[gmx-users] Re: a flat plane boundary condition

Beckett W Sterner bsterner at MIT.EDU
Wed May 25 21:56:56 CEST 2005


Hi,
  Thats looks great for fixing one end of the protein, but I also want to
ensure that the rest of it is restricted to only half of space (the
impenetrable plane boundary condition).  Or maybe I'm missing your
meaning.  The constraint is important because as the protein exits the
pore it should begin to fold but it shouldn't clump around the residue
with fixed position.

Thanks,
Beckett

> You can freeze atoms in one, two or three dimensions. Check mdp options
> on www.gromacs.org




> On Wed, 2005-05-25 at 12:30 -0400, Beckett W Sterner wrote:
> > Hi,
> >   I'm interested in doing a simple simulation of how a protein folds as it
> > slowly emerges from a pore through a cell membrane.  I unfortunately do
> > not have a crystal structure for the pore, and would like to keep
> > computational costs to a minimum, so I'm interested in running an MD
> > simulation on the protein where one end is fixed to a flat plane with a 2d
> > periodic boundary condition.  Is there a way to implement this in GROMACS,
> > perhaps using a force field?



> You can freeze atoms in one, two or three dimensions. Check mdp options
> on www.gromacs.org
> >
> > Thanks,
> > Beckett
> > _______________________________________________
> > gmx-users mailing list
> > gmx-users at gromacs.org
> > http://www.gromacs.org/mailman/listinfo/gmx-users
> > Please don't post (un)subscribe requests to the list. Use the
> > www interface or send it to gmx-users-request at gromacs.org.
> --
> David.
> ________________________________________________________________________
> David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
> Dept. of Cell and Molecular Biology, Uppsala University.
> Husargatan 3, Box 596,          75124 Uppsala, Sweden
> phone:  46 18 471 4205          fax: 46 18 511 755
> spoel at xray.bmc.uu.se    spoel at gromacs.org   http://xray.bmc.uu.se/~spoel
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 25 May 2005 13:55:46 -0400
> From: Anthony Cruz <acb15885 at uprm.edu>
> Subject: Re: [gmx-users] g_rms Fatal error: Error: Too many iterations
> 	in	routine JACOBI
> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
> Message-ID: <200505251355.46962.acb15885 at uprm.edu>
> Content-Type: text/plain;  charset="iso-8859-1"
>
> I do the gmxcheck and this is the result:
>
> Checking file 1scn_bx_w_fullMD_mv.trr
> trn version: GMX_trn_file (single precision)
> Reading frame       0 time    0.000
> # Atoms  110719
> Last frame      10500 time 10500.001
>
>
> Item        #frames Timestep (ps)
> Step         10501    1
> Time         10501    1
> Lambda       10501    1
> Coords       10501    1
> Velocities   10501    1
> Forces           0
> Box          10501    1
> Checking coordinate file 1scn_bx_w_CL_TPR4fullMD.tpr
> Reading file 1scn_bx_w_CL_TPR4fullMD.tpr, VERSION 3.2.1 (single precision)
> Reading file 1scn_bx_w_CL_TPR4fullMD.tpr, VERSION 3.2.1 (single precision)
> 110719 atoms in file
> coordinates found
> box         found
> velocities  found
>
> Kinetic energy: 411492 (kJ/mol)
> Assuming the number of degrees of freedom to be Natoms * 3 or Natoms * 2,
> the velocities correspond to a temperature of the system
> of 297.996 K or 446.995 K respectively.
