Hi Justin,

That is really confusing. I tried to run this PDB file many times. But still I could not get it the topology file. I waited for so long (10 hrs)but still the code looks in a deadlock.

Opening library file /usr/local/gromacs/share/gromacs/top/FF.dat

Select the Force Field:
 0: GROMOS96 43a1 force field
 1: GROMOS96 43a2 force field (improved alkane dihedrals)
 2: GROMOS96 45a3 force field (Schuler JCC 2001 22 1205)
 3: GROMOS96 53a5 force field (JCC 2004 vol 25 pag 1656)
 4: GROMOS96 53a6 force field (JCC 2004 vol 25 pag 1656)
 5: OPLS-AA/L all-atom force field (2001 aminoacid dihedrals)
 6: [DEPRECATED] Gromacs force field (see manual)
 7: [DEPRECATED] Gromacs force field with hydrogens for NMR
 8: Encad all-atom force field, using scaled-down vacuum charges
 9: Encad all-atom force field, using full solvent charges

Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.rtp
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
WARNING: masses will be determined based on residue and atom names,
         this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/atommass.dat
Entries in atommass.dat: 178
WARNING: vdwradii will be determined based on residue and atom names,
         this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/vdwradii.dat
Entries in vdwradii.dat: 28
Opening library file /usr/local/gromacs/share/gromacs/top/dgsolv.dat
Entries in dgsolv.dat: 7
Opening library file /usr/local/gromacs/share/gromacs/top/electroneg.dat
Entries in electroneg.dat: 71
Opening library file /usr/local/gromacs/share/gromacs/top/elements.dat
Entries in elements.dat: 218
Reading JUsti.pdb...
Read 'Tolene.pdb', 7 atoms
Opening library file /usr/local/gromacs/share/gromacs/top/xlateat.dat
26 out of 26 lines of xlateat.dat converted succesfully
Analyzing pdb file
There are 1 chains and 0 blocks of water and 1 residues with 7 atoms

  chain  #res #atoms
  1 ' '     1      7

All occupancy fields zero. This is probably not an X-Ray structure
Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.atp
Atomtype 1

[1]+  Stopped

REMARK   This PDB file is created by CS Chem3D

REMARK

COMPND   Tolene.pdb

ATOM    1  CB  PHE     1      -1.158   0.001   0.000                       C

ATOM    2  CG  PHE     1      -1.158  -1.336   0.000                       C

ATOM    3  CD1 PHE     1      -0.000  -2.004   0.000                       C

ATOM    4  CD2 PHE     1       1.158  -1.336   0.000                       C

ATOM    5  CE1 PHE     1       1.158   0.001   0.000                       C

ATOM    6  CE2 PHE     1      -0.000   0.670   0.000                       C

ATOM    7  CZ  PHE     1      -0.000   2.167   0.000                       C

END



can you please tell me what modifications you have done so that your pdb2gmx works fine.

thank you for your time

Rob


Quoting "Justin A. Lemkul" <jalem...@vt.edu>:



tekle...@ualberta.ca wrote:
Hi Justin,

Thank you pointing out that!

I made all the changes and still cannot go past this line.

REMARK   This PDB file is created by CS Chem3D

REMARK

COMPND   Tolene.pdb

HETATM 1 CB PHE 0 -1.158 0.001 0.000 C

HETATM 2 CG PHE 0 -1.158 -1.336 0.000 C

HETATM 3 CD1 PHE 0 -0.000 -2.004 0.000 C

HETATM 4 CD2 PHE 0 1.158 -1.336 0.000 C

HETATM 5 CE1 PHE 0 1.158 0.001 0.000 C

HETATM 6 CE2 PHE 0 -0.000 0.670 0.000 C

HETATM 7 CZ PHE 0 -0.000 2.167 0.000 C

END


As you can see I used this PDB file but still no topology out put.

