- Chimera-users - RBVI Mailing Lists

Benchmark results
by Daniil Zaitsev 19 Dec '06

19 Dec '06

hi - here is benchmark result for new version of Chimera. Original benchmark progress log file is attached. Graphics NVidia GeForce Go 7200 Processor Intel Core Duo T2050 Clock (MHz) 533 OS Type Windows Surface 990 Mesh 368 Contour 148 Solid 173 Recolor 87 Notes Laptop Test Date 12/06 Chimera Version 2304 Machine HP Pavilion dv2000t Graphics Memory (Mb) 128 Main Memory (Mb) 1024 OS Version XP Home Driver Version 8.4.6.4

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compressed versus gzipped Re: Read compressed PDB files -question, suggestion
by Moo Cow 12 Dec '06

12 Dec '06

A thousand pardons. You are right. I phrased the question wrongly. Chimera does open gzip'd files ( xx.gz). It does not open compress'd files (xx.Z). > You can also open gzipped files with Chimera's "open" command or as > an argument as you start Chimera. [...] > > You can use the Chimera File / Open... dialog to directly open a gzip > > PDB file. This was added to Chimera about one year ago. It does not work Why, you may ask, would anyone use compress these days ? If you mirror or rsync the protein data bank, they are still distributing files that have been squashed with compress and have a ".Z" extension. gunzip will happily eat and uncompress these files. I do not know how chimera handles compressed files. If it reads from a pipe, it might be nice to persuade it to feed .Z files to gunzip. I think it might be more difficult if chimera uses the python/zlib interface. Many thanks -- Search for products and services at: http://search.mail.com

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SDF format
by Randy Heiland 12 Dec '06

12 Dec '06

Just wanted to ask about Chimera's support for reading in SDF formatted files, e.g. from PubChem. It seems not to be one of the supported formats. Obviously we can use a converter to get pdb format, but thought I'd ask the experts. Thanks, Randy

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Transparent Ribbon
by Anna Feldman-Salit 12 Dec '06

12 Dec '06

Dear All, From some reason I cannot find the option of making ribbon representation transparent. Can you please give me a hint? Thanks a lot in advance, Anna

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saving with angles
by Gabor Papai 12 Dec '06

12 Dec '06

Dear everybody, Is there a way in Chimera to save density maps when I rotate them with the modified angles? In practice, I use the 'fit map in map' to align two maps in respect to each other and I would like to save them for further analysis with different softwares. Therefore I would like to conserve their position (shift and rotation). Thanks in advance, Gabor -- Gabor Papai IGBMC Department of Structural Biology and Genomics 1, rue Laurent Fries, BP 10142 67404 Illkirch, France phone +33-3-90244796 Fax +33-3-88653201 E-mail: papai(a)igbmc.u-strasbg.fr

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Delphi Controller
by sette＠uniroma2.it 11 Dec '06

11 Dec '06

Dear all, I have a simple question: does Delphi controller works under unix only or it is possible to work with it under Linux and/or Windows XP? Thanks a lot, Marco Dr.Marco Sette, Ph.D. Department of Chemical Sciences and Technology University of Rome, "Tor Vergata" via della Ricerca Scientifica, 00133, Rome, Italy e-mail: sette(a)uniroma2.it Tel.: +39-0672594424 Fax: +39-0672594328

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Read compressed PDB files -question, suggestion
by Moo Cow 08 Dec '06

08 Dec '06

We store the PDB locally, but compressed. Can one persuade chimera to read coordinates from a pipe ? Maybe this could be done at the python level. It might also not be too hard to use the python binding to the zlib library, but I would not know how to do this. I imagine the interest (or not) would not be limited to reading PDB files. many thanks for any suggestions. -- Search for products and services at: http://search.mail.com

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Apply the symmetry to the fitted models in map
by Hong-Wei Wang 06 Dec '06

