Re: [AMBER] force field parameter and resp charge calculation

From: FyD <>
Date: Wed, 30 Jun 2010 11:27:02 +0200


> What i mean is that, i have done resp calculations on 24 conformations and
> can i average the resp charges?
> As i read this from

These FAQ are old/outdated(2004!) (they should rewritten). Since that
time R.E.D. has changed a lot, and we ALSO did learn a lot.
You are right "charge averaging" is not correct in these FAQ-I:
My mistake. Sorry for that... Thanks for pointing this out.

> "Do you average RESP results on many orientations?"

No, we do use charge fitting based on multiple-orientations and/or
multiple-conformations and/or multiple molecules.

> "Yes, we do average RESP results on 'different' orientations: we called it
> multi-orientation-RESP fit by analogy to the multi-conformational RESP fit,
> see below"

this is ambiguous you are right! multi-orientation-RESP fit is about
"charge fitting" and not "charge averaging". There is not arithmetic
mean in RESP charge fitting/derivation.

> Or do i misunderstand your meaning?
> how many conformations should be use to be useful? is that depends on the
> molecule itself?

You can look at
Cieplak et al Application of the multimolecule and multiconformational
RESP methodology to biopolymers: Charge derivation for DNA, RNA, and
proteins. J. Comput. Chem. 1995, 16, 1357-1377
  & and also:

regards, Francois

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Received on Wed Jun 30 2010 - 02:30:09 PDT
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