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phenix.fmodel: a command line tool to compute structure factors from a model (Fcalc or Fmodel).
by Pavel Afonine 27 Jan '10

27 Jan '10

Starting PHENIX nightly build version 1.6-295 (2010-01-27), a new command line tool phenix.fmodel is available. This is a replacement for "phenix.pdbtools --f-model" command, which is not available anymore. phenix.fmodel is a comprehensive tool to compute structure factors from a model. For more information and usage examples simply run phenix.fmodel . Pavel. P.S. Below is the result of running phenix.fmodel: phenix.fmodel: a tool to compute structure factors, Fmodel: Fmodel = scale * exp(AnisoScale) * (Fcalc + k_sol * exp(-b_sol*s^2/4) * Fmask) where: - Fmodel - total model structure factor (complex value) - AnisoScale = -ht*A(-1)*b_cart*A(-1)th/4 - h - column vector with Miller indices - A - orthogonalization matrix - b_cart - anisotropic scale matrix - t and (-1) denotes transposition and inversion operations - scale - overall scale factor - Fcalc - structure factors calculated from atomic model - k_sol and b_sol - Flat Bulk solvent model parameters - Fmask - structure factors calculated from bulk solvent mask Usage examples: 1) phenix.fmodel model.pdb high_resolution=1.5 will result in a file containing complete set of Fmodel = Fcalc computed from atomic model up to 1.5A resolution. 2) phenix.fmodel model.pdb scale=2 k_sol=0.35 b_sol=50 b_cart="1 2 3 0 4 7" high_res=1.5 low_res=10 will result in a file containing complete set of Fmodel computed using the above formula in resolution range 1.5-20.0A. 3) phenix.fmodel model.pdb high_resolution=1.5 algorithm=direct is similar to "1)" but the Fcalc are computed using direct summation algorithm. 4) phenix.fmodel model.pdb high_res=1.5 format=cns label=FOBS type=real r_free=0.1 will result in CNS formatted file containing complete set of amplitudes of Fmodel = Fcalc computed up to 1.5A resolution, labelled as FOBS, and free-R flags with 10% of test reflections. This is a typical command to simulate Fobs. 5) phenix.fmodel model.pdb high_res=1.5 scattering_table=neutron will result in a file containing complete set of Fmodel = Fcalc computed from atomic model up to 1.5A resolution using neutron scattering table. 6) phenix.fmodel model.pdb parameters.txt will result in a structure factor file, where Fmodel were computed using parameters defined in parameters.txt file. The parameters.txt file can contain all or any subset of parameters listed below. Note, that each { must have a matching one }. 7) phenix.fmodel model.pdb reflection_data.mtz will result in a file containing a set of Fmodel = Fcalc that will match the set of Miller indices of the data in reflection_data.mtz file. 8) phenix.fmodel model.pdb reflection_data.mtz data_column_label="FOBS,SIGMA" similar to "7)", where the specific data array is selected. See below for complete list of available parameters. ------------------------------------------------------------------------------- Parameters to compute Fmodel:: high_resolution = None low_resolution = None r_free_flags_fraction = None add_sigmas = False scattering_table = wk1995 it1992 *n_gaussian neutron data_column_label = None fmodel { k_sol = 0.0 b_sol = 0.0 b_cart = 0 0 0 0 0 0 scale = 1.0 } structure_factors_accuracy { algorithm = *fft direct cos_sin_table = False grid_resolution_factor = 1/3. quality_factor = None u_base = None b_base = None wing_cutoff = None exp_table_one_over_step_size = None } mask { use_asu_masks = True solvent_radius = 1.11 shrink_truncation_radius = 0.9 grid_step_factor = 4.0 verbose = 1 mean_shift_for_mask_update = 0.1 ignore_zero_occupancy_atoms = True ignore_hydrogens = True } output { format = *mtz cns label = FMODEL type = real *complex file_name = None } anomalous_scatterers { group { selection = None f_prime = 0 f_double_prime = 0 } }

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occupancy refinement
by Christian Roth 27 Jan '10

