Re: [IMP-dev] Harmonic restraint on rotation in IMP

[Barak Raveh <barak.raveh@gmail.com>]

thanks! What I want is a similar thing to AngleTripletScore, but for a distance metric over rotation tensor between two reference frames. Computing the distance per se is not the hard part (this could be in Euler angles or between the quaternion or a geodesic on the unit sphere) - the painful part is computing the derivative in Cartesian coordinates form. I was hoping somebody went through this pain already... :)

On Tue, Mar 25, 2014 at 6:55 PM, Ben Webb <" target="_blank">ben@salilab.org> wrote:

On 3/25/14, 6:47 PM, Barak Raveh wrote:

Does anybody know of an existing implementation of a harmonic restraint
on rotational degrees of freedom?

Sure, this is essentially how an angle restraint works in the CHARMM forcefield, for example.

Namely, I have two reference frame of two particles p1 and p2. For
simplicity, assume xyz(p1) = xyz(p2). I would like to add a harmonic
restraint over the delta in their reference frame, for some definition
of that delta.

You just need to encode that delta (e.g. as a PairScore) then plug it into the existing framework. For example, see core::AngleTripletScore.

    Ben
--
" target="_blank">ben@salilab.org           Âhttp://salilab.org/~ben/
"It is a capital mistake to theorize before one has data."
    - Sir Arthur Conan Doyle

--
Barak