>
> Checking for atoms closer than 0.8 and not between 0.4 and 0.7,
> relative to sum of Van der Waals distance:
> WARNING: masses will be determined based on residue and atom names,
>          this can deviate from the real mass of the atom type
> In case you use free energy of solvation predictions:
>
> ++++++++ PLEASE CITE THE FOLLOWING REFERENCE ++++++++
> D. Eisenberg and A. D. McLachlan
> Solvation energy in protein folding and binding
> Nature 319 (1986) pp. 199-203
> -------- -------- --- Thank You --- -------- --------
>
> Opening library file /usr/local/gromacs/share/top/aminoacids.dat
> Opening library file /usr/local/gromacs/share/top/atommass.dat
> Opening library file /usr/local/gromacs/share/top/vdwradii.dat
> Opening library file /usr/local/gromacs/share/top/dgsolv.dat
> #Entries in atommass.dat: 82 vdwradii.dat: 26 dgsolv.dat: 7
> atom# name  residue r_vdw  atom# name  residue r_vdw  distance
>    40   CB  PRO   5 0.15      42   CD  PRO   5 0.15   0.2332
>    50  CD1  TYR   6 0.15      58   CZ  TYR   6 0.15   0.2369
>    52  CD2  TYR   6 0.15      58   CZ  TYR   6 0.15   0.2358
>    78   CA  PRO   9 0.15      80   CG  PRO   9 0.15   0.2383
>    87   CB  LEU  10 0.15      91    C  LEU  10 0.15   0.2399
>   149    C  VAL  16 0.15     153   CA  GLN  17 0.15   0.2398
>   190   CG  PHE  21 0.15     195  CE1  PHE  21 0.15   0.2395
>   191  CD1  PHE  21 0.15     193  CD2  PHE  21 0.15   0.2393
>   193  CD2  PHE  21 0.15     199   CZ  PHE  21 0.15   0.2369
>   244    C  VAL  26 0.15     248   CA LYSH  27 0.15   0.2371
>   277  CG1  VAL  30 0.15     278  CG2  VAL  30 0.15   0.2398
>   302   CB  THR  33 0.15     306    C  THR  33 0.15   0.2383
>   352   CG HISB  39 0.15     355  CE1 HISB  39 0.15   0.2174
>   354  CD2 HISB  39 0.15     355  CE1 HISB  39 0.15   0.2169
>   361   CA  PRO  40 0.15     364   CD  PRO  40 0.15   0.2395
>   362   CB  PRO  40 0.15     364   CD  PRO  40 0.15   0.2387
>   383    C  LEU  42 0.15     387   CA  ASN  43 0.15   0.2391
>   440   CG  PHE  50 0.15     447  CE2  PHE  50 0.15   0.2371
>   441  CD1  PHE  50 0.15     449   CZ  PHE  50 0.15   0.2331
>   443  CD2  PHE  50 0.15     449   CZ  PHE  50 0.15   0.2371
>   459    C  VAL  51 0.15     463   CA  ALA  52 0.15   0.2376
>   492   CG  TYR  56 0.15     497  CE1  TYR  56 0.15   0.2334
>   492   CG  TYR  56 0.15     499  CE2  TYR  56 0.15   0.2398
>   497  CE1  TYR  56 0.15     499  CE2  TYR  56 0.15   0.2375
>   558   CA HISA  63 0.15     560   CG HISA  63 0.15   0.2398
>   560   CG HISA  63 0.15     564  CE1 HISA  63 0.15   0.212
>   563  CD2 HISA  63 0.15     564  CE1 HISA  63 0.15   0.2126
>   586   CG HISB  66 0.15     589  CE1 HISB  66 0.15   0.2163
