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Command: open

openfilename | URL | [ prefix:]identifier ) [ maxModels  M ] [ coordsets  true | false ]  options 

open formats

The command open reads data in several input formats from:

Input files may contain data to be displayed or commands or code to be executed.

For some types of files, associated information is automatically shown in the Log when the file is read. See also: runscript, close, save, help, sym, info, File History, Rapid Access , initial colors, automatic styling, ChimeraX Fast mmCIF Guidelines


open ~/Desktop/maps/myfile.mrc name refined3
open 2gbp
open 1plx format pdb coord T
open emdb:3087
open 3237 from emdb name "gamma-secretase complex"

Input Formats

The command open formats command lists the possible formats and databases in the Log. File types can be categorized as:

File Types
format format-name suffix description
Atomic Structures and Related Data
PDB (Protein Data Bank) pdb .pdb, .pdb1
.ent, .pqr
+ compressed
atomic coordinates and associated annotations; if PQR, sets atomic radius
PDBx/mmCIF mmcif .cif
atomic coordinates and associated annotations
(see assemblies from mmCIF, H-bonds from mmCIF,
ChimeraX Fast mmCIF Guidelines)
MMTF (Macromolecular Transmission Format) mmtf .mmtf
+ compressed
atomic coordinates and associated annotations
MDL Molfile/SDF sdf .mol, .sdf atomic coordinates
PDBQT pdbqt .pdbqt atomic coordinates
(see ViewDockX for analysis of docking results from AutoDock Vina)
Sybyl Mol2 mol2 .mol2 atomic coordinates
(see ViewDockX for analysis of docking results from UCSF DOCK v4-6, DOCK v3.7, or GOLD)
Schrödinger Maestro

*requires installing the Maestro bundle from the ChimeraX Toolshed
mae .mae
atomic coordinates
(see ViewDockX for analysis of docking results from Glide)
Pseudobond file pseudobonds .pb
+ compressed
list of atom pairs to connect with pseudobonds
Trajectory Coordinates
(requires an already-open structure for topology, see the structureModel option)
Amber NetCDF (binary) amber .nc atomic trajectory
DCD coordinates (binary) dcd .dcd atomic trajectory
Gromacs compressed coordinates xtc .xtc atomic trajectory
Gromacs full-precision coordinates (binary) trr .trr atomic trajectory
Volume Data and Related (associated tool: Volume Viewer)
Amira mesh amira .am 3D data
APBS potential apbs .dx electrostatic potential map from Adaptive Poisson-Boltzmann Solver
(see the APBS tool in UCSF Chimera)
BRIX map brix .brix electron density map
CCP4 map ccp4 .ccp4, .map electron density map
Chimera map cmap .cmp, .cmap volume data from Chimera/ChimeraX
(based on the hierarchical data format HDF5)
CNS or XPLOR map xplor .cns, .xplor unformatted ASCII density map
DelPhi or GRASP potential delphi .phi electrostatic potential map from DelPhi (the academic version) or GRASP
DeltaVision map dv .dv light microscopy data
DICOM map dicom .dcm medical image stack; see the verbose option
Directional FSC (Fourier shell correlation) dres .dres
+ compressed
directional resolution to show on a colored globe
(plain text file with four whitespace-separated columns of numbers, an XYZ vector and a resolution or other value to colormap onto the globe)
DOCK scoring grid dock .bmp
UCSF DOCK (versions 4, 5, 6) bump, contact, and energy scoring grids
(suffixes not interchangeable; gridname.bmp required for reading gridname.cnt and/or gridname.nrg)
DSN6 map dsn6 .omap electron density map
EMAN HDF map emanhdf .hdf, .h5, .hdf5 electron density map
(based on the hierarchical data format HDF5; if the EMAN HDF file reader fails, a generic HDF file reader is tried)
Gaussian cube grid cube .cube, .cub orbitals, electron densities, other
gOpenMol grid gopenmol .plt orbitals, electron densities, other
ImageJ or OME TIFF .tif, .tiff microscopy data
(multiple channels and/or time points specified in file header)
Image stack images .tif, .tiff
image stack
(grayscale or RGB image series in multiple files or a single multipage file, in formats supported by PIL); see image stack wildcards and single image
IMAGIC map imagic .hed
density map
(the format consists of two files, filename.hed with header information and filename.img with the map values; both are required, but either can be specified in the open command; IMAGIC support courtesy of Ralf Schmidt and Michael Schatz, Image Science Software)
Imaris map ims .ims 3D-5D image
(could be time series and/or multichannel)
IMOD map imodmap .rec electron density map
(MRC map with signed 8-bit mode interpreted as unsigned)
MacMolPlt grid macmolplt .mmp 3D surfaces
MRC map mrc .mrc electron density map
MTZ crystallographic reflection file

