[Chimera-users] Surface representation

Elaine Meng meng at cgl.ucsf.edu
Mon Apr 22 09:22:13 PDT 2019

Hi Maria,
I see that VMD Quicksurf  makes a density map from the atoms and shows an isosurface.  You can do the same thing in Chimera with the “molmap” command, but the density map is not automatically recalculated at every step of the trajectory.  You would have to use a per-frame script and re-execute molmap at each frame to replace the old map with a new map every time the coordinates change.

The molmap command has a resolution parameter and a grid spacing parameter just like Quicksurf.

You can test by showing one frame of your trajectory and trying various molmap resolution values, e.g. 2.5 angstroms with separate surfaces for protein and non-protein atoms:

molmap protein 2.5 grid .5 model 1
molmap ~protein 2.5 grid .5 model 2

Another issue is that the isosurface level isn’t controlled in the molmap command but could be controlled in a separate volume command, e.g.:

volume #1 level 0.1
vol #2 level 0.13

If you found commands that worked well enough for you, and you are using MD Movie to view the trajectory, in MD Movie menu: Per-Frame… Define Script and enter these commands as Chimera command script to be executed at each frame.

I hope this helps,
Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Apr 21, 2019, at 11:57 AM, MARIA CLARA BLANES MIRA <c.blanes at goumh.umh.es> wrote:
> Hello,
> I would like to know if Chimera could show the surfaces like VMD does with the  command QuickSurf (I attach the image with the protein in yellow and the lipids in green). 
> I have been trying with a lot of different variations of the surface command but I can not find the way to make the surface ’softer'….
> I have also been trying with spheres representation but the image shows too much information. I need a simplest view, similar to the image because this way it is easier see them move in the .dcd file.  It not so important for the protein, just for the lipids.
> Could you help me with this, please?
> Thank you very much,
> clara

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