>   588  CD2 HISB  66 0.15     589  CE1 HISB  66 0.15   0.2109
>   692    C  GLY  79 0.15     696   CA  VAL  80 0.15   0.2391
>   698  CG1  VAL  80 0.15     699  CG2  VAL  80 0.15   0.2384
>   732   CB  PRO  85 0.15     734   CD  PRO  85 0.15   0.2341
>   751    C  VAL  87 0.15     755   CA  SER  88 0.15   0.2397
>   775  CD1  TYR  90 0.15     783   CZ  TYR  90 0.15   0.2391
>   777  CD2  TYR  90 0.15     783   CZ  TYR  90 0.15   0.2398
>   817   CA  VAL  94 0.15     819  CG1  VAL  94 0.15   0.2397
>   890  CD1  TYR 103 0.15     892  CD2  TYR 103 0.15   0.2384
>   894  CE1  TYR 103 0.15     896  CE2  TYR 103 0.15   0.2346
>   929  CG1  VAL 107 0.15     930  CG2  VAL 107 0.15   0.2398
>   969   CG  TRP 112 0.15     975  CE2  TRP 112 0.15   0.2231
>   970  CD1  TRP 112 0.15     972  CD2  TRP 112 0.15   0.2171
>   970  CD1  TRP 112 0.15     975  CE2  TRP 112 0.15   0.2157
>   975  CE2  TRP 112 0.15     976  CE3  TRP 112 0.15   0.2367
>   978  CZ2  TRP 112 0.15     980  CZ3  TRP 112 0.15   0.2378
>  1079    C  MET 123 0.15    1083   CA  SER 124 0.15   0.2396
>  1094  CD1  LEU 125 0.15    1095  CD2  LEU 125 0.15   0.239
>  1216    C  ASN 140 0.15    1220   CA  ALA 141 0.15   0.2389
>  1228   CG  TYR 142 0.15    1233  CE1  TYR 142 0.15   0.2379
>  1229  CD1  TYR 142 0.15    1231  CD2  TYR 142 0.15   0.2377
>  1233  CE1  TYR 142 0.15    1235  CE2  TYR 142 0.15   0.2356
>  1251   CB  ARG 144 0.15    1263    C  ARG 144 0.15   0.2347
>  1347    C  GLY 156 0.15    1351   CA  ASN 157 0.15   0.2398
>  1428   CG  TYR 166 0.15    1433  CE1  TYR 166 0.15   0.238
>  1428   CG  TYR 166 0.15    1435  CE2  TYR 166 0.15   0.2363
>  1443   CA  PRO 167 0.15    1446   CD  PRO 167 0.15   0.2391
>  1473  CD1  TYR 170 0.15    1475  CD2  TYR 170 0.15   0.237
>  1473  CD1  TYR 170 0.15    1481   CZ  TYR 170 0.15   0.2383
>  1477  CE1  TYR 170 0.15    1479  CE2  TYR 170 0.15   0.2392
>  1530  CG1  VAL 176 0.15    1531  CG2  VAL 176 0.15   0.2373
>  1635   CG  PHE 188 0.15    1640  CE1  PHE 188 0.15   0.2336
>  1635   CG  PHE 188 0.15    1642  CE2  PHE 188 0.15   0.2393
>  1640  CE1  PHE 188 0.15    1642  CE2  PHE 188 0.15   0.2399
>  1686   CB  GLU 194 0.15    1691    C  GLU 194 0.15   0.2396
>  1698  CD1  LEU 195 0.15    1699  CD2  LEU 195 0.15   0.2293
>  1736   CA  PRO 200 0.15    1738   CG  PRO 200 0.15   0.2346
>  1762  CG1  VAL 204 0.15    1763  CG2  VAL 204 0.15   0.2344
>  1771  CD1  TYR 205 0.15    1773  CD2  TYR 205 0.15   0.2366
>  1775  CE1  TYR 205 0.15    1777  CE2  TYR 205 0.15   0.2391
>  1806  CD1  TYR 208 0.15    1808  CD2  TYR 208 0.15   0.2383
>  1810  CE1  TYR 208 0.15    1812  CE2  TYR 208 0.15   0.2356
>  1859   CG  TYR 213 0.15    1864  CE1  TYR 213 0.15   0.2375
