AMBER Archive (2003)

Subject: Re: decrease a force const. for angle

From: David A. Case (case_at_scripps.edu)
Date: Mon Feb 10 2003 - 19:04:55 CST

On Mon, Feb 10, 2003, Michal Otyepka wrote:
>
> I wonder if it is possible to easy decrease a force constant for agle
> A-B-C for a general amino acid. I would like to decreace a angle bending
> term Ca-Cb-Cg for only one res. The parm96 applies for the angle 63.0 f.c.
> but i want to use lower f.c. (only for one agle in the protein).

> One way
> how to do it is to creare new residue with modified a. types and to modify
> ff. But can I use e.g. restraint (??with negative sign??) in sander input

Yes, the above sounds like the simplest way. The restraint (negative) would be
added to the ordinary term in the force field. I've not tried a negative
force constant, so you should certainly run some simple tests to make sure
you are getting the energies you want.

.good luck...dac 

-- 

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David A. Case                     |  e-mail:      case_at_scripps.edu
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