- Chimera-users - RBVI Mailing Lists

Using mol2 files
by Pasquale Iacono 03 Jul '07

03 Jul '07

Hi I imported a .mol2 file from Gaussian to Chimera because I want to run an amber minimization with a better parameter set. However, the mol2 files are not like pdb files and do not come with atom types for amber calculations. Is there anyway to (auto?)assign amber atom types to the atoms in my file so your program can run a calculation? Thank you. -Pasquale Iacono, B.S. Ithaca.College

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POVray shininess
by Tom Goddard 03 Jul '07

03 Jul '07

Edward Egelman wrote: > Hi, > The new POV rendering is very nice, but suffers from one problem > that I do not see how to fix. Is there any way to control the surface > properties (reflectivity, "shininess", etc.)? I only see the standard > brightness and transparency for the "save as" feature. > Regards, > Ed Hi Ed, You can control the shininess of surfaces in Chimera using menu entry Tools / Viewing Controls / Shininess. The shininess you set is exported to POVray when you save a raytraced image. The POVray appearance doesn't exactly match the Chimera graphics window appearance so you may need some trial-and-error experimentation to get the desired shininess in the POVray output. Tom

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seg faults
by Tom Goddard 03 Jul '07

03 Jul '07

Edward Egelman wrote: > Hi, > I have a question about very complicated chimera sessions (20 or so > large PDB files, 10 or so large brix volumes). We will sometimes get a > segmentation fault and the session will close. This is on a 32-bit > linux machine with 2GB memory (our only system with stereo display). > If we move to a 64-bit machine with more memory, will we be less > likely to crash? Or is this due to some internal memory limitations in > chimera itself? A second question is whether you have any experience > (or know of others who have) using fast nvidia stereo boards (such as > the Quadro FX3500) to accelerate display operations in chimera. > Regards, > Ed > -- Hi Ed, There are only two Chimera crash situations that I understand and are frequently reported. Computing molecular surfaces of PDB models (menu entry Actions / Surface / show) crashes for many large PDB models. If the surface calculation gives an error but does not crash it has usually corrupted memory and Chimera will crash later. The solvent excluded surface code comes from Michel Sanner and is very complex (~20000 lines of C code). We have been working on a replacement for it for over a year but it is not yet ready. The second type of crash is caused by graphics driver bugs. These are common, more so on higher-end graphics cards where Chimera takes advantage of OpenGL features that are used by few applications, also more common on laptops. Here are some of the graphics driver problems observed in Chimera. http://www.cgl.ucsf.edu/chimera/graphics/graphicsbugs.html#cards I have never had Chimera crash when I am working with large PDB models and maps (using Mac systems with 1-2 Gb memory), but that is probably because I only work with a few models and maps at a time, and for short sessions. It could be that memory allocation failures cause crashes in these situations. I am doubtful that using the 64-bit Linux Chimera will help. Using the 32-bit Linux Chimera on a 64-bit machine almost certainly will not help because the 32-bit address space can only access 4 Gb of memory and segments of that address space are already used by shared libraries and program stack -- so you probably only have 2 Gb of usable space. With 2 Gbytes of physical memory you probably have at least 4 Gb of virtual memory, so the 32-bit address space is the main limitation. Chimera catches memory allocation failures for large allocations (e.g. opening a new map) and those do not cause a crash. It is only when a small allocation that is not checked fails that a crash might happen. The difference in speed rendering surfaces between say a Quadro FX 3400 and an ATI Radeon Pro 9800 (in my 3 year old desktop computer) is about a factor of 4. That is about the speed up to expect between a card that is a couple years old and the latest graphics card. Benchmark scores using Chimera for different cards are on the web http://www.cgl.ucsf.edu/chimera/benchmarks.html although there are few numbers for the latest cards. For volume surfaces look at the Surface column of the table. The score is the grid size of a triangulated cube that can be rendered at 10 frames per second. Since the number of triangles increases as the square of the size you should look at the *square* of the ratio of scores between cards to gauge the increase in speed expected for a fixed size volume. Tom

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Fixing MSMS crash
by Thomas Goddard 02 Jul '07

02 Jul '07

P. Qian sent me a PDB model that caused Chimera to crash when calculating an MSMS surface (menu Actions / Surface / show). He got it not to crash by shifting the coordinates of all atoms (by moving and saving the PDB with "use untransformed coordinates" turned off, and reloading that file). This is a little nicer than changing atom radii as we've advised in the past. Not sure how often a simple shift (or rotation) avoids the crash though. Tom

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Origin question with maps
by Eduardo Sanz-Garcia 29 Jun '07

29 Jun '07

I found that the origin of /mrc/ maps is read correctly and can be used to place one map in respect of another. For example: 1.mrc (origin: 10,0,0) is going to be shifted 10 pixels with respect of map 0.mrc (origin: 0,0,0). I can not reproduce the same behavior with CCP4 format (.map) . The origin is not read correctly. Thank you.

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conjoined unit cells
by Bartosz Siemiński 29 Jun '07

29 Jun '07

Hi all, I was working with Chimera for some time, beeing convinced I don't need no help, until I'd got to this. Is there a possibility of conjoining several (let's say four, nine or sixteen) unit cells? I use the el. density map (converted to cpp4, so it could be loaded by Chimera) for structural alignment and such an operation would be very usefull. Thanks in advance, Bartek ____________________________________________________________________________ Czy już jesteś w Yahoo!? Masz dosyć spamu? Poczta Yahoo! dysponuje najlepszą ochroną przed spamem http://pl.mail.yahoo.com

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mrc maps
by Gorelik, Tatiana 29 Jun '07

29 Jun '07

Hi, I image an .mrc map in Chimera. The surface map is displayed using a selected range. As a result I see blobs. I want to be able to select such a blob and get back its 3d information - coordinates, etc... Would it be possible to implement this feature? Greetings, Tatiana ************************************ Tatiana Gorelik, PhD, Institut für Physikalische Chemie Johannes Gutenberg-Universität Mainz Welderweg 11 55099 Mainz Germany Tel.: 0049 6131 39 22347 Fax: 0049 6131 39 23768 e-mail:gorelik@uni-mainz.de ************************************

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Reading a data set from a text file
by Kyaw Zeyar Myint 29 Jun '07

29 Jun '07

Hi, I am Kyaw Myint, a summer intern at NIAMS branch of NIH. I am working under the supervision of Dr. Bernard Heymann from the Lab of Structural Biology research. The project I am working on currently is to improve the 3D reconstruction of viruses' structures from 2D electron micrographs. The programs I am using include Chimera and Bsoft. For the project, I want to read in a data set from a text file and display the 3D surfaces based on that data set. I'd like to use Chimera for that purpose and I'd really appreciate any suggestion or comment on how I should do that. Thank you very much for your help in advance. Looking forward to hearing from you soon, Kyaw

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rotating items in chimera
by William Jeffrey Triffo 29 Jun '07

29 Jun '07

hello, is there a way to return to a rotational position, without using 'savepos' and 'reset'? For instance, if I don't want to reset translation(s) (which using savepos/reset might do), but just want to return to a 'top down' view, or a specific rotation with respect to the viewer's global axes? I realize that with multiple objects in potentially different rotational orientations, this would require which object to use to calculate the rotation. thanks, -Jeff

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Transformation matrices
by Eduardo Sanz-Garcia 29 Jun '07

29 Jun '07

I am getting the rotation matrices (I am not interested in the translation column) using matrixget command. My naive question: Should I use in this way: x' x y' = [3x3 matrix] y z' z or in this other way? z' z y' = [3x3 matrix'] y x' x Thank you very much.

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