[gmx-users] First frame already out of box, getting very large RMSD

[Justin Lemkul]

On 3/1/15 1:21 PM, yunshi11 . wrote:
> On Sat, Feb 28, 2015 at 4:40 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>
>>
>>
>> On 2/28/15 7:38 PM, yunshi11 . wrote:
>>
>>> On Sat, Feb 28, 2015 at 4:21 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>>>
>>>
>>>>
>>>> On 2/28/15 7:17 PM, yunshi11 . wrote:
>>>>
>>>>   On Sat, Feb 28, 2015 at 3:03 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>>>>>
>>>>>
>>>>>
>>>>>> On 2/28/15 6:00 PM, yunshi11 . wrote:
>>>>>>
>>>>>>    Dear all,
>>>>>>
>>>>>>>
>>>>>>> I am running MD for a protein-ligand complex in a dodecahedron box and
>>>>>>> followed the "Suggested trjconv workflow" from
>>>>>>> http://www.gromacs.org/Documentation/Terminology/
>>>>>>> Periodic_Boundary_Conditions
>>>>>>> .
>>>>>>>
>>>>>>> Now I wonder how to remove jumps (across periodic boxes) when the
>>>>>>> first
>>>>>>> frame (actually the .gro file from equilibration run) is already
>>>>>>> jumping
>>>>>>> across two (or more) boxes (according to visualization in VMD).
>>>>>>>
>>>>>>> I understand that this is just an visualizing artifact, but it seems
>>>>>>> to
>>>>>>> also affect other analyses such as calculations of RMSD along the
>>>>>>> trajectory. I got some impossible RMSD values like 1.5 nm, considering
>>>>>>> other replicate simulations give only ~0.3 nm.
>>>>>>>
>>>>>>> Any idea on how to fix this (the effect on RMSD calculations etc., not
>>>>>>> visualization)?
>>>>>>>
>>>>>>>
>>>>>>>    trjconv -center -pbc mol -ur compact usually solves all problems for
>>>>>>>
>>>>>> such
>>>>>> simple systems.  Center on the protein, everything else gets re-wrapped
>>>>>> around it. More complex operations would be needed for protein
>>>>>> complexes,
>>>>>> membranes, etc. But proteins in water (with or without ligands) are
>>>>>> generally straightforward.
>>>>>>
>>>>>>
>>>>>>    I did try that, and other combinations of -pbc and -ur options. Sorry
>>>>>>
>>>>> that
>>>>> I should have been more specific:
>>>>>
>>>>> My system is a homo dimer of protein, each with two ligands (cofactor +
>>>>> inhibitor) bound symmetrically. Some trjconv options can put the dimer
>>>>> protein together, but the two ligands of the second monomer are always
>>>>> in
>>>>> the other periodic boxes.
>>>>>
>>>>>
>>>>>   This changes the approach considerably; always provide full details in
>>>> the
>>>> first message - you'll arrive at a solution faster!
>>>>
>>>> The centering in this case should be done with respect to one protein or
>>>> some chosen custom group of residues that makes a logical center (e.g.
>>>> the
>>>> interfacial residues of one subunit).  The same concept applies - the
>>>> remaining elements of the system (the other protein, the ligands, etc)
>>>> will
>>>> be wrapped with respect to the centered subunit.
>>>>
>>>>
>>>>   With trjconv -s x.tpr -f x.gro -n x.ndx -center -pbc mol -ur compact -o
>>> x.gro, I tried centering on monomer A, monomer B, and two interfacial
>>> residues of monomer A. None of them worked, and the two ligands of monomer
>>> B are always outside the box.
>>>
>>> Can I send .gro files to the mailing list?
>>>
>>>
>> No. To share files you need to upload them to a file-sharing service and
>> provide a link.  The input files (.tpr, .gro, and .ndx) would be useful.
>>
>>
>> Please have a look at these files at
> https://drive.google.com/folderview?id=0B8xuDbuW-ACESnlTcUVrUEdKSGs&usp=sharing
>
> Please make the .tpr file with the .mdp, .top, and .gro files provided,
> since different versions of gromacs may not be compatible with all .tpr
> file versions.
>

Well, I have just about every GROMACS version available to me, and you could 
just tell me what version you're using.  There's a reason I want to see your 
.tpr file; its contents are part of the consistency check I want to do. 
Moreover, all I'm going to get by using these files is generate a .tpr with the 
coordinates from nvt.gro; there's no purpose to fitting this structure to itself 
and there's no way to check anything this way.

Please provide the .tpr, as requested, as well as provide the *exact* command 
you're using (no "x" substitutions; I need to know exactly what you're doing if 
you want me to try to reproduce or fix it).

-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

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