October 2008 - phenixbb - phenix-online.org

Unmasking cavities
by Frank von Delft 24 Jan '09

24 Jan '09

Hi After being through phenix.refine, I see in my hydrophobic core a big space (a few atoms wide) that is filled with strong negative difference density. I suspect the culprit is the bulk solvent mask, which is defined too tightly. The online manual mentions three parameters, but not what they do. solvent_radius, shrink_truncation_radius, grid_step_factor What *exactly* do they do? (I thought I'd elicit a contribution for the online docs this way :) Cheers phx

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solvent flipping
by Mark Collins 25 Nov '08

25 Nov '08

Hi Is there a solvent flipping (like solomon, ccp4) rather than flattening option in phenix? Mark

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weight optimization
by Raja Dey 04 Nov '08

04 Nov '08

Hi, I was trying to optimize weights as follows, but it came out with the error given below. Can anyone tell me what's wrong? I used phenix.refine ../p65_nat.mtz ../p65_136.1.pdb optimize_wxc=true optimize_wxu=true output.prefix=136.1 ----------xray term weight optimization (wxc)---------- Traceback (most recent call last): File "/usr/local/phenix-1.3b-rc6/phenix/phenix/command_line/refine.py", line 5, in <module> command_line.run(command_name="phenix.refine", args=sys.argv[1:]) File "/usr/local/phenix-1.3b-rc6/phenix/phenix/refinement/command_line.py", line 82, in run call_back_after_monitor_collect=call_back_after_monitor_collect) File "/usr/local/phenix-1.3b-rc6/phenix/phenix/refinement/driver.py", line 1143, in run call_back_after_monitor_collect = call_back_after_monitor_collect) File "/usr/local/phenix-1.3b-rc6/phenix/phenix/refinement/strategies.py", line 449, in refinement_machine log = log) File "/usr/local/phenix-1.3b-rc6/phenix/phenix/refinement/weight_xray_chem.py", line 256, in __init__ self.wxc_optimization() File "/usr/local/phenix-1.3b-rc6/phenix/phenix/refinement/weight_xray_chem.py", line 511, in wxc_optimization wxc = self.holder.wxc AttributeError: weight instance has no attribute 'holder' Thanks... Raja

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DNA sugar pucker
by Laura Murray 27 Oct '08

27 Oct '08

Hi. I'm one of the Richardsons' people. I have more experience with RNA, but have looked at DNA some as well. 1. On C2'-endo and C3'-exo being equivalent: no, not quite equivalent, but related. If you do have C1', C4', and O4' in the plane, then "popping" C2' out on one side or C3' out on the other is relatively similar (sort of) and there's a recognized "twist" conformation where you've got them both out of plane a bit. However, you can really get C3' mostly in-plane with the other three and have a conformation that's distinctly a C2' endo pucker rather than looking like it could be either one. If you're building ideal B-form DNA, it would be better to use a real C2'-endo pucker than the twist, and certainly better than using the C3'-exo. 2. I'm afraid I don't know the appropriate format for use with PHENIX, but there are pucker-specific parameters available on the Nucleic Acid Database site: http://ndbserver.rutgers.edu -- specifically, here: http://ndbserver.rutgers.edu/standards/parameter.html -- these are set up for XPLOR, but the values should help. At any rate, these files distinguish the dihedrals for C2'-endo and C3'-endo sugar puckers. (The set for higher resolution also provides slightly different bond lengths and angles for them, since the ring strains are a bit different.) And I don't think they make a habit of turning up C3'-exo. Laura Murray

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sugar puckering in an ideal B-DNA
by chern 26 Oct '08

26 Oct '08

Hi all, does anybody know why coot and sybil (and may be others that I don't know about) generate an ideal dna with C3*-exo puckers instead of C2*-endo, as text books say. maia

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phenix.refine output map format
by Paul Emsley 25 Oct '08

25 Oct '08

Dear Phenixers, Is is possible for phenix.refine to output a ccp4 map? If so, how? Thanks, Paul.