>  1860  CD1  TYR 213 0.15    1862  CD2  TYR 213 0.15   0.24
>  1862  CD2  TYR 213 0.15    1868   CZ  TYR 213 0.15   0.2396
>  1864  CE1  TYR 213 0.15    1866  CE2  TYR 213 0.15   0.2366
>  1954   CA  PRO 224 0.15    1957   CD  PRO 224 0.15   0.2351
>  1964   CG HISA 225 0.15    1968  CE1 HISA 225 0.15   0.2137
>  1967  CD2 HISA 225 0.15    1968  CE1 HISA 225 0.15   0.2127
>  2012   CB  LEU 232 0.15    2014  CD1  LEU 232 0.15   0.2396
>  2032  CD1  LEU 234 0.15    2033  CD2  LEU 234 0.15   0.2395
>  2063  CD2 HISB 237 0.15    2064  CE1 HISB 237 0.15   0.2173
>  2070   CA  PRO 238 0.15    2072   CG  PRO 238 0.15   0.2387
>  2236   CG  TYR 255 0.15    2243  CE2  TYR 255 0.15   0.2388
>  2241  CE1  TYR 255 0.15    2243  CE2  TYR 255 0.15   0.237
>  2284   CG  PHE 260 0.15    2289  CE1  PHE 260 0.15   0.2363
>  2285  CD1  PHE 260 0.15    2287  CD2  PHE 260 0.15   0.2389
>  2287  CD2  PHE 260 0.15    2293   CZ  PHE 260 0.15   0.2339
>  2301   CG  TYR 261 0.15    2308  CE2  TYR 261 0.15   0.2389
>  2302  CD1  TYR 261 0.15    2310   CZ  TYR 261 0.15   0.2358
>  2304  CD2  TYR 261 0.15    2310   CZ  TYR 261 0.15   0.2395
>  2319   CG  TYR 262 0.15    2326  CE2  TYR 262 0.15   0.2376
>  2324  CE1  TYR 262 0.15    2326  CE2  TYR 262 0.15   0.238
>
> Atoms outside box ( 10.4513 10.4513 10.4513 ):
> (These may occur often and are normally not a problem)
> atom# name  residue r_vdw  coordinate
>  2488   OW  SOL 293 0.105 -0.034   2.79   4.15
>  2491   OW  SOL 294 0.105 -0.031   5.54   9.37
>  2494   OW  SOL 295 0.105 -0.024   3.92   10.1
>  2497   OW  SOL 296 0.105  -0.02   5.24   10.3
>  2500   OW  SOL 297 0.105 -0.018   4.16   8.09
>  2501  HW1  SOL 297 0.04  -0.027   4.18   8.19
>  2503   OW  SOL 298 0.105 -0.018   6.61   5.17
>  2506   OW  SOL 299 0.105 -0.016   1.37    7.5
>  2509   OW  SOL 300 0.105 -0.015   2.23   9.93
>  2511  HW2  SOL 300 0.04  -0.048   2.29     10
> (maybe more)-bash-2.05b$ g_rms -f 1scn_bx_w_fullMD_mv.trr -s
> 1scn_bx_w_CL_TPR4fullMD.tpr -o
>                          :-)  G  R  O  M  A  C  S  (-:
>
>                                Grunge ROck MAChoS
>
>                             :-)  VERSION 3.2.1  (-:
>
>
>       Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
>        Copyright (c) 1991-2000, University of Groningen, The Netherlands.
>              Copyright (c) 2001-2004, The GROMACS development team,
>             check out http://www.gromacs.org for more information.
>
>          This program is free software; you can redistribute it and/or
>           modify it under the terms of the GNU General Public License
>          as published by the Free Software Foundation; either version 2
>              of the License, or (at your option) any later version.