Select the Force Field:
0: GROMOS96 43a1 force field
1: GROMOS96 43a2 force field (improved alkane dihedrals)
2: GROMOS96 45a3 force field (Schuler JCC 2001 22 1205)
3: GROMOS96 53a5 force field (JCC 2004 vol 25 pag 1656)
4: GROMOS96 53a6 force field (JCC 2004 vol 25 pag 1656)
5: OPLS-AA/L all-atom force field (2001 aminoacid dihedrals)
6: [DEPRECATED] Gromacs force field (see manual)
7: [DEPRECATED] Gromacs force field with hydrogens for NMR
8: Encad all-atom force field, using scaled-down vacuum charges
9: Encad all-atom force field, using full solvent charges

Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.rtp
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
WARNING: masses will be determined based on residue and atom names,
        this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/atommass.dat
Entries in atommass.dat: 178
WARNING: vdwradii will be determined based on residue and atom names,
        this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/vdwradii.dat
Entries in vdwradii.dat: 28
Opening library file /usr/local/gromacs/share/gromacs/top/dgsolv.dat
Entries in dgsolv.dat: 7
Opening library file /usr/local/gromacs/share/gromacs/top/electroneg.dat
Entries in electroneg.dat: 71
Opening library file /usr/local/gromacs/share/gromacs/top/elements.dat
Entries in elements.dat: 218
Reading tolene.pdb...
Read 'Tolene.pdb', 7 atoms
Opening library file /usr/local/gromacs/share/gromacs/top/xlateat.dat
26 out of 26 lines of xlateat.dat converted succesfully
Analyzing pdb file
There are 1 chains and 0 blocks of water and 1 residues with 7 atoms

 chain  #res #atoms
 1 ' '     1      7

All occupancy fields zero. This is probably not an X-Ray structure
Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.atp
Atomtype 1


Is this actually where pdb2gmx stops? There's no fatal error here, the program should continue to run, at least until it prints out a real error message. Your .pdb file works fine, I just ran it through pdb2gmx myself.

-Justin

best

Rob


Quoting "Justin A. Lemkul" <jalem...@vt.edu>:



tekle...@ualberta.ca wrote:
Hi Justin,

It does not work. I eliminated the hydrogen atoms and check the entire .pdb file but could not solve the problem.

the modified PDB file.

REMARK   This PDB file is created by CS Chem3D

REMARK

COMPND   Tolene.pdb

HETATM 1 CB PHE 0 -1.158 0.001 0.000 CH2

HETATM 2 CG PHE 0 -1.158 -1.336 0.000 C

HETATM 3 CD1 PHE 0 -0.000 -2.004 0.000 CR1

HETATM 4 CD2 PHE 0 1.158 -1.336 0.000 CR1

HETATM 5 CE1 PHE 0 1.158 0.001 0.000 CR1

HETATM 6 CE2 PHE 0 -0.000 0.670 0.000 CR1

HETATM 7 CZ PHE 0 -0.000 2.167 0.000 CR1

END


Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.rtp
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
Opening library file /usr/local/gromacs/share/gromacs/top/aminoacids.dat
WARNING: masses will be determined based on residue and atom names,
       this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/atommass.dat
Entries in atommass.dat: 178
WARNING: vdwradii will be determined based on residue and atom names,
       this can deviate from the real mass of the atom type
Opening library file /usr/local/gromacs/share/gromacs/top/vdwradii.dat
Entries in vdwradii.dat: 28
Opening library file /usr/local/gromacs/share/gromacs/top/dgsolv.dat
Entries in dgsolv.dat: 7
Opening library file /usr/local/gromacs/share/gromacs/top/electroneg.dat
Entries in electroneg.dat: 71
Opening library file /usr/local/gromacs/share/gromacs/top/elements.dat
Entries in elements.dat: 218
Reading Tolene.pbd.gro...