06 Dec '06

Hi, Tom I remember you were showing docking a model into map with high symmetry (you showed the actomyosin filament example). I am wondering how you generate the symmetry in the docking and if the symmetry information is necessary for the correct fitting. Thanks a lot! Hongwei ----------------------------------- Hongwei Wang, Ph D MS 20A-355, LSD, LBNL 1 Cyclotron Rd, Berkeley, CA 94720 510-642-2222 (O) 510-642-8806 (FAX) hwwang(a)lbl.gov

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volume viewer issue
by Matthew Shawkey 06 Dec '06

06 Dec '06

Hi, I am using chimera to visualize a stack of EM serial sections. I can load them into Chimera (as MRC file), but when I try to view the stack in the volume viewer w the "solids" option all I see is a white square.. w the mesh and surface options the stack shows up as a grainy image on which it's difficult to see any depth.. any suggestions? THanks, Matt

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Uploading several trajectories for MDmovie
by Anna Feldman-Salit 04 Dec '06

04 Dec '06

Dear all, I would like to know if there is any possibility to sequentially upload several trajectories with MDmovie option (or command line) and then to visualize them with "no stop" in between. These trajectories were generated by AMBER with "restart" input files. Such an option happens to be in VMD, but it's more convenient for me to work with Chimera (I have Chimera1.2304). Thanks a lot in advance, Anna

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Fit models to map
by hsosa＠aecom.yu.edu 04 Dec '06

04 Dec '06

I wonder how the "Fit models to map" function do the fitting. Does it find the best cross-correlation value between a 3D density calculated from the atomic model and the 3D density map?. What is the maximum displacements and rotations tested around the current position? What is the step size of the rotations/displacements? Thanks Regards Hernando -- ----------------------------------- Hernando Sosa Dept. of Physiology and Biophysics Albert Einstein College of Medicine 1300 Morris Park Av. Bronx NY 10461 phone (718) 430-3456 FAX (718) 430-8819 email hsosa(a)aecom.yu.edu -----------------------------------

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Re: [Chimera-users] inter-surface calculations in Chimera
by Elaine Meng 01 Dec '06

