Viswanadham Sridhara wrote:
Hello Dr.Spoel and others,
There is one more problem with the simulation of hen egg white lysozyme simulation in water I am running. The timestep I could use is just 0.5 fs or 0.0005ps. Is there any way around to increase the timestep.
This is how a part of my mdp file looks like:

use constraints. please read the manual, chapters 1 and 3.


; RUN CONTROL PARAMETERS =
integrator               = md
;emstep                   = 0.001
;emtol                    = 100
; start time and timestep in ps =
tinit                    = 0.0
dt                       = 0.0005
nsteps                   = 2000000
; number of steps for center of mass motion removal =
comm_mode         = Angular
nstcomm                  = 1
comm_grps = Protein_A
; This selects the subset of atoms for the xtc file. You can =
; select multiple groups. By default all atoms will be written. =
xtc-grps                 =
; Selection of energy groups =
energygrps               = Protein_A SOL Na Cl

; OPTIONS FOR WEAK COUPLING ALGORITHMS =
; Temperature coupling   =
tcoupl                   = Berendsen
; Groups to couple separately =
tc-grps                  = Protein_A SOL Na Cl
; Time constant (ps) and reference temperature (K) =
tau_t                    = 0.1 0.1 0.1 0.1
ref_t                    = 328 328 328 328
; Pressure coupling      =
Pcoupl                   = Berendsen
Pcoupltype               = isotropic
; Time constant (ps), compressibility (1/bar) and reference P (bar) =
tau_p = 1.0 compressibility = 5e-5
ref_p                    =  1.0

; SIMULATED ANNEALING CONTROL =
annealing                = no no no no
; Time at which temperature should be zero (ps) =
;zero_temp_time           = 0

; GENERATE VELOCITIES FOR STARTUP RUN =
gen_vel                  = yes
gen_temp                 = 328
gen_seed                 = 473529

; OPTIONS FOR BONDS     =
constraints              = none
; Type of constraint algorithm =
constraint_algorithm     = SHAKE
; Do not constrain the start configuration =
unconstrained_start      = no
; Relative tolerance of shake =
shake_tol                = 0.00001
; Highest order in the expansion of the constraint coupling matrix =
lincs_order              = 4
; Lincs will write a warning to the stderr if in one step a bond =
; rotates over more degrees than =
lincs_warnangle          = 30
; Convert harmonic bonds to morse potentials =
morse                    = no

; NMR refinement stuff  =
; Distance restraints type: No, Simple or Ensemble =
disre                    = No
; Force weighting of pairs in one distance restraint: Equal or Conservative =
disre_weighting          = Equal
; Use sqrt of the time averaged times the instantaneous violation =
disre_mixed              = no
disre_fc                 = 1000
disre_tau                = 1.25
; Output frequency for pair distances to energy file =
nstdisreout              = 100

; Free energy control stuff =
free_energy              = no
init_lambda              = 0
delta_lambda             = 0
sc-alpha                 = 0
sc-sigma                 = 0.3

Thanks,
-Vissu.

On 8/11/06, *David van der Spoel* <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:

    Viswanadham Sridhara wrote:
     > Hello everyone,
     > I could figure out that parameters for NAG are not that
    important. So, I
     > used free HEWL.
     > I started running it, but I realize that the protein started to
    rotate
     > around the center of mass with a frequency of around 200ps.
     > I used "Linear" as an option for comm_mode and I used "Protein" in
     > comm_grps.
     > Any reason Why the protein is rotating around its center of mass,
    is it
     > normal?

    yes.

    comm_mode = angular

     > Thanks in advance.
     > -Vissu.
     >
     > ---------- Forwarded message ----------
     > From: *David Mobley* < [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]>>>
     > Date: Aug 8, 2006 12:32 AM
     > Subject: Re: [gmx-users] Hen egg white lysozyme.
     > To: Discussion list for GROMACS users < gmx-users@gromacs.org
    <mailto:gmx-users@gromacs.org>
     > <mailto:gmx-users@gromacs.org <mailto:gmx-users@gromacs.org>>>
     >
     > Vissu,
     >
     > Depends on what you are trying to do. Many proteins deposited in the
     > pdb contain "uninteresting" ligands bound to them (i.e. cosolvent
     > molecules, etc.) On the other hand, sometimes ligands are
    functionally
     > important or significantly affect the structure. You have to decide
     > whether you want to include NAG or not; it might help to first figure
     > out what it is and what it's used for (perhaps look up its name, and
     > look at the paper and PDB headers...).
     >
     > It is obviously harder to come up with parameters for NAG than
    not. If
     > you end up deciding it's not important, you can, for example, just
     > remove the HETATM entries dealing with it before running pdb2gmx.
     >
     > David
     >
     >
     > On 8/7/06, Viswanadham Sridhara < [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]>
     > <mailto:[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>> wrote:
     >  > Hi Everyone,
     >  > I am trying to simulate a protein and I am getting the
    following error
     >  > message.
     >  > "NAG" not found in residue topology database. I checked gmx-users
     > discussion
     >  > list to find out if someone ever used 1HEW.pdb . Its a hen
    egg-white
     >  > lysozyme. I did not get even a single archive about this.
     >  > It is under HETATM section of .pdb file. Any help is appreciated.
     >  > I know that I have to add this residue in aminoacids.dat file
    and create
     >  > atoms and bonds in .rtp section. Is there any other way around?
     >  > Thanks in advance,
     >  > -Vissu
     >  >
     >  > --
     >  > Viswanadham Sridhara,
     >  > Graduate Research Assistant,
     >  > Old Dominion University,
     >  > Norfolk, VA-23529.
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     > --
     > Viswanadham Sridhara,
     > Research Assistant,
     > Old Dominion University,
     > Norfolk, Va-23529.
     >
     >
     >
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    --
    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
    [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]>    [EMAIL PROTECTED]
    <mailto:[EMAIL PROTECTED]>   http://folding.bmc.uu.se
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--
Viswanadham Sridhara,
Research Assistant,
Old Dominion University,
Norfolk, Va-23529.


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--
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
[EMAIL PROTECTED]       [EMAIL PROTECTED]   http://folding.bmc.uu.se
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