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Odd behaviour of real-space refinement
by Tristan Croll 21 Feb '15

21 Feb '15

Hi all, I'm just finalising the re-refinement of a 3.6 Angstrom structure. The stats in general are excellent (Rwork/Rfree = 0.219/0.260; Ramachandran outliers 0.12%; Clashscore < 2; rotamer outliers 2.1%) and I've gone through the whole structure to check and double-check fit to the density. I'm very confident that it's effectively correct. When I run through a fairly standard refinement protocol (XYZ coords, Individual B-factors, optimizing weights, secondary structure restraints), all seems fine - the Rfree rattles around within 0.2% or so. But when I include the real-space refinement option, very strange things start to happen. Each rsrl step causes a 3-4% jump in both Rwork and Rfree, and jumps the Clashscore up to 40 or so. Rotamer outliers briefly go to zero but then increase substantially (to 6+%) in subsequent steps, and the number of Ramachandran outliers increases. I thought I'd missed some dreadful error in my structure until I looked more closely at the results. Some very nonsensical changes have been made - for example, an arginine in the middle of a beta-sheet (admittedly with no observable density associated with its sidechain, but register is well determined by surrounding residues and backbone density is clear) was flipped from its original orientation to point directly into the hydrophobic core of the domain. Somewhat surprising, to say the least. Is this a bug in the algorithm, or is it simply that 3.6A is too low resolution for it to work reliably? My version of Phenix is a nightly build from about 2 weeks ago. Happy to share coordinates and log files if necessary. Thanks, Tristan

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Odd behaviour of real-space refinement
by Tristan Croll 21 Feb '15

21 Feb '15

Hi all, I'm just finalising the re-refinement of a 3.6 Angstrom structure. The stats in general are excellent (Rwork/Rfree = 0.219/0.260; Ramachandran outliers 0.12%; Clashscore < 2) and I've gone through the whole structure to check and double-check fit to the density. The only stat that bugs me a little is the rotamer outliers (2.3%). When I run through a fairly standard refinement protocol (XYZ coords, Individual B-factors, optimizing weights, secondary structure restraints), all seems fine - the Rfree rattles around within 0.2% or so. But when I include the real-space option, very strange things start to happen. Each rsrl step causes a 3-4% jump in both Rwork and Rfree, and jumps the Clashscore up to 40 or so. Rotamer outliers briefly go to zero but then increase substantially in subsequent steps, and the number of Ramachandran outliers increases. I thought I'd missed some dreadful error in my structure until I looked more closely at the results. The attached image is an example of what's happened: an exposed arginine in the middle of a beta-sheet (admittedly with no observable density associated with its sidechain, but register is well fixed by surrounding residues) has been flipped from its original orientation (yellow) to point directly into the hydrophobic core of the domain. Somewhat surprising, to say the least. Is this a bug in the algorithm, or is it simply that 3.6A is too low resolution for it to work reliably? My version of Phenix is a nightly build from about 2 weeks ago. Thanks, Tristan

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Re: [phenixbb] Autobuild iterative omit map error
by Terwilliger, Thomas Charles 20 Feb '15

20 Feb '15

Hi Emily, (Back on-list so others can see the answer.) It seems that your PDB file has a "TER" record between residues ASN 446 and ALA 447 of chain B. Our parsing system interprets that as the end of chain B and thinks that ALA 447 is another chain. You can see this by running: phenix.print_sequence xxxxx.pdb I tried deleting the TER record and it looks as though autobuild will get past the interpretation stage with it taken out. Let me know if that doesn't do it! (Also...do you know why the TER record might be there? It is a little surprising!) All the best, Tom T On Feb 20, 2015, at 9:10 AM, Emilia C. Arturo (Emily) wrote: Thank you Tom! Attached are the reflections file, sequence file, input model pdb file, and the log file from phenix. Emily. On Fri, Feb 20, 2015 at 11:01 AM, Terwilliger, Thomas Charles <terwilliger(a)lanl.gov<mailto:[email protected]>> wrote: Hi Emily, I'm sorry for the trouble! I'll be happy to try and help with it. If you send me (off-list) the input files you are using and the full log file I'll have a look. All the best, Tom T On Feb 20, 2015, at 7:53 AM, Emilia C. Arturo (Emily) wrote: > Hello. > > I'd like to use phenix's Autobuild iterative omit map tool, but have run into an error I could use some help with. When the process aborts, the message that phenix outputs is that the input file has duplicate chains. I looked at the pdb file and I do not see duplicate chains; could the ANISOU records for each atom generated by TLS refinement be hanging up the process? I had no error with Autobuild when I started the iterative map process using an input file that had been generated by phenix.refine using the same configuration as the TLS refinement had used (except, of course, for the TLS parameters). > > Thanks for your attention. > Emily. > > _______________________________________________ > phenixbb mailing list > phenixbb(a)phenix-online.org<mailto:[email protected]> > http://phenix-online.org/mailman/listinfo/phenixbb > Unsubscribe: phenixbb-leave(a)phenix-online.org<mailto:[email protected]> <AutoBuild_run_85_1.log><III-40-C2_justscan3_xscale_cutresto29.mtz><PAH.fa><PAH_C2_ref22plus_refine_84.pdb>