27 Jan '10

Dear all, I refine a structure of a protein to 1.4 A and found a few SO4-Ions. I tried to refine this sulfurs and some of these seems to be not fully occupied, as the negative difference density suggest. I tried to refine the occupancy of the sulfate ions to get an idea how strong the different binding sites might be occupied. All sulfate ions are in Chain C of my pdb. I tried to refine the occupancy individually using refine.occupancy.individual SO4 but this lead to different occupnacies for every atom for every atom and theix cant be the case for sure. Then I tried and group occupancy with resname=SO4 but now every sulfate ion has the same occupancy, which is indicated from my previous refinements also not the case, because two ions have no negative difference density. At the momentI can not figure out how I should combine the keywords for the individual occupancy refinement of the different sulfate ions. In my structure. Should I define for every ion a different chain or how I could overcome this problem? I would be very happy if anyone has a idea to sove this problem or tell me what keyword I misunderstood in the documentation. Best regards Christian

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GUI for Auto-MR
by Laurie Betts 27 Jan '10

27 Jan '10

I installed version PHENIX 1-5-2 under Linux, and the main GUI has an option for AutoMR Phaser that says (old PHENIX GUI) - if that crashes is it because we don't have the old GUI installed? THe other main items seem to work fine. The last error message in the terminal window seems to suggest that is the case.... Thx, Laurie BEtts

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twin data set
by r n 26 Jan '10

26 Jan '10

Hi I did processed a data set, which seems P3. I did molecular replacement and end up with solution with higher R factor. Then, I did used xtriage to check the data, it gave me possible space group P321 and few twin laws, this space group did not given me any solution , data seems have translation symmetry along z axis? Also I did processed in P1 and did molecular replacement end up in high R-factor. I really appreciate if any one has any suggestion what is going on with data? I given log file from xtriage, --------------------------------------------------------------------------------------------- | Point group | mean R_used | max R_used | mean R_unused | min R_unused | BIC | choice | ---------------------------------------------------------------------------------------------- | P 3 | None | None | 0.314 | 0.027 | 8.149e+03 | | | P 6 2 2 | 0.314 | 0.460 | None | None | 1.856e+05 | | | P 3 2 1 | 0.027 | 0.027 | 0.446 | 0.432 | 5.667e+03 | <--- | | P 6 | 0.432 | 0.432 | 0.249 | 0.027 | 1.856e+05 | | | P 3 1 2 | 0.460 | 0.460 | 0.242 | 0.027 | 1.859e+05 | | ---------------------------------------------------------------------------------------------- Statistics depending on twin laws ------------------------------------------------------------------ | Operator | type | R obs. | Britton alpha | H alpha | ML alpha | ------------------------------------------------------------------ | -h,-k,l | M | 0.432 | -0.009 | 0.046 | 0.022 | | h,-h-k,-l | M | 0.027 | 0.450 | 0.478 | 0.478 | | -k,-h,-l | M | 0.460 | -0.012 | 0.049 | 0.022 | ------------------------------------------------------------------ Patterson analyses - Largest peak height : 34.261 (corresponding p value : 7.017e-04)

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map averaging
by Gabriela Guédez 25 Jan '10

25 Jan '10

Hi dear Phenixbb, Is there a command tool to make ncs density averaging in a high oligomerization model that has some maps clearer than others? not multi-crystal but the same crystal. Thank you, Gabriela -- ---------------------------------------------------------------------- Gabriela Guédez R. gabriela.guedez(a)bzh.uni-heidelberg.de

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how to convert .cif with multiple datasets
by Zheng Zhou 24 Jan '10

24 Jan '10

Dear phenix experts: I am using phenix.cif_as_mtz to convert a .cif file downloaded from pdb, but when I run ################################################ phenix.cif_as_mtz XXXX-sf.cif Sorry: Crystal symmetry is not defined. Please use the --symmetry option. ################################################ Then I run ############################################### phenix.cif_as_mtz XXXX-sf.cif --symmetry=XXXX.pdb Multiple data sets found => ignored: XXXX-sf.cif What should I do? Thanks for your help. Joe

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explicit pdb output file name (refine)
by Ed Pozharski 21 Jan '10

