[gmx-users] Difficulty preparing a polymer (PEG) for simulation
Dan Sponseller
gromacs at danpeg.com
Thu Mar 27 15:10:50 CET 2014
I’m trying to prepare PEG for simulation in gromacs and running into
considerable difficulties. My PEG chain is
HOC-COC-COC…...COC-COC-COH
with appropriate hydrogens on the carbons. I am using the new CHARM36.ff
Following the procedure for polymers, I added a beginning, and end, and a
central chain piece to ‘merged.rtp’ and modified the atom names in the .pdb
file to match. I have also added the residues to the ‘residuetypes.dat’ as
Non-Protein (I have also tried listing it as a Protein).
pdb2gmx claims I have169 missing atoms but will create the .gro and .top
files anyway with the -missing parameter passed. The .gro file has all the
atoms but the .top seems to be missing much information on bonds and angles.
Probably no point in continuing but after a quick editconfig, grompp gives
me a fatal error: Group Protein referenced in the .mdp file was not found in
the index file.
I am new to gromacs and would really appreciate help getting started on its
use like this. Following is some of my data files.
Daniel Sponseller
PhD student
Computational Science and Informatics
George Mason University
********************************************************************************
Snip from ‘merged.rtp’
;Dan Sponseller
;Copying from DME below for the repeating chain for PEG.
[ LIG ]
[ atoms ]
C1 CC32A -0.010 0
H11 HCA2A 0.090 1
H12 HCA2A 0.090 2
OO2 OC30A -0.340 3
C3 CC32A -0.010 4
H31 HCA2A 0.090 5
H32 HCA2A 0.090 6
[ bonds ]
C1 -C3
C1 H11
C1 H12
C1 OO2
OO2 C3
C3 H31
C3 H32
C3 +C1
;Dan Sponseller
;Next, define begining of chain for PEG. CH2-OH from [ ETOH ]
[ LIGb ]
[ atoms ]
OO1 OG311 -0.650 0
H11 HGP1 0.420 1
C3 CG321 0.050 2
H31 HGA2 0.090 3
H32 HGA2 0.090 4
[ bonds ]
OO1 H11
OO1 C3
C3 H31
C3 H32
C3 +C1
;Dan Sponseller
;Next, define ending of chain for PEG. CH2-OH from [ ETOH ]
[ LIGe ]
[ atoms ]
C1 CG321 0.050 0
H11 HGA2 0.090 1
H12 HGA2 0.090 2
OO2 OG311 -0.650 3
H21 HGP1 0.420 4
[ bonds ]
C1 -C3
C1 H11
C1 H12
C1 OO2
OO2 H21
********************************************************************************
my modified ‘PEG.pdb’ file:
COMPND UNNAMED
AUTHOR GENERATED BY OPEN BABEL
HETATM 1 C1 LIGe 1 -14.784 -1.665 0.506 1.00 0.00
C
HETATM 2 C3 LIG 2 -13.927 -1.410 -0.735 1.00 0.00
C
HETATM 3 OO2 LIG 2 -13.056 -0.302 -0.493 1.00 0.00
O
HETATM 4 H11 LIGe 1 -15.383 -2.563 0.355 1.00 0.00
H
HETATM 5 H12 LIGe 1 -14.137 -1.802 1.372 1.00 0.00
H
HETATM 6 H31 LIG 2 -13.333 -2.297 -0.956 1.00 0.00
H
HETATM 7 H32 LIG 2 -14.573 -1.185 -1.584 1.00 0.00
H
HETATM 8 C1 LIG 2 -12.207 0.022 -1.596 1.00 0.00
C