01 Dec '06

Hi Gali, Eric forwarded your question to me. The Intersurf tool generates a surface between the interacting molecules that is different from the surface of either molecule - it is mainly useful for viewing an interface and showing its properties (for example, with coloring by hydrophobicity or electrostatic potential), but not for measuring the surface area. It is possible to measure volume and surface area in Chimera, but currently it is a long process. We hope to have a simpler process available in the future. I'll describe two different approaches. (1) the simpler and more approximate way to calculate buried surface area and void volume in the complex: approx buried surface area = [(surface area of X) + (surface area of Y) - (surface area of XY)] / 2 approx interface void volume = (volume of XY) - (volume of X) - (volume of Y) The "Measure Volume and Area" tool can be used to calculate the surface areas and volumes. [ http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/measurevol/ measurevol.html ] The trick is to first make a surface that encloses both X and Y and measure its values. Then, make surfaces that separately enclose X and Y and measure again. Here is a concrete example. PDB structure 1cf7 has two protein chains A and B, two DNA chains C and D, and some water. I'd open the structure and delete everything but the protein and DNA. command: open 1cf7 command: select :.a-d command: sel invert command: delete sel command: surfcat complex :.a-d command: surf complex Tools... Surface/Binding Analysis... Measure Volume and Area (measure values for the complex) command: surfcat protein :.a-b command: surf protein (choose the protein surface in Measure Volume and Area, compute again) command: surfcat dna :.c-d command: surf dna (choose the dna surface in Measure Volume and Area, compute again) Finally, use the equations above. All the results can be viewed in the Reply Log (under Favorites). These values are for molecular surfaces (also known as solvent-excluded, where the probe touches), not solvent-accessible (traced by the probe center). For this structure, I calculate approx 530 square angstroms surface area buried, approx 730 cubic angstroms of interface void volume. (2) A more detailed approach can yield different values for the areas buried on X and Y: (surface area of X buried in the XY interface) = (surface area from all atoms of X in surface enclosing XY) - (surface area from all atoms of X in surface enclosing just X) with a similar equation for Y. Currently, the only way to get atomic rather than total surface areas in Chimera is by using the "Area/Volume from Web" tool [ http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/surfvol/ surfvol.html ] which uses a Web server at NCBI and loads the atomic values into Chimera. Because the MSMS option of the server has problems with nucleic acids, the only choice for your complexes is to calculate solvent-accessible surface areas (not the solvent-excluded surface areas calculated by method (1) above). The main trick is to first send only XY to the server (making sure solvent, ions, etc. are NOT included). Then using Attribute Calculator, [ http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/calculator/ calculator.html ] sum the values for the atoms of X in that combined surface, and likewise get a total for Y. Then, delete everything except X and send it to the server again, getting the total for X alone. Close/reopen the structure, delete everything except Y, and send it to the server to get the total for Y alone. Subtract the value for X (Y) in the complex from the total for X (Y) alone. Here is a concrete example. PDB structure 1cf7 has two protein chains A and B, two DNA chains C and D, and some water. I'd open the structure and delete everything but the protein and DNA. command: open 1cf7 command: select :.a-d command: sel invert command: delete sel Tools... Surface/Binding Analysis... Area/Volume from Web - calculate "Accessible Surface (Gerstein)" for the "Molecule" which now consists of only the protein and DNA command: select :.a-b Tools... Structure Analysis... Attribute Calculator calculate an attribute (name doesn't matter) for "models" with the Formula: sum(atom.accessibleSurface) with the option "Restrict formula domain to current selection" write down the total for A-B (which is the PROTEIN IN THE COMPLEX) (I get approx 7473) command: select :.c-d calculate an attribute (name doesn't matter) for "models" with the Formula: sum(atom.accessibleSurface) with the option "Restrict formula domain to current selection" write down the total for C-D (which is the DNA IN THE COMPLEX) (I get approx 4502) command: delete :.c-d now only the protein is left Tools... Surface/Binding Analysis... Area/Volume from Web - calculate "Accessible Surface (Gerstein)" for the "Molecule" which now consists of only the protein - get the total for PROTEIN ALONE (Favorites... Reply Log) (I get approx 8842) command: close 0 command: open 1cf7 command: select :.c-d command: sel invert command: delete sel now only the DNA is left Tools... Surface/Binding Analysis... Area/Volume from Web - calculate "Accessible Surface (Gerstein)" for the "Molecule" which now consists of only the DNA - get the total for DNA ALONE (Favorites... Reply Log) (I get approx 5758) Use the equation above to get the buried solvent-accessible surface areas. I calculate approx 1369 square angstroms buried for the protein, approx 1256 square angstroms buried for the DNA. You can't compare these solvent-accessible areas to the solvent-excluded areas calculated by method (1) ... the solvent-accessible values are generally much larger. PHEW! I congratulate everyone who got this far. The written explanation makes it seem longer than actually performing the process. I hope this helps, Elaine On Nov 30, 2006, at 7:35 AM, galig wrote: > Dear Eric, > > I have a small question regarding the calculation of inter-surfaces in > Chimera: > I have several protein/DNA complexes, and I would like to compare > their protein/DNA interfaces. I used Tools-->surface/binding > analysis-->compute interface surface and chose the protein and DNA > chains. the result, if I understand it correct, is per atom. Is there > a place to find the overall number representing the contact surface? > is this a different or similar calculation? > One more thing- how do I calculate the void intermolecular volume > between the chains? > > Thank you and sorry to bother you, > > Gali Golan > Dept. of Inorganic Chemistry > The Hebrew U. of Jerusalem > Jerusalem 91904 Israel > Tel. 972-2-6585610 > Fax 972-2-6585319 > ----- Elaine C. Meng, Ph.D. meng(a)cgl.ucsf.edu UCSF Computer Graphics Lab and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html

