Question about a shift in rmsd using fixedatom off

From: snoze pa (snoze.pa_at_gmail.com)
Date: Tue May 06 2008 - 11:47:45 CDT

Dear NAMD users,

I did a small simulation using namd. Here is the rmsd plot.

http://img519.imageshack.us/img519/9688/namdtx1.jpg

 I am little bit confused from the figure. As shown in the figure that
the first 50ps of minimization it is working fine.

Now in equilibration, another 100ps is working fine with the lengevin
piston off.

After that i am using the "fixedatom off" and minimize for 100 ps. In
this case there is a sharp fall in rmsd as can be seen from the
figure after 150ps step(50ps of minimization+100ps of minimization
with lengevin piston off). Again after that it goes smoothly with
step wise heating and finally full MD run till 2ns.

Why the rmsd drop sharply at 151ps when "fixedatom off" is used. Am i
doing alright or there is some problem.

I am using the equilibration step taken from

http://www.ks.uiuc.edu/Research/namd/tutorial/NCSA2002/hands-on/09_equil.html

the namd.jpg file can be accessed via

http://img519.imageshack.us/img519/9688/namdtx1.jpg

Thank you very much for your help.

s

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