[Chimera-users] Interpreting field / force direction in Coulombic Surface Coloring

Elaine Meng meng at cgl.ucsf.edu
Fri May 18 10:16:12 PDT 2012

Hi Sumitro,
The interaction energy of a "test" charge at some point would be the charge multiplied by the electrostatic potential.  So if the test charge  is -1 e (like one electron) its interaction energy at a point with potential +10 kcal/(mol.e) would be favorable, -10 kcal/mol. Positive potential favors interaction with negative charges and vice versa.
I hope this clarifies,
Elaine C. Meng, Ph.D.                       
UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab
Department of Pharmaceutical Chemistry
University of California, San Francisco

P.S. better to send questions to chimera-users at cgl.ucsf.edu because if you send to me and I'm on vacation, you might not get answered

On May 18, 2012, at 12:36 AM, Sumitro Harjanto wrote:

> Hi Elaine, 
> I have a simple question regarding the Coulombic Surface Coloring. I understand that the potential are generated by assuming a charged probe that moves along the surface of the model and as it traverses the surface the potential is picked up as the calculated electrostatic force the probe should experience (that's my understanding, correct me if I'm wrong please).
> I am just, however, a little confused about the interpretation of the value. say if I got a blue patch on the surface, which means I'm getting values in the range of ~10 (positive) kcal/(mol·e) at 298 K; does that mean the region indicated by the blue patch should potential attract or repel electron?
> Thanks!
> Cheers,
> Sumitro

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