failed to match (to the dictionary) the following model atom names: SUC C1 C2 C3 C4 C5 C6 O1 O2 O3 O4 O6. That would cause exploding atoms, so the refinement didn't start.")

I haven't specified any custom cif libraries as SUC should be present in the built-in library of both Phenix and Coot. I'm using Phenix v1.7.1-743 and Coot v0.6.2-pre-1-rev3450 on OS X 10.6.7.

Thank you in advance!

Priit Eek

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