*requires installing the Clipper bundle from the ChimeraX Toolshed and specifying a corresponding atomic model (details...)
mtz .mtz reciprocal space map
Priism data priism .xyzw
3D light or EM data
(.xyzt is time series)
PROFEC grid profec .profec interaction free energy grid from PROFEC (in Amber versions 6 and 7)
Purdue image format pif .pif electron density map
Situs map situs .situs, .sit electron density map
SPIDER map spider .spi, .vol electron density map
STORM (STochastic Optical Reconstruction Microscopy) storm .storm
+ compressed
super-resolution microscopy data (details...)
TOM toolbox map tom_em .em electron density map
UHBD potential (binary) uhbd .grd electrostatic potential map from University of Houston Brownian Dynamics
EMDB segmentation sff .sff (XML)
.hff (HDF5)
EM segmentation
IMOD segmentation imod .imod
EM segmentation meshes and contours
Segger segmentation segger .seg segmentation regions
Other 3D Objects
Chimera/ChimeraX BILD bild .bild, .bld
+ compressed
graphical objects
Chimera/ChimeraX markers markers .cmm markers and links
(analogous to atoms and bonds)
COLLADA collada .dae
+ compressed
graphical objects
(TriangleSets only)
GL Transmission Format gltf .glb
+ compressed
graphical objects
Neuron trace
(SWC, see also the NeuroMorpho FAQ)
swc .swc neuron reconstruction, such as from NeuroMorpho.Org
STereoLithography stl .stl
+ compressed
triangle-based format native to stereolithography CAD software
VTK (Visualization ToolKit) PolyData vtk .vtk
+ compressed
lines, polygons [documentation PDF]
(details on ChimeraX VTK export)
Wavefront OBJ obj .obj
+ compressed
graphical objects
(triangles only: vertices, vertex normals, faces; texture colors)
Sequences (associated tool: Sequence Viewer)
Clustal ALN aln .aln, .clustal
.clustalw, .clustalx
+ compressed
sequence alignment
FASTA, aligned FASTA fasta .fasta, .fa
.afasta, .afa
+ compressed
individual sequence(s) or sequence alignment
GCG MSF (Multiple Sequence Format) msf .msf
+ compressed
sequence alignment
GCG RSF (Rich Sequence Format) rsf .rsf
+ compressed
sequence alignment
HSSP hssp .hssp
+ compressed
sequence alignment
(other information not read; see HSSP database)
PIR (NBRF), aligned PIR pir .pir, .ali
+ compressed
individual sequence(s) or sequence alignment
Selex (Pfam) pfam .selex, .slx
+ compressed
sequence alignment
Stockholm stockholm .sth, .sto
+ compressed
sequence alignment
ChimeraX session file session .cxs ChimeraX session; see the Window preferences and Log preferences
IHM (Integrative Hybrid Model) ihm .ihm integrative hybrid model, examples available from PDB-Dev (see database fetch); may create residue attributes
ChimeraX command file cmd .cxc ChimeraX commands
photo (single image) photo .jpg
(other image types .tif,.png, etc. accepted if specified as format photo; details...)
2D image;
see also image stack
Python py .py, .pyc, .pyo
+ compressed
Python code
(see also runscript)
HTML, XHTML html .html, .htm
.xhtml, .xht, .xml
hypertext to render in the ChimeraX browser
ChimeraX model positions positions .positions ChimeraX model names and positions to restore

