[gmx-users] POPC Membrane + protein dynamics

[Justin A. Lemkul]

padhu at ncbs.res.in wrote:
> hi
> i have tried as per your justin lemkul's tutorial.
> 
> after aligning the protein with membrane, subsequently we tried to use
> grompp to generate a tpr file i got the following error.
> 
> -------------------------------------------------------
> Program grompp_mpi, VERSION 3.3.1
> Source code file: grompp.c, line: 448
> 
> Fatal error:
> number of coordinates in coordinate file (pope.pdb, 37867)
>              does not match topology (topol_pope.top, 46779)
> -------------------------------------------------------
> 
> can any one have idea about how to solve this error.
> 

Please see the general advice:

http://www.gromacs.org/Documentation/Errors#Number_of_coordinates_in_coordinate_file_does_not_match_topology

Beyond that, you'll have to post greater details of what step is giving rise to 
this error, what you have done as far as inserting the protein, adding solvent 
and/or ions, etc.

I would also recommend using the latest version of Gromacs (4.0.7), unless for 
some reason you have to use an ancient version (3.3.1).  The speed upgrade is 
incredible :)

-Justin

> thanks in advance,
> Padhu.
> 
>>
>> padhu at ncbs.res.in wrote:
>>> Dear All,
>>> I'm a new comer to gromacs. I need to perform molecular dynamics
>>> simulation of my protein within the POPC membrane. I have downloaded the
>>> 128a popc lipid from Prof.Tieleman's group along with the required
>>> popc.itp. My protein of interest is 458 residues. Since the 128a popc is
>>> already Simulated for 1600 ps, i haven't done membrane only simulation.
>>> So
>>> i directly aligned my protein with the membrane using VMD and have saved
>>> the coordinates. However after i aligned my protein with the membrane, i
>>> felt the membrane was not big enough for my protein of interest, also,
>>> the
>>> N-terminal region and the loop regions in the C-terminal region and
>>> stretching outside water molecule above and below respectively.ow, i
>>> have
>>> two questions here...
>> Yep, if the protein is sticking "out" of the box on both sides, the box is
>> too
>> small.
>>
>>> 1. How would i increase the number of lipids from the existing one?
>> Two options:
>>
>> 1. genconf -nbox will give integer multiples of the lipid system (i.e.,
>> -nbox 2
>> 2 1 will expand the bilayer in the x and y directions and give 512 lipids)
>>
>> 2. genbox -cs popc128a.pdb -box (whatever dimensions) allows you a bit
>> finer
>> control over how large the box is and how many lipids will result.
>>
>>> 2. Also, i should increase increase the number of water molecules above
>>> and below the membrane so that it covers the whole region of N-terminal
>>> and also the loop regions of the C-terminal.
>> Expand the box using editconf and add solvent with genbox.
>>
>>> Now, How to perform these tasks??If i do so will it be compatible with
>>> the
>>> p
> 
> 

-- 
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
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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