21 Jan '10

Do I understand correctly that there is no way to force refine to skip the serial in the output pdb file name, i.e. foo.pdb, not foo_001.pdb? -- Ed Pozharski <epozh001(a)umaryland.edu> University of Maryland - Baltimore

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polygon resolution control
by Young-Jin Cho 21 Jan '10

21 Jan '10

Hi I was using polygon from GUI. One question I have now is how I can control the resolution limit. As I cut the resolution during refinements but polygon gave me from the uncut-high resolution. Is there any way, I can ask polygon to get statistics upto certain resolution as shown on pdb file? As always, thanks in advance. YoungJin

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Re: [phenixbb] polygon resolution control
by Alexandre Urzhumtsev 21 Jan '10

21 Jan '10

Dear YoungJin >I was using polygon from GUI. One question I have now is how I can control >the resolution limit. As I cut the resolution during refinements but >polygon gave me from the uncut-high resolution. Is there any way, I can >ask polygon to get statistics upto certain resolution as shown on pdb file? Honestly, I do not know for the phenix version; let's wait what Pavel & Nat answer you. Very probably they already implemented it and your problem will be solved easy. Another simple solution will be to cut explicitly your MTZ file by the resolution you wish before run the polygon. If not, such an option (to define explicitely the resolution; that will select for comparison the PDB structures refined previously at such a resoluton) exists in the original Tcl/tk based version of the polygon. Please, let me know if your are interested in it. Best regards, Sacha

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occupancy refinement default selections - bug or feature?
by Ed Pozharski 21 Jan '10

21 Jan '10

There is a ligand residue in the structure that have its occupancy set to 0.75. refine with default parameters apparently refines every atom individually, so in the end I have a strange situation where ligand atoms have different occupancies. Of course, regular alternate conformers in the protein part of the structure have single occupancy refined per residue. Interestingly, when I place altLoc identifier "A" in front of the residue name of the ligand, single occupancy value is refined (although there is no second conformation). It settles down near 0.7 (close to what I selected previously based on a traditional approach of eliminating difference density and roughly matching B-factors of hydrogen-bonded protein atoms with ligand), so apparently constraints (e.g. total occupancy for all the conformers) are not applied. Is this intentional behavior (I understand that groups can be defined in the input file but adding altLoc letter seems like a simple trick)? I think most people would initially expect that occupancy will not vary within a residue, so the default behavior may seem like a bug to some (the only situation I can think of where such variation is justified is to model radiation damage). -- Ed Pozharski <epozh001(a)umaryland.edu> University of Maryland - Baltimore

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Dear everybody
by YuYong Tao 21 Jan '10

21 Jan '10

Dear everybody: I installed phenix-1.6, when i run 'phenix.solve', it showed as follows: ustc-lifescience:~> phenix.solve binary=/usr/local/phenix-1.6-288/build/intel-linux-2.6/solve_resolve/exe/solve SOLVEDIR=/usr/local/phenix-1.6-288/solve_resolve/ext_ref_files SYMOP=/usr/local/phenix-1.6-288/solve_resolve/ext_ref_files/symop.lib SYMINFO=/usr/local/phenix-1.6-288/solve_resolve/ext_ref_files/syminfo.lib CCP4_OPEN=UNKNOWN SOLVE_RESOLVE_MALLOC_MAX=399459600 /usr/local/phenix-1.6-288/build/intel-linux-2.6/solve_resolve/exe/solve: error while loading shared libraries: libsvml.so: cannot open shared object file: No such file or directory and when i run 'phenix.resolve' ,it seems to be ok. So i donn't know what to do. Can you tell me? Best Wishes!

