On 5/28/12 4:09 PM, rama david wrote:
Thank you Justin..



        Is these alternative process is right or totally wrong..???


    Using the checkpoint in this instance is wrong.  The only checkpoint you
    have accessible to you at that point is from the end of the pulling
    simulation and corresponds to the final state of the system.  Applying these
    velocities to the intermediate configurations along the reaction coordinate
    is likely to do weird and unreliable things to the trajectory.  It is more
    robust to run NPT and then data collection, or as I said before, proceed
    immediately to a continuous data collection (with gen_vel = yes!) and
    discard the initial few ns of data as equilibration.  In theory, this
    procedure is no different than any other simulation that one conducts.


Check point file has velocity of the last co-ordinates and we are using middle
configuration..
Thank you for explaination ...

I have another query..

In npt equilibration can I use define = -DPOSRES (Position restrain all the
protein along the chain B)
  and in production md define = -DPOSRES_B ( Position restrain for chain B
only..)  ???


If not What is appropriate reason???


You can use either. I have never tried it, but there is no reason to believe there will be any substantive reason during data collection. The production MD period is significantly longer than the equilibration, and the results will likely turn out the same, when considering error estimates. Sufficient sampling of any series of simulations should converge.

-Justin

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

Justin A. Lemkul, Ph.D.
Research Scientist
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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