>
>                                 :-)  g_rms  (-:
>
> Option     Filename  Type         Description
> ------------------------------------------------------------
>   -s 1scn_bx_w_CL_TPR4fullMD.tpr  Input        Structure+mass(db): tpr tpb
>                                    tpa gro g96 pdb xml
>   -f 1scn_bx_w_fullMD_mv.trr  Input        Generic trajectory: xtc trr trj
>                                    gro g96 pdb
>  -f2       traj.xtc  Input, Opt.  Generic trajectory: xtc trr trj gro g96 pdb
>   -n      index.ndx  Input, Opt.  Index file
>   -o       rmsd.xvg  Output       xvgr/xmgr file
> -mir    rmsdmir.xvg  Output, Opt. xvgr/xmgr file
>   -a      avgrp.xvg  Output, Opt. xvgr/xmgr file
> -dist rmsd-dist.xvg  Output, Opt. xvgr/xmgr file
>   -m       rmsd.xpm  Output, Opt. X PixMap compatible matrix file
> -bin       rmsd.dat  Output, Opt. Generic data file
>  -bm       bond.xpm  Output, Opt. X PixMap compatible matrix file
>
>       Option   Type  Value  Description
> ------------------------------------------------------
>       -[no]h   bool     no  Print help info and quit
>       -[no]X   bool     no  Use dialog box GUI to edit command line options
>        -nice    int     19  Set the nicelevel
>           -b   time     -1  First frame (ps) to read from trajectory
>           -e   time     -1  Last frame (ps) to read from trajectory
>          -dt   time     -1  Only use frame when t MOD dt = first time (ps)
>          -tu   enum     ps  Time unit: ps, fs, ns, us, ms, s, m or h
>       -[no]w   bool     no  View output xvg, xpm, eps and pdb files
>        -what   enum   rmsd  Structural difference measure: rmsd, rho or rhosc
>     -[no]pbc   bool    yes  PBC check
>         -fit   enum rot+trans  Fit to reference structure: rot+trans,
>                             translation or none
>        -prev    int      0  Compare with previous frame
>   -[no]split   bool     no  Split graph where time is zero
>        -skip    int      1  Only write every nr-th frame to matrix
>       -skip2    int      1  Only write every nr-th frame to matrix
>         -max   real     -1  Maximum level in comparison matrix
>         -min   real     -1  Minimum level in comparison matrix
>        -bmax   real     -1  Maximum level in bond angle matrix
>        -bmin   real     -1  Minimum level in bond angle matrix
>     -nlevels    int     80  Number of levels in the matrices
>
> Reading file 1scn_bx_w_CL_TPR4fullMD.tpr, VERSION 3.2.1 (single precision)
> Reading file 1scn_bx_w_CL_TPR4fullMD.tpr, VERSION 3.2.1 (single precision)
> Select group for least squares fit
> Opening library file /usr/local/gromacs/share/top/aminoacids.dat
> Group     0 (      System) has 110719 elements
> Group     1 (     Protein) has  2433 elements
> Group     2 (   Protein-H) has  1920 elements
> Group     3 (     C-alpha) has   274 elements
> Group     4 (    Backbone) has   822 elements
> Group     5 (   MainChain) has  1097 elements
> Group     6 (MainChain+Cb) has  1336 elements
> Group     7 ( MainChain+H) has  1364 elements
> Group     8 (   SideChain) has  1069 elements
> Group     9 ( SideChain-H) has   823 elements
> Group    10 ( Prot-Masses) has  2433 elements
> Group    11 ( Non-Protein) has 108286 elements
> Group    12 (          CL) has     4 elements
> Group    13 (         HOH) has   423 elements
> Group    14 (         SOL) has 107856 elements
> Group    15 (          CA) has     2 elements
> Group    16 (          NA) has     1 elements
> Group    17 (       Other) has 108286 elements
> Select a group: 1
> Selected 1: 'Protein'
> How many groups do you want to compare ? 1
> OK. I will compare 1 group
> Select group for RMSD calculation
> Opening library file /usr/local/gromacs/share/top/aminoacids.dat
> Group     0 (      System) has 110719 elements
> Group     1 (     Protein) has  2433 elements
> Group     2 (   Protein-H) has  1920 elements
> Group     3 (     C-alpha) has   274 elements
> Group     4 (    Backbone) has   822 elements
> Group     5 (   MainChain) has  1097 elements
> Group     6 (MainChain+Cb) has  1336 elements
> Group     7 ( MainChain+H) has  1364 elements
> Group     8 (   SideChain) has  1069 elements
> Group     9 ( SideChain-H) has   823 elements
> Group    10 ( Prot-Masses) has  2433 elements
> Group    11 ( Non-Protein) has 108286 elements
> Group    12 (          CL) has     4 elements
> Group    13 (         HOH) has   423 elements
> Group    14 (         SOL) has 107856 elements
> Group    15 (          CA) has     2 elements
> Group    16 (          NA) has     1 elements
> Group    17 (       Other) has 108286 elements
> Select a group: 1
> Selected 1: 'Protein'
> trn version: GMX_trn_file (single precision)
> Reading frame       0 time    0.000   Fatal error: Error: Too many iterations
> in routine JACOBI
>
> How I could resolve the problem???