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How do different sections of TLS groups affect refinment
by Bart, Aaron G 21 Jan '10

21 Jan '10

Greetings everyone, I am still fairly new to crystallography, so forgive me for my naivety. My question involves how the TLSMD server segments my protein and the effects it has on refinement. For instance when i use "Multi-Chain Alignment Analysis", which lines the sequence for all of my chains (a total of 12) and shows how TLS groups are divided among them, it shows varying selections of TLS groups among the different chains. It should be noted that the sequence is the same for all the chains in my protein. Also if a TLS group splits a alpha helix into multiple parts, would this be valid? I have come to understand that helices move more like rigid bodies than segmented groups... Thanks! -Aaron

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K(sol) and B(sol)
by J. Fleming 20 Jan '10

20 Jan '10

Hi, I'm working on a structure but am having problems with K(sol) and B(sol). What are they and how do I get them into range? I thought they might have something to do with my waters but I have no water B-factors <25. Thanks for any help! -Jon

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twin refinement in phenix-1.5-2
by Kelly Daughtry 19 Jan '10

19 Jan '10

Hello all, I am wondering if anyone has run across this problem and knows how to fix it. I have a twinned dateset and I am using phenix.refine to refine the dataset. I have the full 1.5-2 installation. When I include the twin law (-k, -h, -l) in the refinement, I get this error: File "/usr/swr/phenix-1.5-2/cctbx_project/mmtbx/twinning/twin_f_model.py", line 1651, in map_coefficients "m_gradient" AssertionError If I do not include the twin law, I do not get the error and the refinment continues as normal. When I downgraded to Phenix.1.4-3 (full install), And use the same twin law, I am able to run phenix.refine without an error. I have attached my definition file for phenix.1.5-2 amd the log file. Thanks in advance for any help you can provide, Kelly Daughtry ******************************************************* Kelly Daughtry PhD Candidate Department of Physiology and Biophysics Boston University School of Medicine 590 Commonwealth Ave R 390 Boston MA, 02215 (P) 617-358-5548 *******************************************************

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Reflection file conversion
by Nate Nicely 19 Jan '10

19 Jan '10

I use d*TREK to reduce my data and phenix.reflection_file_converter to import the data. I seem to have had a bit of trouble generating the free R flags. It seems that the cap for the max number of free R reflections takes precedence over the percentage, even when the percentage is given expressly on the command line. I find myself setting the cap artificially high on the command line so that a full 10% is set aside. I was taught to set aside 10% for the free R set, only going lower if setting aside the full 10% compromised completeness. I'm just wondering what is the rationale for the numeric cap? Am I making any error(s) with my methodology? Nate N

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Re: [phenixbb] clash guarde failure phenix coot
by Pavel Afonine 19 Jan '10

19 Jan '10

Hi Georg, I think the refinement .log file should contain the lines like these below: Warning: very small nonbonded interaction distances. Nonbonded interactions: 12604 Sorted by model distance: nonbonded pdb=" CG ARG A 3 " pdb=" CG ARG A 4 " model vdw 0.000 3.840 nonbonded pdb=" NE ARG A 3 " pdb=" NE ARG A 4 " model vdw 0.000 3.200 which pinpoints you the offending atoms. Does this answer your question? Pavel. On 1/19/10 9:57 AM, Georg Mlynek wrote: > > Dear All, > > I´m refining a 2.1A with phenix 1.5-2 and get when I click on > automatically add hydrogens to model following error message: > refinement.pdb_interpretation.clash_guard.failure: Number of nonbonded > interaction distances < 0.5:391 > > I suppose that this comes, because coot mixes up the hydrogens. >

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rigid body refinement problem
by Jianghai Zhu 19 Jan '10

19 Jan '10

Hi, I am using phenix.refine_dev_282 for a rigid body refinement. The output pdb file is exactly the same as the input model even though there are obviously some large movements. Here are some information from the log file. Information about total rigid body shift of selected groups: rotation (deg) translation (A) xyz total xyz total group 1: 0.051 -5.493 -1.073 5.60 0.55 -3.15 -1.35 3.47 group 2: 0.254 0.562 0.252 0.67 0.36 -3.99 0.87 4.10 group 3: 3.807 4.001 -2.262 5.92 -0.81 -3.17 1.06 3.44 group 4: 2.275 -4.215 1.909 5.12 -0.18 -2.95 -1.43 3.28 group 5: -1.902 -5.750 -3.206 6.81 -1.99 -4.44 0.27 4.88 group 6: -4.932 -3.939 -5.340 8.16 -0.18 -2.08 -0.25 2.11 group 7: -1.140 -0.769 -7.715 7.83 0.73 -2.91 0.04 3.00 group 8: 2.008 -1.858 -1.236 3.02 -1.10 -5.44 -0.82 5.61 But then the model didn't change at all. stage Deviation of refined model from start model max min mean 0 : 0.000 0.000 0.000 1_bss: 0.000 0.000 0.000 1_rbr: 0.000 0.000 0.000 1_bss: 0.000 0.000 0.000 1_adp: 0.000 0.000 0.000 1_bss: 0.000 0.000 0.000 Is this a bug? -- Jianghai

