October 2010 - Chimera-users - RBVI Mailing Lists

Relax H-bond constraints
by Joern Lenz 15 Oct '10

15 Oct '10

Hi, I used the automated H-bond detection of Chimera to detect H-bonds between an target protein and its docked lignds. On your webpages (http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/findhbond/findhbon…) I found the following: "[...] Relax H-bond constraints indicates that tolerances to Relax constraints by should be applied to the precise geometric criteria [...]; empirically, tolerances of 0.4 angstroms and 20.0 degrees work well for most macromolecular structures." Can you lease tell me if there is a literature which discusses this relaxation in more detail and can be referenced Many thanks for a reply. Cheers Joern

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Per-atom RMSD
by Ibrahim Moustafa 08 Oct '10

08 Oct '10

Dear Chimera, I have a question regarding RMSD: I have two structures to superimpose using certain residues; and I am interested to get the RMSD value for each CA-atom in the structure. I wonder if there is a way to do that in Chimera? I think there is no direct way; but I wonder if there is a script that can be used for that. For the developer: It might be useful to have a tool that can directly do that in Chimera Many thanks for help, Ibrahim -- Ibrahim M. Moustafa, Ph.D. Biochemistry and Molecular Biology Dept. 201 Althouse Lab., University Park, Pennsylvania State University PA 16802 Tel. (814) 863-8703 Fax (814) 865-7927

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Compatibility Question
by ayassin＠wadsworth.org 07 Oct '10

07 Oct '10

Hello, I have had some problems using chimera on a PC/Vista laptop with Intel graphis card. Any advice/experience on using chimera with PC/Windows7 laptop and NVIDEA graphics card? Is it better/more compatible/same type of problems? is it the PC or the graphics card? Thank you very much, any feedback will help... Aymen Yassin IMPORTANT NOTICE: This e-mail and any attachments may contain confidential or sensitive information which is, or may be, legally privileged or otherwise protected by law from further disclosure. It is intended only for the addressee. If you received this in error or from someone who was not authorized to send it to you, please do not distribute, copy or use it or any attachments. Please notify the sender immediately by reply e-mail and delete this from your system. Thank you for your cooperation.

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colour residue by value
by Sumitro Harjanto 07 Oct '10

07 Oct '10

Hi Elaine, I am looking into using CHIMERA to create a diagram. Each residue will be coloured according to an assigned value; say if the value is high, the residue will assume a bright red colour; if the value is low, the residue will be coloured light yellow; residue with a medium value will appear somewhat orange. So my question will be: is there a way to specify the colour of a residue by its RGB value? And how does the command look like (as I will be scripting to do it in large scale)? Thanks! =] Cheers, Sumitro Institute for Infocomm Research disclaimer: "This email is confidential and may be privileged. If you are not the intended recipient, please delete it and notify us immediately. Please do not copy or use it for any purpose, or disclose its contents to any other person. Thank you."

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thousands of black rectangles?
by Brandt, Gabriel S. 06 Oct '10

06 Oct '10

Colleagues - Yesterday, I seem to have acquired a case of the Chimera measles. My proteins are being rendered with spots all over them. When I select any atom, all the spots are selected as well. I initially thought it was a problem with that particular PDB file, but formerly fine files all seem to have this problem. The issue seems like it arose spontaneously - I haven't recently updated any software that I'm aware of. I was running 1.2470 under X Windows (Mac OS 10.4.11). I downloaded a new version (1.4.1, Aqua) but the problem persists. Am I being foolish here? Is it simply a setting that I can change? G Malaria Research Institute Johns Hopkins School of Public Health 615 N. Wolfe St. W8704 Baltimore, MD 21205

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Re: [Chimera-users] [chimera-dev] some questions
by Elaine Meng 04 Oct '10

04 Oct '10

On Oct 4, 2010, at 7:44 AM, Gentile, Maria Antonietta wrote: > Hi, > I would have some information about CHIMERA. Is it possible to obtain the topology of a protein structure by using CHIMERA? How? And the second question is about the secondary structure representation of a protein, in my case wiht CHIMERA I am not able to visualize all secondary structure elements, how can I modify the settings for this problem? > Thank you > Hi Maria, I don't understand what you are asking, but I will try to answer. If by topology you mean give you some classification of what fold the protein has, no, Chimera does not do that. You might try using the "Dali server" or "Cathedral server" (google those) or something similar to compare your structure to a set of other proteins and report back which ones are the most similar. For the secondary structure, Chimera just uses the information in the input PDB file on which parts are the alpha-helices and beta-strands, and these are shown in the ribbon representation. If your structure doesn't have HELIX/SHEET information in the input PDB file, Chimera will run the "ksdssp" program to try to identify them. If you are not seeing helix and strand where you expect helix and strand, it might be that they HELIX/SHEET information in the PDB file is that way, or that the geometry is irregular/distorted so that "ksdssp" does not identify what you expect. EIther way, you could either (A) try re-running the secondary structure identification with different parameters (see the "compute SS" function in the Model Panel, which is itself in the Favorites menu, or the command "ksdssp") <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/modelpanel.html#functions> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/ksdssp.html> (B) just manually change secondary structure assignments. Several ways are described in this previous post: <http://plato.cgl.ucsf.edu/pipermail/chimera-users/2007-April/001514.html> Elaine P.S. for Chimera questions the better address is chimera-users(a)cgl.ucsf.edu (chimera-dev is for chimera-related python programming questions). ---------- Elaine C. Meng, Ph.D. UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco

