[gmx-users] -inf potential with TPIC

[Justin Lemkul]

On 6/10/14, 5:01 PM, Rafael I. Silverman y de la Vega wrote:
> wait, I only changed  the cofactor to gromacs charmm27.ff format
>

Pretty amazing that the simulation even ran with that mash-up of parameters :)

I'd say that's the most likely cause of your problems; nonsensical physical 
model leads to nonsensical output.

-Justin

>
> On Tue, Jun 10, 2014 at 1:58 PM, Rafael I. Silverman y de la Vega <
> rsilverm at ucsc.edu> wrote:
>
>> I suppose something might be wrong with the simulations. I am using
>> gromacs 4.6.5, I am simulating a protein with a cofactor, someone else
>> parametrized it, I changed from charmm to gromacs amber99sb.ff format with
>> a script on the gromacs website.  I did a typical em/nvt/npt equilibration
>> followed by a 5 ns production run. I picked 250 frames out of the
>> trajectory, and altered them to the TPIC input format with a script I
>> wrote, to insert the particle half way between two atoms that I chose. I am
>> inserting a water molecule. When I run the actual insertion some of the
>> frames have a reasonable looking mu, and some have -inf mu. I think it may
>> have to do with cavity size, some frames have too small of a cavity, so the
>> interaction energy of the inserted water diverges...
>>
>>
>> On Mon, Jun 9, 2014 at 6:40 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>>
>>>
>>>
>>> On 6/9/14, 6:41 PM, Rafael I. Silverman y de la Vega wrote:
>>>
>>>> Hi all, I am having a problem with -inf mu coming out of TPIC
>>>> calculations.
>>>> Anyone have some suggestions on how to avoid this? Tabulated potentials?
>>>> Or
>>>> can I modify the source code to reject the absurd values that cause
>>>> this? I
>>>> read a few old discussions on this, I didnt see much on how to handle
>>>> this.
>>>>
>>>>
>>> I'd be much more concerned that something is going wrong in the
>>> simulations.  I have no experience with TPIC, but if you post more detailed
>>> information about what you're doing and which Gromacs version you're using,
>>> you're more likely to get some suggestions.
>>>
>>> -Justin
>>>
>>> --
>>> ==================================================
>>>
>>> Justin A. Lemkul, Ph.D.
>>> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>>>
>>> Department of Pharmaceutical Sciences
>>> School of Pharmacy
>>> Health Sciences Facility II, Room 601
>>> 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 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

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

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