HETATM 9 C3 LIG 3 -11.325 1.216 -1.227 1.00 0.00
C
HETATM 10 OO2 LIG 3 -10.441 0.845 -0.167 1.00 0.00
O
HETATM 11 H12 LIG 2 -11.578 -0.836 -1.835 1.00 0.00
H
HETATM 12 H11 LIG 2 -12.818 0.276 -2.463 1.00 0.00
H
HETATM 13 H31 LIG 3 -10.741 1.519 -2.096 1.00 0.00
H
HETATM 14 H32 LIG 3 -11.953 2.046 -0.903 1.00 0.00
H
HETATM 15 C1 LIG 3 -9.568 1.894 0.257 1.00 0.00
C
HETATM 16 C3 LIG 4 -8.673 1.387 1.389 1.00 0.00
C
HETATM 17 OO2 LIG 4 -7.815 0.358 0.894 1.00 0.00
O
HETATM 18 H11 LIG 3 -8.949 2.211 -0.582 1.00 0.00
H
HETATM 19 H12 LIG 3 -10.160 2.738 0.611 1.00 0.00
H
HETATM 20 H31 LIG 4 -8.070 2.210 1.772 1.00 0.00
H
HETATM 21 H32 LIG 4 -9.294 0.988 2.192 1.00 0.00
H
HETATM 22 C1 LIG 4 -6.933 -0.187 1.877 1.00 0.00
C
HETATM 23 C3 LIG 5 -6.066 -1.274 1.239 1.00 0.00
C
HETATM 24 OO2 LIG 5 -5.215 -0.687 0.252 1.00 0.00
O
HETATM 25 H11 LIG 4 -6.294 0.603 2.270 1.00 0.00
H
HETATM 26 H12 LIG 4 -7.517 -0.619 2.690 1.00 0.00
H
HETATM 27 H32 LIG 5 -5.457 -1.751 2.007 1.00 0.00
H
HETATM 28 H31 LIG 5 -6.707 -2.020 0.768 1.00 0.00
H
HETATM 29 C1 LIG 5 -4.360 -1.621 -0.408 1.00 0.00
C
HETATM 30 C3 LIG 6 -3.499 -0.885 -1.437 1.00 0.00
C
HETATM 31 OO2 LIG 6 -2.622 0.020 -0.764 1.00 0.00
O
HETATM 32 H12 LIG 5 -3.715 -2.105 0.325 1.00 0.00
H
HETATM 33 H11 LIG 5 -4.965 -2.374 -0.913 1.00 0.00
H
HETATM 34 H32 LIG 6 -2.910 -1.608 -2.002 1.00 0.00
H
HETATM 35 H31 LIG 6 -4.143 -0.329 -2.118 1.00 0.00
H
HETATM 36 C1 LIG 6 -1.769 0.762 -1.639 1.00 0.00
C
HETATM 37 C3 LIG 7 -0.879 1.694 -0.814 1.00 0.00
C
HETATM 38 OO2 LIG 7 0.000 0.916 0.000 1.00 0.00
O
HETATM 39 H12 LIG 6 -1.145 0.073 -2.208 1.00 0.00
H
HETATM 40 H11 LIG 6 -2.377 1.353 -2.324 1.00 0.00
H
HETATM 41 H31 LIG 7 -0.293 2.323 -1.484 1.00 0.00
H
HETATM 42 H32 LIG 7 -1.502 2.323 -0.178 1.00 0.00
H
HETATM 43 C1 LIG 7 0.879 1.694 0.814 1.00 0.00
C
HETATM 44 C3 LIG 8 1.769 0.762 1.639 1.00 0.00
C
HETATM 45 OO2 LIG 8 2.622 0.020 0.764 1.00 0.00
O
HETATM 46 H11 LIG 7 1.502 2.323 0.178 1.00 0.00
H
HETATM 47 H12 LIG 7 0.293 2.323 1.484 1.00 0.00
H
HETATM 48 H32 LIG 8 2.377 1.353 2.324 1.00 0.00
H
HETATM 49 H31 LIG 8 1.145 0.073 2.208 1.00 0.00
H
HETATM 50 C1 LIG 8 3.499 -0.885 1.437 1.00 0.00
C
HETATM 51 C3 LIG 9 4.360 -1.621 0.408 1.00 0.00
C
HETATM 52 OO2 LIG 9 5.215 -0.687 -0.252 1.00 0.00
O
HETATM 53 H12 LIG 8 4.143 -0.329 2.118 1.00 0.00
H
HETATM 54 H11 LIG 8 2.910 -1.608 2.002 1.00 0.00
H
HETATM 55 H32 LIG 9 4.965 -2.374 0.913 1.00 0.00
H
HETATM 56 H31 LIG 9 3.715 -2.105 -0.325 1.00 0.00
H
HETATM 57 C1 LIG 9 6.066 -1.274 -1.239 1.00 0.00
C
HETATM 58 C3 LIG 10 6.933 -0.187 -1.877 1.00 0.00
C
HETATM 59 OO2 LIG 10 7.815 0.358 -0.894 1.00 0.00
O
HETATM 60 H12 LIG 9 6.707 -2.020 -0.768 1.00 0.00