>
> then I try g_rms:
>
>
> On Friday 20 May 2005 10:42 am, Anthony Cruz wrote:
> > How I could do that???  a new tpr??
> >
> > On Friday 20 May 2005 7:53 am, Xavier Periole wrote:
> > > Anthony Cruz wrote:
> > > >Hi:
> > > >I run a MD of a protein in water. when I try to analyse the trajectory
> > > > with g_rms the program stop by the following error :
> > > >Fatal error: Error: Too many iterations in routine JACOBI
> > > >What could be the cause? How I can resolve the problem???
> > >
> > > That is certainly due to a mismatch between your reference topology and
> > > the content of
> > > the trajectory ... make an topology that fits the trajectory.
> >
> > _______________________________________________
> > gmx-users mailing list
> > gmx-users at gromacs.org
> > http://www.gromacs.org/mailman/listinfo/gmx-users
> > Please don't post (un)subscribe requests to the list. Use the
> > www interface or send it to gmx-users-request at gromacs.org.
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 25 May 2005 13:48:43 -0500
> From: "Francesco Mercuri" <mercuri at email.com>
> Subject: [gmx-users] Time reversibility and settle
> To: gmx-users at gromacs.org
> Message-ID: <20050525184843.B8250101D9 at ws1-3.us4.outblaze.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> > > Hello and thank you for your reply.
> > > However, my question about the time reversibility of a leap-frog integrator
> > > with settle (e.g. for TIP3P water molecules) was concerned with the
> > > actual implementation in Gromacs, rather than the analytical point
> > > of view. In other words, is this implementation of leap-frog +
> > > settle still time-reversible in the limit of infinite numerical
> > > accuracy?
> > > This question arises since I tried different numerical
> > > accuracies (single, double and quadruple precision numbers and
> > > operations; for the latter I had to rewrite large parts of the
> > > code...) with, in all cases, similar (and pretty large)
> > > deviations from the "forward" trajectory when reversing the time.
> > > On the other hand, just bypassing the "settle" subroutine
> > > (e.g. by commenting all the code related to the original
> > > implementation of settle by Miyamoto and Kollman), it works as
> > > expected: the algorithm is almost perfectly time-reversible
> > > and the only "noise" is due to numerical inaccuracies, with
> > > deviations comparable, in the three different cases (single,
> > > double, long double) to the accuracy of numbers.
> > > Thus, I'm trying to understand whether just resetting the position
> > > of atoms, as done in the current implementation of "settle",
> > > still leads to a time-reversible MD (in the limit of infinite
> > > machine accuracy).
> > > Any suggestion about that?
> >
> > In the limit is should be time-reversible, unless there is a bug in
> > the settle algorithm, which I consider very unlikely.
> > Have you tried to use shake or lincs (with high precision settings)?
> >
> > There could be some other issues, but when the unconstrained
> > dynamics is reversible you have probably taken care of these:
> > You should not use temperature and pressure coupling (the new
> > version will have reversible Nose-Hoover coupling).
