[gmx-users] Very large fluctuations in dg/dl

[Patrick Fuchs]

Hi Berk,
I just wanted a confirmation because it's a critical aspect. Beyond the 
debate between PME and RF, I always read it was important to be consistent
with the (early) force field parameterization when deriving new parameters.
Even if it does not make any difference for solvation free energy, I 
imagine this can give some differences on other properties (e.g. heat of 
vaporization...), or if you want your new parameters to be consistent with
the remaining of the force field.
Ciao,

Patrick

On Tue, 8 May 2007, Berk Hess wrote:

> Hi,
>
> I don't understand why you ask this.
> Or didn't you read or understand my previous answer?
>
> Reaction-field and PME give exactly the same solvation free-energies,
> so you can just as well derive parameters for the GROMOS force-field
> using PME.
>
> Berk.
>
>
>> From: Patrick Fuchs <Patrick.Fuchs at ebgm.jussieu.fr>
>> Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>> Subject: Re: [gmx-users] Very large fluctuations in dg/dl
>> Date: Tue, 8 May 2007 12:45:32 +0200 (CEST)
>> 
>> Hi Berk and Tsjerk,
>> sounds reassuring since the last version of the GROMOS force field (G53a5 
>> and a6) has been parametrized to reproduce DGsol using reaction field.
>> But, you agree Berk that when you want to calculate the solvation free 
>> energy in the "GROMOS philosophy" (e.g. for reproducing or computing new 
>> parameters), you have to use RF even if energy conservation might not
>> be as good as with PME?
>> Thanks for your answers and your interest in the thread.
>> Cheers,
>> 
>> Patrick
>> 
>> On Tue, 8 May 2007, Berk Hess wrote:
>> 
>>> 
>>> 
>>> 
>>>> From: "Tsjerk Wassenaar" <tsjerkw at gmail.com>
>>>> Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>>>> To: "Discussion list for GROMACS users" <gmx-users at gromacs.org>
>>>> Subject: Re: [gmx-users] Very large fluctuations in dg/dl
>>>> Date: Tue, 8 May 2007 06:39:50 +0200
>>>> 
>>>> Hi Berk,
>>>> 
>>>> Just a question relating to your reply (should be a new thread
>>>> maybe...). The Gromos force fields were parameterized (for use) with
>>>> cutoff/RF. PME is of course better for energy conservation, but the
>>>> inclusion of the interactions beyond the cut-off may give rise to
>>>> deviant behaviour from the force field. Could you enlighten me on this
>>>> issue?
>>>> 
>>>> Thanks,
>>>> 
>>>> Tsjerk
>>> 
>>> Luckily it does not.
>>> And PME is not only better for energy conservation, but also captures
>>> long-range interaction, which for instance leads to more stable proteins.
>>> I have compared solvation free energies for G53A6 with reaction-field
>>> and PME and found no differences:
>>> 
>>> B. Hess and N. van der Vegt
>>> Hydration Thermodynamic Properties of Amino Acid Analogues: A Systematic 
>>> Comparison of Biomolecular Force Fields and Water Models
>>> J. Phys. Chem. B 110, 17616 (2006)
>>> http://dx.doi.org/10.1021/jp0641029
>>> 
>>> Berk.
>
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