H
HETATM 61 H11 LIG 9 5.457 -1.751 -2.007 1.00 0.00
H
HETATM 62 H31 LIG 10 7.517 -0.619 -2.690 1.00 0.00
H
HETATM 63 H32 LIG 10 6.294 0.603 -2.270 1.00 0.00
H
HETATM 64 C1 LIG 10 8.673 1.387 -1.389 1.00 0.00
C
HETATM 65 C3 LIG 11 9.568 1.894 -0.257 1.00 0.00
C
HETATM 66 OO2 LIG 11 10.441 0.845 0.167 1.00 0.00
O
HETATM 67 H11 LIG 10 9.294 0.988 -2.192 1.00 0.00
H
HETATM 68 H12 LIG 10 8.070 2.210 -1.772 1.00 0.00
H
HETATM 69 H31 LIG 11 10.160 2.738 -0.611 1.00 0.00
H
HETATM 70 H32 LIG 11 8.949 2.211 0.582 1.00 0.00
H
HETATM 71 C1 LIG 11 11.325 1.216 1.227 1.00 0.00
C
HETATM 72 C3 LIG 12 12.207 0.022 1.596 1.00 0.00
C
HETATM 73 OO2 LIG 12 13.056 -0.302 0.493 1.00 0.00
O
HETATM 74 H11 LIG 11 11.953 2.046 0.903 1.00 0.00
H
HETATM 75 H12 LIG 11 10.741 1.519 2.096 1.00 0.00
H
HETATM 76 H32 LIG 12 12.818 0.276 2.463 1.00 0.00
H
HETATM 77 H31 LIG 12 11.578 -0.836 1.835 1.00 0.00
H
HETATM 78 C1 LIG 12 13.927 -1.410 0.735 1.00 0.00
C
HETATM 79 C3 LIGb 13 14.784 -1.665 -0.506 1.00 0.00
C
HETATM 80 OO1 LIGb 13 15.647 -0.548 -0.727 1.00 0.00
O
HETATM 81 H12 LIG 12 14.573 -1.185 1.584 1.00 0.00
H
HETATM 82 H11 LIG 12 13.333 -2.297 0.956 1.00 0.00
H
HETATM 83 H32 LIGb 13 15.383 -2.563 -0.355 1.00 0.00
H
HETATM 84 H31 LIGb 13 14.137 -1.802 -1.372 1.00 0.00
H
HETATM 85 H11 LIGb 13 16.221 -0.641 -1.500 1.00 0.00
H
HETATM 86 OO2 LIGe 1 -15.647 -0.548 0.727 1.00 0.00
O
HETATM 87 H21 LIGe 1 -16.221 -0.641 1.500 1.00 0.00
H
TER
END
********************************************************************************
snips from pdb2gmx:
WARNING: atom C1 is missing in residue LIGe 1 in the pdb file
WARNING: atom H11 is missing in residue LIGe 1 in the pdb file
You might need to add atom H11 to the hydrogen database of building
block LIGe
in the file merged.hdb (see the manual)
WARNING: atom H12 is missing in residue LIGe 1 in the pdb file
You might need to add atom H12 to the hydrogen database of building
block LIGe
in the file merged.hdb (see the manual)
There were 169 missing atoms in molecule Non-Protein
Number of bonds was 35, now 24
Generating angles, dihedrals and pairs...
Making cmap torsions...There are 0 dihedrals, 0 impropers, 11 angles
0 pairs, 24 bonds and 0 virtual sites
Total mass 546.656 a.m.u.
Total charge 0.000 e
Writing topology
Back Off! I just backed up posre.itp to ./#posre.itp.3#
Writing coordinate file...
Back Off! I just backed up PEG.gro to ./#PEG.gro.3#
--------- PLEASE NOTE ------------
You have successfully generated a topology from: PEG_dan2.pdb.
The Charmm36 force field and the tip3p water model are used.
--------- ETON ESAELP ------------
--
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