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Re: [Chimera-users] Chimera on x86_64?
by Thomas Goddard 29 Nov '06

29 Nov '06

Hi Ben, There's no technical obstacle to us making regular 64-bit linux Chimera distributions. The only issue is having time to do it. The work involves compiling the ~30 third party libraries that Chimera uses. I did this is the past and it took about one day of fiddling. Our Chimera build scripts compile all of the third party libraries automatically and my past hand fiddling to build on 64-bit linux would have to be put into our scripts. That could take a 1 to 5 days of work. We have a 64-bit linux machine to do the work on. So it all comes down to when one of the 4 developers (Tom Goddard, Eric Pettersen, Greg Couch, or Conrad Huang) has time to work on that. I don't think I will have time until January at the earliest. Could you give me a better sense of how much need there is in the Sali lab? Are you really saying you would not install 32-bit Linux system libraries except for Chimera? I would think there are a fair number of applications out there with binary distributions only for 32-bit. The other problem you point out is that 32-bit Chimera Python cannot use your own 64-bit Python modules. Are you using additional C Python modules within Chimera that do not come with Chimera? That is interesting -- what are they? Tom > From: Ben Webb <ben(a)salilab.org> > To: Eric Pettersen <pett(a)cgl.ucsf.edu> > Date: Wed, 29 Nov 2006 12:51:27 -0800 > Subject: Chimera on x86_64? > > I wonder if you could give me a rough idea of when you plan to make > regular builds of Chimera on x86_64 (if at all)? All I've been able to > glean from the download page and the mailing list archive is that you > do make occasional builds, but recommend the 32-bit version. > > Memory isn't so much of an issue for us in particular (although we are > increasingly looking at large EM maps) but the requirement to have > 32-bit libraries is starting to become a problem. All of our new > desktops are x86_64 machines, and it's a pain to require the 32-bit > libraries just for Chimera. Additionally, our users want to > mix-and-match Python modules (including Modeller, of course) and > Chimera is unable to import any module which has a C backend, since > they're compiled for x86_64 and the Python interpreter in Chimera is > 32-bit. (Of course, we could recompile all of our other Python modules > for 32-bit, but that would cause problems with x86_64 apps.) > > If you need people to test x86_64 Chimera builds, we certainly have > some demanding users here to break them. ;) > > Ben > -- > ben(a)salilab.org http://salilab.org/~ben/ > "It is a capital mistake to theorize before one has data." > - Sir Arthur Conan Doyle

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Multiple Volume Viewer Windows and saving PDB file
by Batsal Devkota 28 Nov '06

28 Nov '06

Hi, I am just wondering if there is any way that I can have two or more volume viewer windows open at the same time. I am comparing two density maps and to be able to change the threshold and color for both maps, without having to go back and forth in the same window, would be much easier and useful. Also, I recently fitted a pdb crystal structure into a density map but was not able to save it with relation to the density map (the feature which was available in previous releases). However, if I have multiple pdb files open then I can save the pdb file of my interest with respect to the map. Is there anyway to save a fitted pdb file with respect to a density map without opening other pdb files? Thank you, Batsal. -------------------------------------------------- Batsal Devkota Graduate Student, School of Biology GeorgiaInstitute ofTechnology Atlanta, GA 30332-0400

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Stereo on the 1.2304 version
by Anna Feldman-Salit 28 Nov '06

28 Nov '06

Hello, Unfortunately, I'm facing with a problem of stereo option on the version 1.2304. I can see the stereo when I turn the "stereo" option on, but the quality of the picture is not of the best ones. The main picture is likely screened on background, while it's also impossible to focus on the frontal part. I was playing a bit with camera-viewing parameters, but nothing worked for me. Before, working with pymol I used the "swap sides" option, which helped a lot. I tested our stereo glasses with pymol's stereo option again and it works smoothly. Since I definitely prefer to work with chimera, I would appreciate if this problem would be solved somehow. Do you have any suggestions? Thank you in advance! Best, Anna

