[gmx-users] Fwd: LJ cut-offs

[Justin Lemkul]

On 1/11/17 12:46 PM, Mohsen Ramezanpour wrote:
> Hi Guys,
>
> Thanks for your comments. My question was exactly what Dawid clarified.
> Sure, I will read those as you suggested.
>
> Dawid, regarding this:
> "You need to keep in mind however that each force field was optimized for
> given set of cut-offs and
> they virtually become part of that FF (just like FF formula and
> parameters), so it is strongly recommended
> not to change them"
>
> I agree. BUT, using charmm36 in gromacs or other software requires to
> change some critical parameters like cut-offs to get a better agreements
> with experiments as well as with simulations done with charmm/NAMD.
> This is why.
>

As of version GROMACS 5.1, after which a small bug in force-switching was fixed 
(see the link that Tom posted), this should not be true.  The settings listed in 
the GROMACS website for CHARMM36 should correctly reproduce what people do in 
NAMD or CHARMM using the same cutoffs.  We did a lot of work to make sure this 
was the case.  Cutoffs are a function of the force field, not the software.

For a pure membrane, there is a valid comparison to be made between 0.8/1.2 and 
1.0/1.2 switching as Tom has noted, but for a membrane protein 1.0/1.2 is what 
you should use (and from data I have collected and seen, the differences between 
the two switching ranges are small, in any case).

-Justin

> Cheers
> Mohsen
>
> On Wed, Jan 11, 2017 at 5:54 AM, Justin Lemkul <jalemkul at vt.edu> wrote:
>
>>
>>
>> On 1/10/17 10:40 PM, Mohsen Ramezanpour wrote:
>>
>>> Dear gromacs users,
>>>
>>> Please let me know your opinion on the following question:
>>> Thanks in advance for your comments
>>>
>>>
>> dx.doi.org/10.1002/jcc.21287
>>
>> While that paper (obviously) focuses on CHARMM, there is a vast amount of
>> general MD information described in it, as well as cited literature.  The
>> section on nonbonded interactions probably addresses most of what you want
>> to know.
>>
>> -Justin
>>
>>
>>> ---------- Forwarded message ----------
>>> From: Mohsen Ramezanpour <ramezanpour.mohsen at gmail.com>
>>> Date: Thu, Jan 5, 2017 at 5:20 PM
>>> Subject: LJ cut-offs
>>> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>>>
>>>
>>> Dear Gromacs users,
>>>
>>> Every force field has been parametrized with a specific LJ cut-off which
>>> must be the same for simulations using that force field.
>>> However, I was wondering if there is any reason why people usually take
>>> even numbers (e.g. 8-10, 8-12, 10-12 all with a difference of 2) for LJ
>>> cut-offs in force field development?
>>> Is there any rule that prohibit the use of 9-10, 9-11, or 11-12 for LJ
>>> cut-off?
>>>
>>> Thanks
>>>
>>> Cheers
>>> Mohsen
>>>
>>>
>>>
>>>
>>>
>>>
>> --
>> ==================================================
>>
>> 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

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