[gmx-users] TIP3 water problem

[Justin Lemkul]

On 12/23/16 3:30 AM, nikolaev at spbau.ru wrote:
> Well, as I understand I need to do the following:
>
> Provide pdb file with different chains for protein and waters;
> gmx pdb2gmx -f 3WQJ.pdb -o 3wqj.gro
>
> then go into the topol_Other_chain_X.itp;
> delete everything that after the atom coords;
>

There are no coordinates in any .itp file, so I don't follow.

> then run everything in the same way.
>
> I have tried this and it seems to work, I just want to make sure that I am
> doing everything right.
>

Basically, my recommendation is: don't feed waters to pdb2gmx.  Solvate with 
normal GROMACS tools and use the stock water topology, which accounts for 
everything.

-Justin

> Anyway, thank you for help!
>
> Dmitrii.
>
>
>>
>>
>> On 12/20/16 2:41 PM, nikolaev at spbau.ru wrote:
>>> Hi, all!
>>>
>>> I am working with the protein structure with internal waters of TIP3
>>> type,
>>> and running grompp ends with an error of "No default U-B types", as I
>>> understand because of some internal inconsistency between atom types
>>> (H1,
>>> H2 and OH2 in my tip3, HW1, HW2, OW in sol). I tried to rename atoms in
>>> both topol.top and .gro files, add extra .itp file in charmm27.ff,
>>> nothing
>>> worked.
>>>
>>> However, this problem has already been mentioned here:
>>> https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-users/2014-March/087725.html
>>>
>>> and the solution involved modifying top file (add waters information
>>> manually). Is it really the only solution of this problem? Because as I
>>> understand I need to insert manually all the charges, angles, bond
>>> lenths
>>> for all the water molecules. And it seems quite a problem, if I want to
>>> run more than 1 system.
>>>
>>
>> Water molecules should not have [bonds] and [angles] directives because
>> they
>> should be treated as rigid via SETTLES.  If your topology has explicit
>> bonds and
>> angles, remove them and re-process the coordinates with pdb2gmx to prevent
>> this
>> spurious assignment.  Then just #include "tip3p.itp" and list the waters
>> in
>> [molecules].
>>
>> -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

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