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Re: [Chimera-users] Increase/decrease the sphere
by Eric Pettersen 28 Nov '06

28 Nov '06

I forgot to mention that if you want to control ball/stick size on a more permanent basis, you can use the New Molecule preferences (Favorites->Preferences) to set them for all new molecules you open. --Eric On Nov 27, 2006, at 9:21 PM, tuhin(a)iitk.ac.in wrote: > Thanks for your helpful suggestion, Eric. > > Regards, > TKP > >> Hi, >> Sphere size is the same as the atom's VDW radius. You can change >> atom radii with the "vdwdefine" command, or by selecting atoms and >> bringing up the Selection Inspector (click on the button at the lower >> right of the Chimera interface) and typing a new value into the >> "radius:" field. >> Ball and stick size are controlled on a per-model basis. Use the >> Model Panel (Favorites->Model Panel) and double-click on line with >> the model you want to control. A dialog listing the attributes of >> that model will come up. The "ball scale:" field controls the size >> of balls. It is a fraction that the VDW radius is multiplied by to >> get the ball size (default: 0.25). The "stick scale:" field controls >> stick size and also a fraction that sticks get multiplied by. The >> default stick radius is 0.2 angstroms and default stick scale is 1.0, >> so the final default radius is 0.2 angstroms. The help page for the >> attribute dialog describes why there are two numbers involved if you >> care, and also describes the other attributes if you're interested. >> >> --Eric >> Eric Pettersen >> UCSF Computer Graphics Lab >> pett(a)cgl.ucsf.edu >> http://www.cgl.ucsf.edu >> >> >> On Nov 27, 2006, at 6:56 AM, tuhin(a)iitk.ac.in wrote: >> >>> Dear Chimera users, >>> >>> Could anybody tell me whether there is a way in chimera to >>> increase/decrease the size of the spheres/ball-and-stick in atom >>> display >>> (Action-->Atoms/Bonds-->sphere...). The wireframe has an option in >>> "wire >>> width", is there something like that for the above two options ?? >>> >>> Waiting for yours suggestions. >>> Thanks in advance. >>> >>> Best, >>> TKP >>> _______________________________________________ >>> Chimera-users mailing list >>> Chimera-users(a)cgl.ucsf.edu >>> http://www.cgl.ucsf.edu/mailman/listinfo/chimera-users >> >> >

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Control of the volume viewer from the command line
by Lukas Palatinus 28 Nov '06

28 Nov '06

Hello all, I am trying to make a movie showing an evolution of an electron density map during an iterative optimization. For each optimization step I have one density map as volume data in xplor format. I depict the maps using the volume viewer, where I can set the number and level of the isosurface thresholds as well as their color. However, each newly opened map opens with default threshold setting, which is not suitable for my purposes. I make the movie using a command file of the type: open density1.xplor movie record wait 10 movie stop close 0 open density2.xplor movie record wait 10 movie stop ... I would need to be able to control the properties of the isosurfaces of the newly opened map from the command line or from the script file, or find a way to preserve the properties set for the first map in all subsequently opened maps. The search in Chimera manual did not lead me anywhere. Could anyone give me a hint how to proceed? With best regards Lukas Lukas Palatinus Laboratoire de Cristallographie EPFL Lausanne Tel.: +41 (0)21 693 0639 mailto: palat(a)fzu.cz

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Re: [Chimera-users] Get angles in degree out of Rotation matrix
by Thomas Goddard 27 Nov '06