> > When reversing you should take care to use the proper velocities,
> > as x(t), v(t-t/2dt) is stored you need to take the velocities from
> > the next step when reversing.
> >
> > Berk.
>
> Hi again and thanks for your suggestions.
> Still in the search of better time-reversibility properties, I'd like
> to ask a few more questions.
> If I understood correctly, the leap-frog + settle algorithm is implemented
> in Gromacs according to the following steps:
>
> v'(t+dt/2) = v(t-dt/2) + dt*f(t)/m   ("uncorrected" velocities)
> r'(t+dt) = r(t) + dt*v'(t+dt/2)      (unconstrained move)
> r(t+dt) = settle[r'(t+dt)]           (reset of atomic position calling "csettle")
> v(t+dt/2) = [r(t+dt)-r(t)]/dt        (corrected velocities)
>
> is that correct?
> In this case, is not very clear to me how is it possible to "reverse" it,
> e.g. restarting from a [r(t),v(t+dt/2)] configuration and inverting the
> sign of dt, since the settle procedure modifies the atomic position in a
> way that is, apparently, not "reversible".
> Is any modification of the velocities needed?
>
> Another question concerns the preparation of restart files containing
> configurations like the one cited above for time-reversing purposes,
> i.e. [r(t),v(t+dt/2)] (instead of the default [r(t),v(t-dt/2)] ).
> I tried the quick and dirty way by just running one more MD step,
> converting the .trr file in ascii format, manually editing the
> ascii file in order to get the [r(t),v(t+dt/2)] configuration,
> pasting into a .gro file and converting back the .gro file into
> a .trr file for restarting. However, even if I modified the routine
> pr_rvecs in txtdump.c in order to have more decimal digits in the
> ascii files, the accuracy seems to be limited to the order of
> 1.e-8, whereas I expected a better accuracy for double precision
> numbers. Is there any better way to do that? Which is the accuracy
> with which numbers are stored in the .trr file (with double
> precision compilation)?
> Thank you again and best regards,
>
>              Francesco
>
> --
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> ------------------------------
>
> Message: 5
> Date: Wed, 25 May 2005 20:54:30 +0200
> From: "Jordi Camps" <jcamps at lsi.upc.edu>
> Subject: [gmx-users] Adding ions
> To: "'Discussion list for GROMACS users'" <gmx-users at gromacs.org>
> Message-ID: <200505251854.j4PIsNFw028595 at dagon.lsi.upc.edu>
> Content-Type: text/plain;	charset="US-ASCII"
>
> Here I come with more problems :-(
>
> I have a protein file with 126 residues. I generated the topology from the
> .gro file with pdb2gmx. Then I configured the box with editconf. Then I
> added the solvent with genbox. At least I wanted to neutralize the system
> with genion, but it gave me this error:
> 	Fatal error: pbc_dx called before init_pbc
> This time I think that I followed all the standard steps. Do you know which
> could be the cause of this error?
>
> The command was:
> 	$ genion -s 1agi.water.top -o 1agi.ion.gro -nn 6
> And the last lines before the error are:
> 	Selected 12: 'SOL'
> 	Number of (3-atomic) solvent molecules: 7092
> 	Doing single force calculation...
> 	Replacing solvent molecule 1626 (atom 6216) with Cl
> 	Fatal error: pbc_dx called before init_pbc
>
> Thank you in advance,
>
> --
>
> Jordi Camps Puchades
>
> Instituto Nacional de Bioinformatica (INB) Nodo Computacional GNHC-2
> UPC-CIRI
> c/. Jordi Girona 1-3
> Modul C6-E201                     Tel. : 934 011 650
> E-08034 Barcelona                 Fax  : 934 017 014
> Catalunya (Spain)                 e-mail: jcamps at lsi.upc.edu
>
>
>
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> End of gmx-users Digest, Vol 13, Issue 66
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