trjconv(1) converts and manipulates trajectory files


trjconv -f traj.xtc -o trajout.xtc -s topol.tpr -n index.ndx -fr frames.ndx -sub cluster.ndx -drop drop.xvg -[no]h -[no]version -nice int -b time -e time -tu enum -[no]w -xvg enum -skip int -dt time -[no]round -dump time -t0 time -timestep time -pbc enum -ur enum -[no]center -boxcenter enum -box vector -clustercenter vector -trans vector -shift vector -fit enum -ndec int -[no]vel -[no]force -trunc time -exec string -[no]app -split time -[no]sep -nzero int -dropunder real -dropover real -[no]conect


trjconv can convert trajectory files in many ways:

1. from one format to another

2. select a subset of atoms

3. change the periodicity representation

4. keep multimeric molecules together

5. center atoms in the box

6. fit atoms to reference structure

7. reduce the number of frames

8. change the timestamps of the frames ( -t0 and -timestep)

9. cut the trajectory in small subtrajectories according to information in an index file. This allows subsequent analysis of the subtrajectories that could, for example, be the result of a cluster analysis. Use option -sub. This assumes that the entries in the index file are frame numbers and dumps each group in the index file to a separate trajectory file.

10. select frames within a certain range of a quantity given in an .xvg file.

The program trjcat is better suited for concatenating multiple trajectory files.

Currently seven formats are supported for input and output: .xtc, .trr, .trj, .gro, .g96, .pdb and .g87. The file formats are detected from the file extension. The precision of .xtc and .gro output is taken from the input file for .xtc, .gro and .pdb, and from the -ndec option for other input formats. The precision is always taken from -ndec, when this option is set. All other formats have fixed precision. .trr and .trj output can be single or double precision, depending on the precision of the trjconv binary. Note that velocities are only supported in .trr, .trj, .gro and .g96 files.

Option -app can be used to append output to an existing trajectory file. No checks are performed to ensure integrity of the resulting combined trajectory file.

Option -sep can be used to write every frame to a separate .gro, .g96 or .pdb file. By default, all frames all written to one file. .pdb files with all frames concatenated can be viewed with rasmol -nmrpdb.

It is possible to select part of your trajectory and write it out to a new trajectory file in order to save disk space, e.g. for leaving out the water from a trajectory of a protein in water. ALWAYS put the original trajectory on tape! We recommend to use the portable .xtc format for your analysis to save disk space and to have portable files.

There are two options for fitting the trajectory to a reference either for essential dynamics analysis, etc. The first option is just plain fitting to a reference structure in the structure file. The second option is a progressive fit in which the first timeframe is fitted to the reference structure in the structure file to obtain and each subsequent timeframe is fitted to the previously fitted structure. This way a continuous trajectory is generated, which might not be the case when using the regular fit method, e.g. when your protein undergoes large conformational transitions.

Option -pbc sets the type of periodic boundary condition treatment:

* mol puts the center of mass of molecules in the box.

* res puts the center of mass of residues in the box.

* atom puts all the atoms in the box.

* nojump checks if atoms jump across the box and then puts them back. This has the effect that all molecules will remain whole (provided they were whole in the initial conformation). Note that this ensures a continuous trajectory but molecules may diffuse out of the box. The starting configuration for this procedure is taken from the structure file, if one is supplied, otherwise it is the first frame.

* cluster clusters all the atoms in the selected index such that they are all closest to the center of mass of the cluster, which is iteratively updated. Note that this will only give meaningful results if you in fact have a cluster. Luckily that can be checked afterwards using a trajectory viewer. Note also that if your molecules are broken this will not work either.

The separate option -clustercenter can be used to specify an approximate center for the cluster. This is useful e.g. if you have two big vesicles, and you want to maintain their relative positions.

* whole only makes broken molecules whole.

Option -ur sets the unit cell representation for options mol, res and atom of -pbc. All three options give different results for triclinic boxes and identical results for rectangular boxes. rect is the ordinary brick shape. tric is the triclinic unit cell. compact puts all atoms at the closest distance from the center of the box. This can be useful for visualizing e.g. truncated octahedra. The center for options tric and compact is tric (see below), unless the option -boxcenter is set differently.