27 Nov '06

Hi Michael, Perhaps you can compare the orientation between the exact symmetric placement of a chain and the actual position by measuring the translation and rotation angle needed to align the two. By rotation angle I mean that any rotation can be represented as a rotation about a single axis (which depends on the rotation). I do not understand what you mean by rotation angles about x, y and z axes. As I mentioned that depends on the order of the rotations and therefore is rarely used. In the Chimera match command or matchmaker tool the optimal rotation matrix is computed -- it is *not* decomposed into separate x, y and z rotations during that calculation. I suppose if your system has symmetry about the z axis you could ask what rotation about z best aligns a chain with the exact symmetric chain location. In other words, only a z-axis rotation rather then rotation about an arbitrary axis would be allowed. Chimera does not have code for that and I have never heard that number reported. If you spell out precisely what angle is needed I can give better advice on how to get it from Chimera. Tom > From: "Stohr, Michael" <stohr(a)uni-mainz.de> > To: "Thomas Goddard" <goddard(a)cgl.ucsf.edu> > Date: Mon, 27 Nov 2006 09:51:31 +0100 > Subject: AW: Get angles in degree out of Rotation matrix > > Hi Tom, > > Thanks a lot for your description. It does not fit completely my demand. I will rephrase my question, is there a simple way to determine the three angles between the two 3d-structures of two identical chains? The background is that my molecule is not absolutely symmetrical and I want to quantify the asymmetry. So, I want to be able to say, this angle between this two chains differs from ideal symmetry angle by X degrees for different directions (x, y, z). I thought the rotation matrix would be the way to do so, but it does not seem so. I've found a not very precise method by using the distance tool and trigonometric functions. Therefore, if there is no answer for my question it will be ok at first especially I have to finish my theses very soon. By the way, in which order does for example the tool match or matchmaker rotates a structure or is this not predictable? > > Thanks for your afford, > Michael

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Increase/decrease the sphere
by tuhin＠iitk.ac.in 27 Nov '06

27 Nov '06

Dear Chimera users, Could anybody tell me whether there is a way in chimera to increase/decrease the size of the spheres/ball-and-stick in atom display (Action-->Atoms/Bonds-->sphere...). The wireframe has an option in "wire width", is there something like that for the above two options ?? Waiting for yours suggestions. Thanks in advance. Best, TKP

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Re: [Chimera-users] DelPhi
by Elaine Meng 24 Nov '06

24 Nov '06

Hi Stefano, Oh I see - it appears to be a problem with the Mac DelPhi download. I tried getting this myself, and could not run the executable, with this error message (probably the same problem you had): meng% /Users/meng/Desktop/release1.1/exe/delphiMacOSX; exit dyld: /Users/meng/Desktop/release1.1/exe/delphiMacOSX can't open library: /opt/ibmcmp/lib/libxlf90.dylib (No such file or directory, errno = 2) Trace/BPT trap logout [Process completed] I'm not an expert at understanding these messages, but it looks like the executable is looking for some code library that is not there. If you could run the executable successfully, the next step would be to put it in your "path," so that just typing the name of the executable in a Mac Terminal window would run the program. That would allow DelPhiController to connect properly. You would also want to download the DelPhi "sample data" http://luna.bioc.columbia.edu/honiglab/software/DelPhi/data.tar.gz which has charge and radius parameter files that can be used with the program. Sadly, in our current situation, we cannot use the program. I do not have the programming expertise to fix this library problem, but if any of us figures it out, we will definitely let you know. If you do get a fix from the Honig lab, it would be great if you could let me (or chimera-users) know - probably several of us would like to use this software on a Mac. Sorry about the trouble, Best, Elaine ----- Elaine C. Meng, Ph.D. meng(a)cgl.ucsf.edu UCSF Computer Graphics Lab and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html

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DelPhi
by Stefano Ciurli 24 Nov '06

24 Nov '06

Hello, does anyone know how to implement the DelPhi algorithm into Chimera? I am using a Powerbook G4. Thanks a lot Stefano -- ____________________________________________ Stefano Ciurli Professor of Chemistry Laboratory of Bioinorganic Chemistry Department of Agro-Environmental Science and Technology University of Bologna Viale Giuseppe Fanin, 40 I-40127 Bologna Italy Phone: +39-051-209-6204 Fax: +39-051-209-6203 "Fatti non foste a viver come bruti, ma per seguir virtute e canoscenza" Dante Alighieri - Inferno - Canto XXVI "Ihr seid bestimmt, nicht Tieren gleich zu leben, Nein, Tugend zu erringen und Erkenntnis" "Ye were not form'd to live the life of brutes, But virtue to pursue and knowledge high"

