- Chimera-users - RBVI Mailing Lists

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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multiple frames 1topology
by Francesco Oteri 30 Sep '10

30 Sep '10

Dear AMBER users, I've one file with the AMBER topology of my system, but I saved some rappresentative structures as pdb. Since my system is made of a set of circular DNA, I'd manipulate pdb to obtain the correct connectivity. There is a way to load a correct pdb ( or topology file) and exporting this connectivity on the other pdb? For example, should be useful if I load at the beginning the correct pdb and than I'will load the remaining structure whit the same number of atoms of the first but without CONECT and/or TER tag.

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Finding the angle between two aromatic rings
by Miriam Gochin 30 Sep '10

30 Sep '10

Chimera has an Axes / Planes function where you can define the plane through three atoms. If you define two planes, is there a way to get the angle between the planes? Thanks! Miriam Gochin Touro University - CA miriam.gochin(a)tu.edu 707-638-5463

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ribbon problem
by Francesco Oteri 30 Sep '10

30 Sep '10

Dear all, I'd like to use chimera to do a picture of a circular DNA with ribbon representation. I found the two following problems: 1.If I load the .pdb files, chimera is unable to recognize the topology and shows extra-bond connecting the last base of a strand with the previous of the other strand. 2.If I load the AMBER topology, the connectivity is correctly recognized, but the first base and last are not connected by the ribbon. Is there any solution?

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how to set the transparency of ribbon
by Qinghua Liao 29 Sep '10

29 Sep '10

Dear chimera's users, Could someone tell me how to set the transparency of ribbon of a protein? Thanks very much All the best, Qinghua

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Dielectric ; Steepest descent
by r charbel maroun 29 Sep '10

29 Sep '10

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

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Re: [Chimera-users] Chimera-users Digest, Vol 89, Issue 30
by vamsi krishna 29 Sep '10

29 Sep '10

Hi all, I am very happy to see modeller interface in chimera latest version.Please help me any one how to use (steps) it for modeling. Thank you Best wishes, vamsi On 29/9/2010 3:00 AM, chimera-users-request(a)cgl.ucsf.edu wrote: > Send Chimera-users mailing list submissions to > chimera-users(a)cgl.ucsf.edu > > To subscribe or unsubscribe via the World Wide Web, visit > http://plato.cgl.ucsf.edu/mailman/listinfo/chimera-users > or, via email, send a message with subject or body 'help' to > chimera-users-request(a)cgl.ucsf.edu > > You can reach the person managing the list at > chimera-users-owner(a)cgl.ucsf.edu > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Chimera-users digest..." > > > Today's Topics: > > 1. Re: download of chimera 1.5 (Elaine Meng) > 2. Fwd: Stereo 3D for teaching (Nadir T. Mrabet) > 3. Re: Remove hydrogen (Elaine Meng) > 4. Re: select side chain (Elaine Meng) > 5. Re: Fwd: Stereo 3D for teaching (Elaine Meng) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 28 Sep 2010 09:22:16 -0700 > From: Elaine Meng<meng(a)cgl.ucsf.edu> > Subject: Re: [Chimera-users] download of chimera 1.5 > To: atila petrosian<atila.petrosian(a)gmail.com> > Cc: chimera-users(a)cgl.ucsf.edu > Message-ID:<6FB84799-504C-4FA9-8CFE-4CA7A0E2BB33(a)cgl.ucsf.edu> > Content-Type: text/plain; charset=us-ascii > > Chimera 1.5 daily build downloads are included in the download page. You have to scroll down to the "Daily Builds" section, or click the "Daily Builds" link at the top to go directly to that section (or just click here): > > <http://www.cgl.ucsf.edu/chimera/download.html#daily> > > "alpha" is whatever is not yet an official release, so yes, right now the "alpha" downloads are version 1.5. > Elaine > > > ------------------------------ > > Message: 2 > Date: Tue, 28 Sep 2010 18:30:34 +0200 > From: "Nadir T. Mrabet"<Nadir.Mrabet(a)medecine.uhp-nancy.fr> > Subject: [Chimera-users] Fwd: Stereo 3D for teaching > To: "chimera-users(a)cgl.ucsf.edu BB"<chimera-users(a)cgl.ucsf.edu> > Message-ID:<4CA2182A.3020902(a)medecine.uhp-nancy.fr> > Content-Type: text/plain; charset="iso-8859-1" > > Hi Elaine, > > Could you please react to my last week's mail, forwarded (again) below? > Thanks, > > Nadir Mrabet > > > -------- Original Message -------- > Subject: [Chimera-users] Stereo 3D for teaching > Date: Fri, 24 Sep 2010 17:23:35 +0200 > From: Nadir T. Mrabet<Nadir.Mrabet(a)medecine.uhp-nancy.fr> > Reply-To: Nadir.Mrabet(a)medecine.uhp-nancy.fr > Organization: Nancy University, School of Medicine > To: chimera-users(a)cgl.ucsf.edu BB<chimera-users(a)cgl.ucsf.edu> > > > > Hi, > > I had addressed previously the question about which equipments would > perform best to display molecular structures in 3D for teaching purposes. > Greg Couch had offered to keep me up on the latest technologies offered > at the last SIGGRAPH conference. > But nothing so far. > Can anyone help me with that? > > Many thanks in advance. > > Nadir >

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clustering of docking results
by Bala subramanian 29 Sep '10

29 Sep '10

Friends, I am using viewdock tool for analysing the docking result obtained from autodock. Is there any way to do some clustering of the docked conformations using the energetically best structure as the reference within chimera ? Thanks in advance, Bala

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