March 2009 - Chimera-users - RBVI Mailing Lists

Re: [Chimera-users] accessible surface area for electron density maps
by Elaine Meng 27 Mar '09

27 Mar '09

Hi David, As soon as you show a molecular surface, both the total solvent- excluded (molecular surface by Richards definition) and solvent- accessible areas are reported in the Reply Log. It has been like that since before the July 2008 release. The surface that is actually displayed is the solvent-excluded surface. You can adjust parameters that affect the results such as probe radius and atomic radii, but the defaults are reasonable. The area values are also assigned as per-atom and per-residue attributes named areaSES and areaSAS, so you can use Attribute Calculator to get sums over subparts of the surface. For details, see this page and links therein: <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/ representation.html#surfaces> I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng(a)cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html On Mar 27, 2009, at 8:58 AM, David Chenoweth wrote: > Hi Elaine and Murali, > > I have a similar problem that I've been trying to resolve. > Calculating the accessible surface or solvent accessible surface is > also something I've been interested in doing with Chimera but I > don't think the area of the molecular surface is the same as the > solvent accessible surface area. I believe that accessible surface > comes from the locus of the center of a spherical probe as it rolls > over the Van der Waals surface of a molecule. The molecular surface > uses the locus of the inward facing spherical probe. They both > depend on the spherical probe size which is set to the appropriate > solvent molecule. Can you tell me which of these two methods > Chimera is using when it calculates the area (if either)? Is there > a way to calculate the solvent accessible surface area of a > molecule with Chimera or some way to manipulate the current area > calculator to give this value? I also think that depending on the > quality of the electron density map one could get very different > results for this calculation (especially if there is missing > electron density or at different map contour values). If anyone has > any advice for the best way to calculate solvent accessible surface > area I would really appreciate the help. > > Thanks, > Dave Chenoweth

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Re: [Chimera-users] accessible surface area for electron density maps
by Elaine Meng 27 Mar '09

27 Mar '09

Hi Murali, As far as I know, there is no definition of accessible surface area for an electron density map (and thus no way to calculate it in Chimera), only for atomic structures. I'll describe how to get it for atomic structures in my next message, replying to David. Best, Elaine ----- Elaine C. Meng, Ph.D. meng(a)cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html On Mar 27, 2009, at 8:18 AM, Murali Ayaluru wrote: > Hi Elaine, > > Thanks for the quick reply. I am aware of calculating the total > surface area of the density maps using Chimera and has been using > it for a long time. Now I am interested in the surface area that a > solvent can access (in otherwords called - (solvent) accessible > surface area). This is a part of the total surface area. Please > mail me if this tool is available in Chimera. > > Regards, > Murali

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accessible surface area for electron density maps
by Murali Ayaluru 27 Mar '09

27 Mar '09

Dear Chimera users, I want to calculate the accessible surface area for an electron density map (mrc format) that I am working on. Can anyone, who knows how to do this, tell me how to do this? Thanks in advance for your reply, Regards, Murali

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Bonds vs. Pseudobonds
by Dipl.-Ing. Thomas Mitterfellner 24 Mar '09

24 Mar '09

Hello again! I have a structure containing Germanium bonded to three oxygens and one methyl group. By default, all of the bonds between Germanium and its valences are considered as pseudobonds and hence drawn as such. In the manual, I read that Chimera uses an algorithm that considers atoms classically bonded if the distance is below the sum of their VDW radii (plus a margin of 0.4 A). However, no matter what I set the radius of the Ge atom to (setattr a radius xy Ge), I can't get Chimera to display a regular bond between Ge and its valences. Can you give me a hint how to set a rule when a normal bond is drawn, or how I can draw one manually? Thank you very much, Thomas

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Using per-frame scripts with color by attribute/bfactor
by Andrew M. Simms 24 Mar '09

24 Mar '09

I am making some MD movies using the multiple-pdb file format. I am using coloring by attribute, in this case overriding the "bfactor" attribute for my own purposes. The nature of my analysis is such that the bfactor can change from frame to frame. I use this command in the per-frame script: rangecolor bfactor,a min white max green However, when I try to make a movie, it appears that the bfactor attribute changes are not reflected in the animation. If I look at generated structures individually they are fine. Is there something special I need to specify in per-frame script? Thanks! --Andrew

