[gmx-users] using SPC water with Charmm FF

[Justin Lemkul]

On 12/8/15 8:32 AM, Smith, Micholas D. wrote:
> I would mildly disagree with Justin on this one. Although Charmm should
> ideally be used with TIP3P (as Justin noted being one of the force-field
> developers and all), there have been a number of papers that show that SPC/E
> is not entirely incorrect (see below). What you would need to do is see if
> there is any experimental evidence you can compare to as a sanity check;
> though, many of the papers I cite below do indicate that SPC/E does still get
> the overall dynamics correct even when used with Charmm.
>
> --------------------------------- Citations of interest.
>
> Force-​Field Induced Bias in the Structure of Aβ21-​30: A Comparison of OPLS,
> AMBER, CHARMM, and GROMOS Force-​Fields. DOI: 10.1021/acs.jcim.5b00308
>
> Structure of Aqueous Proline via Parallel Tempering Molecular Dynamics and
> Neutron Diffraction. DOI: 10.1021/jp0714973
>
> Testing the inter-operability of the CHARMM and SPC/Fw force fields for
> conformational sampling. DOI: 10.1080/08927022.2013.824574  (note* this is an
> SPC/E derivative water model, you milage may vary)
>
> Local Order, Energy, and Mobility of Water Molecules in the Hydration Shell
> of Small Peptides. DOI: 10.1021/jp909090u
>
> Free Energy Landscapes of Alanine Oligopeptides in Rigid-Body and Hybrid
> Water Models. DOI: 10.1021/acs.jpcb.5b02937
>

The tests that need to be done would involve whether or not the combination of 
CHARMM + SPC (or SPC/E) reproduce the QM target data of the force field (in 
vacuo water interactions) and condensed-phase behavior (e.g. free energies of 
solvation).  Maybe that exists, but absent that demonstration, my stance remains 
(and that of my PI, who I quote as saying "it's totally wrong to use CHARMM with 
SPC").  Using very complex systems like disordered proteins and tempered MD is 
not a very strong justification to me.  You might get some overarching 
properties more or less correct, but I am very skeptical.  As someone who does 
force field development, never underestimate the subtle effects of a small 
inaccuracy even in a large system.

-Justin

> -Micholas
>
> ________________________________________ From:
> gromacs.org_gmx-users-bounces at maillist.sys.kth.se
> <gromacs.org_gmx-users-bounces at maillist.sys.kth.se> on behalf of Justin
> Lemkul <jalemkul at vt.edu> Sent: Monday, December 07, 2015 8:14 PM To:
> gmx-users at gromacs.org Subject: Re: [gmx-users] using SPC water with Charmm
> FF
>
> On 12/7/15 6:59 PM, jhon espinosa wrote:
>> Hi allI finished running the 50 ns MD Simulation of a very large system (17
>> Million atoms).It is a capsid in water. I used charmm FF for the protein
>> and spc for the water.I am studying temperature triggered structural
>> transitions.Since Charmm FF is build based on TIP3p water model, are my
>> simulation results wrong?Is there any main issue that I should
>> know?ThanksJohn
>>
>
> Sorry to say that is an invalid physical model.  The balance of forces will
> be totally wrong.
>
> -Justin
>
> -- ==================================================
>
> Justin A. Lemkul, Ph.D. Ruth L. Kirschstein NRSA Postdoctoral Fellow
>
> Department of Pharmaceutical Sciences School of Pharmacy Health Sciences
> Facility II, Room 629 University of Maryland, Baltimore 20 Penn St.
> Baltimore, MD 21201
>
> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
> http://mackerell.umaryland.edu/~jalemkul
>
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-- 
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

==================================================