-------------------------------------------------------
Program pdb2gmx, VERSION 4.0.5
Source code file: futil.c, line: 330

File input/output error:
Tolene.pbd.gro
-------------------------------------------------------

"It's So Lonely When You Don't Even


Any comment on that.


It's a pretty obvious typo; .pbd != .pdb.

-Justin

Rob











Quoting "Justin A. Lemkul" <jalem...@vt.edu>:



tekle...@ualberta.ca wrote:
Dear Justin,

It really help all the feedback you gave me and thank you for that,.

I have one issues as well.

I try to generate the topology file the way you recommend me using the pdb2gro but failed to get both the topology and gromacs file.

This is my Toluene file in pdb file

REMARK   This PDB file is created by CS Chem3D

REMARK

COMPND   Tolene.pdb

HETATM 1 CB PHE 0 -1.158 0.001 0.000 C

HETATM 2 CG PHE 0 -1.158 -1.336 0.000 C

HETATM 3 CD1 PHE 0 -0.000 -2.004 0.000 C

HETATM 4 CD2 PHE 0 1.158 -1.336 0.000 C

HETATM 5 CE1 PHE 0 1.158 0.001 0.000 C

HETATM 6 CE2 PHE 0 -0.000 0.670 0.000 C

HETATM 7 CZ PHE 0 -0.000 2.167 0.000 C

HETATM 8 H16 PHE 0 -2.111 0.551 0.000 H

HETATM 9 H17 PHE 0 -2.111 -1.886 0.000 H

HETATM 10 H18 PHE 0 -0.000 -3.104 0.000 H

HETATM 11 H19 PHE 0 2.110 -1.886 0.000 H

HETATM 12 H20 PHE 0 2.110 0.551 0.000 H

HETATM 13 H21 PHE 0 1.049 2.538 0.000 H

HETATM 14 H22 PHE 0 -0.524 2.537 -0.909 H

HETATM 15 H23 PHE 0 -0.525 2.537 0.909 H

END


I run
pdb2gmx -ff G43a1 -f TOL.pdb -o TOL.gro -p TOL.top -missing

but I go the following error.

Opening library file /usr/local/gromacs/share/gromacs/top/electroneg.dat
Entries in electroneg.dat: 71
Opening library file /usr/local/gromacs/share/gromacs/top/elements.dat
Entries in elements.dat: 218
Reading YY.pdb...
Read 'Tolene.pdb', 15 atoms
Opening library file /usr/local/gromacs/share/gromacs/top/xlateat.dat
26 out of 26 lines of xlateat.dat converted succesfully
Analyzing pdb file
There are 1 chains and 0 blocks of water and 1 residues with 15 atoms

chain  #res #atoms
1 ' '     1     15

All occupancy fields zero. This is probably not an X-Ray structure
Opening library file /usr/local/gromacs/share/gromacs/top/ffG43a1.atp
Atomtype 1


I tried many times but could not get the topology file.

Can you comment on this please.


What you've shown isn't an error. It reflects the fact that you don't even have occupancy values in this .pdb file. You will certainly have a nomenclature problem, though - your H atoms are not named according to what the .rtp file expects, so you'll either need to delete the H atoms and let pdb2gmx rebuild them from the .hdb entries, or use -ignh.

-Justin

Rob


Quoting "Justin A. Lemkul" <jalem...@vt.edu>:



tekle...@ualberta.ca wrote:
Dear Gromacs Users,

I have encountered the following issues while I was running my MD simulation. Can anybody comment on what the meaning of these notes are. Is there anything I could do to avoid them.

NOTE 2 [file PAP.top, line unknown]:

The largest charge group contains 12 atoms.

Since atoms only see each other when the centers of geometry of the charge

groups they belong to are within the cut-off distance, too large charge

groups can lead to serious cut-off artifacts.

For efficiency and accuracy, charge group should consist of a few atoms.

For all-atom force fields use: CH3, CH2, CH, NH2, NH, OH, CO2, CO, etc.