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Minimization and dielectric choices
by r charbel maroun 04 Oct '10

04 Oct '10

Hi Conrad, Thanks for your answer. Don't worry, you needn't make a disclaim though. In my opinion, it's not a question of knowing which non-default option is more suitable for use in Chimera, but rather giving the user the choice to use the options that suit him, such as letting him choose the value of the dielectric constant, instead of forcing the value of 1, which would make minimization results useless, i.e. non realistic. It's not either a question of a full-blown MM/MD interface in Chimera, but I feel that the any decent program that does energy minimization should give the user access to steepest-descent *and* conjugate-gradient (CG) methods. Why? Because the 2nd is usually used after the 1st, given that the 1st, as the manual says, is very inefficient if the goal is to find a local minimum of the potential energy. And our purpose is to find energy minima and the conformations that are associated with. To the best of my knowledge, there is no server or free academic program doing energy minimization with these options. Introduction of the choice of dielectric constant and of CG would thus make Chimera rather complete and unique in this sense leading to an increased usage by the community of biocomputational people. Given that MMTK contains CG, what would it take to include the algorithm in Chimera ? Cheers, CM On Wed, Sep 29, 2010 at 8:54 PM, Conrad Huang <conrad(a)cgl.ucsf.edu> wrote: > Before I provide any answers, I have a disclaimer. I only have a > rudimentary familiarity with energy minimization and molecular dynamics. I > understand what force fields are and some of the algorithms used for > minimization and integration, but not much about the details of force field > options. My experience with MMTK is mainly playing with example scripts for > the excellent documentation. So, with that in mind, here are some answers > to your questions. > > The code in MMTKinter uses the Amber 99 forcefield with all default > arguments. THere is an "es_options" parameter that let's you control > electrostatic options, but I'll be the first one to admit that I do not know > which non-default option is more suitable for use in Chimera. The MMTK > documentation ( > http://dirac.cnrs-orleans.fr/Manuals/MMTK_reference/MMTK.ForceFields.Amber.…) > does not explicitly mention dielectric value or functional form for any of > the options. The code that creates the MMTK forcefield instance is in the > MMTKinter_makeUniverse method. (The MMTKinter class is actually designed so > that programmers can pass force field parameters through to MMTK, but > Chimera does not use this capability.) > > As for why only SteepestDescentMinimizer was used, it was mainly for > simplicity. The minimization options that Chimera provides is not very > extensive. Our intent is to provide a tool for simple clean up of small > (regions of) systems. That's why we chose to use default MMTK parameters, > infinite (non-periodic) universe, steepest descent minimizer, etc. The > scope of providing a full-blown MM/MD interface in Chimera is too large for > us to undertake. There are just too many degrees of freedom and we > currently do not have enough resources to do a proper job of it. > > If you are familiar with programming MMTK, there is another way of using > MMTK with Chimera. > http://plato.cgl.ucsf.edu/trac/chimera/wiki/Scripts/MMTK describes an > approach where you can program mostly in MMTK, but display results in > Chimera. Obviously, this is mainly for programmers, but it does let you get > to the full power of MMTK along with visualization from Chimera. > > Conrad > > > On 9/29/2010 8:55 AM, r charbel maroun wrote: > >> Hi everybody, >> >> The value of the dielectric constant used by Chimera is 1, corresponding >> to calculations in vacuo. Is there not an easy way to change this value >> to, say 78 or to include a sigmoid function or the Generalized Born >> approach so as to mime the presence of the solvent ? I looked for it but >> couldn't find it : where in the >> {chimera_install_location}/share/MMMD/MMTKinter.py file can the value of >> the dielectric be changed ? Otherwise, how to mime implicitly the solvent >> ? >> >> Also, it seems that only the Steepest descent, and not the Conjugate >> gradients method, for energy minimization has been implemented in >> Chimera. Why is this so? >> >> It'd be so nice to have these two functionalities added as I don't know >> of any free academic program allowing us to do energy minimization with >> these options without having to parametrize every new ligand (Charmm, >> Namd), a painful task. >> >> Cheers, >> >> Charbel >> >> >> >> _______________________________________________ >> Chimera-users mailing list >> Chimera-users(a)cgl.ucsf.edu >> http://plato.cgl.ucsf.edu/mailman/listinfo/chimera-users >> > -- R. Charbel MAROUN, PhD, HDR Neurobiologie et Pharmacologie Moléculaire Centre de Psychiatrie et de Neurosciences Broca-Sainte Anne (INSERM U894) 2ter rue d'Alésia 75014 Paris FRANCE Tél. +33 1 40 78 92 77 Fax +33 1 45 80 72 93 e-mail rmaroun(a)gmail.com charbel.maroun(a)inserm.fr

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pseudo bonds in mol2 files
by Francesco Pietra 01 Oct '10

01 Oct '10

I am confused about the meaning of pseudobonds for the aromatic portion of mol2 files. Typical example sustiva.mol2 in the antechamber-sustiva tutorial b4 of amber. I have the same representation for aromatic bonds in modified amino acids. In contrast, normal bonds from pdb files of the same molecules. Thanks for clarifying. francesco pietra

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Chimera-users October 2010