AMBER Archive (2005)

Subject: Re: AMBER: a question about varying positions of dihedral restraints with step number

From: David A. Case (case_at_scripps.edu)
Date: Fri Jun 24 2005 - 10:09:21 CDT

On Wed, Jun 22, 2005, Li Su wrote:

> I'm trying to vary positions of dihedral restraints with step number. The
> following is my restraint file, is there something wrong because from the
> output file I can see the dihedral is keeping the values around the initial
> restraint(100) and never changes to the target value (140):
> # torsion resraints
> &rst iat = 5,7,9,15, ifvari=1, ninc=20000, imult=0, ialtd=0, r1=0.,
> r2=100., r3=100., r4=360., rk2=200., rk3=200., r1a=0., r2a=140., r3a=140.,
> r4a=360., rk2a=200., rk3a=200. /
>

I don't see anything wrong. Try changing ninc to a small number (like 100
or so), and running a short simulation with ntpr=1. You should see a sharp
change in the restraint energy at step 100. You might also try setting ninc=0
to see what would happen (again in short test simulations).

...dac
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