AMBER Archive (2004)

Subject: Re: AMBER: X-CA-CT-X dih. FF param ?

From: Guanglei Cui (cuigl_at_csb.sunysb.edu)
Date: Fri Jul 16 2004 - 12:24:46 CDT

Hi,

I've seen a couple of such cases as well with gaff, for example I had to
develop c3-c3-c2-c2, c3-c3-c2-c3, c2-c2-c3-ss to complement with gaff.
These specific terms are necessary for my system to reproduce QM
calculated potential surface profiles, however, they're either missing
or represented by a generic term.

Guanglei

FyD wrote:

> Dear Amber Users,
>
> I have a question about a dihedral force field parameter in parm99 and gaff:
> X-CA-CT-X has a IDIVF=6 and PK=0 phase = 0
>
> Why PK = 0 ?
>
> This seems more or less general for FF param having IDIVF=6 ?
> Is there a particular reason for that ?
>
> I fitted the "CA-CA-CA-NT" FF param to "Eqm-Emm(non-bond)" and PK is really
> different from 0...
>
> Thanks, regards, Francois
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