[gmx-users] (no subject)

He, Yang yang.he at mavs.uta.edu
Mon Apr 20 01:55:20 CEST 2009 

Hi Justin,

In fact, I have tried to use freezegrps to freeze a whole single CG DNA strand  and it works but if I want to freeze some atoms in this single strand, it seems that I have no choice but choose the position restraints. The freezegrps seems not to work for that. But the error  for the position restraints always is fragmentation fault and can not be fixed although many methods have been tried.

I don't know whether this is a bug in the gromacs cause I have followed the steps in manual to simulate a case(about speptide) in manual with position restraints while it still doesn't work. I am confused about that.

Yang
________________________________________
From: gmx-users-bounces at gromacs.org [gmx-users-bounces at gromacs.org] On Behalf Of Justin A. Lemkul [jalemkul at vt.edu]
Sent: Sunday, April 19, 2009 4:41 PM
To: Gromacs Users' List
Subject: Re: [gmx-users] (no subject)

He, Yang wrote:
> It always show the common error  "Invalid order for directive defaults".I suppose it is because I have  defined an atom belonging to two groups . What do you mean "by freezing subgroups of atoms
> within a molecule" ? I just wonder how to make it ?Can you give me some examples?
>

The error is unrelated to your freezegrps.  See here:

http://wiki.gromacs.org/index.php/Errors#Invalid_order_for_directive_defaults

Your index groups should be fine.  A "subgroup" refers to select atoms within a
molecule, as in backbone of the protein, headgroups of lipids, or some such
similar idea.  As I said before, your use of freezegrps and index groups should,
in theory, be fine.

-Justin

> Thank you very much.
>
> Yang
> ________________________________________
> From: gmx-users-bounces at gromacs.org [gmx-users-bounces at gromacs.org] On Behalf Of Justin A. Lemkul [jalemkul at vt.edu]
> Sent: Sunday, April 19, 2009 3:47 PM
> To: Gromacs Users' List
> Subject: Re: [gmx-users] (no subject)
>
> He, Yang wrote:
>> Hi Justin,
>>
>> In fact, I just get the error. I have tried to use the freezegroup but it seems that it only work for the whole group not certain atoms in the whole group.
>>
>
> Alright, so what's the error?  You should be able to freeze subgroups of atoms
> within a molecule; I've done it several times in different instances.
>
> -Justin
>
>> Yang
>> ________________________________________
>> From: gmx-users-bounces at gromacs.org [gmx-users-bounces at gromacs.org] On Behalf Of Justin A. Lemkul [jalemkul at vt.edu]
>> Sent: Sunday, April 19, 2009 1:42 PM
>> To: Discussion list for GROMACS users
>> Subject: Re: [gmx-users] (no subject)
>>
>> He, Yang wrote:
>>> Hi all users,
>>>
>>> I am trying to create the ndx file to define the atoms which I want to add the position restraints to. What I create is like this:
>>>
>>> [God]
>>> 21  22
>>> [Bad]
>>> 61  62
>>>
>>> And  I have defined the atom numbering 21, 22, 61,62 in gro file like this :
>>>
>>> 2MOM   bT   21     0.805      1.330      3.914
>>> 2MOM   bT   22     0.448      1.572      3.576
>>>
>>>  4ICE   bT   61     0.805      4.330      3.914
>>>  4ICE   bT   62     0.448      4.572      3.576
>>>
>>> I know this may cause error cause I just define one atoms in two groups.   I just want to freeze only two atoms in the group[MOM](A single DNA strand) while keep the other atoms in this group move freely , Meanwhile, the two frozen atoms have a bond connection with the other atoms in this [MOM]group ,which is assumed that this single DNA strand will be fixed because of the two fixed atoms and the other atoms will move freely at the same time. I wonder how I can define this position restraints in gromacs .
>>>
>> Are you assuming an error, or have you tried it and actually received an error?
>>   Use these groups as the "freezegrps" in the .mdp file and try it.  It should
>> be fine.
>>
>> -Justin
>>
>>> I hope what  I said is clear to you all and I really appreciate your any suggestions.
>>>
>>> Yang
>>> _______________________________________________
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>> --
>> ========================================
>>
>> Justin A. Lemkul
>> Ph.D. Candidate
>> ICTAS Doctoral Scholar
>> Department of Biochemistry
>> Virginia Tech
>> Blacksburg, VA
>> jalemkul[at]vt.edu | (540) 231-9080
>> http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
>>
>> ========================================
>> _______________________________________________
>> gmx-users mailing list    gmx-users at gromacs.org
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>
> --
> ========================================
>
> Justin A. Lemkul
> Ph.D. Candidate
> ICTAS Doctoral Scholar
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> jalemkul[at]vt.edu | (540) 231-9080
> http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
>
> ========================================
> _______________________________________________
> gmx-users mailing list    gmx-users at gromacs.org
> http://www.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at http://www.gromacs.org/search before posting!
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--
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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