Local Files

Usage: open  filename  [ filename2... ] [ format  format-name ] [ maxModels  M ] [ coordsets  true | false ] [ vseries  true | false ] [ resizeWindow  true | false ]  options 

The filename is generally a pathname to a local file, either absolute or relative to the current working directory as reported by pwd. The working directory can be changed with cd. A pathname may start with “~” to indicate the user's home directory. One or more files can be specified with a single filename by including * (wild card), ? (single-character wild card), and/or square-bracketed character ranges (Unix-style pathname expansion or globbing). For image stacks only, additional wild cards may be used.

Multiple filenames separated by spaces can also be given, which is equivalent to using the open command multiple times with the same options for each filename.

Substituting the word browse for the filename brings up a file browser window for choosing the name and location interactively.

The file format can be indicated with either the filename suffix or the format option (where format-name can be truncated). Certain formats can be read when compressed (.gz, .bz2, or .xz, see details).

Giving browse as the filename brings up a dialog for browsing the filesystem interactively.

Additional ways to open local files:

On a Mac, ChimeraX-associated file types can also be opened by double-clicking them in a Finder window or using “open” in a Terminal window.


alignment  true | false
Whether to interpret a multi-sequence file as an alignment (default, all sequences in one Multalign Viewer window). Otherwise, each sequence will be opened in a separate window. If the sequences (including any gap characters) are of differing lengths, the option must be set to false.
atomic  true | false
Whether to interpret coordinates read from mmCIF or PDB format as an atomic model (true, default). Setting the option to false is appropriate for data such as SAXS models that are simply collections of points (possibly with connecting “bonds”) rather than realistically spaced atoms; it classifies the models as Structure rather than atomicStructure, bypassing chemical perception steps like identifying atom types.
autoAssociate  true | false
Whether structure-chain sequences should be compared to sequences in Multalign Viewer and automatically associated if the number of mismatches is no more than 1/10 the number of residues in the structure chain. Unlike the other options of open, this sets a state that persists within the ChimeraX session unless explicitly changed. The initial setting is true.

For automatic association, the sequence and structure files can be opened in either order. Gaps in the structure sequence relative to the sequence in the alignment file can only occur where residues are missing from the structure (for example, a flexible loop with insufficient density to determine coordinates). Associations are reported in the status line and the Log. A structure (even if it has multiple chains) cannot be associated with more than one sequence, but a single sequence can be associated with more than one structure. If more than one sequence matches a given structure chain, the single best-matching sequence is associated.

