[Chimera-users] External SAS calculation

Elaine Meng meng at cgl.ucsf.edu
Tue Nov 10 08:40:19 PST 2009

Hi Yasser,
The probe radius is also needed for the SES (solvent-excluded  
surface), which is the one displayed in Chimera.  As Tom mentioned,  
the SES is where the surface of the probe goes, while the SAS is where  
the center of the probe goes.  Both SAS and SES area calculations  
require and depend on the probe radius.  It is only the SAS triangles  
for drawing the surface, the locations of the SAS surface points, that  
are not calculated. So if you were planning to save the surface  
points, you could only get the ones for the SES.

This is true for the currently available Chimera.  We are planning to  
make some changes in the surface calculations, so it may change in the  

I hope this helps,

On Nov 10, 2009, at 6:49 AM, Yasser Almeida Hernández wrote:

> Hi Tom...
> I'm actually interested in compute and save the accesible surface as  
> a grid (like DMS).
> If Chimera doesn't compute the SAS surface (with MSMS code), why it  
> ask for the probe radius in Favorites > Preferences > New Surfaces?

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