Re: Preventing rotation of a protein

From: Giacomo Fiorin (
Date: Wed Jul 17 2013 - 21:31:15 CDT

Hello Thomas, the bias is only on the overall rotation, not on the internal
degrees of freedom: any force applied to the orientation colvar doesn't
have a projection along vectors that would change the internal structure of
the protein.


On Wed, Jul 17, 2013 at 10:18 PM, Thomas Albers <>wrote:

> Hello!
> I have got a system with a 400 amino acid dimer that fits into a
> 128*96*96 A oblong water box. That's about 100K atoms. A cubic
> 128*128*128 water box would be about 200K atoms.
> If I restrain the rotation of the protein with an orientation colvar,
> as hinted at on p. 123 of the NAMD 2.9 manual there's a *substantial*
> speed penalty; IIRC it's so bad that I might as well drop the colvar
> and use a cubic box instead. However, in the recent protein-ligand
> binding tutorial (this one:
> the colvar
> is defined only for the backbone of the protein, this is much faster,
> but I fear I might introduce bias in the internal degrees of freedom.
> Does anyone on the list have some input?
> Regards,
> Thomas

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