My SOLVENT IS TOLUENE --- the PRODRG gave me a topology file with only one group charge only.


That's almost certainly wrong. See, for instance, the PHE side chain in the relevant .rtp entry for a more reasonable charge group setup. If you're using PRODRG defaults, then the charges are probably unsatisfactory, as well.

The rationale for the charge group size is summed up here:

http://lists.gromacs.org/pipermail/gmx-users/2008-November/038153.html
NOTE 1 [file nvt.mdp, line unknown]:

The Berendsen thermostat does not generate the correct kinetic energy

distribution. You might want to consider using the V-rescale thermostat.



See the literature about this one, as well as the numerous list archive discussions. For initial equilibration, a weak coupling scheme is probably fine, but you can also use V-rescale. Also of interest:

http://www.gromacs.org/Documentation/Terminology/Thermostats

NOTE 3 [file aminoacids.dat, line 1]:

The optimal PME mesh load for parallel simulations is below 0.5

and for highly parallel simulations between 0.25 and 0.33,

for higher performance, increase the cut-off and the PME grid spacing


This all depends on the size of your system, how much of the work is distributed between the real-space Coulombic interaction and PME.


In addition to the above notes I have also some questions about the NVT and NPT simulation.

1)I am using toluene as a solvent to simulate my polymer, do I need to use the compressibility of toluene which is 9.2e-5 or the default value 4.5e-5 1/bar.

Well, 4.5e-5 corresponds to water, which you aren't using...

For NVT, this won't matter since the box is fixed, but for NPT, the compressibility will affect the response of your system to pressure. The differences may be minimal, but if you know the right value, why accept a wrong one?

2)What about the dielectric constant (the dielectric constant for toluene is 2-2.4), but the default value is 80 ( I assume this is for water- am I right).

Yes, the default again assumes water as the solvent.

3)Is always rvdw = 1.4 nm for GROMOS96. As a result I have to increase my box size of the solute at the beginning to a min of 2*1.4 =2.8 ( min image convection). Is this the right way to do!

At an absolute minimum. Keep in mind that the box vectors will fluctuate under NPT, so if the box decreases even a little bit below 2.8, you will be violating the minimum image convention.

4)I run an NVT simulation to equilibrate my system for 100 ps. When I checked my simulation at the end (successfully completed) I noticed that the shape of my simulation box looks CIRCULAR! some how the rectangular shape looks distorted. What does this tell! Do you guys think something is wrong in my simulation.

This could be some visualization artifact, or the components of your system have condensed within the box. Without actually seeing it, it's hard to tell. If you post an image online (Photobucket, etc) then we might get a better sense of what's going on.

5)I included the polar and aromatic hydrogens in my simulation ( ffG43a1.itp - GROMOS96.1 in PRODRG). Does these hydrogen influence my result as the force field is a united atom force field. Or How can I get rid of them if I want. With or without the aromatic hydrogen gave good results ( besides lower computational cost). Does Gromos96 model correctly aromatic-Aromatic interaction.


Well, "correct" is a relative term for all force fields, but you need to follow the prescribed setup of the force field itself, otherwise you can throw it all away. If you lump the hydrogens into the ring carbons and have an uncharged ring, the result will be different than if you have the hydrogens there with a small charge on each C and H. Again, refer to the force field .rtp file for examples. You can also create a better toluene topology by renaming the residue in your coordinate file PHE and trick pdb2gmx:

pdb2gmx -f toluene.pdb -missing

Then change the mass of the CH2 group (which pdb2gmx thinks is a CB for PHE) to reflect a CH3 group. Make an .itp file out of the resulting .top by removing the unnecessary #includes, [system], and [molecule] directives. Then you don't have to worry about messing with PRODRG. I should note, as well, that this is about the only appropriate use of -missing I can think of at the moment (just for clarity in the archives; I usually warn against using -missing).

-Justin

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

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

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

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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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
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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