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Split colors from Volume Viewer
by Damien Larivière 23 Mar '09

23 Mar '09

Dear Chimera team and users, When opening a map (EMD 1126 for example), the structure is displayed in grey. From the menu Volume and Surface colors, it is then possible to color the structure. I would like to export in the OBJ format the colored structure but this one still appears in grey when I display it in a modeler such as 3DSMax. And effectively, the MTL file created by the exporter only contains one color although the structure displayed in Chimera was multicolored. I look at a tutorial explaining that it is possible to Split map from the menu Volume/color zone. It seemed to me that it is a way to get a multicolored structure in the OBJ format. However, when I want to "split map", a message says "no atom selected". May you tell me how to get a multicolored structure (initially opened from a map) in the .obj format ? All the best Damien

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amd64 installation
by Francesco Pietra 23 Mar '09

23 Mar '09

To deal with very large data files i tried to install chimera-1.3.2577-linux_x86_64.exe in /usr/local/chimera. Mainboard Tyan S2895 dual-opterons; OS Debian amd64 lenny; nvidia chipset 6600, nvidia-glx driver To simplify i made the chimera directory to belong to me as user. The installation from my home succeeded, though chimera did not launch. It appears in part for a moment as if there were no opengl support: francesco@tya64:/usr/local/chimera/bin$ ./chimera X Error of failed request: BadWindow (invalid Window parameter) Major opcode of failed request: 3 (X_GetWindowAttributes) Resource id in failed request: 0xffffffff Serial number of failed request: 626 Current serial number in output stream: 627 I installed libmotif3. Same issue. Once the problem of running chimera is solved, I plan a reinstall in /usr/local/chimera root root. Should I run the installation from my home as superuser? thanks francesco pietra (I run successfully the 32 bit version of chimera on an old Athlon with libmotif3 support)

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addna?
by julien(GWDG) 23 Mar '09

23 Mar '09

Dear all, I would like to know if there is a way in chimera to add nucleic acid to an existing RNA. Something like addna instead of addaa. many thanks Julien -- European Molecular Biology Laboratory Structural and Computational Biology Unit Meyerhofstraße 1 D-69117 Heidelberg Max-Planck-Institute for Biophysical Chemistry NMR based Structural Biology Am Fassberg 11 D-37077 Göttingen

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Re: [Chimera-users] UCSF Chimera
by Elaine Meng 22 Mar '09

22 Mar '09

On Mar 22, 2009, at 8:36 AM, Tarit Mitra wrote: > Dear Dr. Meng, > I am trying to learn to use the Windows version of Chimera. I would > like to contact a Chimera user in UK. Is it possible to do so? Can > you please help? > With kind regards > Yours sincerely > Tarit Dear Tarit, You could try the e-mail list chimera-users(a)cgl.ucsf.edu (actually I cc'ed it on this message). However, you don't need a live person to help you learn how to use the program. The Chimera download includes several tutorials, some for beginners: choose "Help... Tutorials" from the Chimera menu to see the list. Our Web site has additional tutorials (not just the ones in the Help menu): <http://www.cgl.ucsf.edu/Outreach/Tutorials/GettingStarted.html> <http://www.cgl.ucsf.edu/chimera/tutorials/tutorials.html> Besides the tutorials, there is a complete user's manual (choose Help... User's Guide from the Chimera menu). Just start Chimera and try one of the beginner tutorials, or just experiment, and you will gradually learn! Best, Elaine

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Changing properties by command line
by Dipl.-Ing. Thomas Mitterfellner 19 Mar '09

19 Mar '09

Hello again! I could not find out how to change radii of selected atom via the command line. I had hoped this would work via '@/radius=', which I read in the quick reference, but I turns out that I obviously misunderstood the usage of the hints given there. Is it also possible to change the color and linestyle of coordinative bonds in the command line? Related to this: can the status and color of the molecule silhouette be changed from the command line? Thank you very much! P.S.: Chimera really produces great pictures and I especially like the silhouette effect, which I, up to now, always had to (partially) draw myself with some image editor.

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Chimera-users March 2009