Hi Mitch, What program are you using? It looks like you may be reading the ChimeraX help, but ChimeraX is a different program than Chimera. If you are using ChimeraX, you may want to ask questions on the chimerax-users@cgl.ucsf.edu list and not chimera-users@cgl.ucsf.edu ... We try to keep them separate so that people don't get confused. Also if you are actually using ChimeraX, the "coordsets" option of "open" is only for opening PDB or mmCIF files, not XTC. Just leave it out, and simply open both the PSF and XTC with the "coords" option similar to the third example in the ChimeraX help section linked below, except that your trajectory file is XTC and not DCD: <https://rbvi.ucsf.edu/chimerax/docs/user/commands/open.html#traj-options> That just opens the trajectory, it does not play it. To play the trajectory in ChimeraX, you would use the slider GUI and/or the "coordset" command, as mentioned in the help section linked above. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Resource for Biocomputing, Visualization, and Informatics Department of Pharmaceutical Chemistry University of California, San Francisco

On Jan 11, 2024, at 3:57 PM, Mitch Murphy via Chimera-users <chimera-users@cgl.ucsf.edu> wrote:

i tried "open 3ft6.psf coordsets true coords 3ft6.xtc" but i get "'coordsets' has no suffix" error message.

and with "open 3ft6.psf coords 3ft6.xtc coordsets true" i get "Expected a keyword".

how do i play frames of a trajectory. i have the psf and xtc or dcd trajectory files available.