December 2015 - Chimera-users - RBVI Mailing Lists

Write a PDB with Python API
by Jaime Rodríguez-Guerra Pedregal 02 Dec '15

02 Dec '15

Hi again! So in my quest to use OpenMM from Chimera, my first proof-of-concept attempts consist of using a PDB file as intermediate to convert chimera.Molecule objects to OpenMM Topologies (using openmm.app.PDBFile loader). While not ideal yet, it'd be convenient to use StringIO() as a memory file, and I have been more or less successful. This is my strategy: memfile = StringIO() m = chimera.openModels.list() chimera.pdbWrite(m, m[0].openState.xform, memfile) memfile.seek(0) # pass memfile to openmm.app.PDBFile and do OpenMM stuff memfile.close() It works, but some residues are not properly recognised... I dumped the converted PDB to an actual file and saw that the problematic residue (an ARG) is totally messed up! I've attached the results: original file is the mol2, the converted one is the pdb, and also a Chimera session with both superimposed. What's the recommended method to convert a chimera.Molecule to a PDB file (if possible, in-memory) with Chimera Python API? Thanks a lot!

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Matchmaker 'restrict to selection' not working as expected.
by Oliver Clarke 01 Dec '15

01 Dec '15

Hi all, When using Matchmaker, the ‘Further restrict to matching selection’ option does not seem to improve the speed of alignment as much as expected under certain circumstances (when the selection is a subset of a larger chain, as opposed to being an individual chain in a multi chain structure). It seems to still restrict the selection correctly for the final alignment (it is still only aligned on the selected domain), but the “test match” step seems to be conducted on the entire chain, rather than the selection - this makes a big difference to speed for large proteins. For example - I tried aligning two conformations of a protein complex consisting of one chain A ~100 residues, and chain B ~5000 residues. If I select chain A of both structures, and then select ‘Further restrict to matching selection’ for both the reference and the structure to match, the alignment is almost instantaneous - less than 2s. If I perform the same operation, but this time selecting the first 100 residues of chain B in each structure, the alignment takes 3min20s, regardless of whether I leave automatic chain pairing on or select the specific chains to use for alignment manually. It takes only marginally longer - 5 min - if I select the entirety of chain B, a selection that is 50X the size. Incidentally I still get the “test match” message in the status bar even when the selection only contains one chain from each structure, or when I manually select (using the chain pairing options) which chains to align - maybe Chimera is still running test match on the whole chain when it should only do so on the selection (or not at all if the selection only includes one possible match). This seems like a bug? Or am I missing something? Cheers, Oliver.

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domain angel
by Smith Liu 01 Dec '15

01 Dec '15

Dear All, Is any way to calculate the angel between 2 domains by Chimera? Smith

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Installing OpenMM in Chimera
by Jaime Rodríguez-Guerra Pedregal 01 Dec '15

01 Dec '15

Hello, I am trying to install OpenMM in Chimera to script some molecular dynamics. However, I am struggling to make it work, since the build fails with this error: g++ -pthread -fPIC -mtune=generic -m64 -I/home/chimera/chimeraBuild_X11/build/build/include -L/home/chimera/chimeraBuild_X11/build/build/lib -DUSE_DYLD_GLOBAL_NAMESPACE -shared -Wl,--hash-style=both build/temp.linux-x86_64-2.7/src/swig_doxygen/OpenMMSwig.o -L/lib -R/lib -lOpenMM -lOpenMMAmoeba -lOpenMMRPMD -lOpenMMDrude -o build/lib.linux-x86_64-2.7/simtk/openmm/_openmm.so g++: error: unrecognized command line option '-R' which is probably not related to Chimera at all. What I've done so far: 1. Download precompiled binaries for Linux from their site: https://simtk.org/project/xml/downloads.xml?group_id=161 2. Extract that file and merge the contents of the directories "include" and "lib" with those in Chimera root path. 3. Cd into the python directory of the extracted file and run: chimera --nogui --script "setup.py install". Has somebody been successful with this package? I know it seems more of a compiler issue, but maybe Chimera is doing some trickery with the build mechanism too. Thank you in advance, Jaime.

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