Roeland, Have you checked that that water altloc should be B and not A? i.e. if your water replaces side chain altloc A, then water altloc should be B and not A. This works in my lab. -----Original Message----- From: Roeland Boer [mailto:[email protected]] Sent: Fri 5/29/2009 3:58 AM To: [email protected] Subject: [phenixbb] Water/residue alternative conformations Dear all, I'm refining a 1.45 Ang structure in which I have several residues that have alternate conformations. These alternate conformations in some cases coincide with additional density that suggests the presence of a water molecule, appropriately positioned to make hydrogen bonds with near atoms. I have modeled partially occupied waters in these additional densities and linked their occupancies with the alternate conformation that is not clashing with the water in question. My problem is that these partially occupied waters are pushed away by the 'overlapping' alternate conformation of the amino acids. I guess there's an antibump restraint somewhere? How can I tell phenix that these alternate waters are not sterically clashing with the amino acid (since the sum occupancies of the water plus alternate conformation is 1)? The attached image shows one of those disordered residues after refinement. Water 1519 is pushed away from one alt conf (A) of Gln13, whereas the density suggests it should be making a hydrogen bond to OE1 of the altconf B of Gln13. I describe the occupancies of the situation in the attached image as below. refinement { refine { occupancies { constrained_group { selection = chain A and resseq 13 and altloc A selection = (chain A and resseq 13 and altloc B) or (resname HOH and resseq 1519 and altloc A) } } } } Thanks, Roeland Boer.

Hi Roeland, could you please send the fragment of PDB file that contains residues and waters in question, or just send the whole PDB? What you are trying to do is definitely possible in phenix.refine so I presume there must be something obvious (oversight somewhere) that makes it not working as expected. Pavel. On 5/29/09 12:58 AM, Roeland Boer wrote:

Dear all,

I'm refining a 1.45 Ang structure in which I have several residues that have alternate conformations. These alternate conformations in some cases coincide with additional density that suggests the presence of a water molecule, appropriately positioned to make hydrogen bonds with near atoms. I have modeled partially occupied waters in these additional densities and linked their occupancies with the alternate conformation that is not clashing with the water in question. My problem is that these partially occupied waters are pushed away by the 'overlapping' alternate conformation of the amino acids. I guess there's an antibump restraint somewhere? How can I tell phenix that these alternate waters are not sterically clashing with the amino acid (since the sum occupancies of the water plus alternate conformation is 1)?

The attached image shows one of those disordered residues after refinement. Water 1519 is pushed away from one alt conf (A) of Gln13, whereas the density suggests it should be making a hydrogen bond to OE1 of the altconf B of Gln13.

I describe the occupancies of the situation in the attached image as below. refinement { refine { occupancies { constrained_group { selection = chain A and resseq 13 and altloc A selection = (chain A and resseq 13 and altloc B) or (resname HOH and resseq 1519 and altloc A) } } } }

Thanks, Roeland Boer.

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