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difference density map
by 丁玮 19 Jan '10

19 Jan '10

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Where is phenix.refine finding starting r values?
by Bart, Aaron G 19 Jan '10

19 Jan '10

Greetings, I am fairly new to crystallography, and have just started to use Phenix for structural refinement. I am currently working on a 2.8A structure that was run through multiple rounds of rigid body refinement via Refmac and manual revision using Coot. I eventually got stuck where large portions of my molecule had very poor density and the rwork and rfree stayed around 0.3. I then performed a TLS refinement which resulted in better density, and tried running it through phenix.refine with default ADP settings, as well as simulated annealing. It worked beautifully, however when I looked at the log file for the refinement, phenix was reporting a starting rwork and rfree that represented my first stage of refinement in refmac, 0.38/0.44. My question is, is phenix somehow neglecting the refinement that was done in refmac? Regards -Aaron

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Re: [phenixbb] merohedral twinned refinement
by JXQI 19 Jan '10

19 Jan '10

Zwart, Cherney and all, Thanks for the suggestions.The problem is fixed when I tried P31. Best regards J.X. Qi > > 3. If I try P3,the Matthews coeffs tell 2 or 3 molecules in the ASU,the > molecules will crash.Besides,the overall FOM ( lower than 0.4) and the > R/Rfree values (about 0.45/0.56) suggest that the P3 is the wrong sg. try P31 or otherwise P1. You should get a solution in those groups. It could of course mean that there are OD type issues, but I would not jump there yet. Can you send the intensity statistics from xtriage?

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right symmetry?
by Gabriela Guédez 18 Jan '10

18 Jan '10

Hi Phenixbb, I have a data that indexes in P6122, also P61 and P31. Data analysis in phenix.xtriage says no twinning is suspected according to the L-test. However, after MR and twin RB refinement, the model improves from P6122 or P61 to P31 5% Rfacs and 0.5 the FOM. I thought the data might have RPS and twinning not detected with the L-test. So, i ran xtriage to compute the RvsR statistics using the obs_and_calc.mtz file and the results were: in P61 R_abs_twin observed data : 0.112 R_abs_twin calculated data : 0.047 in P31 R_abs_twin observed data : 0.117 R_abs_twin calculated data : 0.139 "misespecified crystal symmetry", according to Lebedev, Vagin, Murshudov et al 2006, Acta Cryst. D62,83-95. I would like to know a test that tells me the right symmetry. I appreciate your help. Thanks, Gabriela

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Re: [phenixbb] merohedral twinned refinement
by JXQI 18 Jan '10

