[gmx-users] g_potential

Justin A. Lemkul jalemkul at vt.edu
Mon Nov 3 16:02:45 CET 2008

minnale wrote:
> Hi,
> I have small doubt that when we calculate elctrostaic potenitial of 
> POPC  ,get system with neutral, POPC positive and water negative values,
> what is the reason behind that POPC has positive and water has negative 
> values.

I'm not terribly familiar with g_potential, but in terms of thermodynamics, 
potential energy can be either positive or negative.

> water has H+ ion and OH- ion it should be neutral but why negative 
> values it showing.

Do you actually have explicit H+ and OH- ions in your system?  If you do, I'd be 
interested in the parameters you used, because AFAIK these species are not 
parameterized for use with most common force fields.

In reality, these species are present in water, but it still has no real bearing 
on whether or not the electrostatic potential should be inherently positive or 


> Any suggestions would be appreciated.
> Thanks in advance.
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Justin A. Lemkul
Graduate Research Assistant
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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