autoStyle  true | false
Setting autoStyle to false bypasses automatic styling, i.e., automatically adjusting the appearance of a newly opened atomic model based on its contents. Bypassing this calculation shows all atoms as white spheres, and may be useful in rare cases where generating the rule-based representation is slow (such as drawing cartoons for very large numbers of models) or when chemical perception is inappropriate (such as for a SAXS bead model). See also: markers and links
channel  N
Assign channel number N to map; typically used for light microscopy data. When multiple maps are opened in a single command (multiple files specified with wild cards or globbing), channel numbers are automatically discerned from the filenames, if possible: for example, a file will be identified as channel 0 if its name contains either of the following: (and 0 could be any whole number). Multichannel data opened from a single file or from multiple files in a single command (as described above) are automatically grouped, in that changing the display style, step size, or plane for one channel in Volume Viewer changes it for all of the channels in the group. The channel option allows manually assigning a channel to data so that it can be saved along with other datasets in a single (multichannel) Chimera map file. See also: image stack wildcards
combineSymAtoms  true | false
Nonstandard PDB or mmCIF files may contain duplicate copies of atoms at symmetry positions; this option indicates whether to merge multiple singleton atoms of the same element at the same 3D position into one (default true) to prevent errors in subsequent calculations such as adding hydrogens.
childModels  true | false
When opening a ChimeraX positions file, whether to explicitly apply matrices for submodels rather than simply allowing them to follow their parent models.
contours  true | false
Whether to read the contours from an IMOD segmentation file.
coordsets  true | false
Whether to open a multi-model file in mmCIF or PDB format as a trajectory and show a slider graphical interface. Only one frame (coordinate set) of a trajectory can be viewed at a time; different frames can be accessed or played back sequentially with the coordset command or the slider interface. By default, the multiple models in the file will be opened not as a trajectory but as separate submodels that can be shown/hidden/specified independently (for example, using #1.1, #1.2, #1.3...) or collectively (for example, using #1).
debug  true | false
Whether to send verbose information to the Log when opening a EMDB segmentation file.
ensembles  true | false
Whether to fetch ensembles associated with an IHM dataset (default false, as these can be quite large).
height  h
Height in physical units of distance (Å) for the photo (single image) being opened.
logInfo  true | false
Whether to show available model information (other than structure title) in the Log. See also: log metadata
matchNames  true | false
When opening a ChimeraX positions file, whether to match models by name instead of simply applying the matrices in order of appearance in the file.
maxModels  M
Maximum number of models to keep when opening a multi-model file in mmCIF or PDB format as multiple models in ChimeraX (coordsets false).
maxSurfaces  N
Maximum number of surface models to create when opening an EMDB segmentation file.
meshes  true | false
Whether to read the meshes from an IMOD segmentation file.
name  model-name
The name of the model (shown in the Model Panel) will be generated automatically from the input filename or database identifier unless another name is given with the name option. If model-name contains spaces, it should be enclosed in quotation marks. Model number is also assigned automatically, starting with the lowest available number. Model name and number can be changed with the rename command.
newTab  true | false
Whether to open an HTML file in a new tab of the ChimeraX browser (default false, replace any current page).
pixelSize  s
Pixel size in physical units of distance (Å) for the photo (single image) being opened.
resizeWindow  true | false
When opening a session, whether to restore its window size along with its contents; overrides the corresponding Window preference. Opening a ChimeraX session automatically runs close session first.
segidChains  true | false
Whether to assign segment IDs in PDB format as the chain IDs in ChimeraX.
structureModel  model-spec
A trajectory coordinate file is automatically opened as trajectory, but to provide topology information, this option must be used to specify an existing model with the same set of atoms (for example: open myfile.trr structureModel #1). The coordinates of the existing model will be replaced with the new, unless replace false is used to indicate appending the new frames instead. This option is also needed to open local MTZ files (details...).
vseries  true | false
When multiple maps with the same grid dimensions are opened in a single command (multiple files specified with wild cards or globbing, or a single multi-map file), this option can be used to enforce loading them as a volume series for playback with vseries or the associated slider (if true), or as independent models (if false). If the option is not used, 3D TIFF images and Chimera map files containing five or more same-sized maps are automatically interpreted as series, if possible. When multiple maps are opened in a single command (multiple files specified with wild cards or globbing), time ordering is automatically discerned from the filenames, if possible: for example, a file will be identified as time point 12 if its name contains either of the following: (and 0012 could be any integer).
verbose  true | false
Whether to show detailed debugging information for DICOM input. If format dicom is specified explicitly, all of the DICOM files in a directory and its subdirectories can be opened with a single open command, for example:

open "~/Desktop/2-CT 5.0 H30s-55580" format dicom

Each stack that is found will be opened as a separate model. Alternatively, the multiple files of a stack can be specified with filename globbing as described above. The option to specify a directory rather than filenames is only available for this format. See also: ChimeraX DICOM Reference

width  w
Width in physical units of distance (Å) for the photo (single image) being opened.