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fitting map into map
by Gabor Papai 24 Nov '06

24 Nov '06

Hi, Does anybody know if there is a way to calculate fitting of EM density map into another EM density map? I know how it goes with PDBs, but couldn't figure out how I can do it with maps. Thanks for help in advance, Gabor -- Gabor Papai IGBMC Department of Structural Biology and Genomics 1, rue Laurent Fries, BP 10142 67404 Illkirch, France phone +33-3-90244796 Fax +33-3-88653201 E-mail: papai(a)igbmc.u-strasbg.fr

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question about using swapaa in Chimera
by Ng, David (NIH/NCI) [E] 22 Nov '06

22 Nov '06

Hi, I'm currently learning to use Chimera. I wish to look at specific amino acid mutations in CDKN2A for effects in conformational changes and changes in protein interactions with known partners. When I type the command "swapaa P #0:24" in chimera to mutate arginine 24 to proline in CDKN2A, I get an error message that says "Value error: No connectivity template for residue P" Can you help me with this issue? Thanks. David Ng, M.D. Staff Clinician

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Re: [Chimera-users] Get angles in degree out of Rotation matrix
by Thomas Goddard 20 Nov '06

20 Nov '06

Hi Michael, It is not very common to specify a 3-dimensional rotation in terms of a x-axis rotation, y-axis rotation and z-axis rotation because this decomposition depends on the order of the x, y, and z rotations. If you rotate 90 degrees about the x-axis, then 90 about the y-axis you get a different orientation than if you do the y-axis rotation first followed by the x-axis rotation. Chimera has a routine to produce the rotation axis (a unit vector in 3-dimensions) and rotation angle about that vector corresponding to a 3x3 rotation matrix. You could use that in Chimera with some Python code. If you just want the rotation angle and don't need the axis then the formula is simple Tr(R) = 1 + 2*cos(theta) where Tr(R) = sum of rotation matrix diagonal elements so the rotation angle theta = arccos((Tr(R) - 1)/2) Below I give the Chimera C++ code that also computes the axis. There are corner cases handled by this code for 0 degree and 180 degree rotations. Tom void Xform::getRotation(Vector *axis, Real *angle) const { Real cosTheta = (rot[0][0] + rot[1][1] + rot[2][2] - 1) / 2; if (fuzzyEqual(cosTheta, 1)) { *angle = 0; (*axis)[0] = (*axis)[1] = 0; (*axis)[2] = 1; return; } if (!fuzzyEqual(cosTheta, -1)) { *angle = degrees(acos(cosTheta)); Real sinTheta = sqrt(1 - cosTheta * cosTheta); (*axis)[0] = (rot[2][1] - rot[1][2]) / 2 / sinTheta; (*axis)[1] = (rot[0][2] - rot[2][0]) / 2 / sinTheta; (*axis)[2] = (rot[1][0] - rot[0][1]) / 2 / sinTheta; return; } *angle = 180; if (rot[0][0] >= rot[1][1]) { if (rot[0][0] >= rot[2][2]) { // rot00 is maximal diagonal term (*axis)[0] = sqrt(rot[0][0] - rot[1][1] - rot[2][2] + 1.0f) / 2; Real halfInverse = 1 / (2 * (*axis)[0]); (*axis)[1] = halfInverse * rot[0][1]; (*axis)[2] = halfInverse * rot[0][2]; } else { // rot22 is maximal diagonal term (*axis)[2] = sqrt(rot[2][2] - rot[0][0] - rot[1][1] + 1.0f) / 2; Real halfInverse = 1 / (2 * (*axis)[2]); (*axis)[0] = halfInverse * rot[0][2]; (*axis)[1] = halfInverse * rot[1][2]; } } else { if (rot[1][1] >= rot[2][2]) { // rot11 is maximal diagonal term (*axis)[1] = sqrt(rot[1][1] - rot[0][0] - rot[2][2] + 1.0f) / 2; Real halfInverse = 1 / (2 * (*axis)[1]); (*axis)[0] = halfInverse * rot[0][1]; (*axis)[2] = halfInverse * rot[1][2]; } else { // rot22 is maximal diagonal term (*axis)[2] = sqrt(rot[2][2] - rot[0][0] - rot[1][1] + 1.0f) / 2; Real halfInverse = 1 / (2 * (*axis)[2]); (*axis)[0] = halfInverse * rot[0][2]; (*axis)[1] = halfInverse * rot[1][2]; } } }

