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Refining atoms on special positions
by Oliver Clarke 08 May '09

08 May '09

Hi, I'm running phenix.refine v1.4-3, and I'm refining a 3.3A structure that has potassium ions present on a crystallographic fourfold axis. I believe (based on previous refinement in REFMAC5.5), that these ions are at full occupancy, so I set the occupancy of each ion to 1. Despite this, there is still a lot (several 7-10sigma peaks in the Fo- Fc) of unexplained positive density, the potassium ions do not converge to their previously refined positions, and their B-factors refine upwards to values several times higher than the surrounding protein. When the same structure is refined in refmac (with ion occupancy set to 0.25), there is little to no unexplained density and the R/Rfree are substantially lower (21.9/25.9 as against 24.5/31) Does anyone have any ideas/suggestions as to what might be going on? Cheers, Oliver

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torsion_angles
by Imre Toeroe 08 May '09

08 May '09

Dear phenixers, I have seen a new strategy option, *torsion_angles* in the def files produced by recent (1.4-5x) phenix.refine. Is it active? How can one use it? Thanks, Imre

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Refining f'/f"?
by Leigh Allen 07 May '09

07 May '09

Hello, I'm new to the world of x-ray crystallography. I just solved my first SAD structure and I'm on to the refinement stage. The difference map generated by phenix.refine has really big positive peaks all around my MET residues. If I switch the atoms to MSE, then I get large negative peaks. Firstly, I'm not sure if I'm supposed to represent these residues as MET or MSE because it's a "native," high resolution (1.85) dataset, but it the protein had MSE residues. When scaling this data, I did not keep F(+) and F(-) separate. The protein's phases were generated using SAD data to 2.7A, which using SHARP led to a remarkably interpretable map that allowed me to build in the protein by hand. My second question is, how should I handle the issue with large + MET/large - MSE peaks? Do I need to rescale my data to treat it as anomalous data or is there something I can do within Phenix to fix my problem. I tried the phenix.refine GUI and set it up to refine f' and f", but it appears that nothing really changed. Thanks! Leigh Allen ******* Ph.D Candidate McCafferty Lab Department of Chemistry Duke University

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phenix.refine Ile peptide bond breaks
by SIPPEL,KATHERINE H 07 May '09

07 May '09

Hi all, I've got a 2.1 angstrom structure that I am refining. The space group is P212121. The structure is a dimer which I am refining without NCS restraints. Each monomer has 333 residues and one ligand, there are 33 Ile residues in each monomer. The first couple of rounds of refinement I had no problems, but during the third round phenix started breaking the main chain at the peptide bond and the side chain between CA and CB on some of the Ile residues. Specifically there are two breaks in chain A and four breaks in chain B, with two additional residues in chain B breaking only the CA-CB bond. Only one of the breaks is between the same residue in both chains. I'll be boring and run through my refinement process. This is the first time I've used phenix for anything but AutoSol and it is very likely that I have messed something up. Feel free to correct anything else I've done wrong along the way. Round 1, I rigid body refined chain A and B independently, performed simulated annealing, and refined individual coordinates. In COOT I manually refined and removed some bad loops. A few of the Ile were deleted but none of the problem ones Round 2, I refined individual_sites and individual_adp and turned off simulated annealing. In COOT I rebuilt some of the loops and fitted the ligand into the density. I generated a .cif file in eLBOW. Round 3, I refined the same as round 2 except that I included the .cif file. This is when I got the peptide bond breaks for Ile residues. I figured it was a fluke, fixed the breaks in COOT and rebuilt a few more residues in the loops. I ran another round of refinement and the same breaks showed up in the pdb file. I double checked the .geo file to see if Real Space Refine had made the bond distances were too long, but all the input distances were within one or two hundredths of an angstrom from ideal. I considered it was maybe the ADP refinement as I was borderline pushing the number of parameters I was refining given the number of reflections I had. I turned off the individual_adp refinement and reran refine_003. No luck. I tried increasing the weight of the geometry restraints over the observed data. I did this by increasing target_weights.wxc_scale = 1.5. (I suspect that I got this wrong. As I understood the wxc_scale is the ratio of the geometry restraints to the observed data. Feel free to point and laugh as long as you also provide an explanation as to what this parameter really means and how I should have done it,please.) Still no luck. For future information none of the problem isoleucines were located near the ligand or near any of the loops I was rebuilding. I think that's everything. Any help would be appreciated, Thanks, Kat -- SIPPEL,KATHERINE H Ph. D. candidate McKenna Lab Department of Biochemistry and Molecular Biology College of Medicine University of Florida

