Hi Gabriel,
You could use the "perframe" command to run "measure sasa" at every frame of the MD during playback with the "coordset" command.  See command help pages for options and details:
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/perframe.html>
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/coordset.html>
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/measure.html#sasa>

Here is my example trajectory of 80 frames, opened using command:

open 1plx coord true

Then I can play the trajectory  back with the "coordset" command and measure sasa at every step with the following.  Be careful what atoms you specify with "measure sasa" -- if you just use model number it will include solvent, ligands, etc.  Probably you only want the protein, as in my example commands:

perframe "measure sasa protein" range 1,80; coordset #1 1,80

... then there would be 80 lines in the Log with the SASA values.  You would have to save the Log to a file (e.g. command "log save") and reformat for your favorite graphing program, as there is no feature to do that inside of ChimeraX currently.
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/log.html#save>

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 Mar 10, 2025, at 9:01 AM, Gabriel López Velázquez via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:
>
> Dear Elaine,
> I am sorry; I did not state the subject of my previous email.
>
> I would ask for help. How can I calculate SASA as a function of time from the MD simulations in Chimerax?
> What archives need to perform it?
> Thanks in advance!
> Gabriel.