18 Jan '10

Dr.Zwart, Thanks for the reply. 2. The systematic absences and the Rsym support the P3121.I already mentioned the model fit very with the map if I use the P3121. 3. If I try P3,the Matthews coeffs tell 2 or 3 molecules in the ASU,the molecules will crash.Besides,the overall FOM ( lower than 0.4) and the R/Rfree values (about 0.45/0.56) suggest that the P3 is the wrong sg. 4. TLS refinement also did not imrove the results. 5. There are totally 88 aa in my protein, I could build 86 aa clearly. The intensity ststistics is attached in the message. J.X. QI ************************************************************************ Shell I/Sigma in resolution shells: Lower Upper % of of reflections with I / Sigma less than limit limit 0 1 2 3 5 10 20 >20 total 50.00 4.95 0.9 1.5 1.9 2.4 2.8 4.0 9.5 90.5 100.0 4.95 3.93 0.0 0.2 0.3 0.5 0.8 2.0 6.6 93.4 100.0 3.93 3.44 0.2 0.3 0.6 1.0 2.5 5.4 15.4 84.6 100.0 3.44 3.12 0.0 0.2 0.5 0.7 2.5 7.6 22.7 77.3 100.0 3.12 2.90 0.3 1.0 2.1 3.2 7.2 17.6 41.4 58.6 100.0 2.90 2.73 0.0 0.7 2.0 3.2 9.9 20.8 52.9 47.1 100.0 2.73 2.59 0.0 1.4 2.9 5.7 12.4 30.0 60.8 39.2 100.0 2.59 2.48 0.7 1.6 4.7 7.7 16.3 36.0 71.5 28.5 100.0 2.48 2.38 0.6 2.1 5.0 10.2 21.9 42.0 76.2 23.8 100.0 2.38 2.30 0.8 2.3 7.4 12.7 25.3 49.4 83.4 16.6 100.0 All hkl 0.4 1.1 2.7 4.7 10.0 21.1 43.4 56.6 100.0 Summary of reflections intensities and R-factors by shells R linear = SUM ( ABS(I - <I>)) / SUM (I) R square = SUM ( (I - <I>) ** 2) / SUM (I ** 2) Chi**2 = SUM ( (I - <I>) ** 2) / (Error ** 2 * N / (N-1) ) ) In all sums single measurements are excluded Shell Lower Upper Average Average Norm. Linear Square limit Angstrom I error stat. Chi**2 R-fac R-fac 50.00 4.95 619.8 13.8 3.5 1.039 0.046 0.050 4.95 3.93 834.6 17.5 5.0 1.156 0.048 0.052 3.93 3.44 521.9 14.6 4.5 1.026 0.059 0.062 3.44 3.12 333.7 11.1 4.1 1.073 0.071 0.068 3.12 2.90 172.5 7.1 3.6 1.153 0.098 0.096 2.90 2.73 131.4 6.0 3.4 1.256 0.116 0.108 2.73 2.59 102.8 5.2 3.4 1.306 0.140 0.130 2.59 2.48 77.7 4.6 3.4 1.381 0.173 0.158 2.48 2.38 64.1 4.3 3.3 1.355 0.195 0.177 2.38 2.30 54.7 4.1 3.3 1.345 0.221 0.197 All reflections 297.8 8.9 3.7 1.209 0.071 0.059 Intensities of systematic absences h k l Intensity Sigma I/Sigma 0 0 2 -0.2 0.4 -0.5 0 0 4 0.1 1.0 0.1 0 0 5 0.4 1.4 0.3 0 0 7 1.1 2.5 0.4 0 0 8 0.4 2.1 0.2 0 0 10 7.3 3.4 2.2 0 0 11 6.0 3.5 1.7 0 0 13 -2.3 4.9 -0.5 0 0 14 6.1 4.3 1.4 0 0 16 8.1 5.1 1.6 0 0 17 3.9 4.9 0.8 0 0 19 0.8 4.5 0.2 0 0 20 4.0 4.6 0.9 ********************************************************************* 1. How do the intensity statistic look like? 2. How did you choose P3121? 3. Did you try solving and refining in P3? 4. TLS? 5. How complete is your model 2010/1/17 JXQI <jxqi at mail.im.ac.cn>: > Dear all, > > I have a 2.3A data set processed with HKL2000. The space group is P3121 with > 63% of solvent content and 1 molecule in the ASU. I used a 40% homology > model to do molecular replacement. Both the Phaser and Molrep gave similar > solution with good packing. After further refinement with phenix, the built > model fit well with the 2mFo-DFc map. However the R/Rfree were stuck to > 0.34/0.38. > > I rechedked the data set with xtriage and found the data set is merohedral > twinned (with twin law"-h,-k,l", the estimated twin fraction is about 0.05). > When I used the twin law in further refinement, the R/Rfree were only > decreased to 0.32/0.36. Any suggestions are appreciated, thanks! > > > J.X. QI > _______________________________________________ > phenixbb mailing list > phenixbb at phenix-online.org > http://phenix-online.org/mailman/listinfo/phenixbb

