On 14/11/2011 8:33 PM, ??? wrote:
Hi Gromacs users,
I am using GROMACS (ver4.5.3) to run molecular dynamics (MD)
simulation. However during my simulation runs, I encountered some
problems as stated below:
1. In NPT condition, the box size undergoes changes, especially at
high temperature simulations. However, during semisotropic pressure
coupling, the box size changed dramatically at x/y or z direction.
That made the box thin and long or flat. On the top of that, it caused
fatal error in the runs and the simulations stopped running
altogether. Can this situation be prevented ? If so, how can it be done?
Perhaps the models in your systems are intrinsically unsuited to these
simulation conditions. To my knowledge, no common biomolecular force
field has been parametrized against high-temperature NPT data. Under
these conditions, the assumptions about safe sizes for integration time
steps need not hold, so you may find smaller steps are more stable.
2. I have found that command "g_helix" can calculate helix properties.
Nevertheless, my concern is with beta sheet. I did not find any tools
in Gromacs that can calculate the ratio of beta sheet from MD
trajectories. Do you have any recommendations?
do_dssp with old-style DSSP installed is the only GROMACS offering that
can address this. Check out manual section 7.4 for overviews of tools.
Mark
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