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Question about occupancy refinement of riding hydrogens
by Schubert, Carsten [PRDUS] 04 Mar '08

04 Mar '08

I just noticed that occupancies of riding hydrogens are being refined by default, in fact I am unable to turn this feature off (CCI-APPs from Jan-8). I was just (very naively) wondering what is the rationale behind this? The B-factor refinement for riding hydrogens is already enabled and should take care of this or not? It looks a bit odd to have hydrogens with occupancy 0.9 sitting on a carbon with occupancy 1.0 at 2.0 A resolution. Cheers Carsten

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Enhancement request for map formats
by Schubert, Carsten [PRDUS] 04 Mar '08

04 Mar '08

Hi, I was wondering if it would be possible to have the choice of generating ccp4 maps in phenix.refine. This type seems to be best compromise so far between compatibility and size. The xplor type ascii maps are 10x the size and do not offer any advantage in a homogeneous OS environment. Converting the maps after the fact is one more step I am trying to eliminate. Cheers Carsten

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Possible to rebuild only certain residues in a molecule?
by Francis E Reyes 03 Mar '08

03 Mar '08

All Can the rebuild process be directed to rebuilding specific residues in the molecule? Can this be extended to build multiple models of a given set of residues? Thanks FR --------------------------------------------- Francis Reyes M.Sc. 215 UCB University of Colorado at Boulder gpg --keyserver pgp.mit.edu --recv-keys 67BA8D5D 8AE2 F2F4 90F7 9640 28BC 686F 78FD 6669 67BA 8D5D

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problem with a twinned data set
by Pascal EGEA 02 Mar '08

02 Mar '08

Hi All This a question of general Crystallography and use of Phenix to deal with twinned data. I am having difficulties with a data set. We have data (2.6 ang resolution) that can be scaled and reduced in P222 with a Rmerge of 7%, the systematic absences show a screw axis ( it is P22(1)2). However MR in Phaser failed in this orthorhombic settings when searching for 2 molecules of the complex in the AU. If we reduce and scale the data in P2(1) and look at the diffraction pattern in HKLVIEW there is a /mmm symmetry. In the monoclinic P2(1) setting we can find 4 molecules of the complex (by MR in Phaser) and can refine it with Phenix to a Rfac/Rfree of 28%/34%. 2 molecules have good electron density whereas the two other ones have one of their domain very poorly defined in density. This is looking very suspicious to me and I am wondering if this refined structure is partially wrong? Meanwhile I used phenix.triage on the data processed in P222 and I am confused with the output. ##----------------------------------------------------## ## Twinning Analyses ## ##----------------------------------------------------## Using data between 10.00 to 3.36 Angstrom. Determining possible twin laws. The following twin laws have been found: ------------------------------------------------------------------------ ------- | Type | Axis | R metric (%) | delta (le Page) | delta (Lebedev) | Twin law | ------------------------------------------------------------------------ ------- | PM | 4-fold | 2.851 | 0.000 | 0.013 | - l,k,h | ------------------------------------------------------------------------ ------- M: Merohedral twin law PM: Pseudomerohedral twin law 0 merohedral twin operators found 1 pseudo-merohedral twin operators found In total, 1 twin operator were found --------------------------------------------- Analysing possible twin law : -l,k,h --------------------------------------------- Results of the H-test on acentric data: (Only 50.0% of the strongest twin pairs were used) mean |H| : 0.368 (0.50: untwinned; 0.0: 50% twinned) mean H^2 : 0.194 (0.33: untwinned; 0.0: 50% twinned) Estimation of twin fraction via mean |H|: 0.132 Estimation of twin fraction via cum. dist. of H: 0.115 Britton analyses Extrapolation performed on 0.14 < alpha < 0.495 Estimated twin fraction: 0.127 Correlation: 0.9955 By comparison if I run the detect_twin routine of CNS it tells me that they are no merohedral twin laws for the point group 222 (using the statistical method of Yeates) ? This is confusing me quite a bit. Assuming that the twinning law suggested by Phenix is correct how should I proceed? I have noticed the section concerning refinement using twinned data in Phenix phenix.refine data.hkl model.pdb twin_law="-k,-h,-l" detwin.map_types.aniso_correct=true but It seems I only have a MR solution in P2(1) but not in P222(1) so how can I refine in P222(1) I will greatly appreciate your input, many thanks. Pascal F. Egea, PhD University of California San Francisco Department of Biophysics and Biochemistry Robert Stroud Laboratory pascal(a)msg.ucsf.edu