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Autobuild iterative omit map error
by Emilia C. Arturo (Emily) 20 Feb '15

20 Feb '15

Hello. I'd like to use phenix's Autobuild iterative omit map tool, but have run into an error I could use some help with. When the process aborts, the message that phenix outputs is that the input file has duplicate chains. I looked at the pdb file and I do not see duplicate chains; could the ANISOU records for each atom generated by TLS refinement be hanging up the process? I had no error with Autobuild when I started the iterative map process using an input file that had been generated by phenix.refine using the same configuration as the TLS refinement had used (except, of course, for the TLS parameters). Thanks for your attention. Emily.

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on Bulk-solvent and scaling
by Smith Lee 20 Feb '15

20 Feb '15

Dear All, Will you please introduce to me briefly on the function of the step of Bulk-solvent and scaling in the Phenix refine and what is the corresponding mechanism? Smith

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On Phenix refinement
by Smith Liu 20 Feb '15

20 Feb '15

Dear All, The default number of cycles for the Phenix refinement graphical interface is 3 (should be macro-cycles). I have done a refinement with 3 default cycles, and I get the acceptable refinement results. Then I kept everything same, except I changed the cycles of refinement from 3 to 5, however the refinement result was ugly which was unacceptable (Rfree increased). The Phenix document regards 5 macrocycles refine is fine. For my situation, do you think the 3 macrocycles refine result is acceptable or not? If not acceptable, what do you suggest for improvement? I am looking forward to getting your reply. Smith

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erraser for DNA?
by Phoebe A. Rice 19 Feb '15

19 Feb '15

I know phenix has lovely DNA restraints, but I think the backbone of my lowish-resolution DNA structure could use more help. Is there anything like erraser for DNA that will make my DNA backbone as B-like as possible? ++++++++++++++++++++++++++++++++++++++++++ Phoebe A. Rice Dept. of Biochemistry & Molecular Biology The University of Chicago PRice(a)uchicago.edu<mailto:[email protected]>

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The discrepancy for determination of Ramachandran outliers by Coot and MolProbity
by Smith Lee 18 Feb '15

18 Feb '15

Dear All, It often finds for the Ramachandran favored determined by Coot, MolProbity regards as Ramachandran outliers. There are earlier posts regards Coot and MolProbity has different database for the determination of the Ramachandran plots. Then will you please let me know the correct way to correct the Ramachandran outliers by Coot in order to meet the MolProbity Standards? I am looking forward to getting your reply. Smith

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SA (torsion angle) along with B factor reset to low value.
by Tarek DawoD 18 Feb '15

18 Feb '15

to remove memory of the old original R-free flags (which is not available) and using a new test set, i reset the B factor and use SA (torsion angle) i got this error: not implemented: support of different sites. individual and sites.torsion_angles selection. what does that mean? thank you in advance TK_DawoD

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on HIS ** both conformations clash in the flipping
by Smith Lee 17 Feb '15

17 Feb '15

Dear All, In the log output of the Phenix refine, for the flipping of the N/Q/H residues before XYZ refinement, it often occurs something like "HIS ** both conformations clash, **PLEASE CHECK MANUALLY**". Will you please tell me what will clash with 1 of the 2 conformations of the specified HIS? I have checked the specified HIS in Coot, and I still do not know what does it mean for "both conformations clash". I am looking forward to getting a reply from you for clarification. Smith

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