Usage: open  URL  [ dataFormat  format-name ] [ maxModels  M ] [ coordsets  true | false ] [ vseries  true | false ] [ resizeWindow  true | false ]  options 

Uniform Resource Locators (URLs) starting with http:, https:, and ftp: are handled. File types and command options are the same as described above for local files. The file type can be indicated by suffix or the dataFormat option (where format-name can be truncated).

Web-fetched data other than those handled by the ChimeraX browser are stored locally as described below.

Fetch from Online Sources

Usage: opensource1:]identifier  [[ source2:]identifier2... ] [ fromDatabase  source ] [ format  format-name ] [ maxModels  M ] [ coordsets  true | false ] [ ignoreCache  true | false ] [ maxAssemblies  N ]  options 

Atomic structures, density maps, and protein sequences can be fetched directly into ChimeraX from online sources. A specific compound or entry is specified by an identifier, and its source (database or web service) can be indicated with either a prefix before the identifier or the fromDatabase option. The default database for a 4-character identifier without prefix is the RCSB Protein Data Bank; the default format for that database is mmcif, although pdb or mmtf can be specified with the format option. Specifying multiple identifiers is equivalent to using the open command multiple times with the same options for each identifier.

Web-fetched data are stored locally in ~/Downloads/ChimeraX/ (where ~ indicates a user's home directory), with subdirectories PDB for atomic coordinates from the Protein Data Bank, EMDB for density maps from the Electron Microscopy Data Bank, etc. For caching, no distinction is made among the different Protein Data Bank sites. If a data file specified for opening is not found in this local cache or ignoreCache is set to true, the file will be fetched and cached.

Multiple biological assemblies are defined for many entries in the PDB. By default, fetching from rcsb_bio or pdbe_bio will return every assembly available for that entry in that database. The maxAssemblies option limits fetching to the first N assemblies. A single assembly from pdbe_bio will be opened as a single model, but even a single assembly from rcsb_bio may be composed of multiple models (opened as submodels of the assembly model).

See also: Web Access preferences

Fetch Sources
database or web service source description format-name
RCSB Protein Data Bank pdb atomic coordinates and associated annotations mmcif (default) or pdb
(see wwPDB formats)
or mmtf
RCSB Protein Data Bank rcsb_bio atomic coordinates for biological assembly or assemblies, see maxAssemblies (no choice, mmcif or pdb depending on the specific entry)
Protein Data Bank
in Europe (PDBe)
pdbe atomic coordinates and associated annotations mmcif (default) or pdb
PDBe pdbe_bio atomic coordinates for biological assembly or assemblies, see maxAssemblies mmcif
PDBe pdbe_updated atomic coordinates and associated annotations,  updated to include small-molecule connectivity and binding-site information as described in Velankar et al., Nucleic Acids Res 44:D385 (2016) mmcif
Protein Data Bank Japan (PDBj) pdbj atomic coordinates and associated annotations mmcif
PDB Chemical Component Dictionary (CCD) ccd idealized structure of PDB chemical component (residue type) ccd
PDBe Electron Density Server (EDS) eds (2Fo-Fc) electron density map for a PDB entry;
not available for all PDB entries
PDBe EDS edsdiff (Fo-Fc) electron density difference map for a PDB entry;
not available for all PDB entries
Electron Microscopy Data Bank
  (ftp from to .edu/.gov hosts, Chinese mirror site to .cn hosts, otherwise from 
emdb electron density map ccp4
PDB-Dev pdbdev integrative hybrid model;
leading zeroes can be omitted from the identifier, for example, accession code PDBDEV_00000001 can be opened with command:
open pdbdev:1
cellPACK cellpack hierarchical model;
see cellPACK Chimera instructions for available identifiers
PubChem3D pubchem modeled atomic coordinates specified by PubChem compound identifier (CID);
available for most but not all entries in PubChem Compound
(partial charges are assigned as the atom attribute named charge)
SMILES → 3D translator smiles modeled atomic coordinates specified by SMILES string, generated using the SMILES translator provided by the National Cancer Institute CADD group, or if that does not produce a structure, the smi23d web service provided by the cheminformatics group at Indiana University; see also Build Structure smiles
UniProt uniprot protein sequence (associated tool: Sequence Viewer) uniprot