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elbow
by chern 25 Oct '08

25 Oct '08

Dear all, could I use eLBOW to create a .cif file for a B-DNA to restrain sugar puckers? Maia

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sugar puckering in DNA
by Maia Cherney 25 Oct '08

25 Oct '08

Hi Yu Seon. I would appreciate it very much if you send me your added restraints to the cif file. Maia YS. Chung wrote: > Hi Maia, > I had the same problem when I was refining with phenix. I ended up > looking at the torsions that were used in 3DNA (the program I used to > analyze the puckerings) and manually added the restraints to the .cif > files used in phenix. I can send you an example if you'd like. The > puckerings improved a lot when I used the modified .cif files. > Yu Seon > > On Fri, 24 Oct 2008 10:43:44 -0600 > "chern" <chern(a)ualberta.ca> wrote: > >> Sorry, I gave a wrong subject name in my previous e-mails. Should've >> been sugar puckering in DNA. >> I am wondering why the default .cif file for DNA does not include all >> >> information about sugar puckers. >> I do not have some fancy nucleotides. They are regular. >> >> Maia >> >> ----- Original Message ----- From: "Ralf W. Grosse-Kunstleve" >> <rwgk(a)cci.lbl.gov> >> To: <phenixbb(a)phenix-online.org> >> Sent: Friday, October 24, 2008 10:03 AM >> Subject: Re: [phenixbb] elbow >> >> >> >>>> The answer is yes but there may be better options. Ralf is the >>>> >> best >> >>>> person to answer this question but one option is to start with the >>>> >> .cif >> >>>> file in the monomer library. >>>> >>> This is more a chemistry question than a formatting question. >>> Since I'm not deeply familiar with the DNA chemistry, I was >>> >> pointing >> >>> Maia to phenixbb in hopes that someone may already have figured out >>> the list of torsion angle restraints to fix sugar puckers. >>> >>> What Maia really wants is: >>> >>> >>>> could you please send me a specific example of how to modify a cif >>>> >> file >> >>>> to specify the sugar puckers in DNA (I want them C2'-endo). >>>> >>> Has anyone on this list done this already? >>> >>> Ralf >>> _______________________________________________ >>> phenixbb mailing list >>> phenixbb(a)phenix-online.org >>> http://www.phenix-online.org/mailman/listinfo/phenixbb >>> >>> >> _______________________________________________ >> phenixbb mailing list >> phenixbb(a)phenix-online.org >> http://www.phenix-online.org/mailman/listinfo/phenixbb >> > >

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Re: [phenixbb] phenix.autobuild
by Matthew Chu 24 Oct '08

24 Oct '08

Thank you for the detailed information Tom, my autobuild job is actually running properly! Just some more minors questions: 1. AutoBuild Wizard will use phenix.elbow to generate geometries for any ligands that are not recognized, but how can I find out which ligands that can actually be recognized by phenix? Or to be save, we better run elbow to generate the libraries for every single ligands? 2. eLBOW can automatically add hydrogens to the input molecules if there are less than a quarter of the possible hydrogens, however this command doesn't work: phenix.elbow input_file.pdb --add-hydrogens=True, and I can't find this option under the elbow manual? And actually I would like to remove those hydrogens so it should be "add-hydrogens=false"? I am now using phenix-1.3-rc2. Thanks again! Matt -- ---------------------------------------------------------------------------- Matthew LH Chu PhD Student School of Pharmacy and Pharmaceutical Sciences University of Manchester ----------------------------------------------------------------------------

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NAG-ASN link geometry
by nihmayerm 24 Oct '08

24 Oct '08

We are refining a 2.7 A structure with multiple ASN-NAG links using phenix-1.3-final. The torsion angle between the Asn amide and the sugar is quite variable, while from the chemistry of this link we would expect a value close to 180°, as reported in the PDB survey by Imberty & Perez (Protein Engineering 8:669-709). A quick look at some entries in the PDB revealed close to textbook geometry for the NAG-ASN link in structures around 1Å resolution (e.g. 1UWC) and gets much worse in some lower resolution structures, including those refined with PHENIX. The NAG-ASN link used by PHENIX does not contain a torsion angle definition, and I would like to ask (i) if its appropriate to use one in refinement, and if so (2) could people share their cif file for this link. Thanks - MLM

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