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merohedral twinned refinement
by JXQI 18 Jan '10

18 Jan '10

Dear all, I have a 2.3A data set processed with HKL2000. The space group is P3121 with 63% of solvent content and 1 molecule in the ASU. I used a 40% homology model to do molecular replacement. Both the Phaser and Molrep gave similar solution with good packing. After further refinement with phenix, the built model fit well with the 2mFo-DFc map. However the R/Rfree were stuck to 0.34/0.38. I rechedked the data set with xtriage and found the data set is merohedral twinned (with twin law"-h,-k,l", the estimated twin fraction is about 0.05). When I used the twin law in further refinement, the R/Rfree were only decreased to 0.32/0.36. Any suggestions are appreciated, thanks! J.X. QI

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Twin fraction in phenix refine
by Pietro Roversi 18 Jan '10

18 Jan '10

Dear all, phenix.xtriage estimates a twin fraction of between 24 and 30% but then when I start the refinement I get 47-49%. In CNS if I fix the twin fraction in a series of refinements the Rfactors jump from 44% (twin fraction 0) to 37% (from 25% to 49%, only marginal improvement upon going from alpha=25% to 49%). Questions: 1. Is the refinement of alpha dependent on the model? 2. I am tempted to work with the 30% that xtriage estimates but do not know how: is there a way to fix alpha? Thanks Pietro -- Sent from my Desktop Pietro Roversi EP Abraham Fellow in Biochemistry - Lincoln College - Oxford Sir William Dunn School of Pathology, Oxford University South Parks Road, Oxford OX1 3RE, England UK Tel. 0044-1865-275385

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Re: [phenixbb] [ccp4bb] Adding H in refinement
by Schubert, Carsten [PRDUS] 13 Jan '10

13 Jan '10

Hi Pavel, sorry I hijacked the thread a bit... A question about the riding Hydrogens and their B-factors. I noticed that at least with earlier versions of PHENIX the B-factor of the Hydrogens was not fixed to the B-factor of the bonded atoms. If I would generate the Hydrogens in reduce they would inherit the appropriate B-factors, but during the course of the refinement and rebuilding they would start to diverge, sometimes drastically. Are you saying the current implementation restrains the B-factors to the bonded atoms and forces them to be equal or are they just inherited and are allowed to float afterwards? Cheers, Carsten > -----Original Message----- > From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of > Pavel Afonine > Sent: Tuesday, January 12, 2010 12:24 PM > To: CCP4BB(a)JISCMAIL.AC.UK > Subject: Re: [ccp4bb] Adding H in refinement > > Hi Sara, > > - what you observe should not happen since phenix.refine uses riding > model for H atoms. The hydrogen's B-factors are automatically inherited > from the atoms these hydrogens are bonded to. For example, in X-H bond > the B-factor of X should be equal to B-factor of H. > > - make sure you are using the latest version of PHENIX: > http://www.phenix-online.org/download/ > > - if this does not help, please contact me directly, and send the data > and model so I can tell you what exactly is not right (all the files > will be handled confidentially). > > - there is PHENIX bulletin board: > http://www.phenix-online.org/mailman/listinfo/phenixbb > > Pavel. > > > I did refinement with phenix of my 1.9-2.0 Angstroem structures and > included the hydrogens (riding). However, when I checked on the > statistics (refinement close to the end), the average B-factor was > extremely high (in phenix.polygon it was higher than with any other > structure in similar resolution range). It makes sense though that this > happens, if you have a residue which has a high B-factor and carries a > lot of hydrogens the average B-factor will raise quite a lot (since the > B-factor of hydrogens is calculated 1-1.5x of B-factor from the atom > it sits on), right? > > (When I removed the hydrogens again, the average B-factor was > fine...) > > > > My question is now did I do something wrong in my refinement (-> do I > have to change something that this does not happen), or is this > something everybody sees? > > > > If this is common, what would happen (during evaluation) if you want > to publish a structure and the statistics show such a high average B- > factor? Is it better to have hydrogens on, but a bad average B, or no > hydrogens on and a good average B... Obviously, I never published a > structure ;) > >

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