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difference density maps
by rpai＠berkeley.edu 06 May '09

06 May '09

Hi, I have a question on difference density maps. We are soaking in a substrate into my enzyme and am trying to see if it is in there by looking at difference density maps. We looked at an fobs-(fobs-fcalc) map and see density and 5 sigma at each catalytic active site in roughly the same place, its not great, but it seems like there is something there. so then, I thought I would confirm this by an fobs-fobs map. But I just used the phenix fobs-fobs difference electron density map and I dont see anything there. So I am curious as to an explanation of the difference. Any ideas? Raj

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SA-omit map
by James Fraser 05 May '09

05 May '09

Is there anyway to get phenix.autobuild to NOT delete multiple conformers when doing a SA-omit map? Thanks, jf -- James Fraser jamesfraser(a)berkeley.edu Alber Lab 356 Stanley Hall, QB3 UC Berkeley Berkeley, CA 94720 http://ucxray.berkeley.edu/~jfraser/

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(no subject)
by Leigh Allen 04 May '09

04 May '09

A Python error was detected. This is almost certainly a bug; please send an email containing this message to phenixbb(a)phenix-online.org so we can fix it. Thanks! AttributeError : 'ResultsNotebook' object has no attribute 'file_base' Traceback: Traceback (most recent call last): File "/usr/local/phenix-1.4-3/phenix/wxGUI2/MainWindow.py", line 257, in launch_coot (file_name, file_prefix) = self.pick_model() File "/usr/local/phenix-1.4-3/phenix/wxGUI2/Refine.py", line 386, in pick_model file_base = result_page.file_base AttributeError: 'ResultsNotebook' object has no attribute 'file_base'

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Missing plotting libraries
by Leigh Allen 04 May '09

04 May '09

How do I fix this? You appear to be missing one or more libraries required by the plotting module; plots will be disabled for now. The original error is shown below. liblapack.so.3: cannot open shared object file: No such file or directory You appear to be missing one or more libraries required by the plotting module; plots will be disabled for now. The original error is shown below. liblapack.so.3: cannot open shared object file: No such file or directory Plot library disabled: wxGUI2.Plot disabled. Graphing will be turned off. You appear to be missing one or more libraries required by the plotting module; plots will be disabled for now. The original error is shown below. liblapack.so.3: cannot open shared object file: No such file or directory You appear to be missing one or more libraries required by the plotting module; plots will be disabled for now. The original error is shown below. liblapack.so.3: cannot open shared object file: No such file or directory Traceback (most recent call last): File "/usr/local/phenix-1.4-55/phenix/phenix/command_line/refine_gui.py", line 16, in <module> run(sys.argv[1:]) File "/usr/local/phenix-1.4-55/phenix/phenix/command_line/refine_gui.py", line 9, in run from wxGUI2.Programs import Refine File "/usr/local/phenix-1.4-55/phenix/wxGUI2/Programs/Refine.py", line 13, in <module> from wxGUI2.Programs import RefineNotebook File "/usr/local/phenix-1.4-55/phenix/wxGUI2/Programs/RefineNotebook.py", line 802, in <module> class ResolutionBinStatsPlot (Plot.Loggraph) : AttributeError: 'NoneType' object has no attribute 'Loggraph'

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Switching off symmetry related van der waals in phenix.refine
by Chandrika Deshpande 01 May '09

01 May '09

Hello everyone, I am using Phenix.refine to refine one of my protein structures. 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 a problem which I need to solve : How can I refine this structure to include the PEG molecule? Is there a way to remove van der Waals repulsion between one half occupancy PEG and its crystallographic symmetry mate ? Is there a way to switch off symmetry related van der waals terms from the penalty function in phenix.refine ? I have already tried refining by changing the occupancy of PEG to 0.5 but this does not work as after running refinement the PEG molecule is pushed out of the electron density map. Thanks, Chandrika

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Geometry analysis
by Ulrich Baumann 29 Apr '09

29 Apr '09

Hi, I am just wondering whether there is a tool/feature in Phenix that (i) prints out all bonds/angles deviating by some specified number of standard deviations, and (ii) reads a user-defined .cif file for ligands as well so that this ligand appears in (i) as well. Phenix.pdbtools prints a bond histogram and I did not manage to include an external .cif file. Most likely this is easy to do and I haven't found it in the manual yet. Thanks in advance, Ulrich

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