Option -center centers the system in the box. The user can select the group which is used to determine the geometrical center. Option -boxcenter sets the location of the center of the box for options -pbc and -center. The center options are: tric: half of the sum of the box vectors, rect: half of the box diagonal, zero: zero. Use option -pbc mol in addition to -center when you want all molecules in the box after the centering.

With -dt, it is possible to reduce the number of frames in the output. This option relies on the accuracy of the times in your input trajectory, so if these are inaccurate use the -timestep option to modify the time (this can be done simultaneously). For making smooth movies, the program g_filter can reduce the number of frames while using low-pass frequency filtering, this reduces aliasing of high frequency motions.

Using -trunc trjconv can truncate .trj in place, i.e. without copying the file. This is useful when a run has crashed during disk I/O (i.e. full disk), or when two contiguous trajectories must be concatenated without having double frames.

Option -dump can be used to extract a frame at or near one specific time from your trajectory.

Option -drop reads an .xvg file with times and values. When options -dropunder and/or -dropover are set, frames with a value below and above the value of the respective options will not be written.


-f traj.xtc Input
 Trajectory: xtc trr trj gro g96 pdb cpt 

-o trajout.xtc Output
 Trajectory: xtc trr trj gro g96 pdb 

-s topol.tpr Input, Opt.
 Structure+mass(db): tpr tpb tpa gro g96 pdb 

-n index.ndx Input, Opt.
 Index file 

-fr frames.ndx Input, Opt.
 Index file 

-sub cluster.ndx Input, Opt.
 Index file 

-drop drop.xvg Input, Opt.
 xvgr/xmgr file 


 Print help info and quit

 Print version info and quit

-nice int 19
 Set the nicelevel

-b time 0
 First frame (ps) to read from trajectory

-e time 0
 Last frame (ps) to read from trajectory

-tu enum ps
 Time unit:  fs ps ns us ms or  s

 View output  .xvg .xpm .eps and  .pdb files

-xvg enum xmgrace
 xvg plot formatting:  xmgrace xmgr or  none

-skip int 1
 Only write every nr-th frame

-dt time 0
 Only write frame when t MOD dt = first time (ps)

 Round measurements to nearest picosecond

-dump time -1
 Dump frame nearest specified time (ps)

-t0 time 0
 Starting time (ps) (default: don't change)

-timestep time 0
 Change time step between input frames (ps)

-pbc enum none
 PBC treatment (see help text for full description):  none mol res atom nojump cluster or  whole

-ur enum rect
 Unit-cell representation:  rect tric or  compact

 Center atoms in box

-boxcenter enum tric
 Center for -pbc and -center:  tric rect or  zero

-box vector 0 0 0
 Size for new cubic box (default: read from input)

-clustercenter vector 0 0 0
 Optional starting point for pbc cluster option

-trans vector 0 0 0
 All coordinates will be translated by trans. This can advantageously be combined with -pbc mol -ur compact.

-shift vector 0 0 0
 All coordinates will be shifted by framenr*shift

-fit enum none
 Fit molecule to ref structure in the structure file:  none rot+trans rotxy+transxy translation transxy or  progressive

-ndec int 3
 Precision for .xtc and .gro writing in number of decimal places

 Read and write velocities if possible

 Read and write forces if possible

-trunc time -1
 Truncate input trajectory file after this time (ps)

-exec string
 Execute command for every output frame with the frame number as argument

 Append output

-split time 0
 Start writing new file when t MOD split = first time (ps)

 Write each frame to a separate .gro, .g96 or .pdb file

-nzero int 0
 If the -sep flag is set, use these many digits for the file numbers and prepend zeros as needed

-dropunder real 0
 Drop all frames below this value

-dropover real 0
 Drop all frames above this value

 Add conect records when writing  .pdb files. Useful for visualization of non-standard molecules, e.g. coarse grained ones