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ligand refinement - elbow
by Christine Gee 01 Mar '08

01 Mar '08

Hi Its taken me a while to get around to it, but I just ran elbow to create a cif file etc for my inhibitor, but the bond lengths are quite different from what I got from the PRODRUG server, and it seems that the pdb file I got out of elbow has a few problems (COOT doesn't join up the aromatic ring for example because the carbons are now too far away on one part of the ring). I was wondering how the bond lengths are selected? It seems it is giving the aromatic carbons a bond length of 1.5, when my previous file (and phenylalanine for example have 1.3). Also, I still am not 100% sure how to add the CONNECT information to make the ligand able to covalently bind to the protein. Regards Christine

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refinement problems
by Christine Gee 29 Feb '08

29 Feb '08

Hi This is a more general crystallography question maybe. I am using phenix.refine and I have a model structure refined against data at 3.4A. The model was built from experimental phasing. I reprocessed the same dataset, to include another angstrom resolution (3.3). It has 50% of the data from 3.4 to 3.3 and the I/sigI is about 2. When I refine my structure at 3.4 the stats are 32 and 36 for R and Rfree, but when I use the phase extended data (and the same reflections are the test set up to 3.4A as long as CCP4i did the job right with setting the Rfree) the stats suddenly jump to 49 and 56 when I refine the model against the higher resolution data. Is there something I am missing? I am doing a rigid and an anneal before individual sites and adp refinement. The space group is P3121. Regards Christine

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input initial TLS parameters
by iulek 24 Feb '08

24 Feb '08

Dear all, I tried to find a way to input initial TLS parameters for the groups into phenix. I know many times this is not advisable, but I wanted to test what comes out from TLSmd server. I could not find any reference on how to do this. Note that I know how to define the groups (a previous question in this bb), the point now is to input initial parameters (origin, T, L, S). Thanks, Jorge

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ligand refinement
by Christine Gee 22 Feb '08

22 Feb '08

Dear Phenix developers I have a covalently bound ligand in my structure and I would like to use phenix to refine the structure. The ligand is bound to the sulfur of a cysteine. What is the best method for defining the ligand. Should I generate a cif file for the whole amino acid and the ligand, or can I make one for just the ligand and add in some restraint somewhere which tells phenix to make a bond between the ligand atom and a nearby sulfur in a cysteine. If I generate a cif file with the whole amino acid and ligand, I assume I will I have to follow some convention in atom naming so that the main chain bonds and angles will form and refine OK? Regards Christine

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Phenix.refine Questions
by Mary Fitzgerald 22 Feb '08

22 Feb '08

First, I have a hopefully easy question. I can't seem to figure it out although feel like I should be able to. Is there a way to run a phenix.refine job in the background? I tried using the & like I usually do and it didn't work. It would be nice to start a job and go home without leaving myself logged into the computer. I didn't see anything in the documentation which makes me think I'm being dull. Second, a technical question. When phenix.refine does ordered solvent, does it use detwinned maps if you've put in the appropriate twin operator and indicated it was twinned? When I've tried running phenix.refine with my perfect twin, it doesn't seem to find waters like I can using the CNS twinned water picking script. Third, is it possible to run phenix.refine in parallel at all. My structure is annoying large and the parallelization of FFT in CNS seems to help speed things up abit. Thanks, Mary X. Fitzgerald Postdoctoral Associate Arnold Lab

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geometry in phenix.refine
by Jianghai Zhu 21 Feb '08

21 Feb '08

Hi, I recently noticed that the geometry in my structure is much worse than my previous model. Here are some examples. The RMSD results after a refinement by phenix 1.3b. stage angl bond chir dihe plan repu 3_bss: 0.711 0.009 0.059 18.282 0.002 3.917 after switching to cci version 2008_02_08_1610, I tried to do a geometry minimization by setting wxc_scale = 0. The RMSD I got from the previous model is as following. stage angl bond chir dihe plan repu 0 : 1.394 0.124 0.147 20.782 0.004 3.925 and after 6 macro cycles of geometry minimization, stage angl bond chir dihe plan repu 6_bss: 0.622 0.011 0.120 13.143 0.003 3.822 It funny that the RMSD are so different for the same model. What happened? Jianghai +++++++++++++++++++++++++++++++ Jianghai Zhu, Ph.D Immune Disease Institute Department of Pathology Harvard Medical School 200 Longwood Ave., Boston, MA 02115 Ph: 617-278-3211 Fx: 618-278-3232 +++++++++++++++++++++++++++++++

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