Image Stack Wildcards

For image stacks only, special wildcards {t}, {c}, {z} can be used in the open command file pathname to specify the stack collectively. These wildcards indicate the parts of the filename with time, channel, and Z-indices, respectively. For example, to open a stack where each file is a 3D volume (each file contains all Z planes for one channel at one timepoint):

open "/Volumes/data/micro/cell8_3 stars/cell8_{c}ch_{t}stack_*msec.tif"
...and the file names look like:
The following example is for files each containing a single Z plane:
open ~/Desktop/latest/r12c09f01p{z}-ch{c}sk{t}fk1fl1.tiff
...where the file names look like:
See also the channel option of the open command.

Compressed Files

Certain file types can be read when compressed, as indicated with a suffix for the type of compression (.gz, .bz2, or .xz following the usual suffix for the type of file). For example, myfile.pdb.gz is a gzipped PDB file.

The file types that can be read by ChimeraX in compressed form (as well as uncompressed) are ALN, BILD, Collada, compiled Python code, directional FSC, FASTA, glTF, HSSP, MMTF, MSF, PDB, Pfam, PIR, pseudobonds, Python code, RSF, STL, Stockholm, STORM, VTK PolyData, and Wavefront OBJ.

Photo (Single Image)

A single image file can be opened as a flat model. Although flat, the model exists in 3D and can be rotated and translated like other models. Several image types (filename suffixes .png, .tif, etc.) are accepted, but except for .jpg, require specifying format photo in the open command. Any of the following options can be used to specify the size of the image within the scene:

width  w
height  h
pixelSize  s

Width, height, and pixel size values are specified in physical units of distance (Å). If width or height is given, the other is set according to the aspect ratio of the image. If both are given and their ratio differs from that of the image, the image will be stretched. Width and height values override any pixel size specification. If no width, height, or pixel size is given, a pixel size of 1.0 will be used. Examples:

open ~/Desktop/headshot.png format photo width 5
open figure1.jpg height 30

Open/Save Options from Clipper

The Clipper bundle from the ChimeraX Toolshed allows opening and saving crystallographic reflection files in MTZ format.

Opening an MTZ file requires specifying an already-open atomic structure with the structureModel option. Structure factors can also be fetched along with the corresponding atomic structure from the RCSB Protein Data Bank by specifying structureFactors true, for example:

open 6cmn structureFactors t
Not all PDB entries have structure factors available. In either case (opening an MTZ file or fetching structure factors), an overSampling value can be given to set the fineness of the real-space grid relative to the data resolution; values in the 1.5-4.0 range are generally recommended, with higher values giving a finer grid.

Saving: Only previously fetched structure factors or those from a previously opened MTZ file can be saved as MTZ, with additional save command options:

preserveInput  true | false
Whether to pass through the original, unmodified structure factors as well as those actually used by Clipper (which may have been modified).
saveMapCoeffs  true | false
Whether to save the current amplitudes and phases for all maps generated by Clipper. If false, just save the experimental data.

Generic HDF File Reader

If EMAN HDF format is expected, but that file reader fails, a generic HDF file reader is tried instead. This generic reader does not look for any metadata; it simply looks for 3-dimensional arrays and tries to open them as volume models with grid spacing of 1. The following open command option can be used to limit which 3D arrays are read:

arrayName  name
In HDF5 format, each array has a directory path within the file and a name (the last part of the pathname). This option indicates reading only arrays with the specified name. Example:
open Cam_long_00003.h5 arrayName Data

UCSF Resource for Biocomputing, Visualization, and Informatics / October 2020