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Re: [Chimera-users] suggestion
by Thomas Goddard 20 Nov '06

20 Nov '06

Hi David, Thanks for your suggestion to add coloring of isosurfaces based on gradient magnitude to Chimera. I think I can add this to the Surface Color tool in an hour or two since the gradient calculation code is already in Chimera (for fitting atomic models in maps). I'll try to put it in soon and send you the code to test. Description of coloring from article: "OpenDX (www.opendx.org) module MAKROVIS was implemented to create masks of different shapes and to analyze disorder in the reconstructions (Figure 1B). For this, isosurface rendering of a given voxel was colored as a function of the maximum density difference between the voxel and its neighbors." Tom > From: "David G. Morgan" <dmorgan(a)ucdavis.edu> > To: goddard(a)cgl.ucsf.edu > Subject: suggestion > Date: Thu, 16 Nov 2006 19:03:50 -0800 > > Tom, > > I have a suggestion for the developers "list of ideas to implement," if > you think there would be enough interest from users and that it is > something that chimera should do. I realize that you get lots of > suggestions, and that some of them are simply outside the realm of what > the chimera developers think chimera is intended to do. But since you > do ask for suggestions, here's my most recent one. > > I'm attaching a recent journal article where the authors used a color > coding scheme to display "order/disorder" regions of an EM > reconstruction. The images are in Fig 1 B and the rather sparse > description of the "algorithm" is a single sentence in the "Image > Processing 3D Reconstruction" section (p 1046). The idea of color > coding some estimate of the better defined regions of a density map is > very nice (and clever), and would be extremely helpful in lots of > situations (my plug for wanting you guys to implement something > similar...). > > The idea behind this is that for any given region of iso-surface, the > density gradient normal to that surface should be a reasonable measure > of how well defined the density is. In other words, a very steep > gradient (e.g., a fast transition between protein and solvent) means > very well defined density and a flat gradient means weakly defined > density (disordered regions, partial occupancy, etc.). The authors > don't do such a complicated calculation, but it seems that what they > implemented at least captures most of this sort of character. > > I think the key to this is that the gradient is calculated "locally." > I've looked at gradients as a function of resolution with the idea of > using it to help chose a proper iso-surface. While it works well with > model data, real reconstructions aren't nearly so well behaved. I > hadn't thought about this in a while, but I think what the authors have > done both helps explain the behavior of my real data (the gradient is > simply too varied) and is a quite useful visualization tool. > > So please think about implementing something like this in the volume > handling tools of chimera. > > David Gene Morgan > Advanced Microscopy & Proteomics > Molecular & Cellular Biology > University of California at Davis > 530 752 2693 (lab) > 530 752 3085 (FAX) > ---- > removed PDF for > > Huiskonen JT, de Haas F, Bubeck D, Bamford DH, Fuller SD, Butcher SJ. > Structure of the bacteriophage phi6 nucleocapsid suggests a mechanism for sequential RNA packaging. > Structure. 2006 Jun;14(6):1039-48.

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