[gmx-users] Adding FE2+ parameters

[CROUZY Serge 119222]

Hello Hannes

I'm perfectly aware how you need to be careful in using metal parameters - checking for which solvent and which coordination they have been created for.
In my case structural metal coordinated to protein amino acids... 
I did try to see in Li/Merz parameters which line could resemble the parameters in Gromacs for Zn2+ but with no success - This brings me back to the original question, where do Zn parameters in Gromacs 54a7 come from ?  Knowing this I could try deduce parameters for Fe2+

Thanx 

Serge Crouzy PhD HDR
Groupe de Modélisation et Chimie Théorique
Laboratoire de Chimie et Biologie des Métaux 
Institut de Biosciences et Biotechnologies de Grenoble
CEA Grenoble  UMR  CEA/CNRS/UJF 5249
17, rue des martyrs
38054 Grenoble Cedex 9
Bat. K  pièce 110   
Tel (33)0438782963
Fax (33)0438785487
http://big.cea.fr/drf/big/CBM/GMCT




-----Message d'origine-----
De : gromacs.org_gmx-users-bounces at maillist.sys.kth.se [mailto:gromacs.org_gmx-users-bounces at maillist.sys.kth.se] De la part de Hannes Loeffler
Envoyé : mardi 10 janvier 2017 17:38
À : gromacs.org_gmx-users at maillist.sys.kth.se
Cc : gmx-users at gromacs.org
Objet : Re: [gmx-users] Adding FE2+ or FE3+ into the system

What are you planning to do with those parameters?

You could have a look into the Li/Merz parameters (and papers!) available with the AmberTools (may not have been converted yet to Gromacs formats and the 12-6-4 sets would need support in the code).
Generally, you should be wary when using simple ion force fields and check carefully how they have been parameterised and what for.
Distinguishing different valencies of the same transition metal atom with only vdW/Coulomb parameters will most likely not capture their complex chemistry.


On Tue, 10 Jan 2017 16:24:47 +0000
CROUZY Serge 119222 <serge.crouzy at cea.fr> wrote:

> I'm interested as well in knowing how to get decent parameters for
> Fe2+
> 
> From gromacs-5.1.2/share/top/gromos54a7.ff/ffnonbonded.itp
> We have Zn2+  (What is a reference for these parameters ?)
> 
> name   bondtype   mass   charge   ptype     C                A
> ;name  at.num   mass      charge  ptype       c6           c12
> ZN2+   30      0.000      0.000     A  0.0004182025  9.4400656e-09
> 
> From which I deduced
> if LJ = v(rij)=C(12)/r12 - C(6)/r6 = A/r^12 -C/r^6 to be compared to 
> the standard V=4*eps*[(sig/r)^12 - (sig/r)^6] A =4*eps*sig^12
> C=4*eps*sig^6
> sig = (A/C)^1/6
> eps=C^2 / (4 A)
> For Zn sig=0.168112  eps=4.631677 kJ/mol
> 
> But no Fe2+
> 
> Regards
> 
> Serge Crouzy PhD HDR
> Groupe de Modélisation et Chimie Théorique Laboratoire de Chimie et 
> Biologie des Métaux Institut de Biosciences et Biotechnologies de 
> Grenoble CEA Grenoble  UMR  CEA/CNRS/UJF 5249 17, rue des martyrs
> 38054 Grenoble Cedex 9
> Bat. K  pièce 110   
> Tel (33)0438782963
> Fax (33)0438785487
> http://big.cea.fr/drf/big/CBM/GMCT
> 
> 
> 
> -----Message d'origine-----
> De : gromacs.org_gmx-users-bounces at maillist.sys.kth.se
> [mailto:gromacs.org_gmx-users-bounces at maillist.sys.kth.se] De la part
> de liming_52 Envoyé : mardi 10 janvier 2017 16:54 À :
> gmx-users at gromacs.org Objet : [gmx-users] Adding FE2+ or FE3+ into
> the system
> 
> Dear gromacs users,
> 
> I want to compare the protein in the buffers with FE2+ and FE3+,
> respectively. 
> 
> How can I add FE2+ or FE3+ into the system? What is the command?
> 
> Thanks in advance.
> 
> 
> 
> 
> 
> --
> 
> With my best wishes,
> Ming Li, PhD
> Chinese Academy of Agricultural Sciences, Beijing, China

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